/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* vim: set ts=8 sts=2 et sw=2 tw=80: */ /* This code is made available to you under your choice of the following sets * of licensing terms: */ /* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ /* Copyright 2014 Mozilla Contributors * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ // This code implements RFC6125-ish name matching, RFC5280-ish name constraint // checking, and related things. // // In this code, identifiers are classified as either "presented" or // "reference" identifiers are defined in // http://tools.ietf.org/html/rfc6125#section-1.8. A "presented identifier" is // one in the subjectAltName of the certificate, or sometimes within a CN of // the certificate's subject. The "reference identifier" is the one we are // being asked to match the certificate against. When checking name // constraints, the reference identifier is the entire encoded name constraint // extension value. #include "pkixcheck.h" #include "pkixutil.h" namespace mozilla { namespace pkix { namespace { // GeneralName ::= CHOICE { // otherName [0] OtherName, // rfc822Name [1] IA5String, // dNSName [2] IA5String, // x400Address [3] ORAddress, // directoryName [4] Name, // ediPartyName [5] EDIPartyName, // uniformResourceIdentifier [6] IA5String, // iPAddress [7] OCTET STRING, // registeredID [8] OBJECT IDENTIFIER } enum class GeneralNameType : uint8_t { // Note that these values are NOT contiguous. Some values have the // der::CONSTRUCTED bit set while others do not. // (The der::CONSTRUCTED bit is for types where the value is a SEQUENCE.) otherName = der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 0, rfc822Name = der::CONTEXT_SPECIFIC | 1, dNSName = der::CONTEXT_SPECIFIC | 2, x400Address = der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 3, directoryName = der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 4, ediPartyName = der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 5, uniformResourceIdentifier = der::CONTEXT_SPECIFIC | 6, iPAddress = der::CONTEXT_SPECIFIC | 7, registeredID = der::CONTEXT_SPECIFIC | 8, // nameConstraints is a pseudo-GeneralName used to signify that a // reference ID is actually the entire name constraint extension. nameConstraints = 0xff }; inline Result ReadGeneralName(Reader& reader, /*out*/ GeneralNameType& generalNameType, /*out*/ Input& value) { uint8_t tag; Result rv = der::ReadTagAndGetValue(reader, tag, value); if (rv != Success) { return rv; } switch (tag) { case static_cast(GeneralNameType::otherName): generalNameType = GeneralNameType::otherName; break; case static_cast(GeneralNameType::rfc822Name): generalNameType = GeneralNameType::rfc822Name; break; case static_cast(GeneralNameType::dNSName): generalNameType = GeneralNameType::dNSName; break; case static_cast(GeneralNameType::x400Address): generalNameType = GeneralNameType::x400Address; break; case static_cast(GeneralNameType::directoryName): generalNameType = GeneralNameType::directoryName; break; case static_cast(GeneralNameType::ediPartyName): generalNameType = GeneralNameType::ediPartyName; break; case static_cast(GeneralNameType::uniformResourceIdentifier): generalNameType = GeneralNameType::uniformResourceIdentifier; break; case static_cast(GeneralNameType::iPAddress): generalNameType = GeneralNameType::iPAddress; break; case static_cast(GeneralNameType::registeredID): generalNameType = GeneralNameType::registeredID; break; default: return Result::ERROR_BAD_DER; } return Success; } enum class MatchResult { NoNamesOfGivenType = 0, Mismatch = 1, Match = 2 }; Result SearchNames(const Input* subjectAltName, Input subject, GeneralNameType referenceIDType, Input referenceID, FallBackToSearchWithinSubject fallBackToCommonName, /*out*/ MatchResult& match); Result SearchWithinRDN(Reader& rdn, GeneralNameType referenceIDType, Input referenceID, FallBackToSearchWithinSubject fallBackToEmailAddress, FallBackToSearchWithinSubject fallBackToCommonName, /*in/out*/ MatchResult& match); Result MatchAVA(Input type, uint8_t valueEncodingTag, Input presentedID, GeneralNameType referenceIDType, Input referenceID, FallBackToSearchWithinSubject fallBackToEmailAddress, FallBackToSearchWithinSubject fallBackToCommonName, /*in/out*/ MatchResult& match); Result ReadAVA(Reader& rdn, /*out*/ Input& type, /*out*/ uint8_t& valueTag, /*out*/ Input& value); void MatchSubjectPresentedIDWithReferenceID(GeneralNameType presentedIDType, Input presentedID, GeneralNameType referenceIDType, Input referenceID, /*in/out*/ MatchResult& match); Result MatchPresentedIDWithReferenceID(GeneralNameType presentedIDType, Input presentedID, GeneralNameType referenceIDType, Input referenceID, /*in/out*/ MatchResult& matchResult); Result CheckPresentedIDConformsToConstraints(GeneralNameType referenceIDType, Input presentedID, Input nameConstraints); uint8_t LocaleInsensitveToLower(uint8_t a); bool StartsWithIDNALabel(Input id); enum class IDRole { ReferenceID = 0, PresentedID = 1, NameConstraint = 2, }; enum class AllowWildcards { No = 0, Yes = 1 }; // DNSName constraints implicitly allow subdomain matching when there is no // leading dot ("foo.example.com" matches a constraint of "example.com"), but // RFC822Name constraints only allow subdomain matching when there is a leading // dot ("foo.example.com" does not match "example.com" but does match // ".example.com"). enum class AllowDotlessSubdomainMatches { No = 0, Yes = 1 }; bool IsValidDNSID(Input hostname, IDRole idRole, AllowWildcards allowWildcards); Result MatchPresentedDNSIDWithReferenceDNSID( Input presentedDNSID, AllowWildcards allowWildcards, AllowDotlessSubdomainMatches allowDotlessSubdomainMatches, IDRole referenceDNSIDRole, Input referenceDNSID, /*out*/ bool& matches); Result MatchPresentedRFC822NameWithReferenceRFC822Name( Input presentedRFC822Name, IDRole referenceRFC822NameRole, Input referenceRFC822Name, /*out*/ bool& matches); } // namespace bool IsValidReferenceDNSID(Input hostname); bool IsValidPresentedDNSID(Input hostname); bool ParseIPv4Address(Input hostname, /*out*/ uint8_t (&out)[4]); bool ParseIPv6Address(Input hostname, /*out*/ uint8_t (&out)[16]); // This is used by the pkixnames_tests.cpp tests. Result MatchPresentedDNSIDWithReferenceDNSID(Input presentedDNSID, Input referenceDNSID, /*out*/ bool& matches) { return MatchPresentedDNSIDWithReferenceDNSID( presentedDNSID, AllowWildcards::Yes, AllowDotlessSubdomainMatches::Yes, IDRole::ReferenceID, referenceDNSID, matches); } // Verify that the given end-entity cert, which is assumed to have been already // validated with BuildCertChain, is valid for the given hostname. hostname is // assumed to be a string representation of an IPv4 address, an IPv6 addresss, // or a normalized ASCII (possibly punycode) DNS name. Result CheckCertHostname(Input endEntityCertDER, Input hostname, NameMatchingPolicy& nameMatchingPolicy) { BackCert cert(endEntityCertDER, EndEntityOrCA::MustBeEndEntity, nullptr); Result rv = cert.Init(); if (rv != Success) { return rv; } Time notBefore(Time::uninitialized); rv = ParseValidity(cert.GetValidity(), ¬Before); if (rv != Success) { return rv; } FallBackToSearchWithinSubject fallBackToSearchWithinSubject; rv = nameMatchingPolicy.FallBackToCommonName(notBefore, fallBackToSearchWithinSubject); if (rv != Success) { return rv; } const Input* subjectAltName(cert.GetSubjectAltName()); Input subject(cert.GetSubject()); // For backward compatibility with legacy certificates, we may fall back to // searching for a name match in the subject common name for DNS names and // IPv4 addresses. We don't do so for IPv6 addresses because we do not think // there are many certificates that would need such fallback, and because // comparisons of string representations of IPv6 addresses are particularly // error prone due to the syntactic flexibility that IPv6 addresses have. // // IPv4 and IPv6 addresses are represented using the same type of GeneralName // (iPAddress); they are differentiated by the lengths of the values. MatchResult match; uint8_t ipv6[16]; uint8_t ipv4[4]; if (IsValidReferenceDNSID(hostname)) { rv = SearchNames(subjectAltName, subject, GeneralNameType::dNSName, hostname, fallBackToSearchWithinSubject, match); } else if (ParseIPv6Address(hostname, ipv6)) { rv = SearchNames(subjectAltName, subject, GeneralNameType::iPAddress, Input(ipv6), FallBackToSearchWithinSubject::No, match); } else if (ParseIPv4Address(hostname, ipv4)) { rv = SearchNames(subjectAltName, subject, GeneralNameType::iPAddress, Input(ipv4), fallBackToSearchWithinSubject, match); } else { return Result::ERROR_BAD_CERT_DOMAIN; } if (rv != Success) { return rv; } switch (match) { case MatchResult::NoNamesOfGivenType: // fall through case MatchResult::Mismatch: return Result::ERROR_BAD_CERT_DOMAIN; case MatchResult::Match: return Success; MOZILLA_PKIX_UNREACHABLE_DEFAULT_ENUM } } // 4.2.1.10. Name Constraints Result CheckNameConstraints(Input encodedNameConstraints, const BackCert& firstChild, KeyPurposeId requiredEKUIfPresent) { for (const BackCert* child = &firstChild; child; child = child->childCert) { FallBackToSearchWithinSubject fallBackToCommonName = (child->endEntityOrCA == EndEntityOrCA::MustBeEndEntity && requiredEKUIfPresent == KeyPurposeId::id_kp_serverAuth) ? FallBackToSearchWithinSubject::Yes : FallBackToSearchWithinSubject::No; MatchResult match; Result rv = SearchNames(child->GetSubjectAltName(), child->GetSubject(), GeneralNameType::nameConstraints, encodedNameConstraints, fallBackToCommonName, match); if (rv != Success) { return rv; } switch (match) { case MatchResult::Match: // fall through case MatchResult::NoNamesOfGivenType: break; case MatchResult::Mismatch: return Result::ERROR_CERT_NOT_IN_NAME_SPACE; } } return Success; } namespace { // SearchNames is used by CheckCertHostname and CheckNameConstraints. // // When called during name constraint checking, referenceIDType is // GeneralNameType::nameConstraints and referenceID is the entire encoded name // constraints extension value. // // The main benefit of using the exact same code paths for both is that we // ensure consistency between name validation and name constraint enforcement // regarding thing like "Which CN attributes should be considered as potential // CN-IDs" and "Which character sets are acceptable for CN-IDs?" If the name // matching and the name constraint enforcement logic were out of sync on these // issues (e.g. if name matching were to consider all subject CN attributes, // but name constraints were only enforced on the most specific subject CN), // trivial name constraint bypasses could result. Result SearchNames(/*optional*/ const Input* subjectAltName, Input subject, GeneralNameType referenceIDType, Input referenceID, FallBackToSearchWithinSubject fallBackToCommonName, /*out*/ MatchResult& match) { Result rv; match = MatchResult::NoNamesOfGivenType; // RFC 6125 says "A client MUST NOT seek a match for a reference identifier // of CN-ID if the presented identifiers include a DNS-ID, SRV-ID, URI-ID, or // any application-specific identifier types supported by the client." // Accordingly, we only consider CN-IDs if there are no DNS-IDs in the // subjectAltName. // // RFC 6125 says that IP addresses are out of scope, but for backward // compatibility we accept them, by considering IP addresses to be an // "application-specific identifier type supported by the client." // // TODO(bug XXXXXXX): Consider strengthening this check to "A client MUST NOT // seek a match for a reference identifier of CN-ID if the certificate // contains a subjectAltName extension." // // TODO(bug XXXXXXX): Consider dropping support for IP addresses as // identifiers completely. if (subjectAltName) { Reader altNames; rv = der::ExpectTagAndGetValueAtEnd(*subjectAltName, der::SEQUENCE, altNames); if (rv != Success) { return rv; } // According to RFC 5280, "If the subjectAltName extension is present, the // sequence MUST contain at least one entry." For compatibility reasons, we // do not enforce this. See bug 1143085. while (!altNames.AtEnd()) { GeneralNameType presentedIDType; Input presentedID; rv = ReadGeneralName(altNames, presentedIDType, presentedID); if (rv != Success) { return rv; } rv = MatchPresentedIDWithReferenceID(presentedIDType, presentedID, referenceIDType, referenceID, match); if (rv != Success) { return rv; } if (referenceIDType != GeneralNameType::nameConstraints && match == MatchResult::Match) { return Success; } if (presentedIDType == GeneralNameType::dNSName || presentedIDType == GeneralNameType::iPAddress) { fallBackToCommonName = FallBackToSearchWithinSubject::No; } } } if (referenceIDType == GeneralNameType::nameConstraints) { rv = CheckPresentedIDConformsToConstraints(GeneralNameType::directoryName, subject, referenceID); if (rv != Success) { return rv; } } FallBackToSearchWithinSubject fallBackToEmailAddress; if (!subjectAltName && (referenceIDType == GeneralNameType::rfc822Name || referenceIDType == GeneralNameType::nameConstraints)) { fallBackToEmailAddress = FallBackToSearchWithinSubject::Yes; } else { fallBackToEmailAddress = FallBackToSearchWithinSubject::No; } // Short-circuit the parsing of the subject name if we're not going to match // any names in it if (fallBackToEmailAddress == FallBackToSearchWithinSubject::No && fallBackToCommonName == FallBackToSearchWithinSubject::No) { return Success; } // Attempt to match the reference ID against the CN-ID, which we consider to // be the most-specific CN AVA in the subject field. // // https://tools.ietf.org/html/rfc6125#section-2.3.1 says: // // To reduce confusion, in this specification we avoid such terms and // instead use the terms provided under Section 1.8; in particular, we // do not use the term "(most specific) Common Name field in the subject // field" from [HTTP-TLS] and instead state that a CN-ID is a Relative // Distinguished Name (RDN) in the certificate subject containing one // and only one attribute-type-and-value pair of type Common Name (thus // removing the possibility that an RDN might contain multiple AVAs // (Attribute Value Assertions) of type CN, one of which could be // considered "most specific"). // // https://tools.ietf.org/html/rfc6125#section-7.4 says: // // [...] Although it would be preferable to // forbid multiple CN-IDs entirely, there are several reasons at this // time why this specification states that they SHOULD NOT (instead of // MUST NOT) be included [...] // // Consequently, it is unclear what to do when there are multiple CNs in the // subject, regardless of whether there "SHOULD NOT" be. // // NSS's CERT_VerifyCertName mostly follows RFC2818 in this instance, which // says: // // If a subjectAltName extension of type dNSName is present, that MUST // be used as the identity. Otherwise, the (most specific) Common Name // field in the Subject field of the certificate MUST be used. // // [...] // // In some cases, the URI is specified as an IP address rather than a // hostname. In this case, the iPAddress subjectAltName must be present // in the certificate and must exactly match the IP in the URI. // // (The main difference from RFC2818 is that NSS's CERT_VerifyCertName also // matches IP addresses in the most-specific CN.) // // NSS's CERT_VerifyCertName finds the most specific CN via // CERT_GetCommoName, which uses CERT_GetLastNameElement. Note that many // NSS-based applications, including Gecko, also use CERT_GetCommonName. It // is likely that other, non-NSS-based, applications also expect only the // most specific CN to be matched against the reference ID. // // "A Layman's Guide to a Subset of ASN.1, BER, and DER" and other sources // agree that an RDNSequence is ordered from most significant (least // specific) to least significant (most specific), as do other references. // // However, Chromium appears to use the least-specific (first) CN instead of // the most-specific; see https://crbug.com/366957. Also, MSIE and some other // popular implementations apparently attempt to match the reference ID // against any/all CNs in the subject. Since we're trying to phase out the // use of CN-IDs, we intentionally avoid trying to match MSIE's more liberal // behavior. // Name ::= CHOICE { -- only one possibility for now -- // rdnSequence RDNSequence } // // RDNSequence ::= SEQUENCE OF RelativeDistinguishedName // // RelativeDistinguishedName ::= // SET SIZE (1..MAX) OF AttributeTypeAndValue Reader subjectReader(subject); return der::NestedOf(subjectReader, der::SEQUENCE, der::SET, der::EmptyAllowed::Yes, [&](Reader& r) { return SearchWithinRDN(r, referenceIDType, referenceID, fallBackToEmailAddress, fallBackToCommonName, match); }); } // RelativeDistinguishedName ::= // SET SIZE (1..MAX) OF AttributeTypeAndValue // // AttributeTypeAndValue ::= SEQUENCE { // type AttributeType, // value AttributeValue } Result SearchWithinRDN(Reader& rdn, GeneralNameType referenceIDType, Input referenceID, FallBackToSearchWithinSubject fallBackToEmailAddress, FallBackToSearchWithinSubject fallBackToCommonName, /*in/out*/ MatchResult& match) { do { Input type; uint8_t valueTag; Input value; Result rv = ReadAVA(rdn, type, valueTag, value); if (rv != Success) { return rv; } rv = MatchAVA(type, valueTag, value, referenceIDType, referenceID, fallBackToEmailAddress, fallBackToCommonName, match); if (rv != Success) { return rv; } } while (!rdn.AtEnd()); return Success; } // AttributeTypeAndValue ::= SEQUENCE { // type AttributeType, // value AttributeValue } // // AttributeType ::= OBJECT IDENTIFIER // // AttributeValue ::= ANY -- DEFINED BY AttributeType // // DirectoryString ::= CHOICE { // teletexString TeletexString (SIZE (1..MAX)), // printableString PrintableString (SIZE (1..MAX)), // universalString UniversalString (SIZE (1..MAX)), // utf8String UTF8String (SIZE (1..MAX)), // bmpString BMPString (SIZE (1..MAX)) } Result MatchAVA(Input type, uint8_t valueEncodingTag, Input presentedID, GeneralNameType referenceIDType, Input referenceID, FallBackToSearchWithinSubject fallBackToEmailAddress, FallBackToSearchWithinSubject fallBackToCommonName, /*in/out*/ MatchResult& match) { // Try to match the CN as a DNSName or an IPAddress. // // id-at-commonName AttributeType ::= { id-at 3 } // // -- Naming attributes of type X520CommonName: // -- X520CommonName ::= DirectoryName (SIZE (1..ub-common-name)) // -- // -- Expanded to avoid parameterized type: // X520CommonName ::= CHOICE { // teletexString TeletexString (SIZE (1..ub-common-name)), // printableString PrintableString (SIZE (1..ub-common-name)), // universalString UniversalString (SIZE (1..ub-common-name)), // utf8String UTF8String (SIZE (1..ub-common-name)), // bmpString BMPString (SIZE (1..ub-common-name)) } // // python DottedOIDToCode.py id-at-commonName 2.5.4.3 static const uint8_t id_at_commonName[] = { 0x55, 0x04, 0x03 }; if (fallBackToCommonName == FallBackToSearchWithinSubject::Yes && InputsAreEqual(type, Input(id_at_commonName))) { // We might have previously found a match. Now that we've found another CN, // we no longer consider that previous match to be a match, so "forget" about // it. match = MatchResult::NoNamesOfGivenType; // PrintableString is a subset of ASCII that contains all the characters // allowed in CN-IDs except '*'. Although '*' is illegal, there are many // real-world certificates that are encoded this way, so we accept it. // // In the case of UTF8String, we rely on the fact that in UTF-8 the octets in // a multi-byte encoding of a code point are always distinct from ASCII. Any // non-ASCII byte in a UTF-8 string causes us to fail to match. We make no // attempt to detect or report malformed UTF-8 (e.g. incomplete or overlong // encodings of code points, or encodings of invalid code points). // // TeletexString is supported as long as it does not contain any escape // sequences, which are not supported. We'll reject escape sequences as // invalid characters in names, which means we only accept strings that are // in the default character set, which is a superset of ASCII. Note that NSS // actually treats TeletexString as ISO-8859-1. Many certificates that have // wildcard CN-IDs (e.g. "*.example.com") use TeletexString because // PrintableString is defined to not allow '*' and because, at one point in // history, UTF8String was too new to use for compatibility reasons. // // UniversalString and BMPString are also deprecated, and they are a little // harder to support because they are not single-byte ASCII superset // encodings, so we don't bother. if (valueEncodingTag != der::PrintableString && valueEncodingTag != der::UTF8String && valueEncodingTag != der::TeletexString) { return Success; } if (IsValidPresentedDNSID(presentedID)) { MatchSubjectPresentedIDWithReferenceID(GeneralNameType::dNSName, presentedID, referenceIDType, referenceID, match); } else { // We don't match CN-IDs for IPv6 addresses. // MatchSubjectPresentedIDWithReferenceID ensures that it won't match an // IPv4 address with an IPv6 address, so we don't need to check that // referenceID is an IPv4 address here. uint8_t ipv4[4]; if (ParseIPv4Address(presentedID, ipv4)) { MatchSubjectPresentedIDWithReferenceID(GeneralNameType::iPAddress, Input(ipv4), referenceIDType, referenceID, match); } } // Regardless of whether there was a match, we keep going in case we find // another CN later. If we do find another one, then this match/mismatch // will be ignored, because we only care about the most specific CN. return Success; } // Match an email address against an emailAddress attribute in the // subject. // // id-emailAddress AttributeType ::= { pkcs-9 1 } // // EmailAddress ::= IA5String (SIZE (1..ub-emailaddress-length)) // // python DottedOIDToCode.py id-emailAddress 1.2.840.113549.1.9.1 static const uint8_t id_emailAddress[] = { 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x09, 0x01 }; if (fallBackToEmailAddress == FallBackToSearchWithinSubject::Yes && InputsAreEqual(type, Input(id_emailAddress))) { if (referenceIDType == GeneralNameType::rfc822Name && match == MatchResult::Match) { // We already found a match; we don't need to match another one return Success; } if (valueEncodingTag != der::IA5String) { return Result::ERROR_BAD_DER; } return MatchPresentedIDWithReferenceID(GeneralNameType::rfc822Name, presentedID, referenceIDType, referenceID, match); } return Success; } void MatchSubjectPresentedIDWithReferenceID(GeneralNameType presentedIDType, Input presentedID, GeneralNameType referenceIDType, Input referenceID, /*in/out*/ MatchResult& match) { Result rv = MatchPresentedIDWithReferenceID(presentedIDType, presentedID, referenceIDType, referenceID, match); if (rv != Success) { match = MatchResult::Mismatch; } } Result MatchPresentedIDWithReferenceID(GeneralNameType presentedIDType, Input presentedID, GeneralNameType referenceIDType, Input referenceID, /*out*/ MatchResult& matchResult) { if (referenceIDType == GeneralNameType::nameConstraints) { // matchResult is irrelevant when checking name constraints; only the // pass/fail result of CheckPresentedIDConformsToConstraints matters. return CheckPresentedIDConformsToConstraints(presentedIDType, presentedID, referenceID); } if (presentedIDType != referenceIDType) { matchResult = MatchResult::Mismatch; return Success; } Result rv; bool foundMatch; switch (referenceIDType) { case GeneralNameType::dNSName: rv = MatchPresentedDNSIDWithReferenceDNSID( presentedID, AllowWildcards::Yes, AllowDotlessSubdomainMatches::Yes, IDRole::ReferenceID, referenceID, foundMatch); break; case GeneralNameType::iPAddress: foundMatch = InputsAreEqual(presentedID, referenceID); rv = Success; break; case GeneralNameType::rfc822Name: rv = MatchPresentedRFC822NameWithReferenceRFC822Name( presentedID, IDRole::ReferenceID, referenceID, foundMatch); break; case GeneralNameType::directoryName: // TODO: At some point, we may add APIs for matching DirectoryNames. // fall through case GeneralNameType::otherName: // fall through case GeneralNameType::x400Address: // fall through case GeneralNameType::ediPartyName: // fall through case GeneralNameType::uniformResourceIdentifier: // fall through case GeneralNameType::registeredID: // fall through case GeneralNameType::nameConstraints: return NotReached("unexpected nameType for SearchType::Match", Result::FATAL_ERROR_INVALID_ARGS); MOZILLA_PKIX_UNREACHABLE_DEFAULT_ENUM } if (rv != Success) { return rv; } matchResult = foundMatch ? MatchResult::Match : MatchResult::Mismatch; return Success; } enum class NameConstraintsSubtrees : uint8_t { permittedSubtrees = der::CONSTRUCTED | der::CONTEXT_SPECIFIC | 0, excludedSubtrees = der::CONSTRUCTED | der::CONTEXT_SPECIFIC | 1 }; Result CheckPresentedIDConformsToNameConstraintsSubtrees( GeneralNameType presentedIDType, Input presentedID, Reader& nameConstraints, NameConstraintsSubtrees subtreesType); Result MatchPresentedIPAddressWithConstraint(Input presentedID, Input iPAddressConstraint, /*out*/ bool& foundMatch); Result MatchPresentedDirectoryNameWithConstraint( NameConstraintsSubtrees subtreesType, Input presentedID, Input directoryNameConstraint, /*out*/ bool& matches); Result CheckPresentedIDConformsToConstraints( GeneralNameType presentedIDType, Input presentedID, Input encodedNameConstraints) { // NameConstraints ::= SEQUENCE { // permittedSubtrees [0] GeneralSubtrees OPTIONAL, // excludedSubtrees [1] GeneralSubtrees OPTIONAL } Reader nameConstraints; Result rv = der::ExpectTagAndGetValueAtEnd(encodedNameConstraints, der::SEQUENCE, nameConstraints); if (rv != Success) { return rv; } // RFC 5280 says "Conforming CAs MUST NOT issue certificates where name // constraints is an empty sequence. That is, either the permittedSubtrees // field or the excludedSubtrees MUST be present." if (nameConstraints.AtEnd()) { return Result::ERROR_BAD_DER; } rv = CheckPresentedIDConformsToNameConstraintsSubtrees( presentedIDType, presentedID, nameConstraints, NameConstraintsSubtrees::permittedSubtrees); if (rv != Success) { return rv; } rv = CheckPresentedIDConformsToNameConstraintsSubtrees( presentedIDType, presentedID, nameConstraints, NameConstraintsSubtrees::excludedSubtrees); if (rv != Success) { return rv; } return der::End(nameConstraints); } Result CheckPresentedIDConformsToNameConstraintsSubtrees( GeneralNameType presentedIDType, Input presentedID, Reader& nameConstraints, NameConstraintsSubtrees subtreesType) { if (!nameConstraints.Peek(static_cast(subtreesType))) { return Success; } Reader subtrees; Result rv = der::ExpectTagAndGetValue(nameConstraints, static_cast(subtreesType), subtrees); if (rv != Success) { return rv; } bool hasPermittedSubtreesMatch = false; bool hasPermittedSubtreesMismatch = false; // GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree // // do { ... } while(...) because subtrees isn't allowed to be empty. do { // GeneralSubtree ::= SEQUENCE { // base GeneralName, // minimum [0] BaseDistance DEFAULT 0, // maximum [1] BaseDistance OPTIONAL } Reader subtree; rv = ExpectTagAndGetValue(subtrees, der::SEQUENCE, subtree); if (rv != Success) { return rv; } GeneralNameType nameConstraintType; Input base; rv = ReadGeneralName(subtree, nameConstraintType, base); if (rv != Success) { return rv; } // http://tools.ietf.org/html/rfc5280#section-4.2.1.10: "Within this // profile, the minimum and maximum fields are not used with any name // forms, thus, the minimum MUST be zero, and maximum MUST be absent." // // Since the default value isn't allowed to be encoded according to the DER // encoding rules for DEFAULT, this is equivalent to saying that neither // minimum or maximum must be encoded. rv = der::End(subtree); if (rv != Success) { return rv; } if (presentedIDType == nameConstraintType) { bool matches; switch (presentedIDType) { case GeneralNameType::dNSName: rv = MatchPresentedDNSIDWithReferenceDNSID( presentedID, AllowWildcards::Yes, AllowDotlessSubdomainMatches::Yes, IDRole::NameConstraint, base, matches); if (rv != Success) { return rv; } break; case GeneralNameType::iPAddress: rv = MatchPresentedIPAddressWithConstraint(presentedID, base, matches); if (rv != Success) { return rv; } break; case GeneralNameType::directoryName: rv = MatchPresentedDirectoryNameWithConstraint(subtreesType, presentedID, base, matches); if (rv != Success) { return rv; } break; case GeneralNameType::rfc822Name: rv = MatchPresentedRFC822NameWithReferenceRFC822Name( presentedID, IDRole::NameConstraint, base, matches); if (rv != Success) { return rv; } break; // RFC 5280 says "Conforming CAs [...] SHOULD NOT impose name // constraints on the x400Address, ediPartyName, or registeredID // name forms. It also says "Applications conforming to this profile // [...] SHOULD be able to process name constraints that are imposed // on [...] uniformResourceIdentifier [...]", but we don't bother. // // TODO: Ask to have spec updated to say ""Conforming CAs [...] SHOULD // NOT impose name constraints on the otherName, x400Address, // ediPartyName, uniformResourceIdentifier, or registeredID name // forms." case GeneralNameType::otherName: // fall through case GeneralNameType::x400Address: // fall through case GeneralNameType::ediPartyName: // fall through case GeneralNameType::uniformResourceIdentifier: // fall through case GeneralNameType::registeredID: // fall through return Result::ERROR_CERT_NOT_IN_NAME_SPACE; case GeneralNameType::nameConstraints: return NotReached("invalid presentedIDType", Result::FATAL_ERROR_LIBRARY_FAILURE); MOZILLA_PKIX_UNREACHABLE_DEFAULT_ENUM } switch (subtreesType) { case NameConstraintsSubtrees::permittedSubtrees: if (matches) { hasPermittedSubtreesMatch = true; } else { hasPermittedSubtreesMismatch = true; } break; case NameConstraintsSubtrees::excludedSubtrees: if (matches) { return Result::ERROR_CERT_NOT_IN_NAME_SPACE; } break; } } } while (!subtrees.AtEnd()); if (hasPermittedSubtreesMismatch && !hasPermittedSubtreesMatch) { // If there was any entry of the given type in permittedSubtrees, then it // required that at least one of them must match. Since none of them did, // we have a failure. return Result::ERROR_CERT_NOT_IN_NAME_SPACE; } return Success; } // We do not distinguish between a syntactically-invalid presentedDNSID and one // that is syntactically valid but does not match referenceDNSID; in both // cases, the result is false. // // We assume that both presentedDNSID and referenceDNSID are encoded in such a // way that US-ASCII (7-bit) characters are encoded in one byte and no encoding // of a non-US-ASCII character contains a code point in the range 0-127. For // example, UTF-8 is OK but UTF-16 is not. // // RFC6125 says that a wildcard label may be of the form *., where // and/or may be empty. However, NSS requires to be empty, and we // follow NSS's stricter policy by accepting wildcards only of the form // *., where may be empty. // // An relative presented DNS ID matches both an absolute reference ID and a // relative reference ID. Absolute presented DNS IDs are not supported: // // Presented ID Reference ID Result // ------------------------------------- // example.com example.com Match // example.com. example.com Mismatch // example.com example.com. Match // example.com. example.com. Mismatch // // There are more subtleties documented inline in the code. // // Name constraints /////////////////////////////////////////////////////////// // // This is all RFC 5280 has to say about DNSName constraints: // // DNS name restrictions are expressed as host.example.com. Any DNS // name that can be constructed by simply adding zero or more labels to // the left-hand side of the name satisfies the name constraint. For // example, www.host.example.com would satisfy the constraint but // host1.example.com would not. // // This lack of specificity has lead to a lot of uncertainty regarding // subdomain matching. In particular, the following questions have been // raised and answered: // // Q: Does a presented identifier equal (case insensitive) to the name // constraint match the constraint? For example, does the presented // ID "host.example.com" match a "host.example.com" constraint? // A: Yes. RFC5280 says "by simply adding zero or more labels" and this // is the case of adding zero labels. // // Q: When the name constraint does not start with ".", do subdomain // presented identifiers match it? For example, does the presented // ID "www.host.example.com" match a "host.example.com" constraint? // A: Yes. RFC5280 says "by simply adding zero or more labels" and this // is the case of adding more than zero labels. The example is the // one from RFC 5280. // // Q: When the name constraint does not start with ".", does a // non-subdomain prefix match it? For example, does "bigfoo.bar.com" // match "foo.bar.com"? [4] // A: No. We interpret RFC 5280's language of "adding zero or more labels" // to mean that whole labels must be prefixed. // // (Note that the above three scenarios are the same as the RFC 6265 // domain matching rules [0].) // // Q: Is a name constraint that starts with "." valid, and if so, what // semantics does it have? For example, does a presented ID of // "www.example.com" match a constraint of ".example.com"? Does a // presented ID of "example.com" match a constraint of ".example.com"? // A: This implementation, NSS[1], and SChannel[2] all support a // leading ".", but OpenSSL[3] does not yet. Amongst the // implementations that support it, a leading "." is legal and means // the same thing as when the "." is omitted, EXCEPT that a // presented identifier equal (case insensitive) to the name // constraint is not matched; i.e. presented DNSName identifiers // must be subdomains. Some CAs in Mozilla's CA program (e.g. HARICA) // have name constraints with the leading "." in their root // certificates. The name constraints imposed on DCISS by Mozilla also // have the it, so supporting this is a requirement for backward // compatibility, even if it is not yet standardized. So, for example, a // presented ID of "www.example.com" matches a constraint of // ".example.com" but a presented ID of "example.com" does not. // // Q: Is there a way to prevent subdomain matches? // A: Yes. // // Some people have proposed that dNSName constraints that do not // start with a "." should be restricted to exact (case insensitive) // matches. However, such a change of semantics from what RFC5280 // specifies would be a non-backward-compatible change in the case of // permittedSubtrees constraints, and it would be a security issue for // excludedSubtrees constraints. // // However, it can be done with a combination of permittedSubtrees and // excludedSubtrees, e.g. "example.com" in permittedSubtrees and // ".example.com" in excudedSubtrees. // // Q: Are name constraints allowed to be specified as absolute names? // For example, does a presented ID of "example.com" match a name // constraint of "example.com." and vice versa. // A: Absolute names are not supported as presented IDs or name // constraints. Only reference IDs may be absolute. // // Q: Is "" a valid DNSName constraints? If so, what does it mean? // A: Yes. Any valid presented DNSName can be formed "by simply adding zero // or more labels to the left-hand side" of "". In particular, an // excludedSubtrees DNSName constraint of "" forbids all DNSNames. // // Q: Is "." a valid DNSName constraints? If so, what does it mean? // A: No, because absolute names are not allowed (see above). // // [0] RFC 6265 (Cookies) Domain Matching rules: // http://tools.ietf.org/html/rfc6265#section-5.1.3 // [1] NSS source code: // https://mxr.mozilla.org/nss/source/lib/certdb/genname.c?rev=2a7348f013cb#1209 // [2] Description of SChannel's behavior from Microsoft: // http://www.imc.org/ietf-pkix/mail-archive/msg04668.html // [3] Proposal to add such support to OpenSSL: // http://www.mail-archive.com/openssl-dev%40openssl.org/msg36204.html // https://rt.openssl.org/Ticket/Display.html?id=3562 // [4] Feedback on the lack of clarify in the definition that never got // incorporated into the spec: // https://www.ietf.org/mail-archive/web/pkix/current/msg21192.html Result MatchPresentedDNSIDWithReferenceDNSID( Input presentedDNSID, AllowWildcards allowWildcards, AllowDotlessSubdomainMatches allowDotlessSubdomainMatches, IDRole referenceDNSIDRole, Input referenceDNSID, /*out*/ bool& matches) { if (!IsValidDNSID(presentedDNSID, IDRole::PresentedID, allowWildcards)) { return Result::ERROR_BAD_DER; } if (!IsValidDNSID(referenceDNSID, referenceDNSIDRole, AllowWildcards::No)) { return Result::ERROR_BAD_DER; } Reader presented(presentedDNSID); Reader reference(referenceDNSID); switch (referenceDNSIDRole) { case IDRole::ReferenceID: break; case IDRole::NameConstraint: { if (presentedDNSID.GetLength() > referenceDNSID.GetLength()) { if (referenceDNSID.GetLength() == 0) { // An empty constraint matches everything. matches = true; return Success; } // If the reference ID starts with a dot then skip the prefix of // of the presented ID and start the comparison at the position of that // dot. Examples: // // Matches Doesn't Match // ----------------------------------------------------------- // original presented ID: www.example.com badexample.com // skipped: www ba // presented ID w/o prefix: .example.com dexample.com // reference ID: .example.com .example.com // // If the reference ID does not start with a dot then we skip the // prefix of the presented ID but also verify that the prefix ends with // a dot. Examples: // // Matches Doesn't Match // ----------------------------------------------------------- // original presented ID: www.example.com badexample.com // skipped: www ba // must be '.': . d // presented ID w/o prefix: example.com example.com // reference ID: example.com example.com // if (reference.Peek('.')) { if (presented.Skip(static_cast( presentedDNSID.GetLength() - referenceDNSID.GetLength())) != Success) { return NotReached("skipping subdomain failed", Result::FATAL_ERROR_LIBRARY_FAILURE); } } else if (allowDotlessSubdomainMatches == AllowDotlessSubdomainMatches::Yes) { if (presented.Skip(static_cast( presentedDNSID.GetLength() - referenceDNSID.GetLength() - 1)) != Success) { return NotReached("skipping subdomains failed", Result::FATAL_ERROR_LIBRARY_FAILURE); } uint8_t b; if (presented.Read(b) != Success) { return NotReached("reading from presentedDNSID failed", Result::FATAL_ERROR_LIBRARY_FAILURE); } if (b != '.') { matches = false; return Success; } } } break; } case IDRole::PresentedID: // fall through return NotReached("IDRole::PresentedID is not a valid referenceDNSIDRole", Result::FATAL_ERROR_INVALID_ARGS); } // We only allow wildcard labels that consist only of '*'. if (presented.Peek('*')) { if (presented.Skip(1) != Success) { return NotReached("Skipping '*' failed", Result::FATAL_ERROR_LIBRARY_FAILURE); } do { // This will happen if reference is a single, relative label if (reference.AtEnd()) { matches = false; return Success; } uint8_t referenceByte; if (reference.Read(referenceByte) != Success) { return NotReached("invalid reference ID", Result::FATAL_ERROR_INVALID_ARGS); } } while (!reference.Peek('.')); } for (;;) { uint8_t presentedByte; if (presented.Read(presentedByte) != Success) { matches = false; return Success; } uint8_t referenceByte; if (reference.Read(referenceByte) != Success) { matches = false; return Success; } if (LocaleInsensitveToLower(presentedByte) != LocaleInsensitveToLower(referenceByte)) { matches = false; return Success; } if (presented.AtEnd()) { // Don't allow presented IDs to be absolute. if (presentedByte == '.') { return Result::ERROR_BAD_DER; } break; } } // Allow a relative presented DNS ID to match an absolute reference DNS ID, // unless we're matching a name constraint. if (!reference.AtEnd()) { if (referenceDNSIDRole != IDRole::NameConstraint) { uint8_t referenceByte; if (reference.Read(referenceByte) != Success) { return NotReached("read failed but not at end", Result::FATAL_ERROR_LIBRARY_FAILURE); } if (referenceByte != '.') { matches = false; return Success; } } if (!reference.AtEnd()) { matches = false; return Success; } } matches = true; return Success; } // https://tools.ietf.org/html/rfc5280#section-4.2.1.10 says: // // For IPv4 addresses, the iPAddress field of GeneralName MUST contain // eight (8) octets, encoded in the style of RFC 4632 (CIDR) to represent // an address range [RFC4632]. For IPv6 addresses, the iPAddress field // MUST contain 32 octets similarly encoded. For example, a name // constraint for "class C" subnet 192.0.2.0 is represented as the // octets C0 00 02 00 FF FF FF 00, representing the CIDR notation // 192.0.2.0/24 (mask 255.255.255.0). Result MatchPresentedIPAddressWithConstraint(Input presentedID, Input iPAddressConstraint, /*out*/ bool& foundMatch) { if (presentedID.GetLength() != 4 && presentedID.GetLength() != 16) { return Result::ERROR_BAD_DER; } if (iPAddressConstraint.GetLength() != 8 && iPAddressConstraint.GetLength() != 32) { return Result::ERROR_BAD_DER; } // an IPv4 address never matches an IPv6 constraint, and vice versa. if (presentedID.GetLength() * 2 != iPAddressConstraint.GetLength()) { foundMatch = false; return Success; } Reader constraint(iPAddressConstraint); Reader constraintAddress; Result rv = constraint.Skip(iPAddressConstraint.GetLength() / 2u, constraintAddress); if (rv != Success) { return rv; } Reader constraintMask; rv = constraint.Skip(iPAddressConstraint.GetLength() / 2u, constraintMask); if (rv != Success) { return rv; } rv = der::End(constraint); if (rv != Success) { return rv; } Reader presented(presentedID); do { uint8_t presentedByte; rv = presented.Read(presentedByte); if (rv != Success) { return rv; } uint8_t constraintAddressByte; rv = constraintAddress.Read(constraintAddressByte); if (rv != Success) { return rv; } uint8_t constraintMaskByte; rv = constraintMask.Read(constraintMaskByte); if (rv != Success) { return rv; } foundMatch = ((presentedByte ^ constraintAddressByte) & constraintMaskByte) == 0; } while (foundMatch && !presented.AtEnd()); return Success; } // AttributeTypeAndValue ::= SEQUENCE { // type AttributeType, // value AttributeValue } // // AttributeType ::= OBJECT IDENTIFIER // // AttributeValue ::= ANY -- DEFINED BY AttributeType Result ReadAVA(Reader& rdn, /*out*/ Input& type, /*out*/ uint8_t& valueTag, /*out*/ Input& value) { return der::Nested(rdn, der::SEQUENCE, [&](Reader& ava) -> Result { Result rv = der::ExpectTagAndGetValue(ava, der::OIDTag, type); if (rv != Success) { return rv; } rv = der::ReadTagAndGetValue(ava, valueTag, value); if (rv != Success) { return rv; } return Success; }); } // Names are sequences of RDNs. RDNS are sets of AVAs. That means that RDNs are // unordered, so in theory we should match RDNs with equivalent AVAs that are // in different orders. Within the AVAs are DirectoryNames that are supposed to // be compared according to LDAP stringprep normalization rules (e.g. // normalizing whitespace), consideration of different character encodings, // etc. Indeed, RFC 5280 says we MUST deal with all of that. // // In practice, many implementations, including NSS, only match Names in a way // that only meets a subset of the requirements of RFC 5280. Those // normalization and character encoding conversion steps appear to be // unnecessary for processing real-world certificates, based on experience from // having used NSS in Firefox for many years. // // RFC 5280 also says "CAs issuing certificates with a restriction of the form // directoryName SHOULD NOT rely on implementation of the full // ISO DN name comparison algorithm. This implies name restrictions MUST // be stated identically to the encoding used in the subject field or // subjectAltName extension." It goes on to say, in the security // considerations: // // In addition, name constraints for distinguished names MUST be stated // identically to the encoding used in the subject field or // subjectAltName extension. If not, then name constraints stated as // excludedSubtrees will not match and invalid paths will be accepted // and name constraints expressed as permittedSubtrees will not match // and valid paths will be rejected. To avoid acceptance of invalid // paths, CAs SHOULD state name constraints for distinguished names as // permittedSubtrees wherever possible. // // For permittedSubtrees, the MUST-level requirement is relaxed for // compatibility in the case of PrintableString and UTF8String. That is, if a // name constraint has been encoded using UTF8String and the presented ID has // been encoded with a PrintableString (or vice-versa), they are considered to // match if they are equal everywhere except for the tag identifying the // encoding. See bug 1150114. // // For excludedSubtrees, we simply prohibit any non-empty directoryName // constraint to ensure we are not being too lenient. We support empty // DirectoryName constraints in excludedSubtrees so that a CA can say "Do not // allow any DirectoryNames in issued certificates." Result MatchPresentedDirectoryNameWithConstraint(NameConstraintsSubtrees subtreesType, Input presentedID, Input directoryNameConstraint, /*out*/ bool& matches) { Reader constraintRDNs; Result rv = der::ExpectTagAndGetValueAtEnd(directoryNameConstraint, der::SEQUENCE, constraintRDNs); if (rv != Success) { return rv; } Reader presentedRDNs; rv = der::ExpectTagAndGetValueAtEnd(presentedID, der::SEQUENCE, presentedRDNs); if (rv != Success) { return rv; } switch (subtreesType) { case NameConstraintsSubtrees::permittedSubtrees: break; // dealt with below case NameConstraintsSubtrees::excludedSubtrees: if (!constraintRDNs.AtEnd() || !presentedRDNs.AtEnd()) { return Result::ERROR_CERT_NOT_IN_NAME_SPACE; } matches = true; return Success; } for (;;) { // The AVAs have to be fully equal, but the constraint RDNs just need to be // a prefix of the presented RDNs. if (constraintRDNs.AtEnd()) { matches = true; return Success; } if (presentedRDNs.AtEnd()) { matches = false; return Success; } Reader constraintRDN; rv = der::ExpectTagAndGetValue(constraintRDNs, der::SET, constraintRDN); if (rv != Success) { return rv; } Reader presentedRDN; rv = der::ExpectTagAndGetValue(presentedRDNs, der::SET, presentedRDN); if (rv != Success) { return rv; } while (!constraintRDN.AtEnd() && !presentedRDN.AtEnd()) { Input constraintType; uint8_t constraintValueTag; Input constraintValue; rv = ReadAVA(constraintRDN, constraintType, constraintValueTag, constraintValue); if (rv != Success) { return rv; } Input presentedType; uint8_t presentedValueTag; Input presentedValue; rv = ReadAVA(presentedRDN, presentedType, presentedValueTag, presentedValue); if (rv != Success) { return rv; } // TODO (bug 1155767): verify that if an AVA is a PrintableString it // consists only of characters valid for PrintableStrings. bool avasMatch = InputsAreEqual(constraintType, presentedType) && InputsAreEqual(constraintValue, presentedValue) && (constraintValueTag == presentedValueTag || (constraintValueTag == der::Tag::UTF8String && presentedValueTag == der::Tag::PrintableString) || (constraintValueTag == der::Tag::PrintableString && presentedValueTag == der::Tag::UTF8String)); if (!avasMatch) { matches = false; return Success; } } if (!constraintRDN.AtEnd() || !presentedRDN.AtEnd()) { matches = false; return Success; } } } // RFC 5280 says: // // The format of an rfc822Name is a "Mailbox" as defined in Section 4.1.2 // of [RFC2821]. A Mailbox has the form "Local-part@Domain". Note that a // Mailbox has no phrase (such as a common name) before it, has no comment // (text surrounded in parentheses) after it, and is not surrounded by "<" // and ">". Rules for encoding Internet mail addresses that include // internationalized domain names are specified in Section 7.5. // // and: // // A name constraint for Internet mail addresses MAY specify a // particular mailbox, all addresses at a particular host, or all // mailboxes in a domain. To indicate a particular mailbox, the // constraint is the complete mail address. For example, // "root@example.com" indicates the root mailbox on the host // "example.com". To indicate all Internet mail addresses on a // particular host, the constraint is specified as the host name. For // example, the constraint "example.com" is satisfied by any mail // address at the host "example.com". To specify any address within a // domain, the constraint is specified with a leading period (as with // URIs). For example, ".example.com" indicates all the Internet mail // addresses in the domain "example.com", but not Internet mail // addresses on the host "example.com". bool IsValidRFC822Name(Input input) { Reader reader(input); // Local-part@. bool startOfAtom = true; for (;;) { uint8_t presentedByte; if (reader.Read(presentedByte) != Success) { return false; } switch (presentedByte) { // atext is defined in https://tools.ietf.org/html/rfc2822#section-3.2.4 case 'A': case 'a': case 'N': case 'n': case '0': case '!': case '#': case 'B': case 'b': case 'O': case 'o': case '1': case '$': case '%': case 'C': case 'c': case 'P': case 'p': case '2': case '&': case '\'': case 'D': case 'd': case 'Q': case 'q': case '3': case '*': case '+': case 'E': case 'e': case 'R': case 'r': case '4': case '-': case '/': case 'F': case 'f': case 'S': case 's': case '5': case '=': case '?': case 'G': case 'g': case 'T': case 't': case '6': case '^': case '_': case 'H': case 'h': case 'U': case 'u': case '7': case '`': case '{': case 'I': case 'i': case 'V': case 'v': case '8': case '|': case '}': case 'J': case 'j': case 'W': case 'w': case '9': case '~': case 'K': case 'k': case 'X': case 'x': case 'L': case 'l': case 'Y': case 'y': case 'M': case 'm': case 'Z': case 'z': startOfAtom = false; break; case '.': if (startOfAtom) { return false; } startOfAtom = true; break; case '@': { if (startOfAtom) { return false; } Input domain; if (reader.SkipToEnd(domain) != Success) { return false; } return IsValidDNSID(domain, IDRole::PresentedID, AllowWildcards::No); } default: return false; } } } Result MatchPresentedRFC822NameWithReferenceRFC822Name(Input presentedRFC822Name, IDRole referenceRFC822NameRole, Input referenceRFC822Name, /*out*/ bool& matches) { if (!IsValidRFC822Name(presentedRFC822Name)) { return Result::ERROR_BAD_DER; } Reader presented(presentedRFC822Name); switch (referenceRFC822NameRole) { case IDRole::PresentedID: return Result::FATAL_ERROR_INVALID_ARGS; case IDRole::ReferenceID: break; case IDRole::NameConstraint: { if (InputContains(referenceRFC822Name, '@')) { // The constraint is of the form "Local-part@Domain". break; } // The constraint is of the form "example.com" or ".example.com". // Skip past the '@' in the presented ID. for (;;) { uint8_t presentedByte; if (presented.Read(presentedByte) != Success) { return Result::FATAL_ERROR_LIBRARY_FAILURE; } if (presentedByte == '@') { break; } } Input presentedDNSID; if (presented.SkipToEnd(presentedDNSID) != Success) { return Result::FATAL_ERROR_LIBRARY_FAILURE; } return MatchPresentedDNSIDWithReferenceDNSID( presentedDNSID, AllowWildcards::No, AllowDotlessSubdomainMatches::No, IDRole::NameConstraint, referenceRFC822Name, matches); } } if (!IsValidRFC822Name(referenceRFC822Name)) { return Result::ERROR_BAD_DER; } Reader reference(referenceRFC822Name); for (;;) { uint8_t presentedByte; if (presented.Read(presentedByte) != Success) { matches = reference.AtEnd(); return Success; } uint8_t referenceByte; if (reference.Read(referenceByte) != Success) { matches = false; return Success; } if (LocaleInsensitveToLower(presentedByte) != LocaleInsensitveToLower(referenceByte)) { matches = false; return Success; } } } // We avoid isdigit because it is locale-sensitive. See // http://pubs.opengroup.org/onlinepubs/009695399/functions/tolower.html. inline uint8_t LocaleInsensitveToLower(uint8_t a) { if (a >= 'A' && a <= 'Z') { // unlikely return static_cast( static_cast(a - static_cast('A')) + static_cast('a')); } return a; } bool StartsWithIDNALabel(Input id) { static const uint8_t IDN_ALABEL_PREFIX[4] = { 'x', 'n', '-', '-' }; Reader input(id); for (size_t i = 0; i < sizeof(IDN_ALABEL_PREFIX); ++i) { uint8_t b; if (input.Read(b) != Success) { return false; } if (b != IDN_ALABEL_PREFIX[i]) { return false; } } return true; } bool ReadIPv4AddressComponent(Reader& input, bool lastComponent, /*out*/ uint8_t& valueOut) { size_t length = 0; unsigned int value = 0; // Must be larger than uint8_t. for (;;) { if (input.AtEnd() && lastComponent) { break; } uint8_t b; if (input.Read(b) != Success) { return false; } if (b >= '0' && b <= '9') { if (value == 0 && length > 0) { return false; // Leading zeros are not allowed. } value = (value * 10) + (b - '0'); if (value > 255) { return false; // Component's value is too large. } ++length; } else if (!lastComponent && b == '.') { break; } else { return false; // Invalid character. } } if (length == 0) { return false; // empty components not allowed } valueOut = static_cast(value); return true; } } // namespace // On Windows and maybe other platforms, OS-provided IP address parsing // functions might fail if the protocol (IPv4 or IPv6) has been disabled, so we // can't rely on them. bool ParseIPv4Address(Input hostname, /*out*/ uint8_t (&out)[4]) { Reader input(hostname); return ReadIPv4AddressComponent(input, false, out[0]) && ReadIPv4AddressComponent(input, false, out[1]) && ReadIPv4AddressComponent(input, false, out[2]) && ReadIPv4AddressComponent(input, true, out[3]); } namespace { bool FinishIPv6Address(/*in/out*/ uint8_t (&address)[16], int numComponents, int contractionIndex) { assert(numComponents >= 0); assert(numComponents <= 8); assert(contractionIndex >= -1); assert(contractionIndex <= 8); assert(contractionIndex <= numComponents); if (!(numComponents >= 0 && numComponents <= 8 && contractionIndex >= -1 && contractionIndex <= 8 && contractionIndex <= numComponents)) { return false; } if (contractionIndex == -1) { // no contraction return numComponents == 8; } if (numComponents >= 8) { return false; // no room left to expand the contraction. } // Shift components that occur after the contraction over. size_t componentsToMove = static_cast(numComponents - contractionIndex); memmove(address + (2u * static_cast(8 - componentsToMove)), address + (2u * static_cast(contractionIndex)), componentsToMove * 2u); // Fill in the contracted area with zeros. std::fill_n(address + 2u * static_cast(contractionIndex), (8u - static_cast(numComponents)) * 2u, static_cast(0u)); return true; } } // namespace // On Windows and maybe other platforms, OS-provided IP address parsing // functions might fail if the protocol (IPv4 or IPv6) has been disabled, so we // can't rely on them. bool ParseIPv6Address(Input hostname, /*out*/ uint8_t (&out)[16]) { Reader input(hostname); int currentComponentIndex = 0; int contractionIndex = -1; if (input.Peek(':')) { // A valid input can only start with ':' if there is a contraction at the // beginning. uint8_t b; if (input.Read(b) != Success || b != ':') { assert(false); return false; } if (input.Read(b) != Success) { return false; } if (b != ':') { return false; } contractionIndex = 0; } for (;;) { // If we encounter a '.' then we'll have to backtrack to parse the input // from startOfComponent to the end of the input as an IPv4 address. Reader::Mark startOfComponent(input.GetMark()); uint16_t componentValue = 0; size_t componentLength = 0; while (!input.AtEnd() && !input.Peek(':')) { uint8_t value; uint8_t b; if (input.Read(b) != Success) { assert(false); return false; } switch (b) { case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': value = static_cast(b - static_cast('0')); break; case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': value = static_cast(b - static_cast('a') + UINT8_C(10)); break; case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': value = static_cast(b - static_cast('A') + UINT8_C(10)); break; case '.': { // A dot indicates we hit a IPv4-syntax component. Backtrack, parsing // the input from startOfComponent to the end of the input as an IPv4 // address, and then combine it with the other components. if (currentComponentIndex > 6) { return false; // Too many components before the IPv4 component } input.SkipToEnd(); Input ipv4Component; if (input.GetInput(startOfComponent, ipv4Component) != Success) { return false; } uint8_t (*ipv4)[4] = reinterpret_cast(&out[2 * currentComponentIndex]); if (!ParseIPv4Address(ipv4Component, *ipv4)) { return false; } assert(input.AtEnd()); currentComponentIndex += 2; return FinishIPv6Address(out, currentComponentIndex, contractionIndex); } default: return false; } if (componentLength >= 4) { // component too long return false; } ++componentLength; componentValue = (componentValue * 0x10u) + value; } if (currentComponentIndex >= 8) { return false; // too many components } if (componentLength == 0) { if (input.AtEnd() && currentComponentIndex == contractionIndex) { if (contractionIndex == 0) { // don't accept "::" return false; } return FinishIPv6Address(out, currentComponentIndex, contractionIndex); } return false; } out[2 * currentComponentIndex] = static_cast(componentValue / 0x100); out[(2 * currentComponentIndex) + 1] = static_cast(componentValue % 0x100); ++currentComponentIndex; if (input.AtEnd()) { return FinishIPv6Address(out, currentComponentIndex, contractionIndex); } uint8_t b; if (input.Read(b) != Success || b != ':') { assert(false); return false; } if (input.Peek(':')) { // Contraction if (contractionIndex != -1) { return false; // multiple contractions are not allowed. } if (input.Read(b) != Success || b != ':') { assert(false); return false; } contractionIndex = currentComponentIndex; if (input.AtEnd()) { // "::" at the end of the input. return FinishIPv6Address(out, currentComponentIndex, contractionIndex); } } } } bool IsValidReferenceDNSID(Input hostname) { return IsValidDNSID(hostname, IDRole::ReferenceID, AllowWildcards::No); } bool IsValidPresentedDNSID(Input hostname) { return IsValidDNSID(hostname, IDRole::PresentedID, AllowWildcards::Yes); } namespace { // RFC 5280 Section 4.2.1.6 says that a dNSName "MUST be in the 'preferred name // syntax', as specified by Section 3.5 of [RFC1034] and as modified by Section // 2.1 of [RFC1123]" except "a dNSName of ' ' MUST NOT be used." Additionally, // we allow underscores for compatibility with existing practice. bool IsValidDNSID(Input hostname, IDRole idRole, AllowWildcards allowWildcards) { if (hostname.GetLength() > 253) { return false; } Reader input(hostname); if (idRole == IDRole::NameConstraint && input.AtEnd()) { return true; } size_t dotCount = 0; size_t labelLength = 0; bool labelIsAllNumeric = false; bool labelEndsWithHyphen = false; // Only presented IDs are allowed to have wildcard labels. And, like // Chromium, be stricter than RFC 6125 requires by insisting that a // wildcard label consist only of '*'. bool isWildcard = allowWildcards == AllowWildcards::Yes && input.Peek('*'); bool isFirstByte = !isWildcard; if (isWildcard) { Result rv = input.Skip(1); if (rv != Success) { assert(false); return false; } uint8_t b; rv = input.Read(b); if (rv != Success) { return false; } if (b != '.') { return false; } ++dotCount; } do { static const size_t MAX_LABEL_LENGTH = 63; uint8_t b; if (input.Read(b) != Success) { return false; } switch (b) { case '-': if (labelLength == 0) { return false; // Labels must not start with a hyphen. } labelIsAllNumeric = false; labelEndsWithHyphen = true; ++labelLength; if (labelLength > MAX_LABEL_LENGTH) { return false; } break; // We avoid isdigit because it is locale-sensitive. See // http://pubs.opengroup.org/onlinepubs/009695399/functions/isdigit.html case '0': case '5': case '1': case '6': case '2': case '7': case '3': case '8': case '4': case '9': if (labelLength == 0) { labelIsAllNumeric = true; } labelEndsWithHyphen = false; ++labelLength; if (labelLength > MAX_LABEL_LENGTH) { return false; } break; // We avoid using islower/isupper/tolower/toupper or similar things, to // avoid any possibility of this code being locale-sensitive. See // http://pubs.opengroup.org/onlinepubs/009695399/functions/isupper.html case 'a': case 'A': case 'n': case 'N': case 'b': case 'B': case 'o': case 'O': case 'c': case 'C': case 'p': case 'P': case 'd': case 'D': case 'q': case 'Q': case 'e': case 'E': case 'r': case 'R': case 'f': case 'F': case 's': case 'S': case 'g': case 'G': case 't': case 'T': case 'h': case 'H': case 'u': case 'U': case 'i': case 'I': case 'v': case 'V': case 'j': case 'J': case 'w': case 'W': case 'k': case 'K': case 'x': case 'X': case 'l': case 'L': case 'y': case 'Y': case 'm': case 'M': case 'z': case 'Z': // We allow underscores for compatibility with existing practices. // See bug 1136616. case '_': labelIsAllNumeric = false; labelEndsWithHyphen = false; ++labelLength; if (labelLength > MAX_LABEL_LENGTH) { return false; } break; case '.': ++dotCount; if (labelLength == 0 && (idRole != IDRole::NameConstraint || !isFirstByte)) { return false; } if (labelEndsWithHyphen) { return false; // Labels must not end with a hyphen. } labelLength = 0; break; default: return false; // Invalid character. } isFirstByte = false; } while (!input.AtEnd()); // Only reference IDs, not presented IDs or name constraints, may be // absolute. if (labelLength == 0 && idRole != IDRole::ReferenceID) { return false; } if (labelEndsWithHyphen) { return false; // Labels must not end with a hyphen. } if (labelIsAllNumeric) { return false; // Last label must not be all numeric. } if (isWildcard) { // If the DNS ID ends with a dot, the last dot signifies an absolute ID. size_t labelCount = (labelLength == 0) ? dotCount : (dotCount + 1); // Like NSS, require at least two labels to follow the wildcard label. // // TODO(bug XXXXXXX): Allow the TrustDomain to control this on a // per-eTLD+1 basis, similar to Chromium. Even then, it might be better to // still enforce that there are at least two labels after the wildcard. if (labelCount < 3) { return false; } // XXX: RFC6125 says that we shouldn't accept wildcards within an IDN // A-Label. The consequence of this is that we effectively discriminate // against users of languages that cannot be encoded with ASCII. if (StartsWithIDNALabel(hostname)) { return false; } // TODO(bug XXXXXXX): Wildcards are not allowed for EV certificates. // Provide an option to indicate whether wildcards should be matched, for // the purpose of helping the application enforce this. } return true; } } // namespace } } // namespace mozilla::pkix