backport mozbug 1334776 - CVE-2017-7797 Header name interning leaks across origins

Potential attack: session supercookie.

[Moz Notes](https://bugzilla.mozilla.org/show_bug.cgi?id=1334776#c5):
"The problem is that for unknown header names we store the first one we see and then later we case-insensitively match against that name *globally*. That means you can track if a user agent has already seen a certain header name used (by using a different casing and observing whether it gets normalized). This would allow you to see if a user has used a sensitive service that uses custom header names, or allows you to track a user across sites, by teaching the browser about a certain header case once and then observing if different casings get normalized to that.

What we should do instead is only store the casing for a header name for each header list and not globally. That way it only leaks where it's expected (and necessary) to leak."

[Moz fix note](https://bugzilla.mozilla.org/show_bug.cgi?id=1334776#c8):
"nsHttpAtom now holds the old nsHttpAtom and a string that is case sensitive (only for not standard headers).
So nsHttpAtom holds a pointer to a header name. (header names are store on a static structure). This is how it used to be. I left that part the same but added a nsCString which holds a string that was used to resoled the header name. So when we parse headers we call ResolveHeader with a char*. If it is a new header name the char* will be stored in a HttpHeapAtom, nsHttpAtom::_val will point to HttpHeapAtom::value and the same strings will be stored in mLocalCaseSensitiveHeader. For the first resolve request they will be the same but for the following maybe not. At the end this nsHttpAtom will be stored in nsHttpHeaderArray. For all operation we will used the old char* except when we are returning it to a script using VisitHeaders."

1 files changed, 83 insertions, 16 deletions

diff --git a/netwerk/protocol/http/nsHttpHeaderArray.cpp b/netwerk/protocol/http/nsHttpHeaderArray.cpp
index 670300dea..1030bc91e 100644
--- a/netwerk/protocol/http/nsHttpHeaderArray.cpp
+++ b/netwerk/protocol/http/nsHttpHeaderArray.cpp
@@ -18,12 +18,37 @@ namespace net {
 //-----------------------------------------------------------------------------
 // nsHttpHeaderArray <public>
 //-----------------------------------------------------------------------------
+
+nsresult
+nsHttpHeaderArray::SetHeader(const nsACString &headerName,
+                             const nsACString &value,
+                             bool merge,
+                             nsHttpHeaderArray::HeaderVariety variety)
+{
+    nsHttpAtom header = nsHttp::ResolveAtom(PromiseFlatCString(headerName).get());
+    if (!header) {
+        NS_WARNING("failed to resolve atom");
+        return NS_ERROR_NOT_AVAILABLE;
+    }
+    return SetHeader(header, headerName, value, merge, variety);
+}
+
 nsresult
 nsHttpHeaderArray::SetHeader(nsHttpAtom header,
                              const nsACString &value,
                              bool merge,
                              nsHttpHeaderArray::HeaderVariety variety)
 {
+    return SetHeader(header, EmptyCString(), value, merge, variety);
+}
+
+nsresult
+nsHttpHeaderArray::SetHeader(nsHttpAtom header,
+                             const nsACString &headerName,
+                             const nsACString &value,
+                             bool merge,
+                             nsHttpHeaderArray::HeaderVariety variety)
+{
     MOZ_ASSERT((variety == eVarietyResponse) ||
                (variety == eVarietyRequestDefault) ||
                (variety == eVarietyRequestOverride),
@@ -51,7 +76,7 @@ nsHttpHeaderArray::SetHeader(nsHttpAtom header,
     MOZ_ASSERT(!entry || variety != eVarietyRequestDefault,
                "Cannot set default entry which overrides existing entry!");
     if (!entry) {
-        return SetHeader_internal(header, value, variety);
+        return SetHeader_internal(header, headerName, value, variety);
     } else if (merge && !IsSingletonHeader(header)) {
         return MergeHeader(header, entry, value, variety);
     } else {
@@ -59,7 +84,7 @@ nsHttpHeaderArray::SetHeader(nsHttpAtom header,
         if (entry->variety == eVarietyResponseNetOriginalAndResponse) {
             MOZ_ASSERT(variety == eVarietyResponse);
             entry->variety = eVarietyResponseNetOriginal;
-            return SetHeader_internal(header, value, variety);
+            return SetHeader_internal(header, headerName, value, variety);
         } else {
             entry->value = value;
             entry->variety = variety;
@@ -71,6 +96,7 @@ nsHttpHeaderArray::SetHeader(nsHttpAtom header,
 
 nsresult
 nsHttpHeaderArray::SetHeader_internal(nsHttpAtom header,
+                                      const nsACString &headerName,
                                       const nsACString &value,
                                       nsHttpHeaderArray::HeaderVariety variety)
 {
@@ -79,14 +105,26 @@ nsHttpHeaderArray::SetHeader_internal(nsHttpAtom header,
         return NS_ERROR_OUT_OF_MEMORY;
     }
     entry->header = header;
+    // Only save original form of a header if it is different than the header
+    // atom string.
+    if (!headerName.Equals(header.get())) {
+        entry->headerNameOriginal = headerName;
+    }
     entry->value = value;
     entry->variety = variety;
     return NS_OK;
 }
 
 nsresult
-nsHttpHeaderArray::SetEmptyHeader(nsHttpAtom header, HeaderVariety variety)
+nsHttpHeaderArray::SetEmptyHeader(const nsACString &headerName,
+                                  HeaderVariety variety)
 {
+    nsHttpAtom header = nsHttp::ResolveAtom(PromiseFlatCString(headerName).get());
+    if (!header) {
+        NS_WARNING("failed to resolve atom");
+        return NS_ERROR_NOT_AVAILABLE;
+    }
+
     MOZ_ASSERT((variety == eVarietyResponse) ||
                (variety == eVarietyRequestDefault) ||
                (variety == eVarietyRequestOverride),
@@ -104,11 +142,12 @@ nsHttpHeaderArray::SetEmptyHeader(nsHttpAtom header, HeaderVariety variety)
         entry->variety = eVarietyResponseNetOriginal;
     }
 
-    return SetHeader_internal(header, EmptyCString(), variety);
+    return SetHeader_internal(header, headerName, EmptyCString(), variety);
 }
 
 nsresult
 nsHttpHeaderArray::SetHeaderFromNet(nsHttpAtom header,
+                                    const nsACString &headerNameOriginal,
                                     const nsACString &value,
                                     bool response)
 {
@@ -125,7 +164,7 @@ nsHttpHeaderArray::SetHeaderFromNet(nsHttpAtom header,
                 LOG(("Ignoring Empty Header: %s\n", header.get()));
                 if (response) {
                     // Set header as original but not as response header.
-                    return SetHeader_internal(header, value,
+                    return SetHeader_internal(header, headerNameOriginal, value,
                                               eVarietyResponseNetOriginal);
                 }
                 return NS_OK; // ignore empty headers by default
@@ -135,7 +174,7 @@ nsHttpHeaderArray::SetHeaderFromNet(nsHttpAtom header,
         if (response) {
             variety = eVarietyResponseNetOriginalAndResponse;
         }
-        return SetHeader_internal(header, value, variety);
+        return SetHeader_internal(header, headerNameOriginal, value, variety);
 
     } else if (!IsSingletonHeader(header)) {
         HeaderVariety variety = eVarietyRequestOverride;
@@ -147,7 +186,7 @@ nsHttpHeaderArray::SetHeaderFromNet(nsHttpAtom header,
             return rv;
         }
         if (response) {
-            rv = SetHeader_internal(header, value,
+            rv = SetHeader_internal(header, headerNameOriginal, value,
                                     eVarietyResponseNetOriginal);
         }
         return rv;
@@ -164,7 +203,7 @@ nsHttpHeaderArray::SetHeaderFromNet(nsHttpAtom header,
 
         }
         if (response) {
-            return SetHeader_internal(header, value,
+            return SetHeader_internal(header, headerNameOriginal, value,
                                       eVarietyResponseNetOriginal);
         }
     }
@@ -174,6 +213,7 @@ nsHttpHeaderArray::SetHeaderFromNet(nsHttpAtom header,
 
 nsresult
 nsHttpHeaderArray::SetResponseHeaderFromCache(nsHttpAtom header,
+                                              const nsACString &headerNameOriginal,
                                               const nsACString &value,
                                               nsHttpHeaderArray::HeaderVariety variety)
 {
@@ -183,7 +223,7 @@ nsHttpHeaderArray::SetResponseHeaderFromCache(nsHttpAtom header,
                "eVarietyResponseNetOriginal");
 
     if (variety == eVarietyResponseNetOriginal) {
-        return SetHeader_internal(header, value,
+        return SetHeader_internal(header, headerNameOriginal, value,
                                   eVarietyResponseNetOriginal);
     } else {
         nsTArray<nsEntry>::index_type index = 0;
@@ -203,7 +243,8 @@ nsHttpHeaderArray::SetResponseHeaderFromCache(nsHttpAtom header,
             }
         } while (index != mHeaders.NoIndex);
         // If we are here, we have not found an entry so add a new one.
-        return SetHeader_internal(header, value, eVarietyResponse);
+        return SetHeader_internal(header, headerNameOriginal, value,
+                                  eVarietyResponse);
     }
 }
 
@@ -260,8 +301,16 @@ nsHttpHeaderArray::GetOriginalHeader(nsHttpAtom aHeader,
             if (entry.variety == eVarietyResponse) {
                 continue;
             }
+
+            nsAutoCString hdr;
+            if (entry.headerNameOriginal.IsEmpty()) {
+                hdr = nsDependentCString(entry.header);
+            } else {
+                hdr = entry.headerNameOriginal;
+            }
+
             rv = NS_OK;
-            if (NS_FAILED(aVisitor->VisitHeader(nsDependentCString(entry.header),
+            if (NS_FAILED(aVisitor->VisitHeader(hdr,
                                                 entry.value))) {
                 break;
             }
@@ -298,8 +347,14 @@ nsHttpHeaderArray::VisitHeaders(nsIHttpHeaderVisitor *visitor, nsHttpHeaderArray
         } else if (filter == eFilterResponseOriginal && entry.variety == eVarietyResponse) {
             continue;
         }
-        rv = visitor->VisitHeader(
-            nsDependentCString(entry.header), entry.value);
+
+        nsAutoCString hdr;
+        if (entry.headerNameOriginal.IsEmpty()) {
+            hdr = nsDependentCString(entry.header);
+        } else {
+            hdr = entry.headerNameOriginal;
+        }
+        rv = visitor->VisitHeader(hdr, entry.value);
         if NS_FAILED(rv) {
             return rv;
         }
@@ -310,6 +365,7 @@ nsHttpHeaderArray::VisitHeaders(nsIHttpHeaderVisitor *visitor, nsHttpHeaderArray
 /*static*/ nsresult
 nsHttpHeaderArray::ParseHeaderLine(const nsACString& line,
                                    nsHttpAtom *hdr,
+                                   nsACString *headerName,
                                    nsACString *val)
 {
     //
@@ -360,6 +416,7 @@ nsHttpHeaderArray::ParseHeaderLine(const nsACString& line,
     // assign return values
     if (hdr) *hdr = atom;
     if (val) val->Assign(p, p2 - p + 1);
+    if (headerName) headerName->Assign(sub);
 
     return NS_OK;
 }
@@ -397,7 +454,11 @@ nsHttpHeaderArray::Flatten(nsACString &buf, bool pruneProxyHeaders,
             continue;
         }
 
-        buf.Append(entry.header);
+        if (entry.headerNameOriginal.IsEmpty()) {
+            buf.Append(entry.header);
+        } else {
+            buf.Append(entry.headerNameOriginal);
+        }
         buf.AppendLiteral(": ");
         buf.Append(entry.value);
         buf.AppendLiteral("\r\n");
@@ -415,7 +476,11 @@ nsHttpHeaderArray::FlattenOriginalHeader(nsACString &buf)
             continue;
         }
 
-        buf.Append(entry.header);
+        if (entry.headerNameOriginal.IsEmpty()) {
+            buf.Append(entry.header);
+        } else {
+            buf.Append(entry.headerNameOriginal);
+        }
         buf.AppendLiteral(": ");
         buf.Append(entry.value);
         buf.AppendLiteral("\r\n");
@@ -423,11 +488,13 @@ nsHttpHeaderArray::FlattenOriginalHeader(nsACString &buf)
 }
 
 const char *
-nsHttpHeaderArray::PeekHeaderAt(uint32_t index, nsHttpAtom &header) const
+nsHttpHeaderArray::PeekHeaderAt(uint32_t index, nsHttpAtom &header,
+                                nsACString &headerNameOriginal) const
 {
     const nsEntry &entry = mHeaders[index];
 
     header = entry.header;
+    headerNameOriginal = entry.headerNameOriginal;
     return entry.value.get();
 }