Add m-esr52 at 52.6.0

1 files changed, 647 insertions, 0 deletions

diff --git a/security/nss/lib/freebl/dsa.c b/security/nss/lib/freebl/dsa.c
new file mode 100644
index 000000000..9324d306b
--- /dev/null
+++ b/security/nss/lib/freebl/dsa.c
@@ -0,0 +1,647 @@
+/*
+ *
+ * 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/. */
+
+#ifdef FREEBL_NO_DEPEND
+#include "stubs.h"
+#endif
+
+#include "prerror.h"
+#include "secerr.h"
+
+#include "prtypes.h"
+#include "prinit.h"
+#include "blapi.h"
+#include "nssilock.h"
+#include "secitem.h"
+#include "blapi.h"
+#include "mpi.h"
+#include "secmpi.h"
+#include "pqg.h"
+
+/* XXX to be replaced by define in blapit.h */
+#define NSS_FREEBL_DSA_DEFAULT_CHUNKSIZE 2048
+
+/*
+ * FIPS 186-2 requires result from random output to be reduced mod q when
+ * generating random numbers for DSA.
+ *
+ * Input: w, 2*qLen bytes
+ *        q, qLen bytes
+ * Output: xj, qLen bytes
+ */
+static SECStatus
+fips186Change_ReduceModQForDSA(const PRUint8 *w, const PRUint8 *q,
+                               unsigned int qLen, PRUint8 *xj)
+{
+    mp_int W, Q, Xj;
+    mp_err err;
+    SECStatus rv = SECSuccess;
+
+    /* Initialize MPI integers. */
+    MP_DIGITS(&W) = 0;
+    MP_DIGITS(&Q) = 0;
+    MP_DIGITS(&Xj) = 0;
+    CHECK_MPI_OK(mp_init(&W));
+    CHECK_MPI_OK(mp_init(&Q));
+    CHECK_MPI_OK(mp_init(&Xj));
+    /*
+     * Convert input arguments into MPI integers.
+     */
+    CHECK_MPI_OK(mp_read_unsigned_octets(&W, w, 2 * qLen));
+    CHECK_MPI_OK(mp_read_unsigned_octets(&Q, q, qLen));
+
+    /*
+     * Algorithm 1 of FIPS 186-2 Change Notice 1, Step 3.3
+     *
+     * xj = (w0 || w1) mod q
+     */
+    CHECK_MPI_OK(mp_mod(&W, &Q, &Xj));
+    CHECK_MPI_OK(mp_to_fixlen_octets(&Xj, xj, qLen));
+cleanup:
+    mp_clear(&W);
+    mp_clear(&Q);
+    mp_clear(&Xj);
+    if (err) {
+        MP_TO_SEC_ERROR(err);
+        rv = SECFailure;
+    }
+    return rv;
+}
+
+/*
+ * FIPS 186-2 requires result from random output to be reduced mod q when
+ * generating random numbers for DSA.
+ */
+SECStatus
+FIPS186Change_ReduceModQForDSA(const unsigned char *w,
+                               const unsigned char *q,
+                               unsigned char *xj)
+{
+    return fips186Change_ReduceModQForDSA(w, q, DSA1_SUBPRIME_LEN, xj);
+}
+
+/*
+ * The core of Algorithm 1 of FIPS 186-2 Change Notice 1.
+ *
+ * We no longer support FIPS 186-2 RNG. This function was exported
+ * for power-up self tests and FIPS tests. Keep this stub, which fails,
+ * to prevent crashes, but also to signal to test code that FIPS 186-2
+ * RNG is no longer supported.
+ */
+SECStatus
+FIPS186Change_GenerateX(PRUint8 *XKEY, const PRUint8 *XSEEDj,
+                        PRUint8 *x_j)
+{
+    PORT_SetError(PR_NOT_IMPLEMENTED_ERROR);
+    return SECFailure;
+}
+
+/*
+ * Specialized RNG for DSA
+ *
+ * As per Algorithm 1 of FIPS 186-2 Change Notice 1, in step 3.3 the value
+ * Xj should be reduced mod q, a 160-bit prime number.  Since this parameter
+ * is only meaningful in the context of DSA, the above RNG functions
+ * were implemented without it.  They are re-implemented below for use
+ * with DSA.
+ */
+
+/*
+** Generate some random bytes, using the global random number generator
+** object.  In DSA mode, so there is a q.
+*/
+static SECStatus
+dsa_GenerateGlobalRandomBytes(const SECItem *qItem, PRUint8 *dest,
+                              unsigned int *destLen, unsigned int maxDestLen)
+{
+    SECStatus rv;
+    SECItem w;
+    const PRUint8 *q = qItem->data;
+    unsigned int qLen = qItem->len;
+
+    if (*q == 0) {
+        ++q;
+        --qLen;
+    }
+    if (maxDestLen < qLen) {
+        /* This condition can occur when DSA_SignDigest is passed a group
+           with a subprime that is larger than DSA_MAX_SUBPRIME_LEN. */
+        PORT_SetError(SEC_ERROR_INVALID_ARGS);
+        return SECFailure;
+    }
+    w.data = NULL; /* otherwise SECITEM_AllocItem asserts */
+    if (!SECITEM_AllocItem(NULL, &w, 2 * qLen)) {
+        return SECFailure;
+    }
+    *destLen = qLen;
+
+    rv = RNG_GenerateGlobalRandomBytes(w.data, w.len);
+    if (rv == SECSuccess) {
+        rv = fips186Change_ReduceModQForDSA(w.data, q, qLen, dest);
+    }
+
+    SECITEM_FreeItem(&w, PR_FALSE);
+    return rv;
+}
+
+static void
+translate_mpi_error(mp_err err)
+{
+    MP_TO_SEC_ERROR(err);
+}
+
+static SECStatus
+dsa_NewKeyExtended(const PQGParams *params, const SECItem *seed,
+                   DSAPrivateKey **privKey)
+{
+    mp_int p, g;
+    mp_int x, y;
+    mp_err err;
+    PLArenaPool *arena;
+    DSAPrivateKey *key;
+    /* Check args. */
+    if (!params || !privKey || !seed || !seed->data) {
+        PORT_SetError(SEC_ERROR_INVALID_ARGS);
+        return SECFailure;
+    }
+    /* Initialize an arena for the DSA key. */
+    arena = PORT_NewArena(NSS_FREEBL_DSA_DEFAULT_CHUNKSIZE);
+    if (!arena) {
+        PORT_SetError(SEC_ERROR_NO_MEMORY);
+        return SECFailure;
+    }
+    key = (DSAPrivateKey *)PORT_ArenaZAlloc(arena, sizeof(DSAPrivateKey));
+    if (!key) {
+        PORT_SetError(SEC_ERROR_NO_MEMORY);
+        PORT_FreeArena(arena, PR_TRUE);
+        return SECFailure;
+    }
+    key->params.arena = arena;
+    /* Initialize MPI integers. */
+    MP_DIGITS(&p) = 0;
+    MP_DIGITS(&g) = 0;
+    MP_DIGITS(&x) = 0;
+    MP_DIGITS(&y) = 0;
+    CHECK_MPI_OK(mp_init(&p));
+    CHECK_MPI_OK(mp_init(&g));
+    CHECK_MPI_OK(mp_init(&x));
+    CHECK_MPI_OK(mp_init(&y));
+    /* Copy over the PQG params */
+    CHECK_MPI_OK(SECITEM_CopyItem(arena, &key->params.prime,
+                                  &params->prime));
+    CHECK_MPI_OK(SECITEM_CopyItem(arena, &key->params.subPrime,
+                                  &params->subPrime));
+    CHECK_MPI_OK(SECITEM_CopyItem(arena, &key->params.base, &params->base));
+    /* Convert stored p, g, and received x into MPI integers. */
+    SECITEM_TO_MPINT(params->prime, &p);
+    SECITEM_TO_MPINT(params->base, &g);
+    OCTETS_TO_MPINT(seed->data, &x, seed->len);
+    /* Store x in private key */
+    SECITEM_AllocItem(arena, &key->privateValue, seed->len);
+    PORT_Memcpy(key->privateValue.data, seed->data, seed->len);
+    /* Compute public key y = g**x mod p */
+    CHECK_MPI_OK(mp_exptmod(&g, &x, &p, &y));
+    /* Store y in public key */
+    MPINT_TO_SECITEM(&y, &key->publicValue, arena);
+    *privKey = key;
+    key = NULL;
+cleanup:
+    mp_clear(&p);
+    mp_clear(&g);
+    mp_clear(&x);
+    mp_clear(&y);
+    if (key)
+        PORT_FreeArena(key->params.arena, PR_TRUE);
+    if (err) {
+        translate_mpi_error(err);
+        return SECFailure;
+    }
+    return SECSuccess;
+}
+
+SECStatus
+DSA_NewRandom(PLArenaPool *arena, const SECItem *q, SECItem *seed)
+{
+    int retries = 10;
+    unsigned int i;
+    PRBool good;
+
+    if (q == NULL || q->data == NULL || q->len == 0 ||
+        (q->data[0] == 0 && q->len == 1)) {
+        PORT_SetError(SEC_ERROR_INVALID_ARGS);
+        return SECFailure;
+    }
+
+    if (!SECITEM_AllocItem(arena, seed, q->len)) {
+        return SECFailure;
+    }
+
+    do {
+        /* Generate seed bytes for x according to FIPS 186-1 appendix 3 */
+        if (dsa_GenerateGlobalRandomBytes(q, seed->data, &seed->len,
+                                          seed->len)) {
+            goto loser;
+        }
+        /* Disallow values of 0 and 1 for x. */
+        good = PR_FALSE;
+        for (i = 0; i < seed->len - 1; i++) {
+            if (seed->data[i] != 0) {
+                good = PR_TRUE;
+                break;
+            }
+        }
+        if (!good && seed->data[i] > 1) {
+            good = PR_TRUE;
+        }
+    } while (!good && --retries > 0);
+
+    if (!good) {
+        PORT_SetError(SEC_ERROR_NEED_RANDOM);
+    loser:
+        if (arena != NULL) {
+            SECITEM_FreeItem(seed, PR_FALSE);
+        }
+        return SECFailure;
+    }
+
+    return SECSuccess;
+}
+
+/*
+** Generate and return a new DSA public and private key pair,
+**  both of which are encoded into a single DSAPrivateKey struct.
+**  "params" is a pointer to the PQG parameters for the domain
+**  Uses a random seed.
+*/
+SECStatus
+DSA_NewKey(const PQGParams *params, DSAPrivateKey **privKey)
+{
+    SECItem seed;
+    SECStatus rv;
+
+    rv = PQG_Check(params);
+    if (rv != SECSuccess) {
+        return rv;
+    }
+    seed.data = NULL;
+
+    rv = DSA_NewRandom(NULL, &params->subPrime, &seed);
+    if (rv == SECSuccess) {
+        if (seed.len != PQG_GetLength(&params->subPrime)) {
+            PORT_SetError(SEC_ERROR_INVALID_ARGS);
+            rv = SECFailure;
+        } else {
+            rv = dsa_NewKeyExtended(params, &seed, privKey);
+        }
+    }
+    SECITEM_FreeItem(&seed, PR_FALSE);
+    return rv;
+}
+
+/* For FIPS compliance testing. Seed must be exactly the size of subPrime  */
+SECStatus
+DSA_NewKeyFromSeed(const PQGParams *params,
+                   const unsigned char *seed,
+                   DSAPrivateKey **privKey)
+{
+    SECItem seedItem;
+    seedItem.data = (unsigned char *)seed;
+    seedItem.len = PQG_GetLength(&params->subPrime);
+    return dsa_NewKeyExtended(params, &seedItem, privKey);
+}
+
+static SECStatus
+dsa_SignDigest(DSAPrivateKey *key, SECItem *signature, const SECItem *digest,
+               const unsigned char *kb)
+{
+    mp_int p, q, g; /* PQG parameters */
+    mp_int x, k;    /* private key & pseudo-random integer */
+    mp_int r, s;    /* tuple (r, s) is signature) */
+    mp_int t;       /* holding tmp values */
+    mp_err err = MP_OKAY;
+    SECStatus rv = SECSuccess;
+    unsigned int dsa_subprime_len, dsa_signature_len, offset;
+    SECItem localDigest;
+    unsigned char localDigestData[DSA_MAX_SUBPRIME_LEN];
+    SECItem t2 = { siBuffer, NULL, 0 };
+
+    /* FIPS-compliance dictates that digest is a SHA hash. */
+    /* Check args. */
+    if (!key || !signature || !digest) {
+        PORT_SetError(SEC_ERROR_INVALID_ARGS);
+        return SECFailure;
+    }
+
+    dsa_subprime_len = PQG_GetLength(&key->params.subPrime);
+    dsa_signature_len = dsa_subprime_len * 2;
+    if ((signature->len < dsa_signature_len) ||
+        (digest->len > HASH_LENGTH_MAX) ||
+        (digest->len < SHA1_LENGTH)) {
+        PORT_SetError(SEC_ERROR_INVALID_ARGS);
+        return SECFailure;
+    }
+
+    /* DSA accepts digests not equal to dsa_subprime_len, if the
+     * digests are greater, then they are truncated to the size of
+     * dsa_subprime_len, using the left most bits. If they are less
+     * then they are padded on the left.*/
+    PORT_Memset(localDigestData, 0, dsa_subprime_len);
+    offset = (digest->len < dsa_subprime_len) ? (dsa_subprime_len - digest->len) : 0;
+    PORT_Memcpy(localDigestData + offset, digest->data,
+                dsa_subprime_len - offset);
+    localDigest.data = localDigestData;
+    localDigest.len = dsa_subprime_len;
+
+    /* Initialize MPI integers. */
+    MP_DIGITS(&p) = 0;
+    MP_DIGITS(&q) = 0;
+    MP_DIGITS(&g) = 0;
+    MP_DIGITS(&x) = 0;
+    MP_DIGITS(&k) = 0;
+    MP_DIGITS(&r) = 0;
+    MP_DIGITS(&s) = 0;
+    MP_DIGITS(&t) = 0;
+    CHECK_MPI_OK(mp_init(&p));
+    CHECK_MPI_OK(mp_init(&q));
+    CHECK_MPI_OK(mp_init(&g));
+    CHECK_MPI_OK(mp_init(&x));
+    CHECK_MPI_OK(mp_init(&k));
+    CHECK_MPI_OK(mp_init(&r));
+    CHECK_MPI_OK(mp_init(&s));
+    CHECK_MPI_OK(mp_init(&t));
+    /*
+    ** Convert stored PQG and private key into MPI integers.
+    */
+    SECITEM_TO_MPINT(key->params.prime, &p);
+    SECITEM_TO_MPINT(key->params.subPrime, &q);
+    SECITEM_TO_MPINT(key->params.base, &g);
+    SECITEM_TO_MPINT(key->privateValue, &x);
+    OCTETS_TO_MPINT(kb, &k, dsa_subprime_len);
+    /*
+    ** FIPS 186-1, Section 5, Step 1
+    **
+    ** r = (g**k mod p) mod q
+    */
+    CHECK_MPI_OK(mp_exptmod(&g, &k, &p, &r)); /* r = g**k mod p */
+    CHECK_MPI_OK(mp_mod(&r, &q, &r));         /* r = r mod q    */
+    /*
+    ** FIPS 186-1, Section 5, Step 2
+    **
+    ** s = (k**-1 * (HASH(M) + x*r)) mod q
+    */
+    if (DSA_NewRandom(NULL, &key->params.subPrime, &t2) != SECSuccess) {
+        PORT_SetError(SEC_ERROR_NEED_RANDOM);
+        rv = SECFailure;
+        goto cleanup;
+    }
+    SECITEM_TO_MPINT(t2, &t);                /* t <-$ Zq */
+    CHECK_MPI_OK(mp_mulmod(&k, &t, &q, &k)); /* k = k * t mod q */
+    CHECK_MPI_OK(mp_invmod(&k, &q, &k));     /* k = k**-1 mod q */
+    CHECK_MPI_OK(mp_mulmod(&k, &t, &q, &k)); /* k = k * t mod q */
+    SECITEM_TO_MPINT(localDigest, &s);       /* s = HASH(M)     */
+    CHECK_MPI_OK(mp_mulmod(&x, &r, &q, &x)); /* x = x * r mod q */
+    CHECK_MPI_OK(mp_addmod(&s, &x, &q, &s)); /* s = s + x mod q */
+    CHECK_MPI_OK(mp_mulmod(&s, &k, &q, &s)); /* s = s * k mod q */
+    /*
+    ** verify r != 0 and s != 0
+    ** mentioned as optional in FIPS 186-1.
+    */
+    if (mp_cmp_z(&r) == 0 || mp_cmp_z(&s) == 0) {
+        PORT_SetError(SEC_ERROR_NEED_RANDOM);
+        rv = SECFailure;
+        goto cleanup;
+    }
+    /*
+    ** Step 4
+    **
+    ** Signature is tuple (r, s)
+    */
+    err = mp_to_fixlen_octets(&r, signature->data, dsa_subprime_len);
+    if (err < 0)
+        goto cleanup;
+    err = mp_to_fixlen_octets(&s, signature->data + dsa_subprime_len,
+                              dsa_subprime_len);
+    if (err < 0)
+        goto cleanup;
+    err = MP_OKAY;
+    signature->len = dsa_signature_len;
+cleanup:
+    PORT_Memset(localDigestData, 0, DSA_MAX_SUBPRIME_LEN);
+    mp_clear(&p);
+    mp_clear(&q);
+    mp_clear(&g);
+    mp_clear(&x);
+    mp_clear(&k);
+    mp_clear(&r);
+    mp_clear(&s);
+    mp_clear(&t);
+    SECITEM_FreeItem(&t2, PR_FALSE);
+    if (err) {
+        translate_mpi_error(err);
+        rv = SECFailure;
+    }
+    return rv;
+}
+
+/* signature is caller-supplied buffer of at least 40 bytes.
+** On input,  signature->len == size of buffer to hold signature.
+**            digest->len    == size of digest.
+** On output, signature->len == size of signature in buffer.
+** Uses a random seed.
+*/
+SECStatus
+DSA_SignDigest(DSAPrivateKey *key, SECItem *signature, const SECItem *digest)
+{
+    SECStatus rv;
+    int retries = 10;
+    unsigned char kSeed[DSA_MAX_SUBPRIME_LEN];
+    unsigned int kSeedLen = 0;
+    unsigned int i;
+    unsigned int dsa_subprime_len = PQG_GetLength(&key->params.subPrime);
+    PRBool good;
+
+    PORT_SetError(0);
+    do {
+        rv = dsa_GenerateGlobalRandomBytes(&key->params.subPrime,
+                                           kSeed, &kSeedLen, sizeof kSeed);
+        if (rv != SECSuccess)
+            break;
+        if (kSeedLen != dsa_subprime_len) {
+            PORT_SetError(SEC_ERROR_INVALID_ARGS);
+            rv = SECFailure;
+            break;
+        }
+        /* Disallow a value of 0 for k. */
+        good = PR_FALSE;
+        for (i = 0; i < kSeedLen; i++) {
+            if (kSeed[i] != 0) {
+                good = PR_TRUE;
+                break;
+            }
+        }
+        if (!good) {
+            PORT_SetError(SEC_ERROR_NEED_RANDOM);
+            rv = SECFailure;
+            continue;
+        }
+        rv = dsa_SignDigest(key, signature, digest, kSeed);
+    } while (rv != SECSuccess && PORT_GetError() == SEC_ERROR_NEED_RANDOM &&
+             --retries > 0);
+    return rv;
+}
+
+/* For FIPS compliance testing. Seed must be exactly 20 bytes. */
+SECStatus
+DSA_SignDigestWithSeed(DSAPrivateKey *key,
+                       SECItem *signature,
+                       const SECItem *digest,
+                       const unsigned char *seed)
+{
+    SECStatus rv;
+    rv = dsa_SignDigest(key, signature, digest, seed);
+    return rv;
+}
+
+/* signature is caller-supplied buffer of at least 20 bytes.
+** On input,  signature->len == size of buffer to hold signature.
+**            digest->len    == size of digest.
+*/
+SECStatus
+DSA_VerifyDigest(DSAPublicKey *key, const SECItem *signature,
+                 const SECItem *digest)
+{
+    /* FIPS-compliance dictates that digest is a SHA hash. */
+    mp_int p, q, g;      /* PQG parameters */
+    mp_int r_, s_;       /* tuple (r', s') is received signature) */
+    mp_int u1, u2, v, w; /* intermediate values used in verification */
+    mp_int y;            /* public key */
+    mp_err err;
+    unsigned int dsa_subprime_len, dsa_signature_len, offset;
+    SECItem localDigest;
+    unsigned char localDigestData[DSA_MAX_SUBPRIME_LEN];
+    SECStatus verified = SECFailure;
+
+    /* Check args. */
+    if (!key || !signature || !digest) {
+        PORT_SetError(SEC_ERROR_INVALID_ARGS);
+        return SECFailure;
+    }
+
+    dsa_subprime_len = PQG_GetLength(&key->params.subPrime);
+    dsa_signature_len = dsa_subprime_len * 2;
+    if ((signature->len != dsa_signature_len) ||
+        (digest->len > HASH_LENGTH_MAX) ||
+        (digest->len < SHA1_LENGTH)) {
+        PORT_SetError(SEC_ERROR_INVALID_ARGS);
+        return SECFailure;
+    }
+
+    /* DSA accepts digests not equal to dsa_subprime_len, if the
+     * digests are greater, than they are truncated to the size of
+     * dsa_subprime_len, using the left most bits. If they are less
+     * then they are padded on the left.*/
+    PORT_Memset(localDigestData, 0, dsa_subprime_len);
+    offset = (digest->len < dsa_subprime_len) ? (dsa_subprime_len - digest->len) : 0;
+    PORT_Memcpy(localDigestData + offset, digest->data,
+                dsa_subprime_len - offset);
+    localDigest.data = localDigestData;
+    localDigest.len = dsa_subprime_len;
+
+    /* Initialize MPI integers. */
+    MP_DIGITS(&p) = 0;
+    MP_DIGITS(&q) = 0;
+    MP_DIGITS(&g) = 0;
+    MP_DIGITS(&y) = 0;
+    MP_DIGITS(&r_) = 0;
+    MP_DIGITS(&s_) = 0;
+    MP_DIGITS(&u1) = 0;
+    MP_DIGITS(&u2) = 0;
+    MP_DIGITS(&v) = 0;
+    MP_DIGITS(&w) = 0;
+    CHECK_MPI_OK(mp_init(&p));
+    CHECK_MPI_OK(mp_init(&q));
+    CHECK_MPI_OK(mp_init(&g));
+    CHECK_MPI_OK(mp_init(&y));
+    CHECK_MPI_OK(mp_init(&r_));
+    CHECK_MPI_OK(mp_init(&s_));
+    CHECK_MPI_OK(mp_init(&u1));
+    CHECK_MPI_OK(mp_init(&u2));
+    CHECK_MPI_OK(mp_init(&v));
+    CHECK_MPI_OK(mp_init(&w));
+    /*
+    ** Convert stored PQG and public key into MPI integers.
+    */
+    SECITEM_TO_MPINT(key->params.prime, &p);
+    SECITEM_TO_MPINT(key->params.subPrime, &q);
+    SECITEM_TO_MPINT(key->params.base, &g);
+    SECITEM_TO_MPINT(key->publicValue, &y);
+    /*
+    ** Convert received signature (r', s') into MPI integers.
+    */
+    OCTETS_TO_MPINT(signature->data, &r_, dsa_subprime_len);
+    OCTETS_TO_MPINT(signature->data + dsa_subprime_len, &s_, dsa_subprime_len);
+    /*
+    ** Verify that 0 < r' < q and 0 < s' < q
+    */
+    if (mp_cmp_z(&r_) <= 0 || mp_cmp_z(&s_) <= 0 ||
+        mp_cmp(&r_, &q) >= 0 || mp_cmp(&s_, &q) >= 0) {
+        /* err is zero here. */
+        PORT_SetError(SEC_ERROR_BAD_SIGNATURE);
+        goto cleanup; /* will return verified == SECFailure */
+    }
+    /*
+    ** FIPS 186-1, Section 6, Step 1
+    **
+    ** w = (s')**-1 mod q
+    */
+    CHECK_MPI_OK(mp_invmod(&s_, &q, &w)); /* w = (s')**-1 mod q */
+    /*
+    ** FIPS 186-1, Section 6, Step 2
+    **
+    ** u1 = ((Hash(M')) * w) mod q
+    */
+    SECITEM_TO_MPINT(localDigest, &u1);        /* u1 = HASH(M')     */
+    CHECK_MPI_OK(mp_mulmod(&u1, &w, &q, &u1)); /* u1 = u1 * w mod q */
+    /*
+    ** FIPS 186-1, Section 6, Step 3
+    **
+    ** u2 = ((r') * w) mod q
+    */
+    CHECK_MPI_OK(mp_mulmod(&r_, &w, &q, &u2));
+    /*
+    ** FIPS 186-1, Section 6, Step 4
+    **
+    ** v = ((g**u1 * y**u2) mod p) mod q
+    */
+    CHECK_MPI_OK(mp_exptmod(&g, &u1, &p, &g)); /* g = g**u1 mod p */
+    CHECK_MPI_OK(mp_exptmod(&y, &u2, &p, &y)); /* y = y**u2 mod p */
+    CHECK_MPI_OK(mp_mulmod(&g, &y, &p, &v));   /* v = g * y mod p */
+    CHECK_MPI_OK(mp_mod(&v, &q, &v));          /* v = v mod q     */
+    /*
+    ** Verification:  v == r'
+    */
+    if (mp_cmp(&v, &r_)) {
+        PORT_SetError(SEC_ERROR_BAD_SIGNATURE);
+        verified = SECFailure; /* Signature failed to verify. */
+    } else {
+        verified = SECSuccess; /* Signature verified. */
+    }
+cleanup:
+    mp_clear(&p);
+    mp_clear(&q);
+    mp_clear(&g);
+    mp_clear(&y);
+    mp_clear(&r_);
+    mp_clear(&s_);
+    mp_clear(&u1);
+    mp_clear(&u2);
+    mp_clear(&v);
+    mp_clear(&w);
+    if (err) {
+        translate_mpi_error(err);
+    }
+    return verified;
+}