On Windows, prepare to generate SHA-1 signatures for TLS 1.2 client authentication.

net/third_party/nss/ssl/ssl3con.c

Index: net/third_party/nss/ssl/ssl3con.c
===================================================================
--- net/third_party/nss/ssl/ssl3con.c	(revision 219612)
+++ net/third_party/nss/ssl/ssl3con.c	(working copy)
@@ -3933,6 +3933,22 @@
 		ssl_MapLowLevelError(SSL_ERROR_DIGEST_FAILURE);
 		return SECFailure;
 	    }
+
+#ifdef _WIN32
+	    /* A backup SHA-1 hash for a potential client auth signature. */
+	    if (!ss->sec.isServer) {
+		ss->ssl3.hs.md5 = PK11_CreateDigestContext(SEC_OID_SHA1);
+		if (ss->ssl3.hs.md5 == NULL) {
+		    ssl_MapLowLevelError(SSL_ERROR_SHA_DIGEST_FAILURE);
+		    return SECFailure;
+		}
+
+		if (PK11_DigestBegin(ss->ssl3.hs.md5) != SECSuccess) {
+		    ssl_MapLowLevelError(SSL_ERROR_SHA_DIGEST_FAILURE);
+		    return SECFailure;
+		}
+	    }
+#endif
 	} else {
 	    /* Both ss->ssl3.hs.md5 and ss->ssl3.hs.sha should be NULL or
 	     * created successfully. */
@@ -4043,6 +4059,13 @@
 	    ssl_MapLowLevelError(SSL_ERROR_DIGEST_FAILURE);
 	    return rv;
 	}
+	if (ss->ssl3.hs.md5) {
+	    rv = PK11_DigestOp(ss->ssl3.hs.md5, b, l);
+	    if (rv != SECSuccess) {
+		ssl_MapLowLevelError(SSL_ERROR_SHA_DIGEST_FAILURE);
+		return rv;
+	    }
+	}
     } else {
 	rv = PK11_DigestOp(ss->ssl3.hs.md5, b, l);
 	if (rv != SECSuccess) {
@@ -4791,6 +4814,30 @@
     return rv;
 }
 
+static SECStatus
+ssl3_ComputeBackupHandshakeHashes(sslSocket * ss,
+				  SSL3Hashes * hashes) /* output goes here. */
+{
+    SECStatus rv = SECSuccess;
+
+    PORT_Assert( ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss) );
+    PORT_Assert( ss->ssl3.hs.hashType == handshake_hash_single );
+
+    rv = PK11_DigestFinal(ss->ssl3.hs.md5, hashes->u.raw, &hashes->len,
+			  sizeof(hashes->u.raw));
+    if (rv != SECSuccess) {
+	ssl_MapLowLevelError(SSL_ERROR_SHA_DIGEST_FAILURE);
+	rv = SECFailure;
+	goto loser;
+    }
+    hashes->hashAlg = SEC_OID_SHA1;
+
+loser:
+    PK11_DestroyContext(ss->ssl3.hs.md5, PR_TRUE);
+    ss->ssl3.hs.md5 = NULL;
+    return rv;
+}
+
 /*
  * SSL 2 based implementations pass in the initial outbound buffer
  * so that the handshake hash can contain the included information.
@@ -6044,7 +6091,17 @@
 		SSL_GETPID(), ss->fd));
 
     ssl_GetSpecReadLock(ss);
-    rv = ssl3_ComputeHandshakeHashes(ss, ss->ssl3.pwSpec, &hashes, 0);
+    /* In TLS 1.2, ssl3_ComputeHandshakeHashes always uses the handshake hash
+     * function (SHA-256). If the server or the client does not support SHA-256
+     * as a signature hash, we can either maintain a backup SHA-1 handshake
+     * hash or buffer all handshake messages.
+     */
+    if (ss->ssl3.hs.hashType == handshake_hash_single && ss->ssl3.hs.md5) {
+	rv = ssl3_ComputeBackupHandshakeHashes(ss, &hashes);

[agl, 2013/08/28 22:16:03]

(doesn't matter): here you are using tabs rather than 8 spaces at the beginning
of the line (which I believe is NSS style), but codereview isn't showing that in
other parts of the file.

+	PORT_Assert(ss->ssl3.hs.md5 == NULL);
+    } else {
+	rv = ssl3_ComputeHandshakeHashes(ss, ss->ssl3.pwSpec, &hashes, 0);
+    }
     ssl_ReleaseSpecReadLock(ss);
     if (rv != SECSuccess) {
 	goto done;	/* err code was set by ssl3_ComputeHandshakeHashes */
@@ -6098,11 +6155,6 @@
 	if (rv != SECSuccess) {
 	    goto done;
 	}
-	/* We always sign using the handshake hash function. It's possible that
-	 * a server could support SHA-256 as the handshake hash but not as a
-	 * signature hash. In that case we wouldn't be able to do client
-	 * certificates with it. The alternative is to buffer all handshake
-	 * messages. */
 	sigAndHash.hashAlg = hashes.hashAlg;
 
 	rv = ssl3_AppendSignatureAndHashAlgorithm(ss, &sigAndHash);
@@ -6994,6 +7046,35 @@
 		}
 		goto send_no_certificate;
 	    }
+
+	    if (isTLS12 && ss->ssl3.hs.md5) {
+		PRBool need_backup_hash = PR_FALSE;
+#ifdef _WIN32
+		/* If the key is in CAPI, check if the CAPI service provider
+		 * supports SHA-256. Use SHA-1 if it doesn't. */
+		if (ss->ssl3.platformClientKey->dwKeySpec !=
+		    CERT_NCRYPT_KEY_SPEC) {
+		    HCRYPTPROV prov = ss->ssl3.platformClientKey->hCryptProv;
+		    PROV_ENUMALGS alg_info;
+		    DWORD size = sizeof(alg_info);
+		    DWORD flags = CRYPT_FIRST;
+		    need_backup_hash = PR_TRUE;
+		    while (CryptGetProvParam(prov, PP_ENUMALGS,

[wtc, 2013/08/28 22:05:45]

It may be cheaper to check SHA-256 support by trying to create
a SHA-256 hash object in the CAPI service provider...

+			(BYTE *)&alg_info, &size, flags)) {
+			if (alg_info.aiAlgid == CALG_SHA_256) {
+			    need_backup_hash = PR_FALSE;
+			    break;
+			}
+			size = sizeof(alg_info);
+			flags = CRYPT_NEXT;
+		    }
+		}
+#endif  /* _WIN32 */
+		if (!need_backup_hash) {
+		    PK11_DestroyContext(ss->ssl3.hs.md5, PR_TRUE);
+		    ss->ssl3.hs.md5 = NULL;
+		}
+	    }
 	    break;  /* not an error */
 	}
 #endif   /* NSS_PLATFORM_CLIENT_AUTH */
@@ -7227,6 +7308,13 @@
 		     (ss->ssl3.platformClientKey ||
 		     ss->ssl3.clientPrivateKey != NULL);
 
+    if (!sendClientCert &&
+	ss->ssl3.hs.hashType == handshake_hash_single && ss->ssl3.hs.md5) {
+	/* Don't need the backup handshake hash. */
+	PK11_DestroyContext(ss->ssl3.hs.md5, PR_TRUE);
+	ss->ssl3.hs.md5 = NULL;
+    }
+
     /* We must wait for the server's certificate to be authenticated before
      * sending the client certificate in order to disclosing the client
      * certificate to an attacker that does not have a valid cert for the