Do not delete - used in Better Informatics, Secure Programming, 2014 May

ssl.c

static OSStatus
SSLVerifySignedServerKeyExchange(SSLContext * ctx,
  bool isRsa, SSLBuffer signedParams,
  uint8_t * signature, UInt16 signatureLen)
{
  OSStatus err;
  SSLBuffer hashOut, hashCtx, clientRandom, serverRandom;
  uint8_t hashes[SSL_SHA1_DIGEST_LEN + SSL_MD5_DIGEST_LEN];
  SSLBuffer signedHashes;
  uint8_t * dataToSign;
  size_t dataToSignLen;

  signedHashes.data = 0;
  hashCtx.data = 0;

  clientRandom.data = ctx - > clientRandom;
  clientRandom.length = SSL_CLIENT_SRVR_RAND_SIZE;
  serverRandom.data = ctx - > serverRandom;
  serverRandom.length = SSL_CLIENT_SRVR_RAND_SIZE;

  
  if (isRsa) {
    /* skip this if signing with DSA */
    dataToSign = hashes;
    dataToSignLen = SSL_SHA1_DIGEST_LEN + SSL_MD5_DIGEST_LEN;
    hashOut.data = hashes;
    hashOut.length = SSL_MD5_DIGEST_LEN;

    if ((err = ReadyHash( & SSLHashMD5, & hashCtx)) != 0)
      goto fail;
    if ((err = SSLHashMD5.update( & hashCtx, & clientRandom)) != 0)
      goto fail;
    if ((err = SSLHashMD5.update( & hashCtx, & serverRandom)) != 0)
      goto fail;
    if ((err = SSLHashMD5.update( & hashCtx, & signedParams)) != 0)
      goto fail;
    if ((err = SSLHashMD5.final( & hashCtx, & hashOut)) != 0)
      goto fail;
  }
  else {
    /* DSA, ECDSA - just use the SHA1 hash */
    dataToSign = & hashes[SSL_MD5_DIGEST_LEN];
    dataToSignLen = SSL_SHA1_DIGEST_LEN;
  }

  hashOut.data = hashes + SSL_MD5_DIGEST_LEN;
  hashOut.length = SSL_SHA1_DIGEST_LEN;
  if ((err = SSLFreeBuffer( & hashCtx)) != 0)
    goto fail;

  if ((err = ReadyHash( & SSLHashSHA1, & hashCtx)) != 0)
    goto fail;
  if ((err = SSLHashSHA1.update( & hashCtx, & clientRandom)) != 0)
    goto fail;
  if ((err = SSLHashSHA1.update( & hashCtx, & serverRandom)) != 0)
    goto fail;
  if ((err = SSLHashSHA1.update( & hashCtx, & signedParams)) != 0)
    goto fail;
    goto fail;
  if ((err = SSLHashSHA1.final( & hashCtx, & hashOut)) != 0)
    goto fail;

  err = sslRawVerify(ctx,
    ctx - > peerPubKey,
    dataToSign, /* plaintext */
    dataToSignLen, /* plaintext length */
    signature,
    signatureLen);
  if (err) {
    sslErrorLog("SSLDecodeSignedServerKeyExchange: sslRawVerify "
      "returned %d\n", (int) err);
    goto fail;
  }

  fail:
    SSLFreeBuffer( & signedHashes);
    SSLFreeBuffer( & hashCtx);
    return err;

}