Factor out CA list parsing.

This will get shared between TLS 1.2 and 1.3.

Change-Id: I9c0d73a087942ac4f8f2075a44bd55647c0dd70b
Reviewed-on: https://boringssl-review.googlesource.com/8777
Reviewed-by: David Benjamin <davidben@google.com>

ssl/handshake_client.c

@@ -1375,15 +1375,7 @@ err:
   return -1;
 }
 
-static int ca_dn_cmp(const X509_NAME **a, const X509_NAME **b) {
-  return X509_NAME_cmp(*a, *b);
-}
-
 static int ssl3_get_certificate_request(SSL *ssl) {
-  int ret = 0;
-  X509_NAME *xn = NULL;
-  STACK_OF(X509_NAME) *ca_sk = NULL;
-
   int msg_ret = ssl->method->ssl_get_message(ssl, -1, ssl_hash_message);
   if (msg_ret <= 0) {
     return msg_ret;
@@ -1402,30 +1394,24 @@ static int ssl3_get_certificate_request(SSL *ssl) {
   if (ssl->s3->tmp.message_type != SSL3_MT_CERTIFICATE_REQUEST) {
     ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);
     OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_MESSAGE);
-    goto err;
+    return -1;
   }
 
   CBS cbs;
   CBS_init(&cbs, ssl->init_msg, ssl->init_num);
 
-  ca_sk = sk_X509_NAME_new(ca_dn_cmp);
+  /* Get the certificate types. */
-  if (ca_sk == NULL) {
-    OPENSSL_PUT_ERROR(SSL, ERR_R_MALLOC_FAILURE);
-    goto err;
-  }
-
-  /* get the certificate types */
   CBS certificate_types;
   if (!CBS_get_u8_length_prefixed(&cbs, &certificate_types)) {
     ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
     OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
-    goto err;
+    return -1;
   }
 
   if (!CBS_stow(&certificate_types, &ssl->s3->tmp.certificate_types,
                 &ssl->s3->tmp.num_certificate_types)) {
     ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
-    goto err;
+    return -1;
   }
 
   if (ssl3_protocol_version(ssl) >= TLS1_2_VERSION) {
@@ -1434,56 +1420,21 @@ static int ssl3_get_certificate_request(SSL *ssl) {
         !tls1_parse_peer_sigalgs(ssl, &supported_signature_algorithms)) {
       ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
       OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
-      goto err;
+      return -1;
     }
   }
 
-  /* get the CA RDNs */
+  uint8_t alert;
-  CBS certificate_authorities;
+  STACK_OF(X509_NAME) *ca_sk = ssl_parse_client_CA_list(ssl, &alert, &cbs);
-  if (!CBS_get_u16_length_prefixed(&cbs, &certificate_authorities)) {
+  if (ca_sk == NULL) {
-    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
+    ssl3_send_alert(ssl, SSL3_AL_FATAL, alert);
-    OPENSSL_PUT_ERROR(SSL, SSL_R_LENGTH_MISMATCH);
+    return -1;
-    goto err;
   }
 
-  while (CBS_len(&certificate_authorities) > 0) {
-    CBS distinguished_name;
-    if (!CBS_get_u16_length_prefixed(&certificate_authorities,
-                                     &distinguished_name)) {
-      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
-      OPENSSL_PUT_ERROR(SSL, SSL_R_CA_DN_TOO_LONG);
-      goto err;
-    }
-
-    const uint8_t *data = CBS_data(&distinguished_name);
-    /* A u16 length cannot overflow a long. */
-    xn = d2i_X509_NAME(NULL, &data, (long)CBS_len(&distinguished_name));
-    if (xn == NULL ||
-        data != CBS_data(&distinguished_name) + CBS_len(&distinguished_name)) {
-      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
-      OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
-      goto err;
-    }
-
-    if (!sk_X509_NAME_push(ca_sk, xn)) {
-      OPENSSL_PUT_ERROR(SSL, ERR_R_MALLOC_FAILURE);
-      goto err;
-    }
-    xn = NULL;
-  }
-
-  /* we should setup a certificate to return.... */
   ssl->s3->tmp.cert_request = 1;
   sk_X509_NAME_pop_free(ssl->s3->tmp.ca_names, X509_NAME_free);
   ssl->s3->tmp.ca_names = ca_sk;
-  ca_sk = NULL;
+  return 1;
-
-  ret = 1;
-
-err:
-  X509_NAME_free(xn);
-  sk_X509_NAME_pop_free(ca_sk, X509_NAME_free);
-  return ret;
 }
 
 static int ssl3_get_server_hello_done(SSL *ssl) {

ssl/internal.h

@@ -747,6 +747,13 @@ int ssl_add_cert_to_cbb(CBB *cbb, X509 *x509);
  * empty certificate list. It returns one on success and zero on error. */
 int ssl_add_cert_chain(SSL *ssl, CBB *cbb);
 
+/* ssl_parse_client_CA_list parses a CA list from |cbs| in the format used by a
+ * TLS CertificateRequest message. On success, it returns a newly-allocated
+ * |X509_NAME| list and advances |cbs|. Otherwise, it returns NULL and sets
+ * |*out_alert| to an alert to send to the peer. */
+STACK_OF(X509_NAME) *
+    ssl_parse_client_CA_list(SSL *ssl, uint8_t *out_alert, CBS *cbs);
+
 /* ssl_add_client_CA_list adds the configured CA list to |cbb| in the format
  * used by a TLS CertificateRequest message. It returns one on success and zero
  * on error. */

ssl/ssl_cert.c

@@ -501,6 +501,61 @@ int ssl_add_cert_chain(SSL *ssl, CBB *cbb) {
   return CBB_flush(cbb);
 }
 
+static int ca_dn_cmp(const X509_NAME **a, const X509_NAME **b) {
+  return X509_NAME_cmp(*a, *b);
+}
+
+STACK_OF(X509_NAME) *
+    ssl_parse_client_CA_list(SSL *ssl, uint8_t *out_alert, CBS *cbs) {
+  STACK_OF(X509_NAME) *ret = sk_X509_NAME_new(ca_dn_cmp);
+  X509_NAME *name = NULL;
+  if (ret == NULL) {
+    *out_alert = SSL_AD_INTERNAL_ERROR;
+    OPENSSL_PUT_ERROR(SSL, ERR_R_MALLOC_FAILURE);
+    return NULL;
+  }
+
+  CBS child;
+  if (!CBS_get_u16_length_prefixed(cbs, &child)) {
+    *out_alert = SSL_AD_DECODE_ERROR;
+    OPENSSL_PUT_ERROR(SSL, SSL_R_LENGTH_MISMATCH);
+    goto err;
+  }
+
+  while (CBS_len(&child) > 0) {
+    CBS distinguished_name;
+    if (!CBS_get_u16_length_prefixed(&child, &distinguished_name)) {
+      *out_alert = SSL_AD_DECODE_ERROR;
+      OPENSSL_PUT_ERROR(SSL, SSL_R_CA_DN_TOO_LONG);
+      goto err;
+    }
+
+    const uint8_t *ptr = CBS_data(&distinguished_name);
+    /* A u16 length cannot overflow a long. */
+    name = d2i_X509_NAME(NULL, &ptr, (long)CBS_len(&distinguished_name));
+    if (name == NULL ||
+        ptr != CBS_data(&distinguished_name) + CBS_len(&distinguished_name)) {
+      *out_alert = SSL_AD_DECODE_ERROR;
+      OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
+      goto err;
+    }
+
+    if (!sk_X509_NAME_push(ret, name)) {
+      *out_alert = SSL_AD_INTERNAL_ERROR;
+      OPENSSL_PUT_ERROR(SSL, ERR_R_MALLOC_FAILURE);
+      goto err;
+    }
+    name = NULL;
+  }
+
+  return ret;
+
+err:
+  X509_NAME_free(name);
+  sk_X509_NAME_pop_free(ret, X509_NAME_free);
+  return NULL;
+}
+
 int ssl_add_client_CA_list(SSL *ssl, CBB *cbb) {
   CBB child, name_cbb;
   if (!CBB_add_u16_length_prefixed(cbb, &child)) {