mbedtls: implement CURLOPT_PINNEDPUBLICKEY

1 files changed, 52 insertions, 1 deletions

diff --git a/lib/vtls/mbedtls.c b/lib/vtls/mbedtls.c
index cfebedf53..05af46212 100644
--- a/lib/vtls/mbedtls.c
+++ b/lib/vtls/mbedtls.c
@@ -6,7 +6,7 @@
  *                             \___|\___/|_| \_\_____|
  *
  * Copyright (C) 2010 - 2011, Hoi-Ho Chan, <hoiho.chan@gmail.com>
- * Copyright (C) 2012 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 2012 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -141,6 +141,53 @@ const mbedtls_x509_crt_profile mbedtls_x509_crt_profile_fr =
     1024,      /* RSA min key len */
 };
 
+/* See https://tls.mbed.org/discussions/generic/
+   howto-determine-exact-buffer-len-for-mbedtls_pk_write_pubkey_der
+*/
+#define RSA_PUB_DER_MAX_BYTES   (38 + 2 * MBEDTLS_MPI_MAX_SIZE)
+#define ECP_PUB_DER_MAX_BYTES   (30 + 2 * MBEDTLS_ECP_MAX_BYTES)
+
+#define PUB_DER_MAX_BYTES   (RSA_PUB_DER_MAX_BYTES > ECP_PUB_DER_MAX_BYTES ? \
+                            RSA_PUB_DER_MAX_BYTES : ECP_PUB_DER_MAX_BYTES)
+
+static int
+mbedtls_verify_pinned_crt(void *p, mbedtls_x509_crt *crt,
+                          int depth, unsigned int *flags)
+{
+  struct SessionHandle *data = p;
+  unsigned char pubkey[PUB_DER_MAX_BYTES];
+  int ret;
+  int size;
+  char *pinned_cert = data->set.str[STRING_SSL_PINNEDPUBLICKEY];
+
+  /* Skip intermediate and root certificates */
+  if(depth) {
+    return 0;
+  }
+
+  if(pinned_cert == NULL || crt == NULL) {
+    *flags |= MBEDTLS_X509_BADCERT_NOT_TRUSTED;
+    return 1;
+  }
+
+  /* Extract pubkey */
+  size = mbedtls_pk_write_pubkey_der(&crt->pk, pubkey, PUB_DER_MAX_BYTES);
+  if(size <= 0) {
+    *flags |= MBEDTLS_X509_BADCERT_NOT_TRUSTED;
+    return 1;
+  }
+
+  /* mbedtls_pk_write_pubkey_der writes data at the end of the buffer. */
+  ret = Curl_pin_peer_pubkey(data, pinned_cert,
+                             &pubkey[PUB_DER_MAX_BYTES - size], size);
+  if(ret == CURLE_OK) {
+    return 0;
+  }
+
+  *flags |= MBEDTLS_X509_BADCERT_NOT_TRUSTED;
+  return 1;
+}
+
 static Curl_recv mbedtls_recv;
 static Curl_send mbedtls_send;
 
@@ -636,6 +683,10 @@ mbedtls_connect_common(struct connectdata *conn,
   long timeout_ms;
   int what;
 
+  if(data->set.str[STRING_SSL_PINNEDPUBLICKEY]) {
+    mbedtls_ssl_conf_verify(&connssl->config, mbedtls_verify_pinned_crt, data);
+  }
+
   /* check if the connection has already been established */
   if(ssl_connection_complete == connssl->state) {
     *done = TRUE;