openssl: fix peer certificate leak in channel binding

Reported-by: Stanislav Fort
Bug: https://hackerone.com/reports/3373640
Closes #18917

diff --git a/lib/vtls/openssl.c b/lib/vtls/openssl.c
index fb5cc1836230939fb8c8bcd964c46f5901a81222..bd0e315fd8203ba60119e04cbd0ed96622ee6d8b 100644 (file)
--- a/lib/vtls/openssl.c
+++ b/lib/vtls/openssl.c
@@ -5628,6 +5628,7 @@ static CURLcode ossl_get_channel_binding(struct Curl_easy *data, int sockindex,
   struct connectdata *conn = data->conn;
   struct Curl_cfilter *cf = conn->cfilter[sockindex];
   struct ossl_ctx *octx = NULL;
+  CURLcode result = CURLE_OK;
 
   do {
     const struct Curl_cftype *cft = cf->cft;
@@ -5649,15 +5650,15 @@ static CURLcode ossl_get_channel_binding(struct Curl_easy *data, int sockindex,
   }
 
   cert = SSL_get1_peer_certificate(octx->ssl);
-  if(!cert) {
+  if(!cert)
     /* No server certificate, don't do channel binding */
     return CURLE_OK;
-  }
 
   if(!OBJ_find_sigid_algs(X509_get_signature_nid(cert), &algo_nid, NULL)) {
     failf(data,
           "Unable to find digest NID for certificate signature algorithm");
-    return CURLE_SSL_INVALIDCERTSTATUS;
+    result = CURLE_SSL_INVALIDCERTSTATUS;
+    goto error;
   }
 
   /* https://datatracker.ietf.org/doc/html/rfc5929#section-4.1 */
@@ -5670,23 +5671,28 @@ static CURLcode ossl_get_channel_binding(struct Curl_easy *data, int sockindex,
       algo_name = OBJ_nid2sn(algo_nid);
       failf(data, "Could not find digest algorithm %s (NID %d)",
             algo_name ? algo_name : "(null)", algo_nid);
-      return CURLE_SSL_INVALIDCERTSTATUS;
+      result = CURLE_SSL_INVALIDCERTSTATUS;
+      goto error;
     }
   }
 
   if(!X509_digest(cert, algo_type, buf, &length)) {
     failf(data, "X509_digest() failed");
-    return CURLE_SSL_INVALIDCERTSTATUS;
+    result = CURLE_SSL_INVALIDCERTSTATUS;
+    goto error;
   }
 
   /* Append "tls-server-end-point:" */
-  if(curlx_dyn_addn(binding, prefix, sizeof(prefix) - 1) != CURLE_OK)
-    return CURLE_OUT_OF_MEMORY;
+  result = curlx_dyn_addn(binding, prefix, sizeof(prefix) - 1);
+  if(result)
+    goto error;
+
   /* Append digest */
-  if(curlx_dyn_addn(binding, buf, length))
-    return CURLE_OUT_OF_MEMORY;
+  result = curlx_dyn_addn(binding, buf, length);
 
-  return CURLE_OK;
+error:
+  X509_free(cert);
+  return result;
 #else
   /* No X509_get_signature_nid support */
   (void)data;