X-Git-Url: http://sjero.net/git/?p=wget;a=blobdiff_plain;f=src%2Fopenssl.c;h=de335c086a021aec355014f7a7aa25b1bbaece93;hp=a6e77adcd5618e0c4bcedc1f07bd0b9687e133fb;hb=57c9e17e6cfef9bc0e8ab9fa8edf9d131a233e57;hpb=d5e283b1a75c5f8249300b465b4e7b55130bec49

diff --git a/src/openssl.c b/src/openssl.c
index a6e77adc..de335c08 100644
--- a/src/openssl.c
+++ b/src/openssl.c
@@ -569,9 +569,11 @@ ssl_check_certificate (int fd, const char *host)
      - Ensure that ASN1 strings from the certificate are encoded as
        UTF-8 which can be meaningfully compared to HOST.  */
 
+  X509_NAME *xname = X509_get_subject_name(cert);
   common_name[0] = '\0';
-  X509_NAME_get_text_by_NID (X509_get_subject_name (cert),
-                             NID_commonName, common_name, sizeof (common_name));
+  X509_NAME_get_text_by_NID (xname, NID_commonName, common_name,
+                             sizeof (common_name));
+
   if (!pattern_match (common_name, host))
     {
       logprintf (LOG_NOTQUIET, _("\
@@ -579,6 +581,41 @@ ssl_check_certificate (int fd, const char *host)
                  severity, quote (common_name), quote (host));
       success = false;
     }
+  else
+    {
+      /* We now determine the length of the ASN1 string. If it differs from
+       * common_name's length, then there is a \0 before the string terminates.
+       * This can be an instance of a null-prefix attack.
+       *
+       * https://www.blackhat.com/html/bh-usa-09/bh-usa-09-archives.html#Marlinspike
+       * */
+
+      int i = -1, j;
+      X509_NAME_ENTRY *xentry;
+      ASN1_STRING *sdata;
+
+      if (xname) {
+        for (;;)
+          {
+            j = X509_NAME_get_index_by_NID (xname, NID_commonName, i);
+            if (j == -1) break;
+            i = j;
+          }
+      }
+
+      xentry = X509_NAME_get_entry(xname,i);
+      sdata = X509_NAME_ENTRY_get_data(xentry);
+      if (strlen (common_name) != ASN1_STRING_length (sdata)) 
+        {
+          logprintf (LOG_NOTQUIET, _("\
+%s: certificate common name is invalid (contains a NUL character).\n\
+This may be an indication that the host is not who it claims to be\n\
+(that is, it is not the real %s).\n"),
+                     severity, quote (host));
+          success = false;
+        }
+    }
+  
 
   if (success)
     DEBUGP (("X509 certificate successfully verified and matches host %s\n",