Bug 3966: Add KeyEncipherment when ssl-bump substitues RSA for EC.

Libnss3, which is used by Firefox to verify the certificate chain, has
different requirements for RSA keys than it does for EC keys.  In particular,
RSA keys with the keyUsage extension, must set the KeyEncipherment flag.

This fix was brought to you by the Samizdat project.
http://samizdat.childrenofmay.org

diff --git a/src/ssl/gadgets.cc b/src/ssl/gadgets.cc
index c6f8d253a53107ccdf174b35a19a68125c86c15e..a740cf53fb0a79a4ad50f8fa7c4eafe783288181 100644 (file)
--- a/src/ssl/gadgets.cc
+++ b/src/ssl/gadgets.cc
@@ -263,11 +263,42 @@ mimicExtensions(Ssl::X509_Pointer & cert, Ssl::X509_Pointer const & mimicCert)
         0
     };
 
+    // key usage bit names
+    enum {
+        DigitalSignature,
+        NonRepudiation,
+        KeyEncipherment, // NSS requires for RSA but not EC
+        DataEncipherment,
+        KeyAgreement,
+        KeyCertificateSign,
+        CRLSign,
+        EncipherOnly,
+        DecipherOnly
+    };
+
+    int mimicAlgo = OBJ_obj2nid(mimicCert.get()->cert_info->key->algor->algorithm);
+
     int nid;
     for (int i = 0; (nid = extensions[i]) != 0; ++i) {
         const int pos = X509_get_ext_by_NID(mimicCert.get(), nid, -1);
-        if (X509_EXTENSION *ext = X509_get_ext(mimicCert.get(), pos))
+        if (X509_EXTENSION *ext = X509_get_ext(mimicCert.get(), pos)) {
+            // Mimic extension exactly.
             X509_add_ext(cert.get(), ext, -1);
+            if ( nid == NID_key_usage && mimicAlgo != NID_rsaEncryption ) {
+                // NSS does not requre the KeyEncipherment flag on EC keys
+                // but it does require it for RSA keys.  Since ssl-bump
+                // substitutes RSA keys for EC ones, we need to ensure that
+                // that the more stringent requirements are met.
+
+                const int p = X509_get_ext_by_NID(cert.get(), NID_key_usage, -1);
+                if ((ext = X509_get_ext(cert.get(), p)) != NULL) {
+                    ASN1_BIT_STRING *keyusage = (ASN1_BIT_STRING *)X509V3_EXT_d2i(ext);
+                    ASN1_BIT_STRING_set_bit(keyusage, KeyEncipherment, 1);
+                    X509_EXTENSION_set_data( ext, (ASN1_OCTET_STRING*)keyusage );
+                    ASN1_BIT_STRING_free(keyusage);
+                }
+            }
+        }
     }
 
     // We could also restrict mimicking of the CA extension to CA:FALSE