commit a57dcfb69c475b13f8675f6bfbe2f2cf8dad3667
author Matthew Braithwaite <mab@google.com> Fri Feb 17 22:08:23 2017 -0800
committer Matt Braithwaite <mab@google.com> Wed Feb 22 00:09:27 2017 +0000
tree 8ad2d291ee4d13ae7c9a6cbb105dc54aea10120a
parent c4796c92e0aced2342ed5687201aea07189c3bc1

Add new cipherlist-setting APIs that reject nonsense.

The new APIs are SSL_CTX_set_strict_cipher_list() and
SSL_set_strict_cipher_list().  They have two motivations:

First, typos in cipher lists can go undetected for a long time, and
can have surprising consequences when silently ignored.

Second, there is a tendency to use superstition in the construction of
cipher lists, for example by "turning off" things that do not actually
exist.  This leads to the corrosive belief that DEFAULT and ALL ought
not to be trusted.  This belief is false.

Change-Id: I42909b69186e0b4cf45457e5c0bc968f6bbf231a
Reviewed-on: https://boringssl-review.googlesource.com/13925
Commit-Queue: Matt Braithwaite <mab@google.com>
Reviewed-by: Matt Braithwaite <mab@google.com>

ssl/ssl_lib.c

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index d0151bb..e37f9f9 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -277,7 +277,7 @@
   }
 
   ssl_create_cipher_list(ret->method, &ret->cipher_list,
-                         SSL_DEFAULT_CIPHER_LIST);
+                         SSL_DEFAULT_CIPHER_LIST, 1 /* strict */);
   if (ret->cipher_list == NULL ||
       sk_SSL_CIPHER_num(ret->cipher_list->ciphers) <= 0) {
     OPENSSL_PUT_ERROR(SSL, SSL_R_LIBRARY_HAS_NO_CIPHERS);
@@ -1506,7 +1506,25 @@
 
 int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str) {
   STACK_OF(SSL_CIPHER) *cipher_list =
-      ssl_create_cipher_list(ctx->method, &ctx->cipher_list, str);
+      ssl_create_cipher_list(ctx->method, &ctx->cipher_list, str,
+                             0 /* not strict */);
+  if (cipher_list == NULL) {
+    return 0;
+  }
+
+  /* |ssl_create_cipher_list| may succeed but return an empty cipher list. */
+  if (sk_SSL_CIPHER_num(cipher_list) == 0) {
+    OPENSSL_PUT_ERROR(SSL, SSL_R_NO_CIPHER_MATCH);
+    return 0;
+  }
+
+  return 1;
+}
+
+int SSL_CTX_set_strict_cipher_list(SSL_CTX *ctx, const char *str) {
+  STACK_OF(SSL_CIPHER) *cipher_list =
+      ssl_create_cipher_list(ctx->method, &ctx->cipher_list, str,
+                             1 /* strict */);
   if (cipher_list == NULL) {
     return 0;
   }
@@ -1522,7 +1540,25 @@
 
 int SSL_set_cipher_list(SSL *ssl, const char *str) {
   STACK_OF(SSL_CIPHER) *cipher_list =
-      ssl_create_cipher_list(ssl->ctx->method, &ssl->cipher_list, str);
+      ssl_create_cipher_list(ssl->ctx->method, &ssl->cipher_list, str,
+                             0 /* not strict */);
+  if (cipher_list == NULL) {
+    return 0;
+  }
+
+  /* |ssl_create_cipher_list| may succeed but return an empty cipher list. */
+  if (sk_SSL_CIPHER_num(cipher_list) == 0) {
+    OPENSSL_PUT_ERROR(SSL, SSL_R_NO_CIPHER_MATCH);
+    return 0;
+  }
+
+  return 1;
+}
+
+int SSL_set_strict_cipher_list(SSL *ssl, const char *str) {
+  STACK_OF(SSL_CIPHER) *cipher_list =
+      ssl_create_cipher_list(ssl->ctx->method, &ssl->cipher_list, str,
+                             1 /* strict */);
   if (cipher_list == NULL) {
     return 0;
   }