diff options
Diffstat (limited to 'ssl')
| -rw-r--r-- | ssl/statem/extensions.c | 28 |
1 files changed, 27 insertions, 1 deletions
diff --git a/ssl/statem/extensions.c b/ssl/statem/extensions.c index 505337a44a..f0f5a02124 100644 --- a/ssl/statem/extensions.c +++ b/ssl/statem/extensions.c @@ -160,8 +160,34 @@ static const EXTENSION_DEFINITION ext_defs[] = { final_ec_pt_formats }, { + /* + * "supported_groups" is spread across several specifications. + * It was originally specified as "elliptic_curves" in RFC 4492, + * and broadened to include named FFDH groups by RFC 7919. + * Both RFCs 4492 and 7919 do not include a provision for the server + * to indicate to the client the complete list of groups supported + * by the server, with the server instead just indicating the + * selected group for this connection in the ServerKeyExchange + * message. TLS 1.3 adds a scheme for the server to indicate + * to the client its list of supported groups in the + * EncryptedExtensions message, but none of the relevant + * specifications permit sending supported_groups in the ServerHello. + * Nonetheless (possibly due to the close proximity to the + * "ec_point_formats" extension, which is allowed in the ServerHello), + * there are several servers that send this extension in the + * ServerHello anyway. Up to and including the 1.1.0 release, + * we did not check for the presence of nonpermitted extensions, + * so to avoid a regression, we must permit this extension in the + * TLS 1.2 ServerHello as well. + * + * Note that there is no tls_parse_stoc_supported_groups function, + * so we do not perform any additional parsing, validation, or + * processing on the server's group list -- this is just a minimal + * change to preserve compatibility with these misbehaving servers. + */ TLSEXT_TYPE_supported_groups, - SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS, + SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS + | SSL_EXT_TLS1_2_SERVER_HELLO, NULL, tls_parse_ctos_supported_groups, NULL, tls_construct_stoc_supported_groups, tls_construct_ctos_supported_groups, NULL |