Rewrite EllipticCurves TLS extension handling using CBB/CBS and the new

extension framework.

input + ok jsing@

1 files changed, 120 insertions, 1 deletions

diff --git a/src/lib/libssl/ssl_tlsext.c b/src/lib/libssl/ssl_tlsext.c
index ad30f43389..c050224c70 100644
--- a/src/lib/libssl/ssl_tlsext.c
+++ b/src/lib/libssl/ssl_tlsext.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_tlsext.c,v 1.5 2017/08/11 06:30:41 jsing Exp $ */
+/* $OpenBSD: ssl_tlsext.c,v 1.6 2017/08/11 20:14:13 doug Exp $ */
 /*
  * Copyright (c) 2016, 2017 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2017 Doug Hogan <doug@openbsd.org>
@@ -21,6 +21,116 @@
 #include "bytestring.h"
 #include "ssl_tlsext.h"
 
+
+/*
+ * Supported Elliptic Curves - RFC 4492 section 5.1.1
+ */
+int
+tlsext_ec_clienthello_needs(SSL *s)
+{
+        return ssl_has_ecc_ciphers(s);
+}
+
+int
+tlsext_ec_clienthello_build(SSL *s, CBB *cbb)
+{
+        CBB curvelist;
+        size_t curves_len;
+        int i;
+        const uint16_t *curves;
+
+        tls1_get_curvelist(s, 0, &curves, &curves_len);
+
+        if (curves_len == 0) {
+                SSLerror(s, ERR_R_INTERNAL_ERROR);
+                return 0;
+        }
+
+        if (!CBB_add_u16_length_prefixed(cbb, &curvelist))
+                return 0;
+
+        for (i = 0; i < curves_len; i++) {
+                if (!CBB_add_u16(&curvelist, curves[i]))
+                        return 0;
+        }
+
+        if (!CBB_flush(cbb))
+                return 0;
+
+        return 1;
+}
+
+int
+tlsext_ec_clienthello_parse(SSL *s, CBS *cbs, int *alert)
+{
+        CBS curvelist;
+        size_t curves_len;
+
+        if (!CBS_get_u16_length_prefixed(cbs, &curvelist))
+                goto err;
+        if (CBS_len(cbs) != 0)
+                goto err;
+
+        curves_len = CBS_len(&curvelist);
+        if (curves_len == 0 || curves_len % 2 != 0)
+                goto err;
+        curves_len /= 2;
+
+        if (!s->internal->hit) {
+                int i;
+                uint16_t *curves;
+
+                if (SSI(s)->tlsext_supportedgroups != NULL)
+                        goto err;
+
+                if ((curves = reallocarray(NULL, curves_len,
+                    sizeof(uint16_t))) == NULL) {
+                        *alert = TLS1_AD_INTERNAL_ERROR;
+                        return 0;
+                }
+
+                for (i = 0; i < curves_len; i++) {
+                        if (!CBS_get_u16(&curvelist, &curves[i])) {
+                                free(curves);
+                                goto err;
+                        }
+                }
+
+                if (CBS_len(&curvelist) != 0) {
+                        free(curves);
+                        goto err;
+                }
+
+                SSI(s)->tlsext_supportedgroups = curves;
+                SSI(s)->tlsext_supportedgroups_length = curves_len;
+        }
+
+        return 1;
+
+ err:
+        *alert = TLS1_AD_DECODE_ERROR;
+        return 0;
+}
+
+/* This extension is never used by the server. */
+int
+tlsext_ec_serverhello_needs(SSL *s)
+{
+        return 0;
+}
+
+int
+tlsext_ec_serverhello_build(SSL *s, CBB *cbb)
+{
+        return 0;
+}
+
+int
+tlsext_ec_serverhello_parse(SSL *s, CBS *cbs, int *alert)
+{
+        return 0;
+}
+
 /*
  * Supported Point Formats Extension - RFC 4492 section 5.1.2
  */
@@ -420,6 +530,15 @@ static struct tls_extension tls_extensions[] = {
                 .serverhello_build = tlsext_ecpf_serverhello_build,
                 .serverhello_parse = tlsext_ecpf_serverhello_parse,
         },
+        {
+                .type = TLSEXT_TYPE_elliptic_curves,
+                .clienthello_needs = tlsext_ec_clienthello_needs,
+                .clienthello_build = tlsext_ec_clienthello_build,
+                .clienthello_parse = tlsext_ec_clienthello_parse,
+                .serverhello_needs = tlsext_ec_serverhello_needs,
+                .serverhello_build = tlsext_ec_serverhello_build,
+                .serverhello_parse = tlsext_ec_serverhello_parse,
+        },
 };
 
 #define N_TLS_EXTENSIONS (sizeof(tls_extensions) / sizeof(*tls_extensions))