Introduce SSL_CTX_set_stateless_cookie_{generate,verify}_cb

These functions are similar to SSL_CTX_set_cookie_{generate,verify}_cb,
but used for the application-controlled portion of TLS1.3 stateless
handshake cookies rather than entire DTLSv1 cookies.

Reviewed-by: Ben Kaduk <kaduk@mit.edu>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5463)

3 files changed, 31 insertions, 6 deletions

diff --git a/ssl/ssl_locl.h b/ssl/ssl_locl.h
index 9eb58342a8..246605c81e 100644
--- a/ssl/ssl_locl.h
+++ b/ssl/ssl_locl.h
@@ -820,6 +820,14 @@ struct ssl_ctx_st {
     int (*app_verify_cookie_cb) (SSL *ssl, const unsigned char *cookie,
                                  unsigned int cookie_len);
 
+    /* TLS1.3 app-controlled cookie generate callback */
+    int (*gen_stateless_cookie_cb) (SSL *ssl, unsigned char *cookie,
+                                    size_t *cookie_len);
+
+    /* TLS1.3 verify app-controlled cookie callback */
+    int (*verify_stateless_cookie_cb) (SSL *ssl, const unsigned char *cookie,
+                                       size_t cookie_len);
+
     CRYPTO_EX_DATA ex_data;
 
     const EVP_MD *md5;          /* For SSLv3/TLSv1 'ssl3-md5' */
diff --git a/ssl/ssl_sess.c b/ssl/ssl_sess.c
index f78c9cde5f..1873237c70 100644
--- a/ssl/ssl_sess.c
+++ b/ssl/ssl_sess.c
@@ -1301,4 +1301,22 @@ int SSL_SESSION_get0_ticket_appdata(SSL_SESSION *ss, void **data, size_t *len)
     return 1;
 }
 
+void SSL_CTX_set_stateless_cookie_generate_cb(
+    SSL_CTX *ctx,
+    int (*cb) (SSL *ssl,
+               unsigned char *cookie,
+               size_t *cookie_len))
+{
+    ctx->gen_stateless_cookie_cb = cb;
+}
+
+void SSL_CTX_set_stateless_cookie_verify_cb(
+    SSL_CTX *ctx,
+    int (*cb) (SSL *ssl,
+               const unsigned char *cookie,
+               size_t cookie_len))
+{
+    ctx->verify_stateless_cookie_cb = cb;
+}
+
 IMPLEMENT_PEM_rw(SSL_SESSION, SSL_SESSION, PEM_STRING_SSL_SESSION, SSL_SESSION)
diff --git a/ssl/statem/extensions_srvr.c b/ssl/statem/extensions_srvr.c
index 74acdb2d21..425cd80efe 100644
--- a/ssl/statem/extensions_srvr.c
+++ b/ssl/statem/extensions_srvr.c
@@ -729,7 +729,7 @@ int tls_parse_ctos_cookie(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
     unsigned long tm, now;
 
     /* Ignore any cookie if we're not set up to verify it */
-    if (s->ctx->app_verify_cookie_cb == NULL
+    if (s->ctx->verify_stateless_cookie_cb == NULL
             || (s->s3->flags & TLS1_FLAGS_STATELESS) == 0)
         return 1;
 
@@ -852,7 +852,7 @@ int tls_parse_ctos_cookie(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
     }
 
     /* Verify the app cookie */
-    if (s->ctx->app_verify_cookie_cb(s, PACKET_data(&appcookie),
+    if (s->ctx->verify_stateless_cookie_cb(s, PACKET_data(&appcookie),
                                      PACKET_remaining(&appcookie)) == 0) {
         SSLfatal(s, SSL_AD_ILLEGAL_PARAMETER, SSL_F_TLS_PARSE_CTOS_COOKIE,
                  SSL_R_COOKIE_MISMATCH);
@@ -1676,8 +1676,7 @@ EXT_RETURN tls_construct_stoc_cookie(SSL *s, WPACKET *pkt, unsigned int context,
 {
     unsigned char *hashval1, *hashval2, *appcookie1, *appcookie2, *cookie;
     unsigned char *hmac, *hmac2;
-    size_t startlen, ciphlen, totcookielen, hashlen, hmaclen;
-    unsigned int appcookielen;
+    size_t startlen, ciphlen, totcookielen, hashlen, hmaclen, appcookielen;
     EVP_MD_CTX *hctx;
     EVP_PKEY *pkey;
     int ret = EXT_RETURN_FAIL;
@@ -1685,7 +1684,7 @@ EXT_RETURN tls_construct_stoc_cookie(SSL *s, WPACKET *pkt, unsigned int context,
     if ((s->s3->flags & TLS1_FLAGS_STATELESS) == 0)
         return EXT_RETURN_NOT_SENT;
 
-    if (s->ctx->app_gen_cookie_cb == NULL) {
+    if (s->ctx->gen_stateless_cookie_cb == NULL) {
         SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_TLS_CONSTRUCT_STOC_COOKIE,
                  SSL_R_NO_COOKIE_CALLBACK_SET);
         return EXT_RETURN_FAIL;
@@ -1733,7 +1732,7 @@ EXT_RETURN tls_construct_stoc_cookie(SSL *s, WPACKET *pkt, unsigned int context,
     }
 
     /* Generate the application cookie */
-    if (s->ctx->app_gen_cookie_cb(s, appcookie1, &appcookielen) == 0) {
+    if (s->ctx->gen_stateless_cookie_cb(s, appcookie1, &appcookielen) == 0) {
         SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_TLS_CONSTRUCT_STOC_COOKIE,
                  SSL_R_COOKIE_GEN_CALLBACK_FAILURE);
         return EXT_RETURN_FAIL;