Split configuration of TLSv1.3 ciphers from older ciphers

With the current mechanism, old cipher strings that used to work in 1.1.0,
may inadvertently disable all TLSv1.3 ciphersuites causing connections to
fail. This is confusing for users.

In reality TLSv1.3 are quite different to older ciphers. They are much
simpler and there are only a small number of them so, arguably, they don't
need the same level of control that the older ciphers have.

This change splits the configuration of TLSv1.3 ciphers from older ones.
By default the TLSv1.3 ciphers are on, so you cannot inadvertently disable
them through your existing config.

Fixes #5359

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5392)

1 files changed, 117 insertions, 5 deletions

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 0814fb362b..a4e7374969 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -653,7 +653,9 @@ int SSL_CTX_set_ssl_version(SSL_CTX *ctx, const SSL_METHOD *meth)
 
     ctx->method = meth;
 
-    sk = ssl_create_cipher_list(ctx->method, &(ctx->cipher_list),
+    sk = ssl_create_cipher_list(ctx->method,
+                                ctx->tls13_ciphersuites,
+                                &(ctx->cipher_list),
                                 &(ctx->cipher_list_by_id),
                                 SSL_DEFAULT_CIPHER_LIST, ctx->cert);
     if ((sk == NULL) || (sk_SSL_CIPHER_num(sk) <= 0)) {
@@ -712,6 +714,11 @@ SSL *SSL_new(SSL_CTX *ctx)
     s->max_cert_list = ctx->max_cert_list;
     s->max_early_data = ctx->max_early_data;
 
+    /* Shallow copy of the ciphersuites stack */
+    s->tls13_ciphersuites = sk_SSL_CIPHER_dup(ctx->tls13_ciphersuites);
+    if (s->tls13_ciphersuites == NULL)
+        goto err;
+
     /*
      * Earlier library versions used to copy the pointer to the CERT, not
      * its contents; only when setting new parameters for the per-SSL
@@ -1156,6 +1163,7 @@ void SSL_free(SSL *s)
     /* add extra stuff */
     sk_SSL_CIPHER_free(s->cipher_list);
     sk_SSL_CIPHER_free(s->cipher_list_by_id);
+    sk_SSL_CIPHER_free(s->tls13_ciphersuites);
 
     /* Make the next call work :-) */
     if (s->session != NULL) {
@@ -2520,8 +2528,9 @@ int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str)
 {
     STACK_OF(SSL_CIPHER) *sk;
 
-    sk = ssl_create_cipher_list(ctx->method, &ctx->cipher_list,
-                                &ctx->cipher_list_by_id, str, ctx->cert);
+    sk = ssl_create_cipher_list(ctx->method, ctx->tls13_ciphersuites,
+                                &ctx->cipher_list, &ctx->cipher_list_by_id, str,
+                                ctx->cert);
     /*
      * ssl_create_cipher_list may return an empty stack if it was unable to
      * find a cipher matching the given rule string (for example if the rule
@@ -2543,8 +2552,9 @@ int SSL_set_cipher_list(SSL *s, const char *str)
 {
     STACK_OF(SSL_CIPHER) *sk;
 
-    sk = ssl_create_cipher_list(s->ctx->method, &s->cipher_list,
-                                &s->cipher_list_by_id, str, s->cert);
+    sk = ssl_create_cipher_list(s->ctx->method, s->tls13_ciphersuites,
+                                &s->cipher_list, &s->cipher_list_by_id, str,
+                                s->cert);
     /* see comment in SSL_CTX_set_cipher_list */
     if (sk == NULL)
         return 0;
@@ -2555,6 +2565,99 @@ int SSL_set_cipher_list(SSL *s, const char *str)
     return 1;
 }
 
+static int ciphersuite_cb(const char *elem, int len, void *arg)
+{
+    STACK_OF(SSL_CIPHER) *ciphersuites = (STACK_OF(SSL_CIPHER) *)arg;
+    const SSL_CIPHER *cipher;
+    /* Arbitrary sized temp buffer for the cipher name. Should be big enough */
+    char name[80];
+
+    if (len > (int)(sizeof(name) - 1)) {
+        SSLerr(SSL_F_CIPHERSUITE_CB, SSL_R_NO_CIPHER_MATCH);
+        return 0;
+    }
+
+    memcpy(name, elem, len);
+    name[len] = '\0';
+
+    cipher = ssl3_get_cipher_by_std_name(name);
+    if (cipher == NULL) {
+        SSLerr(SSL_F_CIPHERSUITE_CB, SSL_R_NO_CIPHER_MATCH);
+        return 0;
+    }
+
+    if (!sk_SSL_CIPHER_push(ciphersuites, cipher)) {
+        SSLerr(SSL_F_CIPHERSUITE_CB, ERR_R_INTERNAL_ERROR);
+        return 0;
+    }
+
+    return 1;
+}
+
+static int set_ciphersuites(STACK_OF(SSL_CIPHER) **currciphers, const char *str)
+{
+    STACK_OF(SSL_CIPHER) *newciphers = sk_SSL_CIPHER_new_null();
+
+    if (newciphers == NULL)
+        return 0;
+
+    /* Parse the list. We explicitly allow an empty list */
+    if (*str != '\0'
+            && !CONF_parse_list(str, ':', 1, ciphersuite_cb, newciphers)) {
+        sk_SSL_CIPHER_free(newciphers);
+        return 0;
+    }
+    sk_SSL_CIPHER_free(*currciphers);
+    *currciphers = newciphers;
+
+    return 1;
+}
+
+static int update_cipher_list(STACK_OF(SSL_CIPHER) *cipher_list,
+                              STACK_OF(SSL_CIPHER) *tls13_ciphersuites)
+{
+    int i;
+
+    /*
+     * Delete any existing TLSv1.3 ciphersuites. These are always first in the
+     * list.
+     */
+    while (sk_SSL_CIPHER_num(cipher_list) > 0
+           && sk_SSL_CIPHER_value(cipher_list, 0)->min_tls == TLS1_3_VERSION)
+        sk_SSL_CIPHER_delete(cipher_list, 0);
+
+    /* Insert the new TLSv1.3 ciphersuites */
+    for (i = 0; i < sk_SSL_CIPHER_num(tls13_ciphersuites); i++)
+        sk_SSL_CIPHER_insert(cipher_list,
+                             sk_SSL_CIPHER_value(tls13_ciphersuites, i), i);
+
+    return 1;
+}
+
+int SSL_CTX_set_ciphersuites(SSL_CTX *ctx, const char *str)
+{
+    int ret = set_ciphersuites(&(ctx->tls13_ciphersuites), str);
+
+    if (ret && ctx->cipher_list != NULL) {
+        /* We already have a cipher_list, so we need to update it */
+        return update_cipher_list(ctx->cipher_list, ctx->tls13_ciphersuites);
+    }
+
+    return ret;
+}
+
+int SSL_set_ciphersuites(SSL *s, const char *str)
+{
+    int ret = set_ciphersuites(&(s->tls13_ciphersuites), str);
+
+    if (ret && s->cipher_list != NULL) {
+        /* We already have a cipher_list, so we need to update it */
+        return update_cipher_list(s->cipher_list, s->tls13_ciphersuites);
+    }
+
+    return ret;
+}
+
 char *SSL_get_shared_ciphers(const SSL *s, char *buf, int len)
 {
     char *p;
@@ -2915,7 +3018,15 @@ SSL_CTX *SSL_CTX_new(const SSL_METHOD *meth)
     if (ret->ctlog_store == NULL)
         goto err;
 #endif
+
+    if (!SSL_CTX_set_ciphersuites(ret,
+            "TLS_AES_256_GCM_SHA384:"
+            "TLS_CHACHA20_POLY1305_SHA256:"
+            "TLS_AES_128_GCM_SHA256"))
+        goto err;
+
     if (!ssl_create_cipher_list(ret->method,
+                                ret->tls13_ciphersuites,
                                 &ret->cipher_list, &ret->cipher_list_by_id,
                                 SSL_DEFAULT_CIPHER_LIST, ret->cert)
         || sk_SSL_CIPHER_num(ret->cipher_list) <= 0) {
@@ -3075,6 +3186,7 @@ void SSL_CTX_free(SSL_CTX *a)
 #endif
     sk_SSL_CIPHER_free(a->cipher_list);
     sk_SSL_CIPHER_free(a->cipher_list_by_id);
+    sk_SSL_CIPHER_free(a->tls13_ciphersuites);
     ssl_cert_free(a->cert);
     sk_X509_NAME_pop_free(a->ca_names, X509_NAME_free);
     sk_X509_pop_free(a->extra_certs, X509_free);