Rework the decrypt ticket callback

Don't call the decrypt ticket callback if we've already encountered a
fatal error. Do call it if we have an empty ticket present.

Change the return code to have 5 distinct returns codes and separate it
from the input status value.

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6198)

5 files changed, 108 insertions, 56 deletions

diff --git a/ssl/ssl_locl.h b/ssl/ssl_locl.h
index b32b23bedf..c066e14b70 100644
--- a/ssl/ssl_locl.h
+++ b/ssl/ssl_locl.h
@@ -2473,9 +2473,9 @@ void tls1_get_supported_groups(SSL *s, const uint16_t **pgroups,
 
 __owur int tls1_set_server_sigalgs(SSL *s);
 
-__owur SSL_TICKET_RETURN tls_get_ticket_from_client(SSL *s, CLIENTHELLO_MSG *hello,
+__owur SSL_TICKET_STATUS tls_get_ticket_from_client(SSL *s, CLIENTHELLO_MSG *hello,
                                                     SSL_SESSION **ret);
-__owur SSL_TICKET_RETURN tls_decrypt_ticket(SSL *s, const unsigned char *etick,
+__owur SSL_TICKET_STATUS tls_decrypt_ticket(SSL *s, const unsigned char *etick,
                                             size_t eticklen,
                                             const unsigned char *sess_id,
                                             size_t sesslen, SSL_SESSION **psess);
diff --git a/ssl/ssl_sess.c b/ssl/ssl_sess.c
index f936cb687f..541f82a851 100644
--- a/ssl/ssl_sess.c
+++ b/ssl/ssl_sess.c
@@ -485,9 +485,14 @@ int ssl_get_prev_session(SSL *s, CLIENTHELLO_MSG *hello)
     SSL_SESSION *ret = NULL;
     int fatal = 0, discard;
     int try_session_cache = 0;
-    SSL_TICKET_RETURN r;
+    SSL_TICKET_STATUS r;
 
     if (SSL_IS_TLS13(s)) {
+        /*
+         * By default we will send a new ticket. This can be overridden in the
+         * ticket processing.
+         */
+        s->ext.ticket_expected = 1;
         if (!tls_parse_extension(s, TLSEXT_IDX_psk_kex_modes,
                                  SSL_EXT_CLIENT_HELLO, hello->pre_proc_exts,
                                  NULL, 0)
diff --git a/ssl/statem/extensions_srvr.c b/ssl/statem/extensions_srvr.c
index adf63d80bf..ec4e1b8139 100644
--- a/ssl/statem/extensions_srvr.c
+++ b/ssl/statem/extensions_srvr.c
@@ -1030,6 +1030,7 @@ int tls_parse_ctos_psk(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
         return 0;
     }
 
+    s->ext.ticket_expected = 0;
     for (id = 0; PACKET_remaining(&identities) != 0; id++) {
         PACKET identity;
         unsigned long ticket_agel;
@@ -1127,9 +1128,17 @@ int tls_parse_ctos_psk(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
                 s->ext.early_data_ok = 1;
         } else {
             uint32_t ticket_age = 0, now, agesec, agems;
-            int ret = tls_decrypt_ticket(s, PACKET_data(&identity),
-                                         PACKET_remaining(&identity), NULL, 0,
-                                         &sess);
+            int ret;
+
+            ret = tls_decrypt_ticket(s, PACKET_data(&identity),
+                                     PACKET_remaining(&identity), NULL, 0,
+                                     &sess);
+
+            if (ret == SSL_TICKET_EMPTY) {
+                SSLfatal(s, SSL_AD_DECODE_ERROR, SSL_F_TLS_PARSE_CTOS_PSK,
+                         SSL_R_BAD_EXTENSION);
+                return 0;
+            }
 
             if (ret == SSL_TICKET_FATAL_ERR_MALLOC
                     || ret == SSL_TICKET_FATAL_ERR_OTHER) {
@@ -1137,7 +1146,7 @@ int tls_parse_ctos_psk(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
                          SSL_F_TLS_PARSE_CTOS_PSK, ERR_R_INTERNAL_ERROR);
                 return 0;
             }
-            if (ret == SSL_TICKET_NO_DECRYPT)
+            if (ret == SSL_TICKET_NONE || ret == SSL_TICKET_NO_DECRYPT)
                 continue;
 
             /* Check for replay */
diff --git a/ssl/statem/statem_srvr.c b/ssl/statem/statem_srvr.c
index 3f56ff1389..22786bed13 100644
--- a/ssl/statem/statem_srvr.c
+++ b/ssl/statem/statem_srvr.c
@@ -489,10 +489,10 @@ static WRITE_TRAN ossl_statem_server13_write_transition(SSL *s)
         st->hand_state = TLS_ST_SW_SESSION_TICKET;
         if (s->post_handshake_auth == SSL_PHA_REQUESTED) {
             s->post_handshake_auth = SSL_PHA_EXT_RECEIVED;
-        } else if (s->hit && !s->ext.ticket_expected) {
+        } else if (!s->ext.ticket_expected) {
             /*
-             * If we resumed and we're not going to renew the ticket then we
-             * just finish the handshake at this point.
+             * If we're not going to renew the ticket then we just finish the
+             * handshake at this point.
              */
             st->hand_state = TLS_ST_OK;
         }
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 2e8de7a09c..b312a14fab 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -1194,20 +1194,8 @@ int tls1_set_server_sigalgs(SSL *s)
  *   hello: The parsed ClientHello data
  *   ret: (output) on return, if a ticket was decrypted, then this is set to
  *       point to the resulting session.
- *
- * If s->tls_session_secret_cb is set then we are expecting a pre-shared key
- * ciphersuite, in which case we have no use for session tickets and one will
- * never be decrypted, nor will s->ext.ticket_expected be set to 1.
- *
- * Side effects:
- *   Sets s->ext.ticket_expected to 1 if the server will have to issue
- *   a new session ticket to the client because the client indicated support
- *   (and s->tls_session_secret_cb is NULL) but the client either doesn't have
- *   a session ticket or we couldn't use the one it gave us, or if
- *   s->ctx->ext.ticket_key_cb asked to renew the client's ticket.
- *   Otherwise, s->ext.ticket_expected is set to 0.
  */
-SSL_TICKET_RETURN tls_get_ticket_from_client(SSL *s, CLIENTHELLO_MSG *hello,
+SSL_TICKET_STATUS tls_get_ticket_from_client(SSL *s, CLIENTHELLO_MSG *hello,
                                              SSL_SESSION **ret)
 {
     size_t size;
@@ -1229,23 +1217,6 @@ SSL_TICKET_RETURN tls_get_ticket_from_client(SSL *s, CLIENTHELLO_MSG *hello,
         return SSL_TICKET_NONE;
 
     size = PACKET_remaining(&ticketext->data);
-    if (size == 0) {
-        /*
-         * The client will accept a ticket but doesn't currently have
-         * one.
-         */
-        s->ext.ticket_expected = 1;
-        return SSL_TICKET_EMPTY;
-    }
-    if (s->ext.session_secret_cb) {
-        /*
-         * Indicate that the ticket couldn't be decrypted rather than
-         * generating the session from ticket now, trigger
-         * abbreviated handshake based on external mechanism to
-         * calculate the master secret later.
-         */
-        return SSL_TICKET_NO_DECRYPT;
-    }
 
     return tls_decrypt_ticket(s, PACKET_data(&ticketext->data), size,
                               hello->session_id, hello->session_id_len, ret);
@@ -1254,6 +1225,19 @@ SSL_TICKET_RETURN tls_get_ticket_from_client(SSL *s, CLIENTHELLO_MSG *hello,
 /*-
  * tls_decrypt_ticket attempts to decrypt a session ticket.
  *
+ * If s->tls_session_secret_cb is set and we're not doing TLSv1.3 then we are
+ * expecting a pre-shared key ciphersuite, in which case we have no use for
+ * session tickets and one will never be decrypted, nor will
+ * s->ext.ticket_expected be set to 1.
+ *
+ * Side effects:
+ *   Sets s->ext.ticket_expected to 1 if the server will have to issue
+ *   a new session ticket to the client because the client indicated support
+ *   (and s->tls_session_secret_cb is NULL) but the client either doesn't have
+ *   a session ticket or we couldn't use the one it gave us, or if
+ *   s->ctx->ext.ticket_key_cb asked to renew the client's ticket.
+ *   Otherwise, s->ext.ticket_expected is set to 0.
+ *
  *   etick: points to the body of the session ticket extension.
  *   eticklen: the length of the session tickets extension.
  *   sess_id: points at the session ID.
@@ -1261,21 +1245,40 @@ SSL_TICKET_RETURN tls_get_ticket_from_client(SSL *s, CLIENTHELLO_MSG *hello,
  *   psess: (output) on return, if a ticket was decrypted, then this is set to
  *       point to the resulting session.
  */
-SSL_TICKET_RETURN tls_decrypt_ticket(SSL *s, const unsigned char *etick,
+SSL_TICKET_STATUS tls_decrypt_ticket(SSL *s, const unsigned char *etick,
                                      size_t eticklen, const unsigned char *sess_id,
                                      size_t sesslen, SSL_SESSION **psess)
 {
-    SSL_SESSION *sess;
+    SSL_SESSION *sess = NULL;
     unsigned char *sdec;
     const unsigned char *p;
     int slen, renew_ticket = 0, declen;
-    SSL_TICKET_RETURN ret = SSL_TICKET_FATAL_ERR_OTHER;
+    SSL_TICKET_STATUS ret = SSL_TICKET_FATAL_ERR_OTHER;
     size_t mlen;
     unsigned char tick_hmac[EVP_MAX_MD_SIZE];
     HMAC_CTX *hctx = NULL;
     EVP_CIPHER_CTX *ctx = NULL;
     SSL_CTX *tctx = s->session_ctx;
 
+    if (eticklen == 0) {
+        /*
+         * The client will accept a ticket but doesn't currently have
+         * one (TLSv1.2 and below), or treated as a fatal error in TLSv1.3
+         */
+        ret = SSL_TICKET_EMPTY;
+        goto end;
+    }
+    if (!SSL_IS_TLS13(s) && s->ext.session_secret_cb) {
+        /*
+         * Indicate that the ticket couldn't be decrypted rather than
+         * generating the session from ticket now, trigger
+         * abbreviated handshake based on external mechanism to
+         * calculate the master secret later.
+         */
+        ret = SSL_TICKET_NO_DECRYPT;
+        goto end;
+    }
+
     /* Need at least keyname + iv */
     if (eticklen < TLSEXT_KEYNAME_LENGTH + EVP_MAX_IV_LENGTH) {
         ret = SSL_TICKET_NO_DECRYPT;
@@ -1394,7 +1397,6 @@ SSL_TICKET_RETURN tls_decrypt_ticket(SSL *s, const unsigned char *etick,
             memcpy(sess->session_id, sess_id, sesslen);
             sess->session_id_length = sesslen;
         }
-        *psess = sess;
         if (renew_ticket)
             ret = SSL_TICKET_SUCCESS_RENEW;
         else
@@ -1412,18 +1414,56 @@ SSL_TICKET_RETURN tls_decrypt_ticket(SSL *s, const unsigned char *etick,
     HMAC_CTX_free(hctx);
 
     /*
-     * If set, the decrypt_ticket_cb() is always called regardless of the
-     * return value determined above. The callback is responsible for checking
-     * |ret| before it performs any action
+     * If set, the decrypt_ticket_cb() is called unless a fatal error was
+     * detected above. The callback is responsible for checking |ret| before it
+     * performs any action
      */
-    if (s->session_ctx->decrypt_ticket_cb != NULL) {
+    if (s->session_ctx->decrypt_ticket_cb != NULL
+            && (ret == SSL_TICKET_EMPTY
+                || ret == SSL_TICKET_NO_DECRYPT
+                || ret == SSL_TICKET_SUCCESS
+                || ret == SSL_TICKET_SUCCESS_RENEW)) {
         size_t keyname_len = eticklen;
+        int retcb;
 
         if (keyname_len > TLSEXT_KEYNAME_LENGTH)
             keyname_len = TLSEXT_KEYNAME_LENGTH;
-        ret = s->session_ctx->decrypt_ticket_cb(s, *psess, etick, keyname_len,
-                                                ret,
-                                                s->session_ctx->ticket_cb_data);
+        retcb = s->session_ctx->decrypt_ticket_cb(s, sess, etick, keyname_len,
+                                                  ret,
+                                                  s->session_ctx->ticket_cb_data);
+        switch (retcb) {
+        case SSL_TICKET_RETURN_ABORT:
+            ret = SSL_TICKET_FATAL_ERR_OTHER;
+            break;
+
+        case SSL_TICKET_RETURN_IGNORE:
+            ret = SSL_TICKET_NONE;
+            SSL_SESSION_free(sess);
+            sess = NULL;
+            break;
+
+        case SSL_TICKET_RETURN_IGNORE_RENEW:
+            if (ret != SSL_TICKET_EMPTY && ret != SSL_TICKET_NO_DECRYPT)
+                ret = SSL_TICKET_NO_DECRYPT;
+            /* else the value of |ret| will already do the right thing */
+            SSL_SESSION_free(sess);
+            sess = NULL;
+            break;
+
+        case SSL_TICKET_RETURN_USE:
+        case SSL_TICKET_RETURN_USE_RENEW:
+            if (ret != SSL_TICKET_SUCCESS
+                    && ret != SSL_TICKET_SUCCESS_RENEW)
+                ret = SSL_TICKET_FATAL_ERR_OTHER;
+            else if (retcb == SSL_TICKET_RETURN_USE)
+                ret = SSL_TICKET_SUCCESS;
+            else
+                ret = SSL_TICKET_SUCCESS_RENEW;
+            break;
+
+        default:
+            ret = SSL_TICKET_FATAL_ERR_OTHER;
+        }
     }
 
     switch (ret) {
@@ -1431,13 +1471,11 @@ SSL_TICKET_RETURN tls_decrypt_ticket(SSL *s, const unsigned char *etick,
     case SSL_TICKET_SUCCESS_RENEW:
     case SSL_TICKET_EMPTY:
         s->ext.ticket_expected = 1;
-        /* Fall through */
-    case SSL_TICKET_SUCCESS:
-    case SSL_TICKET_NONE:
-        return ret;
     }
 
-    return SSL_TICKET_FATAL_ERR_OTHER;
+    *psess = sess;
+
+    return ret;
 }
 
 /* Check to see if a signature algorithm is allowed */