dtls: Add preferences for client/server CID length

Add preferences for default client and server Connection ID length
to be used when Client Hello and Server Hello is missing.

Allocate buffer for AAD in packet scope to remove the need for
buffers with the size of DTLS_MAX_CID_LENGTH.

Fixes #17701.

1 files changed, 18 insertions, 21 deletions

diff --git a/epan/dissectors/packet-tls-utils.c b/epan/dissectors/packet-tls-utils.c
index 3cc3a65f1c..aaa5f4854f 100644
--- a/epan/dissectors/packet-tls-utils.c
+++ b/epan/dissectors/packet-tls-utils.c
@@ -4664,6 +4664,8 @@ tls_decrypt_aead_record(SslDecryptSession *ssl, SslDecoder *decoder,
     const guint8    draft_version = ssl->session.tls13_draft_version;
     const guchar   *auth_tag_wire;
     guchar          auth_tag_calc[16];
+    guchar         *aad = NULL;
+    guint           aad_len = 0;
 #else
     guchar          nonce_with_counter[16] = { 0 };
 #endif
@@ -4774,10 +4776,9 @@ tls_decrypt_aead_record(SslDecryptSession *ssl, SslDecoder *decoder,
 
     /* (D)TLS 1.2 needs specific AAD, TLS 1.3 (before -25) uses empty AAD. */
     if (is_cid) { /* if connection ID */
-        guchar aad[23+DTLS_MAX_CID_LENGTH];
-        guint aad_len;
         if (ssl->session.deprecated_cid) {
-            aad_len = 13 + 1 + cidl;
+            aad_len = 14 + cidl;
+            aad = wmem_alloc(wmem_packet_scope(), aad_len);
             phton64(aad, decoder->seq);         /* record sequence number */
             phton16(aad, decoder->epoch);       /* DTLS 1.2 includes epoch. */
             aad[8] = ct;                        /* TLSCompressed.type */
@@ -4786,7 +4787,8 @@ tls_decrypt_aead_record(SslDecryptSession *ssl, SslDecoder *decoder,
             aad[11 + cidl] = cidl;              /* cid_length */
             phton16(aad + 12 + cidl, ciphertext_len);  /* TLSCompressed.length */
         } else {
-            aad_len = 13 + 8 + 1 + 1 + cidl;
+            aad_len = 23 + cidl;
+            aad = wmem_alloc(wmem_packet_scope(), aad_len);
             memset(aad, 0xFF, 8);               /* seq_num_placeholder */
             aad[8] = ct;                        /* TLSCompressed.type */
             aad[9] = cidl;                      /* cid_length */
@@ -4797,14 +4799,9 @@ tls_decrypt_aead_record(SslDecryptSession *ssl, SslDecoder *decoder,
             memcpy(aad + 21, cid, cidl);        /* cid */
             phton16(aad + 21 + cidl, ciphertext_len);  /* TLSCompressed.length */
         }
-        ssl_print_data("AAD", aad, aad_len);
-        err = gcry_cipher_authenticate(decoder->evp, aad, aad_len);
-        if (err) {
-            ssl_debug_printf("%s failed to set AAD: %s\n", G_STRFUNC, gcry_strerror(err));
-            return FALSE;
-        }
     } else if (is_v12) {
-        guchar aad[13];
+        aad_len = 13;
+        aad = wmem_alloc(wmem_packet_scope(), aad_len);
         phton64(aad, decoder->seq);         /* record sequence number */
         if (version == DTLSV1DOT2_VERSION) {
             phton16(aad, decoder->epoch);   /* DTLS 1.2 includes epoch. */
@@ -4812,19 +4809,17 @@ tls_decrypt_aead_record(SslDecryptSession *ssl, SslDecoder *decoder,
         aad[8] = ct;                        /* TLSCompressed.type */
         phton16(aad + 9, record_version);   /* TLSCompressed.version */
         phton16(aad + 11, ciphertext_len);  /* TLSCompressed.length */
-        ssl_print_data("AAD", aad, sizeof(aad));
-        err = gcry_cipher_authenticate(decoder->evp, aad, sizeof(aad));
-        if (err) {
-            ssl_debug_printf("%s failed to set AAD: %s\n", G_STRFUNC, gcry_strerror(err));
-            return FALSE;
-        }
     } else if (draft_version >= 25 || draft_version == 0) {
-        guchar aad[5];
+        aad_len = 5;
+        aad = wmem_alloc(wmem_packet_scope(), aad_len);
         aad[0] = ct;                        /* TLSCiphertext.opaque_type (23) */
         phton16(aad + 1, record_version);   /* TLSCiphertext.legacy_record_version (0x0303) */
         phton16(aad + 3, inl);              /* TLSCiphertext.length */
-        ssl_print_data("AAD", aad, sizeof(aad));
-        err = gcry_cipher_authenticate(decoder->evp, aad, sizeof(aad));
+    }
+
+    if (aad && aad_len > 0) {
+        ssl_print_data("AAD", aad, aad_len);
+        err = gcry_cipher_authenticate(decoder->evp, aad, aad_len);
         if (err) {
             ssl_debug_printf("%s failed to set AAD: %s\n", G_STRFUNC, gcry_strerror(err));
             return FALSE;
@@ -5433,7 +5428,7 @@ int
 ssl_packet_from_server(SslSession *session, dissector_table_t table, packet_info *pinfo)
 {
     gint ret;
-    if (session->srv_addr.type != AT_NONE) {
+    if (session && session->srv_addr.type != AT_NONE) {
         ret = (session->srv_ptype == pinfo->ptype) &&
               (session->srv_port == pinfo->srcport) &&
               addresses_equal(&session->srv_addr, &pinfo->src);
@@ -8498,9 +8493,11 @@ ssl_dissect_hnd_hello_ext_connection_id(ssl_common_dissect_t *hf, tvbuff_t *tvb,
 
     switch (hnd_type) {
     case SSL_HND_CLIENT_HELLO:
+        session->client_cid_len_present = TRUE;
         return ssl_dissect_ext_connection_id(hf, tvb, pinfo, tree, offset, ssl,
                                              cidl, &session->client_cid, &session->client_cid_len);
     case SSL_HND_SERVER_HELLO:
+        session->server_cid_len_present = TRUE;
         return ssl_dissect_ext_connection_id(hf, tvb, pinfo, tree, offset, ssl,
                                              cidl, &session->server_cid, &session->server_cid_len);
     default: