Start of DTLS rekey support, clean up comments about protocol

diff --git a/anyconnect.h b/anyconnect.h
index c6fc7c5..2bb8989 100644 (file)
--- a/anyconnect.h
+++ b/anyconnect.h
@@ -65,6 +65,8 @@ struct anyconnect_info {
        SSL *dtls_ssl;
        int dtls_keepalive;
        int dtls_dpd;
+       int dtls_rekey;
+       time_t last_dtls_rekey;
        time_t last_dtls_tx;
        time_t last_dtls_rx;
        time_t last_dtls_dpd;

diff --git a/dtls.c b/dtls.c
index a06b775..a68690b 100644 (file)
--- a/dtls.c
+++ b/dtls.c
@@ -34,20 +34,23 @@
  * connection, are enough to 'resume' a DTLS session, bypassing all
  * the normal setup of a normal DTLS connection.
  *
- * This code works when run against Cisco's own libssl.so.0.9.8, but
- * fails (Bad Record MAC on receipt of the Server Hello) when run
- * against my own build of OpenSSL-0.9.8f.
+ * Cisco use a version of the protocol which predates RFC4347, but
+ * isn't quite the same as the pre-RFC version of the protocol which
+ * was in OpenSSL 0.9.8e -- it includes backports of some later
+ * OpenSSL patches.
  *
- * It lookslike they've reverted _some_ of the changes beween 0.9.8e
- * and 0.9.8f, but not all of them. In particular, they use
- * DTLS1_BAD_VER for the protocol version.
+ * The openssl/ directory of this source tree should contain both a 
+ * small patch against OpenSSL 0.9.8e to make it support Cisco's 
+ * snapshot of the protocol, and a larger patch against newer OpenSSL
+ * which gives us an option to use the old protocol again.
  *
- * Using OpenSSL-0.9.8e, which was the last release of OpenSSL to use
- * DTLS1_BAD_VER, also fails similarly.
- *
- * Hopefully they're just using something equivalent to a snapshot
- * between 0.9.8e and 0.9.8f, and they don't have their own "special"
- * changes on top.
+ * Cisco's server also seems to respond to the official version of the
+ * protocol, with a change in the ChangeCipherSpec packet which implies
+ * that it does know the difference and isn't just repeating the version
+ * number seen in the ClientHello. But although I can make the handshake
+ * complete by hacking tls1_mac() to use the _old_ protocol version
+ * number when calculating the MAC, the server still seems to be ignoring
+ * my subsequent data packets.
  */   
 
 static unsigned char nybble(unsigned char n)
@@ -63,7 +66,8 @@ static unsigned char hex(const char *data)
        return (nybble(data[0]) << 4) | nybble(data[1]);
 }
 
-static int connect_dtls_socket(struct anyconnect_info *vpninfo, int dtls_port)
+static int connect_dtls_socket(struct anyconnect_info *vpninfo, SSL **ret_ssl,
+                              int *ret_fd)
 {
        SSL_METHOD *dtls_method;
        SSL_CTX *dtls_ctx;
@@ -74,18 +78,6 @@ static int connect_dtls_socket(struct anyconnect_info *vpninfo, int dtls_port)
        int dtls_fd;
        int ret;
 
-       if (vpninfo->peer_addr->sa_family == AF_INET) {
-               struct sockaddr_in *sin = (void *)vpninfo->peer_addr;
-               sin->sin_port = htons(dtls_port);
-       } else if (vpninfo->peer_addr->sa_family == AF_INET6) {
-               struct sockaddr_in6 *sin = (void *)vpninfo->peer_addr;
-               sin->sin6_port = htons(dtls_port);
-       } else {
-               fprintf(stderr, "Unknown protocol family %d. Cannot do DTLS\n",
-                       vpninfo->peer_addr->sa_family);
-               return -EINVAL;
-       }
-
        dtls_fd = socket(vpninfo->peer_addr->sa_family, SOCK_DGRAM, IPPROTO_UDP);
        if (dtls_fd < 0) {
                perror("Open UDP socket for DTLS:");
@@ -160,12 +152,18 @@ static int connect_dtls_socket(struct anyconnect_info *vpninfo, int dtls_port)
                return -EINVAL;
        }
 
-       vpninfo->dtls_fd = dtls_fd;
-       vpninfo->dtls_ssl = dtls_ssl;
+       *ret_fd = dtls_fd;
+       *ret_ssl = dtls_ssl;
 
        return 0;
 }
 
+static int dtls_rekey(struct anyconnect_info *vpninfo)
+{
+       printf("FIXME: Implement DTLS rekey\n");
+       return -EINVAL;
+}
+
 int setup_dtls(struct anyconnect_info *vpninfo)
 {
        struct vpn_option *dtls_opt = vpninfo->dtls_options;
@@ -192,6 +190,8 @@ int setup_dtls(struct anyconnect_info *vpninfo)
                        vpninfo->dtls_keepalive = atol(dtls_opt->value);
                } else if (!strcmp(dtls_opt->option + 7, "DPD")) {
                        vpninfo->dtls_dpd = atol(dtls_opt->value);
+               } else if (!strcmp(dtls_opt->option + 7, "Rekey-Time")) {
+                       vpninfo->dtls_rekey = atol(dtls_opt->value);
                }
                        
                dtls_opt = dtls_opt->next;
@@ -199,7 +199,19 @@ int setup_dtls(struct anyconnect_info *vpninfo)
        if (!sessid_found || !dtls_port)
                return -EINVAL;
 
-       if (connect_dtls_socket(vpninfo, dtls_port))
+       if (vpninfo->peer_addr->sa_family == AF_INET) {
+               struct sockaddr_in *sin = (void *)vpninfo->peer_addr;
+               sin->sin_port = htons(dtls_port);
+       } else if (vpninfo->peer_addr->sa_family == AF_INET6) {
+               struct sockaddr_in6 *sin = (void *)vpninfo->peer_addr;
+               sin->sin6_port = htons(dtls_port);
+       } else {
+               fprintf(stderr, "Unknown protocol family %d. Cannot do DTLS\n",
+                       vpninfo->peer_addr->sa_family);
+               return -EINVAL;
+       }
+
+       if (connect_dtls_socket(vpninfo, &vpninfo->dtls_ssl, &vpninfo->dtls_fd))
                return -EINVAL;
 
        BIO_set_nbio(SSL_get_rbio(vpninfo->dtls_ssl),1);
@@ -208,7 +220,8 @@ int setup_dtls(struct anyconnect_info *vpninfo)
        fcntl(vpninfo->dtls_fd, F_SETFL, fcntl(vpninfo->dtls_fd, F_GETFL) | O_NONBLOCK);
 
        vpn_add_pollfd(vpninfo, vpninfo->dtls_fd, POLLIN|POLLHUP|POLLERR);
-       vpninfo->last_dtls_rx = vpninfo->last_dtls_tx = time(NULL);
+       vpninfo->last_dtls_rekey = vpninfo->last_dtls_rx =
+               vpninfo->last_dtls_tx = time(NULL);
 
        if (verbose)
                printf("DTLS connected. DPD %d, Keepalive %d\n",
@@ -276,7 +289,7 @@ int dtls_mainloop(struct anyconnect_info *vpninfo, int *timeout)
                        
                if (now > overdue) {
                        fprintf(stderr, "DTLS Dead Peer Detection detected dead peer!\n");
-                       /* FIXME: Can we call fack to SSL instead? */
+                       /* Fall back to SSL */
                        SSL_free(vpninfo->dtls_ssl);
                        close(vpninfo->dtls_fd);
                        vpninfo->dtls_ssl = NULL;
@@ -326,6 +339,30 @@ int dtls_mainloop(struct anyconnect_info *vpninfo, int *timeout)
                        *timeout = (due - now) * 1000;
        }
 
+       if (vpninfo->dtls_rekey) {
+               time_t now = time(NULL);
+               time_t due = vpninfo->last_dtls_rekey + vpninfo->dtls_rekey;
+
+               if (now > due) {
+                       if (verbose)
+                               printf("DTLS rekey due\n");
+                       if (dtls_rekey(vpninfo)) {
+                               fprintf(stderr, "DTLS rekey failed\n");
+                               /* Fall back to SSL */
+                               SSL_free(vpninfo->dtls_ssl);
+                               close(vpninfo->dtls_fd);
+                               vpninfo->dtls_ssl = NULL;
+                               vpninfo->dtls_fd = -1;
+                               return 1;
+                       }
+                       vpninfo->last_dtls_rekey = time(NULL);
+                       due = vpninfo->last_dtls_rekey + vpninfo->dtls_rekey;
+               }
+               if (verbose)
+                       printf("Next DTLS rekey due in %ld seconds\n", (due - now));
+               if (*timeout > (due - now) * 1000)
+                       *timeout = (due - now) * 1000;
+       }
 
        /* FIXME: Keepalive */
        return work_done;