Send back SOCKS5 errors for all of the address related failures.

Cases that now send errors:
 * Malformed IP address (SOCKS5_GENERAL_ERROR)
 * CONNECT/RESOLVE request with IP, when SafeSocks is set
   (SOCKS5_NOT_ALLOWED)
 * RESOLVE_PTR request with FQDN (SOCKS5_ADDRESS_TYPE_NOT_SUPPORTED)
 * Malformed FQDN (SOCKS5_GENERAL_ERROR)
 * Unknown address type (SOCKS5_ADDRESS_TYPE_NOT_SUPPORTED)

Fixes bug 13314.

changes/bug13314

@@ -0,0 +1,4 @@
+  o Bugfixes:
+    - Handle malformed SOCKS5 requests properly by responding with an
+      appropriate error message before closing a TCP connection to the
+      user. Fixes bug 13314.

src/or/buffers.c

@@ -2009,6 +2009,7 @@ parse_socks(const char *data, size_t datalen, socks_request_t *req,
           tor_addr_to_str(tmpbuf, &destaddr, sizeof(tmpbuf), 1);
 
           if (strlen(tmpbuf)+1 > MAX_SOCKS_ADDR_LEN) {
+            socks_request_set_socks5_error(req, SOCKS5_GENERAL_ERROR);
             log_warn(LD_APP,
                      "socks5 IP takes %d bytes, which doesn't fit in %d. "
                      "Rejecting.",
@@ -2021,14 +2022,18 @@ parse_socks(const char *data, size_t datalen, socks_request_t *req,
           if (req->command != SOCKS_COMMAND_RESOLVE_PTR &&
               !addressmap_have_mapping(req->address,0)) {
             log_unsafe_socks_warning(5, req->address, req->port, safe_socks);
-            if (safe_socks)
+            if (safe_socks) {
+              socks_request_set_socks5_error(req, SOCKS5_NOT_ALLOWED);
               return -1;
+            }
           }
           return 1;
         }
         case 3: /* fqdn */
           log_debug(LD_APP,"socks5: fqdn address type");
           if (req->command == SOCKS_COMMAND_RESOLVE_PTR) {
+            socks_request_set_socks5_error(req,
+                                           SOCKS5_ADDRESS_TYPE_NOT_SUPPORTED);
             log_warn(LD_APP, "socks5 received RESOLVE_PTR command with "
                      "hostname type. Rejecting.");
             return -1;
@@ -2039,6 +2044,7 @@ parse_socks(const char *data, size_t datalen, socks_request_t *req,
             return 0; /* not yet */
           }
           if (len+1 > MAX_SOCKS_ADDR_LEN) {
+            socks_request_set_socks5_error(req, SOCKS5_GENERAL_ERROR);
             log_warn(LD_APP,
                      "socks5 hostname is %d bytes, which doesn't fit in "
                      "%d. Rejecting.", len+1,MAX_SOCKS_ADDR_LEN);
@@ -2049,6 +2055,7 @@ parse_socks(const char *data, size_t datalen, socks_request_t *req,
           req->port = ntohs(get_uint16(data+5+len));
           *drain_out = 5+len+2;
           if (!tor_strisprint(req->address) || strchr(req->address,'\"')) {
+            socks_request_set_socks5_error(req, SOCKS5_GENERAL_ERROR);
             log_warn(LD_PROTOCOL,
                      "Your application (using socks5 to port %d) gave Tor "
                      "a malformed hostname: %s. Rejecting the connection.",
@@ -2062,6 +2069,8 @@ parse_socks(const char *data, size_t datalen, socks_request_t *req,
                   "necessary. This is good.", req->port);
           return 1;
         default: /* unsupported */
+          socks_request_set_socks5_error(req,
+                                         SOCKS5_ADDRESS_TYPE_NOT_SUPPORTED);
           log_warn(LD_APP,"socks5: unsupported address type %d. Rejecting.",
                    (int) *(data+3));
           return -1;

src/test/test_socks.c

@@ -384,6 +384,77 @@ test_socks_5_auth_before_negotiation(void *ptr)
   ;
 }
 
+/** Perform malformed SOCKS 5 commands */
+static void
+test_socks_5_malformed_commands(void *ptr)
+{
+  SOCKS_TEST_INIT();
+
+  /* XXX: Stringified address length > MAX_SOCKS_ADDR_LEN will never happen */
+
+  /* SOCKS 5 Send CONNECT [01] to IP address 2.2.2.2:4369, with SafeSocks set */
+  ADD_DATA(buf, "\x05\x01\x00");
+  ADD_DATA(buf, "\x05\x01\x00\x01\x02\x02\x02\x02\x11\x11");
+  tt_int_op(fetch_from_buf_socks(buf, socks, get_options()->TestSocks, 1),==,
+                                 -1);
+
+  tt_int_op(5,==,socks->socks_version);
+  tt_int_op(10,==,socks->replylen);
+  tt_int_op(5,==,socks->reply[0]);
+  tt_int_op(SOCKS5_NOT_ALLOWED,==,socks->reply[1]);
+  tt_int_op(1,==,socks->reply[3]);
+
+  buf_clear(buf);
+  socks_request_clear(socks);
+
+  /* SOCKS 5 Send RESOLVE_PTR [F1] for FQDN torproject.org */
+  ADD_DATA(buf, "\x05\x01\x00");
+  ADD_DATA(buf, "\x05\xF1\x00\x03\x0Etorproject.org\x11\x11");
+  tt_int_op(fetch_from_buf_socks(buf, socks, get_options()->TestSocks,
+                                   get_options()->SafeSocks),==, -1);
+
+  tt_int_op(5,==,socks->socks_version);
+  tt_int_op(10,==,socks->replylen);
+  tt_int_op(5,==,socks->reply[0]);
+  tt_int_op(SOCKS5_ADDRESS_TYPE_NOT_SUPPORTED,==,socks->reply[1]);
+  tt_int_op(1,==,socks->reply[3]);
+
+  buf_clear(buf);
+  socks_request_clear(socks);
+
+  /* XXX: len + 1 > MAX_SOCKS_ADDR_LEN (FQDN request) will never happen */
+
+  /* SOCKS 5 Send CONNECT [01] to FQDN """"".com */
+  ADD_DATA(buf, "\x05\x01\x00");
+  ADD_DATA(buf, "\x05\x01\x00\x03\x09\"\"\"\"\".com\x11\x11");
+  tt_int_op(fetch_from_buf_socks(buf, socks, get_options()->TestSocks,
+                                   get_options()->SafeSocks),==, -1);
+
+  tt_int_op(5,==,socks->socks_version);
+  tt_int_op(10,==,socks->replylen);
+  tt_int_op(5,==,socks->reply[0]);
+  tt_int_op(SOCKS5_GENERAL_ERROR,==,socks->reply[1]);
+  tt_int_op(1,==,socks->reply[3]);
+
+  buf_clear(buf);
+  socks_request_clear(socks);
+
+  /* SOCKS 5 Send CONNECT [01] to address type 0x23 */
+  ADD_DATA(buf, "\x05\x01\x00");
+  ADD_DATA(buf, "\x05\x01\x00\x23\x02\x02\x02\x02\x11\x11");
+  tt_int_op(fetch_from_buf_socks(buf, socks, get_options()->TestSocks,
+                                   get_options()->SafeSocks),==, -1);
+
+  tt_int_op(5,==,socks->socks_version);
+  tt_int_op(10,==,socks->replylen);
+  tt_int_op(5,==,socks->reply[0]);
+  tt_int_op(SOCKS5_ADDRESS_TYPE_NOT_SUPPORTED,==,socks->reply[1]);
+  tt_int_op(1,==,socks->reply[3]);
+
+ done:
+  ;
+}
+
 #define SOCKSENT(name)                                  \
   { #name, test_socks_##name, TT_FORK, &socks_setup, NULL }
 
@@ -397,6 +468,7 @@ struct testcase_t socks_tests[] = {
   SOCKSENT(5_auth_before_negotiation),
   SOCKSENT(5_authenticate),
   SOCKSENT(5_authenticate_with_data),
+  SOCKSENT(5_malformed_commands),
 
   END_OF_TESTCASES
 };