Parse LocalForward from SSH config (#697)

* Parse LocalForward from SSH config

* review

Author: gabrielrussoc

src/terminal/ParseConfigFile.hpp

@@ -9,6 +9,8 @@
 #include <fstream>
 #include <iostream>
 #include <string>
+#include <utility>
+#include <vector>
 
 /* This is needed for a standard getpwuid_r on opensolaris */
 #define _POSIX_PTHREAD_SEMANTICS
@@ -84,6 +86,7 @@ enum ssh_config_opcode_e {
   SOC_PROXYJUMP,
   SOC_FORWARDAGENT,
   SOC_IDENTITYAGENT,
+  SOC_LOCALFORWARD,
   SOC_END /* Keep this one last in the list */
 };
 
@@ -121,7 +124,8 @@ enum ssh_options_e {
   SSH_OPTIONS_HMAC_S_C,
   SSH_OPTIONS_PROXYJUMP,
   SSH_OPTIONS_FORWARDAGENT,
-  SSH_OPTIONS_IDENTITYAGENT
+  SSH_OPTIONS_IDENTITYAGENT,
+  SSH_OPTIONS_LOCALFORWARD
 };
 
 struct Options {
@@ -141,6 +145,7 @@ struct Options {
   int gss_delegate_creds;
   int forward_agent;
   char *identity_agent;
+  vector<pair<int, int>> local_forwards;
 };
 
 struct ssh_config_keyword_table_s {
@@ -166,6 +171,7 @@ static struct ssh_config_keyword_table_s ssh_config_keyword_table[] = {
     {"proxyjump", SOC_PROXYJUMP},
     {"forwardagent", SOC_FORWARDAGENT},
     {"identityagent", SOC_IDENTITYAGENT},
+    {"localforward", SOC_LOCALFORWARD},
     {NULL, SOC_UNSUPPORTED}};
 
 static enum ssh_config_opcode_e ssh_config_get_opcode(char *keyword) {
@@ -1036,6 +1042,36 @@ int ssh_options_set(struct Options *options, enum ssh_options_e type,
         }
       }
       break;
+    case SSH_OPTIONS_LOCALFORWARD:
+      v = static_cast<const char *>(value);
+      if (v == NULL || v[0] == '\0') {
+        CLOG(INFO, "stdout") << "invalid error" << endl;
+        return -1;
+      } else {
+        char *forward_entry = strdup(v);
+        if (forward_entry == NULL) {
+          CLOG(INFO, "stdout") << "error" << endl;
+          return -1;
+        }
+
+        // Format is [bind_address:]port host:hostport
+        char *local_port_str = strtok(forward_entry, " ");
+        char *remote_part = strtok(NULL, " ");
+
+        // TODO: Support bind_address before the local port.
+        if (local_port_str && remote_part) {
+          int local_port = atoi(local_port_str);
+          char *colon_pos = strrchr(remote_part, ':');
+          if (colon_pos) {
+            int remote_port = atoi(colon_pos + 1);
+            options->local_forwards.push_back(
+                make_pair(local_port, remote_port));
+          }
+        }
+
+        SAFE_FREE(forward_entry);
+      }
+      break;
 
     default:
       CLOG(INFO, "stdout") << "Unknown ssh option" << endl;
@@ -1233,7 +1269,8 @@ static int ssh_config_parse_line(const char *targethost,
 
   opcode = ssh_config_get_opcode(keyword);
   if (*parsing == 1 && opcode != SOC_HOST && opcode != SOC_MATCH &&
-      opcode != SOC_UNSUPPORTED && opcode != SOC_INCLUDE) {
+      opcode != SOC_UNSUPPORTED && opcode != SOC_INCLUDE &&
+      opcode != SOC_LOCALFORWARD) {
     if (seen[opcode] != 0) {
       SAFE_FREE(x);
       return 0;
@@ -1401,6 +1438,17 @@ static int ssh_config_parse_line(const char *targethost,
         SAFE_FREE(filename);
       }
       break;
+    case SOC_LOCALFORWARD:
+      p = ssh_config_get_str_tok(&s, NULL);
+      if (p && *parsing) {
+        const char *remote_part = ssh_config_get_str_tok(&s, NULL);
+        if (remote_part) {
+          char forward_str[1024];
+          snprintf(forward_str, sizeof(forward_str), "%s %s", p, remote_part);
+          ssh_options_set(options, SSH_OPTIONS_LOCALFORWARD, forward_str);
+        }
+      }
+      break;
     case SOC_UNSUPPORTED:
       LOG(INFO) << "unsupported config line: " << string(line) << ", ignored";
       break;

src/terminal/TerminalClient.cpp

@@ -30,7 +30,11 @@ TerminalClient::TerminalClient(
         auto pfsresponse =
             portForwardHandler->createSource(pfsr, nullptr, -1, -1);
         if (pfsresponse.has_error()) {
-          throw std::runtime_error(pfsresponse.error());
+          LOG(WARNING) << "Failed to establish port forward "
+                       << pfsr.source().port() << ":"
+                       << pfsr.destination().port() << " - "
+                       << pfsresponse.error();
+          continue;
         }
 #endif
       }

src/terminal/TerminalClientMain.cpp

@@ -75,7 +75,8 @@ int main(int argc, char** argv) {
       NULL,  // gss_client_identity
       0,     // gss_delegate_creds
       0,     // forward_agent
-      NULL   // identity_agent
+      NULL,  // identity_agent
+      {}     // local_forwards (empty vector)
   };
 
   // Parse command line arguments
@@ -380,6 +381,19 @@ int main(int argc, char** argv) {
         extractSingleOptionWithDefault<string>(result, options, "tunnel", "");
     string r_tunnel_arg = extractSingleOptionWithDefault<string>(
         result, options, "reversetunnel", "");
+
+    for (const auto& localForward : sshConfigOptions.local_forwards) {
+      string tunnelEntry =
+          to_string(localForward.first) + ":" + to_string(localForward.second);
+      LOG(INFO) << "Adding tunnel from SSH config LocalForward: "
+                << tunnelEntry;
+      if (tunnel_arg.empty()) {
+        tunnel_arg = tunnelEntry;
+      } else {
+        tunnel_arg += "," + tunnelEntry;
+      }
+    }
+
     TerminalClient terminalClient(clientSocket, clientPipeSocket,
                                   socketEndpoint, id, passkey, console,
                                   is_jumphost, tunnel_arg, r_tunnel_arg,