upstream commit

ssh proxy mux mode (-O proxy; idea from Simon Tatham): - mux
client speaks the ssh-packet protocol directly over unix-domain socket. - mux
server acts as a proxy, translates channel IDs and relays to the server. - no
filedescriptor passing necessary. - combined with unix-domain forwarding it's
even possible to run mux client   and server on different machines. feedback
& ok djm@

Upstream-ID: 666a2fb79f58e5c50e246265fb2b9251e505c25b

1 files changed, 62 insertions, 7 deletions

diff --git a/mux.c b/mux.c
index a8a753b54..ec42bf520 100644
--- a/mux.c
+++ b/mux.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mux.c,v 1.61 2016/08/08 22:40:57 dtucker Exp $ */
+/* $OpenBSD: mux.c,v 1.62 2016/09/30 09:19:13 markus Exp $ */
 /*
  * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
  *
@@ -79,6 +79,7 @@
 #include "key.h"
 #include "readconf.h"
 #include "clientloop.h"
+#include "ssherr.h"
 
 /* from ssh.c */
 extern int tty_flag;
@@ -144,6 +145,7 @@ struct mux_master_state {
 #define MUX_C_CLOSE_FWD         0x10000007
 #define MUX_C_NEW_STDIO_FWD     0x10000008
 #define MUX_C_STOP_LISTENING    0x10000009
+#define MUX_C_PROXY             0x1000000f
 #define MUX_S_OK                0x80000001
 #define MUX_S_PERMISSION_DENIED 0x80000002
 #define MUX_S_FAILURE           0x80000003
@@ -152,6 +154,7 @@ struct mux_master_state {
 #define MUX_S_SESSION_OPENED    0x80000006
 #define MUX_S_REMOTE_PORT       0x80000007
 #define MUX_S_TTY_ALLOC_FAIL    0x80000008
+#define MUX_S_PROXY             0x8000000f
 
 /* type codes for MUX_C_OPEN_FWD and MUX_C_CLOSE_FWD */
 #define MUX_FWD_LOCAL   1
@@ -169,6 +172,7 @@ static int process_mux_open_fwd(u_int, Channel *, Buffer *, Buffer *);
 static int process_mux_close_fwd(u_int, Channel *, Buffer *, Buffer *);
 static int process_mux_stdio_fwd(u_int, Channel *, Buffer *, Buffer *);
 static int process_mux_stop_listening(u_int, Channel *, Buffer *, Buffer *);
+static int process_mux_proxy(u_int, Channel *, Buffer *, Buffer *);
 
 static const struct {
         u_int type;
@@ -182,6 +186,7 @@ static const struct {
         { MUX_C_CLOSE_FWD, process_mux_close_fwd },
         { MUX_C_NEW_STDIO_FWD, process_mux_stdio_fwd },
         { MUX_C_STOP_LISTENING, process_mux_stop_listening },
+        { MUX_C_PROXY, process_mux_proxy },
         { 0, NULL }
 };
 
@@ -1110,6 +1115,18 @@ process_mux_stop_listening(u_int rid, Channel *c, Buffer *m, Buffer *r)
         return 0;
 }
 
+static int
+process_mux_proxy(u_int rid, Channel *c, Buffer *m, Buffer *r)
+{
+        debug("%s: channel %d: proxy request", __func__, c->self);
+
+        c->mux_rcb = channel_proxy_downstream;
+        buffer_put_int(r, MUX_S_PROXY);
+        buffer_put_int(r, rid);
+
+        return 0;
+}
+
 /* Channel callbacks fired on read/write from mux slave fd */
 static int
 mux_master_read_cb(Channel *c)
@@ -1960,6 +1977,41 @@ mux_client_request_session(int fd)
 }
 
 static int
+mux_client_proxy(int fd)
+{
+        Buffer m;
+        char *e;
+        u_int type, rid;
+
+        buffer_init(&m);
+        buffer_put_int(&m, MUX_C_PROXY);
+        buffer_put_int(&m, muxclient_request_id);
+        if (mux_client_write_packet(fd, &m) != 0)
+                fatal("%s: write packet: %s", __func__, strerror(errno));
+
+        buffer_clear(&m);
+
+        /* Read their reply */
+        if (mux_client_read_packet(fd, &m) != 0) {
+                buffer_free(&m);
+                return 0;
+        }
+        type = buffer_get_int(&m);
+        if (type != MUX_S_PROXY) {
+                e = buffer_get_string(&m, NULL);
+                fatal("%s: master returned error: %s", __func__, e);
+        }
+        if ((rid = buffer_get_int(&m)) != muxclient_request_id)
+                fatal("%s: out of sequence reply: my id %u theirs %u",
+                    __func__, muxclient_request_id, rid);
+        buffer_free(&m);
+
+        debug3("%s: done", __func__);
+        muxclient_request_id++;
+        return 0;
+}
+
+static int
 mux_client_request_stdio_fwd(int fd)
 {
         Buffer m;
@@ -2105,7 +2157,7 @@ mux_client_request_stop_listening(int fd)
 }
 
 /* Multiplex client main loop. */
-void
+int
 muxclient(const char *path)
 {
         struct sockaddr_un addr;
@@ -2128,7 +2180,7 @@ muxclient(const char *path)
         case SSHCTL_MASTER_NO:
                 break;
         default:
-                return;
+                return -1;
         }
 
         memset(&addr, '\0', sizeof(addr));
@@ -2164,14 +2216,14 @@ muxclient(const char *path)
                             strerror(errno));
                 }
                 close(sock);
-                return;
+                return -1;
         }
         set_nonblock(sock);
 
         if (mux_client_hello_exchange(sock) != 0) {
                 error("%s: master hello exchange failed", __func__);
                 close(sock);
-                return;
+                return -1;
         }
 
         switch (muxclient_command) {
@@ -2191,10 +2243,10 @@ muxclient(const char *path)
         case SSHMUX_COMMAND_OPEN:
                 if (mux_client_forwards(sock, 0) != 0) {
                         error("%s: master forward request failed", __func__);
-                        return;
+                        return -1;
                 }
                 mux_client_request_session(sock);
-                return;
+                return -1;
         case SSHMUX_COMMAND_STDIO_FWD:
                 mux_client_request_stdio_fwd(sock);
                 exit(0);
@@ -2207,6 +2259,9 @@ muxclient(const char *path)
                         error("%s: master cancel forward request failed",
                             __func__);
                 exit(0);
+        case SSHMUX_COMMAND_PROXY:
+                mux_client_proxy(sock);
+                return (sock);
         default:
                 fatal("unrecognised muxclient_command %d", muxclient_command);
         }