On Wed, Nov 23, 2016 at 01:35:17PM -0500, Jiri B wrote:
> I was using ssh socks5 tunnel (-D9999) today and I saw many:
>
> channel 4: open failed: administratively prohibited: open failed
>
> messages. It seems non-resolvable hostnames on my gw (ie. end of ssh
> socks5 tunnel) is passed to client as "prohibited" event.
>
> This seems odd and confusing. GW is an older 6.0-current amd64.
The code in sshd where the response is composed doesn't know what the
reason for the failure is. I suspect thid dates back to the original
Protocol 1 code becuase Protocol 1 didn't (I think) have a reason field.
This passes the reason back up the stack and sends it to the client.
Index: channels.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/channels.c,v
retrieving revision 1.356
diff -u -p -r1.356 channels.c
--- channels.c 18 Oct 2016 17:32:54 -0000 1.356
+++ channels.c 24 Nov 2016 04:36:58 -0000
@@ -3038,7 +3038,7 @@ channel_input_port_open(int type, u_int3
}
packet_check_eom();
c = channel_connect_to_port(host, host_port,
- "connected socket", originator_string);
+ "connected socket", originator_string, NULL, NULL);
free(originator_string);
free(host);
if (c == NULL) {
@@ -3995,7 +3995,8 @@ channel_connect_ctx_free(struct channel_
/* Return CONNECTING channel to remote host:port or local socket path */
static Channel *
-connect_to(const char *name, int port, char *ctype, char *rname)
+connect_to(const char *name, int port, char *ctype, char *rname, int *reason,
+ char **errmsg)
{
struct addrinfo hints;
int gaierr;
@@ -4036,7 +4037,12 @@ connect_to(const char *name, int port, c
hints.ai_family = IPv4or6;
hints.ai_socktype = SOCK_STREAM;
snprintf(strport, sizeof strport, "%d", port);
- if ((gaierr = getaddrinfo(name, strport, &hints, &cctx.aitop))
!= 0) {
+ if ((gaierr = getaddrinfo(name, strport, &hints, &cctx.aitop))
+ != 0) {
+ if (errmsg != NULL)
+ *errmsg = ssh_gai_strerror(gaierr);
+ if (reason != NULL)
+ *reason = SSH2_OPEN_CONNECT_FAILED;
error("connect_to %.100s: unknown host (%s)", name,
ssh_gai_strerror(gaierr));
return NULL;
@@ -4076,7 +4082,8 @@ channel_connect_by_listen_address(const
return permitted_opens[i].downstream;
return connect_to(
permitted_opens[i].host_to_connect,
- permitted_opens[i].port_to_connect, ctype, rname);
+ permitted_opens[i].port_to_connect, ctype, rname,
+ NULL, NULL);
}
}
error("WARNING: Server requests forwarding for unknown listen_port %d",
@@ -4093,7 +4100,8 @@ channel_connect_by_listen_path(const cha
if (open_listen_match_streamlocal(&permitted_opens[i], path)) {
return connect_to(
permitted_opens[i].host_to_connect,
- permitted_opens[i].port_to_connect, ctype, rname);
+ permitted_opens[i].port_to_connect, ctype, rname,
+ NULL, NULL);
}
}
error("WARNING: Server requests forwarding for unknown path %.100s",
@@ -4103,7 +4111,8 @@ channel_connect_by_listen_path(const cha
/* Check if connecting to that port is permitted and connect. */
Channel *
-channel_connect_to_port(const char *host, u_short port, char *ctype, char
*rname)
+channel_connect_to_port(const char *host, u_short port, char *ctype,
+ char *rname, int *reason, char **errmsg)
{
int i, permit, permit_adm = 1;
@@ -4128,9 +4137,10 @@ channel_connect_to_port(const char *host
if (!permit || !permit_adm) {
logit("Received request to connect to host %.100s port %d, "
"but the request was denied.", host, port);
+ *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
return NULL;
}
- return connect_to(host, port, ctype, rname);
+ return connect_to(host, port, ctype, rname, reason, errmsg);
}
/* Check if connecting to that path is permitted and connect. */
@@ -4162,7 +4172,7 @@ channel_connect_to_path(const char *path
"but the request was denied.", path);
return NULL;
}
- return connect_to(path, PORT_STREAMLOCAL, ctype, rname);
+ return connect_to(path, PORT_STREAMLOCAL, ctype, rname, NULL, NULL);
}
void
Index: channels.h
===================================================================
RCS file: /cvs/src/usr.bin/ssh/channels.h,v
retrieving revision 1.120
diff -u -p -r1.120 channels.h
--- channels.h 18 Oct 2016 17:32:54 -0000 1.120
+++ channels.h 24 Nov 2016 04:36:58 -0000
@@ -272,7 +272,8 @@ void channel_update_permitted_opens(int
void channel_clear_permitted_opens(void);
void channel_clear_adm_permitted_opens(void);
void channel_print_adm_permitted_opens(void);
-Channel *channel_connect_to_port(const char *, u_short, char *, char *);
+Channel *channel_connect_to_port(const char *, u_short, char *, char *,
int *,
+ char **);
Channel *channel_connect_to_path(const char *, char *, char *);
Channel *channel_connect_stdio_fwd(const char*, u_short, int, int);
Channel *channel_connect_by_listen_address(const char *, u_short,
Index: serverloop.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/serverloop.c,v
retrieving revision 1.187
diff -u -p -r1.187 serverloop.c
--- serverloop.c 23 Oct 2016 22:04:05 -0000 1.187
+++ serverloop.c 24 Nov 2016 04:36:58 -0000
@@ -423,7 +423,7 @@ server_input_keep_alive(int type, u_int3
}
static Channel *
-server_request_direct_tcpip(void)
+server_request_direct_tcpip(int *reason, char **errmsg)
{
Channel *c = NULL;
char *target, *originator;
@@ -442,11 +442,12 @@ server_request_direct_tcpip(void)
if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
!no_port_forwarding_flag) {
c = channel_connect_to_port(target, target_port,
- "direct-tcpip", "direct-tcpip");
+ "direct-tcpip", "direct-tcpip", reason, errmsg);
} else {
logit("refused local port forward: "
"originator %s port %d, target %s port %d",
originator, originator_port, target, target_port);
+ *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
}
free(originator);
@@ -563,8 +564,8 @@ static int
server_input_channel_open(int type, u_int32_t seq, void *ctxt)
{
Channel *c = NULL;
- char *ctype;
- int rchan;
+ char *ctype, *errmsg = NULL;
+ int rchan, reason = SSH2_OPEN_CONNECT_FAILED;
u_int rmaxpack, rwindow, len;
ctype = packet_get_string(&len);
@@ -578,7 +579,7 @@ server_input_channel_open(int type, u_in
if (strcmp(ctype, "session") == 0) {
c = server_request_session();
} else if (strcmp(ctype, "direct-tcpip") == 0) {
- c = server_request_direct_tcpip();
+ c = server_request_direct_tcpip(&reason, &errmsg);
} else if (strcmp(ctype, "direct-streamlo...@openssh.com") == 0) {
c = server_request_direct_streamlocal();
} else if (strcmp(ctype, "t...@openssh.com") == 0) {
@@ -601,9 +602,9 @@ server_input_channel_open(int type, u_in
debug("server_input_channel_open: failure %s", ctype);
packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
packet_put_int(rchan);
- packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
+ packet_put_int(reason);
if (!(datafellows & SSH_BUG_OPENFAILURE)) {
- packet_put_cstring("open failed");
+ packet_put_cstring(errmsg ? errmsg : "open failed");
packet_put_cstring("");
}
packet_send();
--
Darren Tucker (dtucker at zip.com.au)
GPG key 11EAA6FA / A86E 3E07 5B19 5880 E860 37F4 9357 ECEF 11EA A6FA (new)
Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.
