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dtucker pushed a commit to branch master
in repository openssh.

commit 858252fb1d451ebb0969cf9749116c8f0ee42753
Author: dtucker@openbsd.org <dtucker@openbsd.org>
Date: Wed Feb 1 02:59:09 2017 +0000

upstream commit

Return true reason for port forwarding failures where
feasible rather than always "administratively prohibited". bz#2674, ok djm@

Upstream-ID: d901d9887951774e604ca970e1827afaaef9e419
---
channels.c | 33 ++++++++++++++++++++++++++-------
channels.h | 5 +++--
serverloop.c | 17 ++++++++++-------
3 files changed, 39 insertions(+), 16 deletions(-)

diff --git a/channels.c b/channels.c
index bef8ad6..398da9a 100644
--- a/channels.c
+++ b/channels.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.c,v 1.356 2016/10/18 17:32:54 dtucker Exp $ */
+/* $OpenBSD: channels.c,v 1.357 2017/02/01 02:59:09 dtucker Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -3065,7 +3065,7 @@ channel_input_port_open(int type, u_int32_t seq, void *ctxt)
}
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) {
@@ -4026,9 +4026,13 @@ channel_connect_ctx_free(struct channel_connect *cctx)
memset(cctx, 0, sizeof(*cctx));
}

-/* Return CONNECTING channel to remote host:port or local socket path */
+/*
+ * Return CONNECTING channel to remote host:port or local socket path,
+ * passing back the failure reason if appropriate.
+ */
static Channel *
-connect_to(const char *name, int port, char *ctype, char *rname)
+connect_to_reason(const char *name, int port, char *ctype, char *rname,
+ int *reason, const char **errmsg)
{
struct addrinfo hints;
int gaierr;
@@ -4069,7 +4073,12 @@ connect_to(const char *name, int port, char *ctype, char *rname)
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;
@@ -4092,6 +4101,13 @@ connect_to(const char *name, int port, char *ctype, char *rname)
return c;
}

+/* Return CONNECTING channel to remote host:port or local socket path */
+static Channel *
+connect_to(const char *name, int port, char *ctype, char *rname)
+{
+ return connect_to_reason(name, port, ctype, rname, NULL, NULL);
+}
+
/*
* returns either the newly connected channel or the downstream channel
* that needs to deal with this connection.
@@ -4136,7 +4152,8 @@ channel_connect_by_listen_path(const char *path, char *ctype, char *rname)

/* 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, const char **errmsg)
{
int i, permit, permit_adm = 1;

@@ -4161,9 +4178,11 @@ channel_connect_to_port(const char *host, u_short port, char *ctype, char *rname
if (!permit || !permit_adm) {
logit("Received request to connect to host %.100s port %d, "
"but the request was denied.", host, port);
+ if (reason != NULL)
+ *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
return NULL;
}
- return connect_to(host, port, ctype, rname);
+ return connect_to_reason(host, port, ctype, rname, reason, errmsg);
}

/* Check if connecting to that path is permitted and connect. */
diff --git a/channels.h b/channels.h
index 09c3c36..ce43236 100644
--- a/channels.h
+++ b/channels.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.h,v 1.120 2016/10/18 17:32:54 dtucker Exp $ */
+/* $OpenBSD: channels.h,v 1.121 2017/02/01 02:59:09 dtucker Exp $ */

/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -275,7 +275,8 @@ void channel_update_permitted_opens(int, 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 *,
+ const 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,
diff --git a/serverloop.c b/serverloop.c
index bdb944f..2976f55 100644
--- a/serverloop.c
+++ b/serverloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: serverloop.c,v 1.190 2017/01/04 05:37:40 djm Exp $ */
+/* $OpenBSD: serverloop.c,v 1.191 2017/02/01 02:59:09 dtucker Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -430,7 +430,7 @@ server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
}

static Channel *
-server_request_direct_tcpip(void)
+server_request_direct_tcpip(int *reason, const char **errmsg)
{
Channel *c = NULL;
char *target, *originator;
@@ -449,11 +449,13 @@ server_request_direct_tcpip(void)
if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
!no_port_forwarding_flag && !options.disable_forwarding) {
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);
+ if (reason != NULL)
+ *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
}

free(originator);
@@ -581,7 +583,8 @@ server_input_channel_open(int type, u_int32_t seq, void *ctxt)
{
Channel *c = NULL;
char *ctype;
- int rchan;
+ const char *errmsg = NULL;
+ int rchan, reason = SSH2_OPEN_CONNECT_FAILED;
u_int rmaxpack, rwindow, len;

ctype = packet_get_string(&len);
@@ -595,7 +598,7 @@ server_input_channel_open(int type, u_int32_t seq, void *ctxt)
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-streamlocal@openssh.com") == 0) {
c = server_request_direct_streamlocal();
} else if (strcmp(ctype, "tun@openssh.com") == 0) {
@@ -618,9 +621,9 @@ server_input_channel_open(int type, u_int32_t seq, void *ctxt)
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();

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