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SUSE:SLE-12-SP3:GA
openssh.10219
openssh-6.6p1-untrusted_X_forwarding.patch
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File openssh-6.6p1-untrusted_X_forwarding.patch of Package openssh.10219
# HG changeset patch # Parent 6c50ec85ae480cf2aa8ebce8c9f4ff17265dde6e Prevent X clients from circumventing X SECURITY restrictions by falling back to implicit authentication upon MIT-MAGIC-COOKIE authentication fail by disallowing X11 authentication after ForwardX11Timeout. CVE-2016-1908 bsc#962313 c.f. https://thejh.net/written-stuff/openssh-6.8-xsecurity Backport of upstream: commit f98a09cacff7baad8748c9aa217afd155a4d493f Author: mmcc@openbsd.org <mmcc@openbsd.org> Date: Tue Oct 20 03:36:35 2015 +0000 Replace a function-local allocation with stack memory. ok djm@ Upstream-ID: c09fbbab637053a2ab9f33ca142b4e20a4c5a17e commit ed4ce82dbfa8a3a3c8ea6fa0db113c71e234416c Author: djm@openbsd.org <djm@openbsd.org> Date: Wed Jan 13 23:04:47 2016 +0000 upstream commit eliminate fallback from untrusted X11 forwarding to trusted forwarding when the X server disables the SECURITY extension; Reported by Thomas Hoger; ok deraadt@ Upstream-ID: f76195bd2064615a63ef9674a0e4096b0713f938 diff --git a/openssh-6.6p1/clientloop.c b/openssh-6.6p1/clientloop.c --- a/openssh-6.6p1/clientloop.c +++ b/openssh-6.6p1/clientloop.c @@ -286,105 +286,121 @@ set_control_persist_exit_time(void) } #define SSH_X11_VALID_DISPLAY_CHARS ":/.-_" static int client_x11_display_valid(const char *display) { size_t i, dlen; + if (display == NULL) + return 0; + dlen = strlen(display); for (i = 0; i < dlen; i++) { if (!isalnum((u_char)display[i]) && strchr(SSH_X11_VALID_DISPLAY_CHARS, display[i]) == NULL) { debug("Invalid character '%c' in DISPLAY", display[i]); return 0; } } return 1; } #define SSH_X11_PROTO "MIT-MAGIC-COOKIE-1" #define X11_TIMEOUT_SLACK 60 -void +int client_x11_get_proto(const char *display, const char *xauth_path, u_int trusted, u_int timeout, char **_proto, char **_data) { - char cmd[1024]; - char line[512]; - char xdisplay[512]; + char cmd[1024], line[512], xdisplay[512]; + char xauthfile[PATH_MAX], xauthdir[PATH_MAX]; static char proto[512], data[512]; FILE *f; - int got_data = 0, generated = 0, do_unlink = 0, i; - char *xauthdir, *xauthfile; + int got_data = 0, generated = 0, do_unlink = 0, i, r; struct stat st; u_int now, x11_timeout_real; - xauthdir = xauthfile = NULL; *_proto = proto; *_data = data; - proto[0] = data[0] = '\0'; + proto[0] = data[0] = xauthfile[0] = xauthdir[0] = '\0'; - if (xauth_path == NULL ||(stat(xauth_path, &st) == -1)) { + if (!client_x11_display_valid(display)) { + logit("DISPLAY \"%s\" invalid; disabling X11 forwarding", + display); + return -1; + } + if (xauth_path != NULL && stat(xauth_path, &st) == -1) { debug("No xauth program."); - } else if (!client_x11_display_valid(display)) { - logit("DISPLAY '%s' invalid, falling back to fake xauth data", - display); - } else { - if (display == NULL) { - debug("x11_get_proto: DISPLAY not set"); - return; - } + xauth_path = NULL; + } + + if (xauth_path != NULL) { /* * Handle FamilyLocal case where $DISPLAY does * not match an authorization entry. For this we * just try "xauth list unix:displaynum.screennum". * XXX: "localhost" match to determine FamilyLocal * is not perfect. */ if (strncmp(display, "localhost:", 10) == 0) { - snprintf(xdisplay, sizeof(xdisplay), "unix:%s", - display + 10); + if ((r = snprintf(xdisplay, sizeof(xdisplay), "unix:%s", + display + 10)) < 0 || + (size_t)r >= sizeof(xdisplay)) { + error("%s: display name too long", __func__); + return -1; + } display = xdisplay; } if (trusted == 0) { - xauthdir = xmalloc(MAXPATHLEN); - xauthfile = xmalloc(MAXPATHLEN); - mktemp_proto(xauthdir, MAXPATHLEN); /* + * Generate an untrusted X11 auth cookie. + * * The authentication cookie should briefly outlive * ssh's willingness to forward X11 connections to * avoid nasty fail-open behaviour in the X server. */ + mktemp_proto(xauthdir, sizeof(xauthdir)); + if (mkdtemp(xauthdir) == NULL) { + error("%s: mkdtemp: %s", + __func__, strerror(errno)); + return -1; + } + do_unlink = 1; + if ((r = snprintf(xauthfile, sizeof(xauthfile), + "%s/xauthfile", xauthdir)) < 0 || + (size_t)r >= sizeof(xauthfile)) { + error("%s: xauthfile path too long", __func__); + unlink(xauthfile); + rmdir(xauthdir); + return -1; + } + if (timeout >= UINT_MAX - X11_TIMEOUT_SLACK) x11_timeout_real = UINT_MAX; else x11_timeout_real = timeout + X11_TIMEOUT_SLACK; - if (mkdtemp(xauthdir) != NULL) { - do_unlink = 1; - snprintf(xauthfile, MAXPATHLEN, "%s/xauthfile", - xauthdir); - snprintf(cmd, sizeof(cmd), - "%s -f %s generate %s " SSH_X11_PROTO - " untrusted timeout %u 2>" _PATH_DEVNULL, - xauth_path, xauthfile, display, - x11_timeout_real); - debug2("x11_get_proto: %s", cmd); - if (x11_refuse_time == 0) { - now = monotime() + 1; - if (UINT_MAX - timeout < now) - x11_refuse_time = UINT_MAX; - else - x11_refuse_time = now + timeout; - channel_set_x11_refuse_time( - x11_refuse_time); - } - if (system(cmd) == 0) - generated = 1; + if ((r = snprintf(cmd, sizeof(cmd), + "%s -f %s generate %s " SSH_X11_PROTO + " untrusted timeout %u 2>" _PATH_DEVNULL, + xauth_path, xauthfile, display, + x11_timeout_real)) < 0 || + (size_t)r >= sizeof(cmd)) + fatal("%s: cmd too long", __func__); + debug2("%s: %s", __func__, cmd); + if (x11_refuse_time == 0) { + now = monotime() + 1; + if (UINT_MAX - timeout < now) + x11_refuse_time = UINT_MAX; + else + x11_refuse_time = now + timeout; + channel_set_x11_refuse_time(x11_refuse_time); } + if (system(cmd) == 0) + generated = 1; } /* * When in untrusted mode, we read the cookie only if it was * successfully generated as an untrusted one in the step * above. */ if (trusted || generated) { @@ -396,27 +412,30 @@ client_x11_get_proto(const char *display display); debug2("x11_get_proto: %s", cmd); f = popen(cmd, "r"); if (f && fgets(line, sizeof(line), f) && sscanf(line, "%*s %511s %511s", proto, data) == 2) got_data = 1; if (f) pclose(f); - } else - error("Warning: untrusted X11 forwarding setup failed: " - "xauth key data not generated"); + } } if (do_unlink) { unlink(xauthfile); rmdir(xauthdir); } - free(xauthdir); - free(xauthfile); + + /* Don't fall back to fake X11 data for untrusted forwarding */ + if (!trusted && !got_data) { + error("Warning: untrusted X11 forwarding setup failed: " + "xauth key data not generated"); + return -1; + } /* * If we didn't get authentication data, just make up some * data. The forwarding code will check the validity of the * response anyway, and substitute this data. The X11 * server, however, will ignore this fake data and use * whatever authentication mechanisms it was using otherwise * for the local connection. @@ -430,16 +449,18 @@ client_x11_get_proto(const char *display for (i = 0; i < 16; i++) { if (i % 4 == 0) rnd = arc4random(); snprintf(data + 2 * i, sizeof data - 2 * i, "%02x", rnd & 0xff); rnd >>= 8; } } + + return 0; } /* * This is called when the interactive is entered. This checks if there is * an EOF coming on stdin. We must check this explicitly, as select() does * not appear to wake up when redirecting from /dev/null. */ diff --git a/openssh-6.6p1/clientloop.h b/openssh-6.6p1/clientloop.h --- a/openssh-6.6p1/clientloop.h +++ b/openssh-6.6p1/clientloop.h @@ -1,9 +1,9 @@ -/* $OpenBSD: clientloop.h,v 1.31 2013/06/02 23:36:29 dtucker Exp $ */ +/* $OpenBSD: clientloop.h,v 1.32 2016/01/13 23:04:47 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland * All rights reserved * * As far as I am concerned, the code I have written for this software * can be used freely for any purpose. Any derived versions of this @@ -34,17 +34,17 @@ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include <termios.h> /* Client side main loop for the interactive session. */ int client_loop(int, int, int); -void client_x11_get_proto(const char *, const char *, u_int, u_int, +int client_x11_get_proto(const char *, const char *, u_int, u_int, char **, char **); void client_global_request_reply_fwd(int, u_int32_t, void *); void client_session2_setup(int, int, int, const char *, struct termios *, int, Buffer *, char **); int client_request_tun_fwd(int, int, int); void client_stop_mux(void); /* Escape filter for protocol 2 sessions */ diff --git a/openssh-6.6p1/mux.c b/openssh-6.6p1/mux.c --- a/openssh-6.6p1/mux.c +++ b/openssh-6.6p1/mux.c @@ -1256,26 +1256,28 @@ mux_session_confirm(int id, int success, goto done; } display = getenv("DISPLAY"); if (cctx->want_x_fwd && options.forward_x11 && display != NULL) { char *proto, *data; /* Get reasonable local authentication information. */ - client_x11_get_proto(display, options.xauth_location, + if (client_x11_get_proto(display, options.xauth_location, options.forward_x11_trusted, options.forward_x11_timeout, - &proto, &data); - /* Request forwarding with authentication spoofing. */ - debug("Requesting X11 forwarding with authentication " - "spoofing."); - x11_request_forwarding_with_spoofing(id, display, proto, - data, 1); - client_expect_confirm(id, "X11 forwarding", CONFIRM_WARN); - /* XXX exit_on_forward_failure */ + &proto, &data) == 0) { + /* Request forwarding with authentication spoofing. */ + debug("Requesting X11 forwarding with authentication " + "spoofing."); + x11_request_forwarding_with_spoofing(id, display, proto, + data, 1); + /* XXX exit_on_forward_failure */ + client_expect_confirm(id, "X11 forwarding", + CONFIRM_WARN); + } } if (cctx->want_agent_fwd && options.forward_agent) { debug("Requesting authentication agent forwarding."); channel_request_start(id, "auth-agent-req@openssh.com", 0); packet_send(); } diff --git a/openssh-6.6p1/ssh.c b/openssh-6.6p1/ssh.c --- a/openssh-6.6p1/ssh.c +++ b/openssh-6.6p1/ssh.c @@ -1413,16 +1413,17 @@ static int ssh_session(void) { int type; int interactive = 0; int have_tty = 0; struct winsize ws; char *cp; const char *display; + char *proto = NULL, *data = NULL; /* Enable compression if requested. */ if (options.compression) { debug("Requesting compression at level %d.", options.compression_level); if (options.compression_level < 1 || options.compression_level > 9) @@ -1481,23 +1482,19 @@ ssh_session(void) logit("Warning: Remote host failed or refused to " "allocate a pseudo tty."); else packet_disconnect("Protocol error waiting for pty " "request response."); } /* Request X11 forwarding if enabled and DISPLAY is set. */ display = getenv("DISPLAY"); - if (options.forward_x11 && display != NULL) { - char *proto, *data; - /* Get reasonable local authentication information. */ - client_x11_get_proto(display, options.xauth_location, - options.forward_x11_trusted, - options.forward_x11_timeout, - &proto, &data); + if (options.forward_x11 && client_x11_get_proto(display, + options.xauth_location, options.forward_x11_trusted, + options.forward_x11_timeout, &proto, &data) == 0) { /* Request forwarding with authentication spoofing. */ debug("Requesting X11 forwarding with authentication " "spoofing."); x11_request_forwarding_with_spoofing(0, display, proto, data, 0); /* Read response from the server. */ type = packet_read(); if (type == SSH_SMSG_SUCCESS) { @@ -1577,27 +1574,25 @@ ssh_session(void) /* request pty/x11/agent/tcpfwd/shell for channel */ static void ssh_session2_setup(int id, int success, void *arg) { extern char **environ; const char *display; int interactive = tty_flag; + char *proto = NULL, *data = NULL; if (!success) return; /* No need for error message, channels code sens one */ display = getenv("DISPLAY"); - if (options.forward_x11 && display != NULL) { - char *proto, *data; - /* Get reasonable local authentication information. */ - client_x11_get_proto(display, options.xauth_location, - options.forward_x11_trusted, - options.forward_x11_timeout, &proto, &data); + if (options.forward_x11 && client_x11_get_proto(display, + options.xauth_location, options.forward_x11_trusted, + options.forward_x11_timeout, &proto, &data) == 0) { /* Request forwarding with authentication spoofing. */ debug("Requesting X11 forwarding with authentication " "spoofing."); x11_request_forwarding_with_spoofing(id, display, proto, data, 1); client_expect_confirm(id, "X11 forwarding", CONFIRM_WARN); /* XXX exit_on_forward_failure */ interactive = 1;
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