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SUSE:SLE-12-SP1:GA
openssh.11051
openssh-6.6p1-X11_forwarding_timeout.patch
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File openssh-6.6p1-X11_forwarding_timeout.patch of Package openssh.11051
# HG changeset patch # Parent a41ab00d88841b5e8899b6e4014d6c891701d30a Better way of refusing ForwardX11Trusted=no connections attempted after ForwardX11Timeout expires. CVE-2015-5352 bsc#936695 upstream commit: 1bf477d3cdf1a864646d59820878783d42357a1d diff --git a/openssh-6.6p1/channels.c b/openssh-6.6p1/channels.c --- a/openssh-6.6p1/channels.c +++ b/openssh-6.6p1/channels.c @@ -146,16 +146,19 @@ static char *x11_saved_display = NULL; /* Saved X11 authentication protocol name. */ static char *x11_saved_proto = NULL; /* Saved X11 authentication data. This is the real data. */ static char *x11_saved_data = NULL; static u_int x11_saved_data_len = 0; +/* Deadline after which all X11 connections are refused */ +static u_int x11_refuse_time; + /* * Fake X11 authentication data. This is what the server will be sending us; * we should replace any occurrences of this by the real data. */ static u_char *x11_fake_data = NULL; static u_int x11_fake_data_len; @@ -889,16 +892,23 @@ channel_pre_output_draining(Channel *c, * Returns: 0 = need more data, -1 = wrong cookie, 1 = ok */ static int x11_open_helper(Buffer *b) { u_char *ucp; u_int proto_len, data_len; + /* Is this being called after the refusal deadline? */ + if (x11_refuse_time != 0 && (u_int)monotime() >= x11_refuse_time) { + verbose("Rejected X11 connection after ForwardX11Timeout " + "expired"); + return -1; + } + /* Check if the fixed size part of the packet is in buffer. */ if (buffer_len(b) < 12) return 0; /* Parse the lengths of variable-length fields. */ ucp = buffer_ptr(b); if (ucp[0] == 0x42) { /* Byte order MSB first. */ proto_len = 256 * ucp[6] + ucp[7]; @@ -1452,16 +1462,22 @@ channel_set_reuseaddr(int fd) /* * Set socket options. * Allow local port reuse in TIME_WAIT. */ if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) == -1) error("setsockopt SO_REUSEADDR fd %d: %s", fd, strerror(errno)); } +void +channel_set_x11_refuse_time(u_int refuse_time) +{ + x11_refuse_time = refuse_time; +} + /* * This socket is listening for connections to a forwarded TCP/IP port. */ /* ARGSUSED */ static void channel_post_port_listener(Channel *c, fd_set *readset, fd_set *writeset) { Channel *nc; diff --git a/openssh-6.6p1/channels.h b/openssh-6.6p1/channels.h --- a/openssh-6.6p1/channels.h +++ b/openssh-6.6p1/channels.h @@ -274,16 +274,17 @@ int channel_setup_local_fwd_listener(co int channel_request_rforward_cancel(const char *host, u_short port); int channel_setup_remote_fwd_listener(const char *, u_short, int *, int); int channel_cancel_rport_listener(const char *, u_short); int channel_cancel_lport_listener(const char *, u_short, int, int); int permitopen_port(const char *); /* x11 forwarding */ +void channel_set_x11_refuse_time(u_int); int x11_connect_display(void); int x11_create_display_inet(int, int, int, u_int *, int **); void x11_input_open(int, u_int32_t, void *); void x11_request_forwarding_with_spoofing(int, const char *, const char *, const char *, int); void deny_input_open(int, u_int32_t, void *); /* agent forwarding */ 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 @@ -159,17 +159,17 @@ static int stdin_eof; /* EOF has been e static Buffer stdin_buffer; /* Buffer for stdin data. */ static Buffer stdout_buffer; /* Buffer for stdout data. */ static Buffer stderr_buffer; /* Buffer for stderr data. */ static u_int buffer_high; /* Soft max buffer size. */ static int connection_in; /* Connection to server (input). */ static int connection_out; /* Connection to server (output). */ static int need_rekeying; /* Set to non-zero if rekeying is requested. */ static int session_closed; /* In SSH2: login session closed. */ -static int x11_refuse_time; /* If >0, refuse x11 opens after this time. */ +static u_int x11_refuse_time; /* If >0, refuse x11 opens after this time. */ static void client_init_dispatch(void); int session_ident = -1; int session_resumed = 0; /* Track escape per proto2 channel */ struct escape_filter_ctx { @@ -297,30 +297,31 @@ client_x11_display_valid(const char *dis 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 SSH_X11_PROTO "MIT-MAGIC-COOKIE-1" +#define X11_TIMEOUT_SLACK 60 void 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]; static char proto[512], data[512]; FILE *f; int got_data = 0, generated = 0, do_unlink = 0, i; char *xauthdir, *xauthfile; struct stat st; - u_int now; + u_int now, x11_timeout_real; xauthdir = xauthfile = NULL; *_proto = proto; *_data = data; proto[0] = data[0] = '\0'; if (xauth_path == NULL ||(stat(xauth_path, &st) == -1)) { debug("No xauth program."); @@ -343,34 +344,46 @@ client_x11_get_proto(const char *display snprintf(xdisplay, sizeof(xdisplay), "unix:%s", display + 10); display = xdisplay; } if (trusted == 0) { xauthdir = xmalloc(MAXPATHLEN); xauthfile = xmalloc(MAXPATHLEN); mktemp_proto(xauthdir, MAXPATHLEN); + /* + * The authentication cookie should briefly outlive + * ssh's willingness to forward X11 connections to + * avoid nasty fail-open behaviour in the X server. + */ + 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, timeout); + xauth_path, xauthfile, display, + x11_timeout_real); debug2("x11_get_proto: %s", cmd); - if (system(cmd) == 0) - generated = 1; 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. */ @@ -1879,17 +1892,17 @@ client_request_x11(const char *request_t int sock; if (!options.forward_x11) { error("Warning: ssh server tried X11 forwarding."); error("Warning: this is probably a break-in attempt by a " "malicious server."); return NULL; } - if (x11_refuse_time != 0 && monotime() >= x11_refuse_time) { + if (x11_refuse_time != 0 && (u_int)monotime() >= x11_refuse_time) { verbose("Rejected X11 connection after ForwardX11Timeout " "expired"); return NULL; } originator = packet_get_string(NULL); if (datafellows & SSH_BUG_X11FWD) { debug2("buggy server: x11 request w/o originator_port"); originator_port = 0;
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