[patch] openssh_4.7p1-blacklist.patch

openssh_4.7p1-blacklist.patch (text/plain), 28.38 KB, created by Robert Buchholz (RETIRED) on 2008-05-14 22:47:53 UTC

openssh (1:4.7p1-9) unstable; urgency=critical

  * Mitigate OpenSSL security vulnerability (CVE-2008-0166):
    - Add key blacklisting support. Keys listed in
      /etc/ssh/blacklist.TYPE-LENGTH will be rejected for authentication by
      sshd, unless "PermitBlacklistedKeys yes" is set in
      /etc/ssh/sshd_config.
    - Add a new program, ssh-vulnkey, which can be used to check keys
      against these blacklists.

 -- Colin Watson <[e-mail]>  Tue, 13 May 2008 12:33:38 +0100

Index: openssh-4.7p1/sshd_config.5
===================================================================
--- openssh-4.7p1.orig/sshd_config.5
+++ openssh-4.7p1/sshd_config.5
@@ -677,6 +677,20 @@ are refused if the number of unauthentic
 Specifies whether password authentication is allowed.
 The default is
 .Dq yes .
+.It Cm PermitBlacklistedKeys
+Specifies whether
+.Xr sshd 8
+should allow keys recorded in its blacklist of known-compromised keys (see
+.Xr ssh-vulnkey 1 ) .
+If
+.Dq yes ,
+then attempts to authenticate with compromised keys will be logged but
+accepted.
+If
+.Dq no ,
+then attempts to authenticate with compromised keys will be rejected.
+The default is
+.Dq no .
 .It Cm PermitEmptyPasswords
 When password authentication is allowed, it specifies whether the
 server allows login to accounts with empty password strings.
Index: openssh-4.7p1/sshd.c
===================================================================
--- openssh-4.7p1.orig/sshd.c
+++ openssh-4.7p1/sshd.c
@@ -1469,6 +1469,21 @@ main(int ac, char **av)
 
 	for (i = 0; i < options.num_host_key_files; i++) {
 		key = key_load_private(options.host_key_files[i], "", NULL);
+		if (key && blacklisted_key(key)) {
+			char *fp;
+			fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
+			if (options.permit_blacklisted_keys)
+				error("Host key %s blacklisted (see "
+				    "ssh-vulnkey(1)); continuing anyway", fp);
+			else
+				error("Host key %s blacklisted (see "
+				    "ssh-vulnkey(1))", fp);
+			xfree(fp);
+			if (!options.permit_blacklisted_keys) {
+				sensitive_data.host_keys[i] = NULL;
+				continue;
+			}
+		}
 		sensitive_data.host_keys[i] = key;
 		if (key == NULL) {
 			error("Could not load host key: %s",
Index: openssh-4.7p1/servconf.c
===================================================================
--- openssh-4.7p1.orig/servconf.c
+++ openssh-4.7p1/servconf.c
@@ -130,6 +130,7 @@ initialize_server_options(ServerOptions 
 	options->password_authentication = -1;
 	options->kbd_interactive_authentication = -1;
 	options->challenge_response_authentication = -1;
+	options->permit_blacklisted_keys = -1;
 	options->permit_empty_passwd = -1;
 	options->permit_user_env = -1;
 	options->use_login = -1;
@@ -248,6 +249,8 @@ fill_default_server_options(ServerOption
 		options->kbd_interactive_authentication = 0;
 	if (options->challenge_response_authentication == -1)
 		options->challenge_response_authentication = 1;
+	if (options->permit_blacklisted_keys == -1)
+		options->permit_blacklisted_keys = 0;
 	if (options->permit_empty_passwd == -1)
 		options->permit_empty_passwd = 0;
 	if (options->permit_user_env == -1)
@@ -349,7 +352,7 @@ typedef enum {
 	sListenAddress, sAddressFamily,
 	sPrintMotd, sPrintLastLog, sIgnoreRhosts,
 	sX11Forwarding, sX11DisplayOffset, sX11UseLocalhost,
-	sStrictModes, sEmptyPasswd, sTCPKeepAlive,
+	sStrictModes, sPermitBlacklistedKeys, sEmptyPasswd, sTCPKeepAlive,
 	sPermitUserEnvironment, sUseLogin, sAllowTcpForwarding, sCompression,
 	sAllowUsers, sDenyUsers, sAllowGroups, sDenyGroups,
 	sIgnoreUserKnownHosts, sCiphers, sMacs, sProtocol, sPidFile,
@@ -439,6 +442,7 @@ static struct {
 	{ "x11uselocalhost", sX11UseLocalhost, SSHCFG_ALL },
 	{ "xauthlocation", sXAuthLocation, SSHCFG_GLOBAL },
 	{ "strictmodes", sStrictModes, SSHCFG_GLOBAL },
+	{ "permitblacklistedkeys", sPermitBlacklistedKeys, SSHCFG_GLOBAL },
 	{ "permitemptypasswords", sEmptyPasswd, SSHCFG_GLOBAL },
 	{ "permituserenvironment", sPermitUserEnvironment, SSHCFG_GLOBAL },
 	{ "uselogin", sUseLogin, SSHCFG_GLOBAL },
@@ -1003,6 +1007,10 @@ parse_flag:
 		intptr = &options->tcp_keep_alive;
 		goto parse_flag;
 
+	case sPermitBlacklistedKeys:
+		intptr = &options->permit_blacklisted_keys;
+		goto parse_flag;
+
 	case sEmptyPasswd:
 		intptr = &options->permit_empty_passwd;
 		goto parse_flag;
Index: openssh-4.7p1/servconf.h
===================================================================
--- openssh-4.7p1.orig/servconf.h
+++ openssh-4.7p1/servconf.h
@@ -117,6 +117,7 @@ typedef struct {
 						 * authentication. */
 	int     kbd_interactive_authentication;	/* If true, permit */
 	int     challenge_response_authentication;
+	int     permit_blacklisted_keys;	/* If true, permit */
 	int     permit_empty_passwd;	/* If false, do not permit empty
 					 * passwords. */
 	int     permit_user_env;	/* If true, read ~/.ssh/environment */
Index: openssh-4.7p1/Makefile.in
===================================================================
--- openssh-4.7p1.orig/Makefile.in
+++ openssh-4.7p1/Makefile.in
@@ -73,7 +73,7 @@ INSTALL_SSH_RAND_HELPER=@INSTALL_SSH_RAN
 SSHX509_OBJS=ssh-x509.o ssh-xkalg.o x509_nm_cmp.o
 X509STORE_OBJS=x509store.o $(LDAP_OBJS) $(OCSP_OBJS)
 
-TARGETS=ssh$(EXEEXT) sshd$(EXEEXT) ssh-add$(EXEEXT) ssh-keygen$(EXEEXT) ssh-keyscan${EXEEXT} ssh-keysign${EXEEXT} ssh-agent$(EXEEXT) scp$(EXEEXT) ssh-rand-helper${EXEEXT} sftp-server$(EXEEXT) sftp$(EXEEXT)
+TARGETS=ssh$(EXEEXT) sshd$(EXEEXT) ssh-add$(EXEEXT) ssh-keygen$(EXEEXT) ssh-keyscan${EXEEXT} ssh-keysign${EXEEXT} ssh-agent$(EXEEXT) scp$(EXEEXT) ssh-rand-helper${EXEEXT} sftp-server$(EXEEXT) sftp$(EXEEXT) ssh-vulnkey$(EXEEXT)
 
 LIBSSH_OBJS=acss.o authfd.o authfile.o bufaux.o bufbn.o buffer.o \
 	canohost.o channels.o cipher.o cipher-acss.o cipher-aes.o \
@@ -101,8 +101,8 @@ SSHDOBJS=sshd.o auth-rhosts.o auth-passw
 	loginrec.o auth-pam.o auth-shadow.o auth-sia.o md5crypt.o \
 	audit.o audit-bsm.o platform.o $(X509STORE_OBJS)
 
-MANPAGES	= scp.1.out ssh-add.1.out ssh-agent.1.out ssh-keygen.1.out ssh-keyscan.1.out ssh.1.out sshd.8.out sftp-server.8.out sftp.1.out ssh-rand-helper.8.out ssh-keysign.8.out sshd_config.5.out ssh_config.5.out
-MANPAGES_IN	= scp.1 ssh-add.1 ssh-agent.1 ssh-keygen.1 ssh-keyscan.1 ssh.1 sshd.8 sftp-server.8 sftp.1 ssh-rand-helper.8 ssh-keysign.8 sshd_config.5 ssh_config.5
+MANPAGES	= scp.1.out ssh-add.1.out ssh-agent.1.out ssh-keygen.1.out ssh-keyscan.1.out ssh.1.out sshd.8.out sftp-server.8.out sftp.1.out ssh-rand-helper.8.out ssh-keysign.8.out ssh-vulnkey.1.out sshd_config.5.out ssh_config.5.out
+MANPAGES_IN	= scp.1 ssh-add.1 ssh-agent.1 ssh-keygen.1 ssh-keyscan.1 ssh.1 sshd.8 sftp-server.8 sftp.1 ssh-rand-helper.8 ssh-keysign.8 ssh-vulnkey.1 sshd_config.5 ssh_config.5
 MANTYPE		= @MANTYPE@
 
 CONFIGFILES=sshd_config.out ssh_config.out moduli.out
@@ -182,6 +182,9 @@ sftp$(EXEEXT): $(LIBCOMPAT) libssh.a sft
 ssh-rand-helper${EXEEXT}: $(LIBCOMPAT) libssh.a ssh-rand-helper.o
 	$(LD) -o $@ ssh-rand-helper.o $(LDFLAGS) -lssh -lopenbsd-compat $(LIBS)
 
+ssh-vulnkey$(EXEEXT): $(LIBCOMPAT) libssh.a ssh-vulnkey.o
+	$(LD) -o $@ ssh-vulnkey.o $(LDFLAGS) -lssh -lopenbsd-compat $(LIBS)
+
 # test driver for the loginrec code - not built by default
 logintest: logintest.o $(LIBCOMPAT) libssh.a loginrec.o
 	$(LD) -o $@ logintest.o $(LDFLAGS) loginrec.o -lopenbsd-compat -lssh $(LIBS)
@@ -284,6 +287,7 @@ install-files: scard-install
 	$(INSTALL) -m 4711 $(STRIP_OPT) ssh-keysign $(DESTDIR)$(SSH_KEYSIGN)
 	$(INSTALL) -m 0755 $(STRIP_OPT) sftp $(DESTDIR)$(bindir)/sftp
 	$(INSTALL) -m 0755 $(STRIP_OPT) sftp-server $(DESTDIR)$(SFTP_SERVER)
+	$(INSTALL) -m 0755 $(STRIP_OPT) ssh-vulnkey $(DESTDIR)$(bindir)/ssh-vulnkey
 	$(INSTALL) -m 644 ssh.1.out $(DESTDIR)$(mandir)/$(mansubdir)1/ssh.1
 	$(INSTALL) -m 644 scp.1.out $(DESTDIR)$(mandir)/$(mansubdir)1/scp.1
 	$(INSTALL) -m 644 ssh-add.1.out $(DESTDIR)$(mandir)/$(mansubdir)1/ssh-add.1
@@ -299,6 +303,7 @@ install-files: scard-install
 	$(INSTALL) -m 644 sftp.1.out $(DESTDIR)$(mandir)/$(mansubdir)1/sftp.1
 	$(INSTALL) -m 644 sftp-server.8.out $(DESTDIR)$(mandir)/$(mansubdir)8/sftp-server.8
 	$(INSTALL) -m 644 ssh-keysign.8.out $(DESTDIR)$(mandir)/$(mansubdir)8/ssh-keysign.8
+	$(INSTALL) -m 644 ssh-vulnkey.1.out $(DESTDIR)$(mandir)/$(mansubdir)1/ssh-vulnkey.1
 	-rm -f $(DESTDIR)$(bindir)/slogin
 	ln -s ./ssh$(EXEEXT) $(DESTDIR)$(bindir)/slogin
 	-rm -f $(DESTDIR)$(mandir)/$(mansubdir)1/slogin.1
@@ -380,6 +385,7 @@ uninstall:
 	-rm -f $(DESTDIR)$(bindir)/ssh-agent$(EXEEXT)
 	-rm -f $(DESTDIR)$(bindir)/ssh-keygen$(EXEEXT)
 	-rm -f $(DESTDIR)$(bindir)/ssh-keyscan$(EXEEXT)
+	-rm -f $(DESTDIR)$(bindir)/ssh-vulnkey$(EXEEXT)
 	-rm -f $(DESTDIR)$(bindir)/sftp$(EXEEXT)
 	-rm -f $(DESTDIR)$(sbindir)/sshd$(EXEEXT)
 	-rm -r $(DESTDIR)$(SFTP_SERVER)$(EXEEXT)
@@ -392,6 +398,7 @@ uninstall:
 	-rm -f $(DESTDIR)$(mandir)/$(mansubdir)1/ssh-keygen.1
 	-rm -f $(DESTDIR)$(mandir)/$(mansubdir)1/sftp.1
 	-rm -f $(DESTDIR)$(mandir)/$(mansubdir)1/ssh-keyscan.1
+	-rm -f $(DESTDIR)$(mandir)/$(mansubdir)1/ssh-vulnkey.1
 	-rm -f $(DESTDIR)$(mandir)/$(mansubdir)8/sshd.8
 	-rm -f $(DESTDIR)$(mandir)/$(mansubdir)8/ssh-rand-helper.8
 	-rm -f $(DESTDIR)$(mandir)/$(mansubdir)8/sftp-server.8
Index: openssh-4.7p1/auth-rh-rsa.c
===================================================================
--- openssh-4.7p1.orig/auth-rh-rsa.c
+++ openssh-4.7p1/auth-rh-rsa.c
@@ -20,6 +20,7 @@
 #include <pwd.h>
 #include <stdarg.h>
 
+#include "xmalloc.h"
 #include "packet.h"
 #include "uidswap.h"
 #include "log.h"
@@ -27,6 +28,7 @@
 #include "servconf.h"
 #include "key.h"
 #include "hostfile.h"
+#include "authfile.h"
 #include "pathnames.h"
 #include "auth.h"
 #include "canohost.h"
@@ -42,8 +44,22 @@ int
 auth_rhosts_rsa_key_allowed(struct passwd *pw, char *cuser, char *chost,
     Key *client_host_key)
 {
+	char *fp;
 	HostStatus host_status;
 
+	if (blacklisted_key(client_host_key)) {
+		fp = key_fingerprint(client_host_key, SSH_FP_MD5, SSH_FP_HEX);
+		if (options.permit_blacklisted_keys)
+			logit("Public key %s blacklisted (see "
+			    "ssh-vulnkey(1)); continuing anyway", fp);
+		else
+			logit("Public key %s blacklisted (see "
+			    "ssh-vulnkey(1))", fp);
+		xfree(fp);
+		if (!options.permit_blacklisted_keys)
+			return 0;
+	}
+
 	/* Check if we would accept it using rhosts authentication. */
 	if (!auth_rhosts(pw, cuser))
 		return 0;
Index: openssh-4.7p1/authfile.h
===================================================================
--- openssh-4.7p1.orig/authfile.h
+++ openssh-4.7p1/authfile.h
@@ -23,4 +23,7 @@ Key	*key_load_private_type(int, const ch
 Key	*key_load_private_pem(int, int, const char *, char **);
 int	 key_perm_ok(int, const char *);
 
+char	*blacklist_filename(const Key *key);
+int	 blacklisted_key(const Key *key);
+
 #endif
Index: openssh-4.7p1/ssh-vulnkey.1
===================================================================
--- /dev/null
+++ openssh-4.7p1/ssh-vulnkey.1
@@ -0,0 +1,151 @@
+.\" Copyright (c) 2008 Canonical Ltd.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.\"
+.Dd $Mdocdate: May 12 2008 $
+.Dt SSH-VULNKEY 1
+.Os
+.Sh NAME
+.Nm ssh-vulnkey
+.Nd check blacklist of compromised keys
+.Sh SYNOPSIS
+.Nm
+.Op Fl q
+.Ar file ...
+.Nm
+.Fl a
+.Sh DESCRIPTION
+.Nm
+checks a key against a blacklist of compromised keys.
+.Pp
+A substantial number of keys are known to have been generated using a broken
+version of OpenSSL distributed by Debian which failed to seed its random
+number generator correctly.
+Keys generated using these OpenSSL versions should be assumed to be
+compromised.
+This tool may be useful in checking for such keys.
+.Pp
+Keys that are compromised cannot be repaired; replacements must be generated
+using
+.Xr ssh-keygen 1 .
+Make sure to update
+.Pa authorized_keys
+files on all systems where compromised keys were permitted to authenticate.
+.Pp
+The argument list will be interpreted as a list of paths to public key files
+or
+.Pa authorized_keys
+files.
+If no suitable file is found at a given path,
+.Nm
+will append
+.Pa .pub
+and retry, in case it was given a private key file.
+If no files are given as arguments,
+.Nm
+will check
+.Pa ~/.ssh/id_rsa ,
+.Pa ~/.ssh/id_dsa ,
+.Pa ~/.ssh/identity ,
+.Pa ~/.ssh/authorized_keys
+and
+.Pa ~/.ssh/authorized_keys2 ,
+as well as the system's host keys if readable.
+.Pp
+If
+.Dq -
+is given as an argument,
+.Nm
+will read from standard input.
+This can be used to process output from
+.Xr ssh-keyscan 1 ,
+for example:
+.Pp
+.Dl $ ssh-keyscan -t rsa remote.example.org | ssh-vulnkey -
+.Pp
+.Nm
+will exit zero if any of the given keys were in the compromised list,
+otherwise non-zero.
+.Pp
+Unless the
+.Cm PermitBlacklistedKeys
+option is used,
+.Xr sshd 8
+will reject attempts to authenticate with keys in the compromised list.
+.Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl a
+Check keys of all users on the system.
+You will typically need to run
+.Nm
+as root to use this option.
+For each user,
+.Nm
+will check
+.Pa ~/.ssh/id_rsa ,
+.Pa ~/.ssh/id_dsa ,
+.Pa ~/.ssh/identity ,
+.Pa ~/.ssh/authorized_keys
+and
+.Pa ~/.ssh/authorized_keys2 .
+It will also check the system's host keys.
+.It Fl q
+Quiet mode.
+Normally,
+.Nm
+outputs the fingerprint of each key scanned, with a description of its
+status.
+This option suppresses that output.
+.El
+.Sh BLACKLIST FILE FORMAT
+The blacklist file may start with comments, on lines starting with
+.Dq # .
+After these initial comments, it must follow a strict format:
+.Pp
+.Bl -bullet -offset indent -compact
+.It
+All the lines must be exactly the same length (20 characters followed by a
+newline) and must be in sorted order.
+.It
+Each line must consist of the lower-case hexadecimal MD5 key fingerprint,
+without colons, and with the first 12 characters removed (that is, the least
+significant 80 bits of the fingerprint).
+.El
+.Pp
+The key fingerprint may be generated using
+.Xr ssh-keygen 1 :
+.Pp
+.Dl $ ssh-keygen -l -f /path/to/key
+.Pp
+This strict format is necessary to allow the blacklist file to be checked
+quickly, using a binary-search algorithm.
+.Sh SEE ALSO
+.Xr ssh-keygen 1 ,
+.Xr sshd 8
+.Sh AUTHORS
+.An -nosplit
+.An Colin Watson Aq [e-mail]
+.Pp
+Florian Weimer suggested the option to check keys of all users, and the idea
+of processing
+.Xr ssh-keyscan 1
+output.
Index: openssh-4.7p1/auth2-hostbased.c
===================================================================
--- openssh-4.7p1.orig/auth2-hostbased.c
+++ openssh-4.7p1/auth2-hostbased.c
@@ -40,6 +40,7 @@
 #include "compat.h"
 #include "key.h"
 #include "hostfile.h"
+#include "authfile.h"
 #include "auth.h"
 #include "canohost.h"
 #ifdef GSSAPI
@@ -170,10 +171,24 @@ int
 hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
     Key *key)
 {
+	char *fp;
 	const char *resolvedname, *ipaddr, *lookup;
 	HostStatus host_status;
 	int len;
 
+	if (blacklisted_key(key)) {
+		fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
+		if (options.permit_blacklisted_keys)
+			logit("Public key %s blacklisted (see "
+			    "ssh-vulnkey(1)); continuing anyway", fp);
+		else
+			logit("Public key %s blacklisted (see "
+			    "ssh-vulnkey(1))", fp);
+		xfree(fp);
+		if (!options.permit_blacklisted_keys)
+			return 0;
+	}
+
 	resolvedname = get_canonical_hostname(options.use_dns);
 	ipaddr = get_remote_ipaddr();
 
Index: openssh-4.7p1/authfile.c
===================================================================
--- openssh-4.7p1.orig/authfile.c
+++ openssh-4.7p1/authfile.c
@@ -68,6 +68,7 @@
 #include "ssh-x509.h"
 #include "misc.h"
 #include "atomicio.h"
+#include "pathnames.h"
 
 /* Version identification string for SSH v1 identity files. */
 static const char authfile_id_string[] =
@@ -696,3 +697,113 @@ key_load_public(const char *filename, ch
 	key_free(pub);
 	return NULL;
 }
+
+char *
+blacklist_filename(const Key *key)
+{
+	char *name;
+
+	xasprintf(&name, "%s.%s-%u",
+	    _PATH_BLACKLIST, key_type(key), key_size(key));
+	return name;
+}
+
+/* Scan a blacklist of known-vulnerable keys. */
+int
+blacklisted_key(const Key *key)
+{
+	char *blacklist_file;
+	int fd = -1;
+	char *dgst_hex = NULL;
+	char *dgst_packed = NULL, *p;
+	int i;
+	size_t line_len;
+	struct stat st;
+	char buf[256];
+	off_t start, lower, upper;
+	int ret = 0;
+
+	blacklist_file = blacklist_filename(key);
+	debug("Checking blacklist file %s", blacklist_file);
+	fd = open(blacklist_file, O_RDONLY);
+	if (fd < 0)
+		goto out;
+
+	dgst_hex = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
+	/* Remove all colons */
+	dgst_packed = xcalloc(1, strlen(dgst_hex) + 1);
+	for (i = 0, p = dgst_packed; dgst_hex[i]; i++)
+		if (dgst_hex[i] != ':')
+			*p++ = dgst_hex[i];
+	/* Only compare least-significant 80 bits (to keep the blacklist
+	 * size down)
+	 */
+	line_len = strlen(dgst_packed + 12);
+	if (line_len > 32)
+		goto out;
+
+	/* Skip leading comments */
+	start = 0;
+	for (;;) {
+		ssize_t r;
+		char *newline;
+
+		r = atomicio(read, fd, buf, 256);
+		if (r <= 0)
+			goto out;
+		if (buf[0] != '#')
+			break;
+
+		newline = memchr(buf, '\n', 256);
+		if (!newline)
+			goto out;
+		start += newline + 1 - buf;
+		if (lseek(fd, start, SEEK_SET) < 0)
+			goto out;
+	}
+
+	/* Initialise binary search record numbers */
+	if (fstat(fd, &st) < 0)
+		goto out;
+	lower = 0;
+	upper = (st.st_size - start) / (line_len + 1);
+
+	while (lower != upper) {
+		off_t cur;
+		char buf[32];
+		int cmp;
+
+		cur = lower + (upper - lower) / 2;
+
+		/* Read this line and compare to digest; this is
+		 * overflow-safe since cur < max(off_t) / (line_len + 1) */
+		if (lseek(fd, start + cur * (line_len + 1), SEEK_SET) < 0)
+			break;
+		if (atomicio(read, fd, buf, line_len) != line_len)
+			break;
+		cmp = memcmp(buf, dgst_packed + 12, line_len);
+		if (cmp < 0) {
+			if (cur == lower)
+				break;
+			lower = cur;
+		} else if (cmp > 0) {
+			if (cur == upper)
+				break;
+			upper = cur;
+		} else {
+			debug("Found %s in blacklist", dgst_hex);
+			ret = 1;
+			break;
+		}
+	}
+
+out:
+	if (dgst_packed)
+		xfree(dgst_packed);
+	if (dgst_hex)
+		xfree(dgst_hex);
+	if (fd >= 0)
+		close(fd);
+	xfree(blacklist_file);
+	return ret;
+}
Index: openssh-4.7p1/ssh-vulnkey.c
===================================================================
--- /dev/null
+++ openssh-4.7p1/ssh-vulnkey.c
@@ -0,0 +1,311 @@
+/*
+ * Copyright (c) 2008 Canonical Ltd.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (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 "includes.h"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <string.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <openssl/evp.h>
+
+#include "xmalloc.h"
+#include "ssh.h"
+#include "log.h"
+#include "key.h"
+#include "authfile.h"
+#include "pathnames.h"
+#include "misc.h"
+
+extern char *__progname;
+
+/* Default files to check */
+static char *default_host_files[] = {
+	_PATH_HOST_RSA_KEY_FILE,
+	_PATH_HOST_DSA_KEY_FILE,
+	_PATH_HOST_KEY_FILE,
+	NULL
+};
+static char *default_files[] = {
+	_PATH_SSH_CLIENT_ID_RSA,
+	_PATH_SSH_CLIENT_ID_DSA,
+	_PATH_SSH_CLIENT_IDENTITY,
+	_PATH_SSH_USER_PERMITTED_KEYS,
+	_PATH_SSH_USER_PERMITTED_KEYS2,
+	NULL
+};
+
+static int quiet = 0;
+
+static void
+usage(void)
+{
+	fprintf(stderr, "usage: %s [-aq] [file ...]\n", __progname);
+	fprintf(stderr, "Options:\n");
+	fprintf(stderr, "  -a          Check keys of all users.\n");
+	fprintf(stderr, "  -q          Quiet mode.\n");
+	exit(1);
+}
+
+void
+describe_key(const char *msg, const Key *key, const char *comment)
+{
+	char *fp;
+
+	fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
+	if (!quiet)
+		printf("%s: %u %s %s\n", msg, key_size(key), fp, comment);
+	xfree(fp);
+}
+
+int
+do_key(const Key *key, const char *comment)
+{
+	char *blacklist_file;
+	struct stat st;
+	int ret = 1;
+
+	blacklist_file = blacklist_filename(key);
+	if (stat(blacklist_file, &st) < 0)
+		describe_key("Unknown (no blacklist information)",
+		    key, comment);
+	else if (blacklisted_key(key)) {
+		describe_key("COMPROMISED", key, comment);
+		ret = 0;
+	} else
+		describe_key("Not blacklisted", key, comment);
+	xfree(blacklist_file);
+
+	return ret;
+}
+
+int
+do_filename(const char *filename, int quiet_open)
+{
+	FILE *f;
+	char line[SSH_MAX_PUBKEY_BYTES];
+	char *cp;
+	u_long linenum = 0;
+	Key *key;
+	char *comment = NULL;
+	int found = 0, ret = 1;
+
+	/* Copy much of key_load_public's logic here so that we can read
+	 * several keys from a single file (e.g. authorized_keys).
+	 */
+
+	if (strcmp(filename, "-") != 0) {
+		f = fopen(filename, "r");
+		if (!f) {
+			char pubfile[MAXPATHLEN];
+			if (strlcpy(pubfile, filename, sizeof pubfile) <
+			    sizeof(pubfile) &&
+			    strlcat(pubfile, ".pub", sizeof pubfile) <
+			    sizeof(pubfile))
+				f = fopen(pubfile, "r");
+		}
+		if (!f) {
+			if (!quiet_open)
+				perror(filename);
+			return -1;
+		}
+	} else
+		f = stdin;
+	while (read_keyfile_line(f, filename, line, sizeof(line),
+		    &linenum) != -1) {
+		cp = line;
+		switch (*cp) {
+		case '#':
+		case '\n':
+		case '\0':
+			continue;
+		}
+		/* Skip leading whitespace. */
+		for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)
+			;
+		/* Cope with ssh-keyscan output. */
+		comment = NULL;
+		if (*cp) {
+			char *space;
+			int type;
+
+			space = strchr(cp, ' ');
+			if (!space)
+				continue;
+			*space = '\0';
+			type = key_type_from_name(cp);
+			if (type == KEY_UNSPEC) {
+				comment = xstrdup(cp);
+				cp = space + 1;
+			}
+			*space = ' ';
+		}
+		if (!comment)
+			comment = xstrdup(filename);
+		if (*cp) {
+			key = key_new(KEY_RSA1);
+			if (key_read(key, &cp) == 1) {
+				if (!do_key(key, comment))
+					ret = 0;
+				key_free(key);
+				found = 1;
+			} else {
+				key_free(key);
+				key = key_new(KEY_UNSPEC);
+				if (key_read(key, &cp) == 1) {
+					if (!do_key(key, comment))
+						ret = 0;
+					key_free(key);
+					found = 1;
+				}
+			}
+		}
+		xfree(comment);
+		comment = NULL;
+	}
+	if (f != stdin)
+		fclose(f);
+
+	if (!found && filename) {
+		key = key_load_public(filename, &comment);
+		if (key) {
+			if (!do_key(key, comment))
+				ret = 0;
+			found = 1;
+		}
+		if (comment)
+			xfree(comment);
+	}
+
+	return ret;
+}
+
+int
+do_host(void)
+{
+	int i;
+	struct stat st;
+	int ret = 1;
+
+	for (i = 0; default_host_files[i]; i++) {
+		if (stat(default_host_files[i], &st) < 0)
+			continue;
+		if (!do_filename(default_host_files[i], 1))
+			ret = 0;
+	}
+
+	return ret;
+}
+
+int
+do_user(const char *dir)
+{
+	int i;
+	char buf[MAXPATHLEN];
+	struct stat st;
+	int ret = 1;
+
+	for (i = 0; default_files[i]; i++) {
+		snprintf(buf, sizeof(buf), "%s/%s", dir, default_files[i]);
+		if (stat(buf, &st) < 0)
+			continue;
+		if (!do_filename(buf, 0))
+			ret = 0;
+	}
+
+	return ret;
+}
+
+int
+main(int argc, char **argv)
+{
+	int opt, all_users = 0;
+	int ret = 1;
+	extern int optind;
+
+	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
+	sanitise_stdfd();
+
+	__progname = ssh_get_progname(argv[0]);
+
+	SSLeay_add_all_algorithms();
+	log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1);
+
+	/* We don't need the RNG ourselves, but symbol references here allow
+	 * ld to link us properly.
+	 */
+	init_rng();
+	seed_rng();
+
+	while ((opt = getopt(argc, argv, "ahq")) != -1) {
+		switch (opt) {
+		case 'a':
+			all_users = 1;
+			break;
+		case 'q':
+			quiet = 1;
+			break;
+		case 'h':
+		default:
+			usage();
+		}
+	}
+
+	if (all_users) {
+		struct passwd *pw;
+
+		if (!do_host())
+			ret = 0;
+
+		while ((pw = getpwent()) != NULL) {
+			if (pw->pw_dir) {
+				if (!do_user(pw->pw_dir))
+					ret = 0;
+			}
+		}
+	} else if (optind == argc) {
+		struct passwd *pw;
+
+		if (!do_host())
+			ret = 0;
+
+		if ((pw = getpwuid(getuid())) == NULL)
+			fprintf(stderr, "No user found with uid %u\n",
+			    (u_int)getuid());
+		else {
+			if (!do_user(pw->pw_dir))
+				ret = 0;
+		}
+	} else {
+		while (optind < argc)
+			if (!do_filename(argv[optind++], 0))
+				ret = 0;
+	}
+
+	return ret;
+}
Index: openssh-4.7p1/auth-rsa.c
===================================================================
--- openssh-4.7p1.orig/auth-rsa.c
+++ openssh-4.7p1/auth-rsa.c
@@ -40,6 +40,7 @@
 #include "servconf.h"
 #include "key.h"
 #include "hostfile.h"
+#include "authfile.h"
 #include "auth.h"
 #ifdef GSSAPI
 #include "ssh-gss.h"
@@ -221,6 +222,7 @@ auth_rsa_key_allowed(struct passwd *pw, 
 		char *cp;
 		char *key_options;
 		int keybits;
+		char *fp;
 
 		/* Skip leading whitespace, empty and comment lines. */
 		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
@@ -265,6 +267,19 @@ auth_rsa_key_allowed(struct passwd *pw, 
 			    "actual %d vs. announced %d.",
 			    file, linenum, BN_num_bits(key->rsa->n), bits);
 
+		if (blacklisted_key(key)) {
+			fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
+			if (options.permit_blacklisted_keys)
+				logit("Public key %s blacklisted (see "
+				    "ssh-vulnkey(1)); continuing anyway", fp);
+			else
+				logit("Public key %s blacklisted (see "
+				    "ssh-vulnkey(1))", fp);
+			xfree(fp);
+			if (!options.permit_blacklisted_keys)
+				continue;
+		}
+
 		/* We have found the desired key. */
 		/*
 		 * If our options do not allow this key to be used,
Index: openssh-4.7p1/pathnames.h
===================================================================
--- openssh-4.7p1.orig/pathnames.h
+++ openssh-4.7p1/pathnames.h
@@ -66,6 +66,8 @@
 /* Backwards compatibility */
 #define _PATH_DH_PRIMES			SSHDIR "/primes"
 
+#define _PATH_BLACKLIST			SSHDIR "/blacklist"
+
 #ifndef _PATH_SSH_PROGRAM
 #define _PATH_SSH_PROGRAM		"/usr/bin/ssh"
 #endif
Index: openssh-4.7p1/auth2-pubkey.c
===================================================================
--- openssh-4.7p1.orig/auth2-pubkey.c
+++ openssh-4.7p1/auth2-pubkey.c
@@ -47,6 +47,7 @@
 #include "compat.h"
 #include "key.h"
 #include "hostfile.h"
+#include "authfile.h"
 #include "auth.h"
 #include "pathnames.h"
 #include "uidswap.h"
@@ -411,9 +412,23 @@ user_key_allowed2(struct passwd *pw, Key
 int
 user_key_allowed(struct passwd *pw, Key *key)
 {
+	char *fp;
 	int success;
 	char *file;
 
+	if (blacklisted_key(key)) {
+		fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
+		if (options.permit_blacklisted_keys)
+			logit("Public key %s blacklisted (see "
+			    "ssh-vulnkey(1)); continuing anyway", fp);
+		else
+			logit("Public key %s blacklisted (see "
+			    "ssh-vulnkey(1))", fp);
+		xfree(fp);
+		if (!options.permit_blacklisted_keys)
+			return 0;
+	}
+
 	file = authorized_keys_file(pw);
 	success = user_key_allowed2(pw, key, file);
 	xfree(file);