@@ -, +, @@ * 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 Tue, 13 May 2008 12:33:38 +0100 --- openssh-4.7p1/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. --- openssh-4.7p1/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", --- openssh-4.7p1/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; --- openssh-4.7p1/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 */ --- openssh-4.7p1/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 --- openssh-4.7p1/auth-rh-rsa.c +++ openssh-4.7p1/auth-rh-rsa.c @@ -20,6 +20,7 @@ #include #include +#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; --- openssh-4.7p1/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 --- openssh-4.7p1/ssh-vulnkey.1 +++ 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 cjwatson@ubuntu.com +.Pp +Florian Weimer suggested the option to check keys of all users, and the idea +of processing +.Xr ssh-keyscan 1 +output. --- openssh-4.7p1/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(); --- openssh-4.7p1/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; +} --- openssh-4.7p1/ssh-vulnkey.c +++ 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 +#include + +#include +#include +#include +#include + +#include + +#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; +} --- openssh-4.7p1/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, --- openssh-4.7p1/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 --- openssh-4.7p1/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);