[patch] openssh-5.0p1-blacklist.patch

openssh-5.0p1-blacklist.patch (text/plain), 16.72 KB, created by SpanKY on 2008-05-31 09:50:44 UTC

--- openssh-5.0p1/Makefile.in
+++ openssh-5.0p1/Makefile.in
@@ -62,7 +62,7 @@
 
 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)
 
-LIBSSH_OBJS=acss.o authfd.o authfile.o bufaux.o bufbn.o buffer.o \
+LIBSSH_OBJS=acss.o authfd.o authfile.o blacklist.o bufaux.o bufbn.o buffer.o \
 	canohost.o channels.o cipher.o cipher-acss.o cipher-aes.o \
 	cipher-bf1.o cipher-ctr.o cipher-3des1.o cleanup.o \
 	compat.o compress.o crc32.o deattack.o fatal.o hostfile.o \
--- openssh-5.0p1/auth-rh-rsa.c
+++ openssh-5.0p1/auth-rh-rsa.c
@@ -34,6 +34,7 @@
 #include "ssh-gss.h"
 #endif
 #include "monitor_wrap.h"
+#include "blacklist.h"
 
 /* import */
 extern ServerOptions options;
@@ -48,6 +49,9 @@
 	if (!auth_rhosts(pw, cuser))
 		return 0;
 
+	if (blacklisted_key(client_host_key, 0))
+		return 0;
+
 	host_status = check_key_in_hostfiles(pw, client_host_key,
 	    chost, _PATH_SSH_SYSTEM_HOSTFILE,
 	    options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
--- openssh-5.0p1/auth-rsa.c
+++ openssh-5.0p1/auth-rsa.c
@@ -47,6 +47,7 @@
 #include "monitor_wrap.h"
 #include "ssh.h"
 #include "misc.h"
+#include "blacklist.h"
 
 /* import */
 extern ServerOptions options;
@@ -265,6 +272,9 @@
 			    "actual %d vs. announced %d.",
 			    file, linenum, BN_num_bits(key->rsa->n), bits);
 
+		if (blacklisted_key(key, 0))
+			continue;
+
 		/* We have found the desired key. */
 		/*
 		 * If our options do not allow this key to be used,
--- openssh-5.0p1/auth2-hostbased.c
+++ openssh-5.0p1/auth2-hostbased.c
@@ -47,6 +47,7 @@
 #endif
 #include "monitor_wrap.h"
 #include "pathnames.h"
+#include "blacklist.h"
 
 /* import */
 extern ServerOptions options;
@@ -145,6 +146,9 @@
 	HostStatus host_status;
 	int len;
 
+	if (blacklisted_key(key, 0))
+		return 0;
+
 	resolvedname = get_canonical_hostname(options.use_dns);
 	ipaddr = get_remote_ipaddr();
 
--- openssh-5.0p1/auth2-pubkey.c
+++ openssh-5.0p1/auth2-pubkey.c
@@ -52,6 +52,7 @@
 #endif
 #include "monitor_wrap.h"
 #include "misc.h"
+#include "blacklist.h"
 
 /* import */
 extern ServerOptions options;
@@ -272,6 +273,9 @@
 	int success;
 	char *file;
 
+	if (blacklisted_key(key, 0))
+		return 0;
+
 	file = authorized_keys_file(pw);
 	success = user_key_allowed2(pw, key, file);
 	xfree(file);
new file mode 100644
--- /dev/null
+++ openssh-5.0p1/blacklist.c
@@ -0,0 +1,267 @@
+/*
+ * Support for RSA/DSA key blacklisting based on partial fingerprints,
+ * developed under Openwall Project for Owl - http://www.openwall.com/Owl/
+ *
+ * Copyright (c) 2008 Dmitry V. Levin <ldv at cvs.openwall.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * The blacklist encoding was designed by Solar Designer and Dmitry V. Levin.
+ * No intellectual property rights to the encoding scheme are claimed.
+ *
+ * This effort was supported by CivicActions - http://www.civicactions.com
+ *
+ * The file size to encode 294,903 of 48-bit fingerprints is just 1.3 MB,
+ * which corresponds to less than 4.5 bytes per fingerprint.
+ */
+
+#include "includes.h"
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+
+#include "atomicio.h"
+#include "blacklist.h"
+#include "canohost.h"
+#include "log.h"
+#include "pathnames.h"
+#include "servconf.h"
+#include "xmalloc.h"
+
+extern ServerOptions options;
+
+typedef struct
+{
+	/* format version identifier */
+	char    version[8];
+	/* index size, in bits */
+	uint8_t index_size;
+	/* offset size, in bits */
+	uint8_t offset_size;
+	/* record size, in bits */
+	uint8_t record_bits;
+	/* number of records */
+	uint8_t records[3];
+	/* offset shift */
+	uint8_t shift[2];
+
+} __attribute__((packed)) blacklist_header;
+
+static unsigned
+c2u(uint8_t c)
+{
+	return (c >= 'a') ? (c - 'a' + 10) : (c - '0');
+}
+
+static blacklist_error_t
+validate_blacklist(const char *fname, int fd, unsigned *bytes,
+		   unsigned *records, unsigned *shift)
+{
+	unsigned expected;
+	struct stat st;
+	blacklist_header header;
+
+	if (fstat(fd, &st)) {
+		error("fstat for blacklist file %s failed: %m", fname);
+		return BLACKLIST_ERROR_ACCESS;
+	}
+
+	if (atomicio(read, fd, &header, sizeof(header)) != sizeof(header)) {
+		error("read blacklist file %s header failed: %m", fname);
+		return BLACKLIST_ERROR_ACCESS;
+	}
+
+	if (memcmp(header.version, "SSH-FP", 6)) {
+		error("blacklist file %s has unrecognized format", fname);
+		return BLACKLIST_ERROR_FORMAT;
+	}
+
+	if (header.index_size != 16 || header.offset_size != 16 ||
+	    memcmp(header.version, "SSH-FP00", 8)) {
+		error("blacklist file %s has unsupported format", fname);
+		return BLACKLIST_ERROR_VERSION;
+	}
+
+	*bytes = (header.record_bits >> 3) - 2;
+	*records =
+		(((header.records[0] << 8) +
+		  header.records[1]) << 8) + header.records[2];
+	*shift = (header.shift[0] << 8) + header.shift[1];
+
+	expected = sizeof(header) + 0x20000 + (*records) * (*bytes);
+	if (st.st_size != expected) {
+		error("blacklist file %s size mismatch: "
+		      "expected size %u, found size %lu",
+		      fname, expected, (unsigned long) st.st_size);
+		return BLACKLIST_ERROR_ACCESS;
+	}
+
+	return BLACKLIST_ERROR_NONE;
+}
+
+static int
+expected_offset(uint16_t index, uint16_t shift, unsigned records)
+{
+	return ((index * (long long) records) >> 16) - shift;
+}
+
+static int
+xlseek(const char *fname, int fd, unsigned seek)
+{
+	if (lseek(fd, seek, SEEK_SET) != seek) {
+		error("lseek for blacklist file %s failed: %m", fname);
+		return BLACKLIST_ERROR_ACCESS;
+	}
+	return BLACKLIST_ERROR_NONE;
+}
+
+static blacklist_error_t
+check(const char *fname, int fd, const char *s)
+{
+	unsigned bytes, records, shift;
+	unsigned num, i, j;
+	int     off_start, off_end;
+	blacklist_error_t rc;
+	uint16_t index;
+	/* max number of bytes stored in record_bits, minus two bytes used for index */
+	uint8_t buf[(0xff >> 3) - 2];
+
+	if ((rc = validate_blacklist(fname, fd, &bytes, &records, &shift)))
+		return rc;
+
+	index = (((((c2u(s[0]) << 4) | c2u(s[1])) << 4) |
+		  c2u(s[2])) << 4) | c2u(s[3]);
+	if (xlseek(fname, fd, sizeof(blacklist_header) + index * 2))
+		return BLACKLIST_ERROR_ACCESS;
+
+	if (atomicio(read, fd, buf, 4) != 4) {
+		error("read blacklist file %s offsets failed: %m", fname);
+		return BLACKLIST_ERROR_ACCESS;
+	}
+
+	off_start = (buf[0] << 8) + buf[1] +
+		expected_offset(index, shift, records);
+	if (off_start < 0 || (unsigned) off_start > records) {
+		error("blacklist file %s off_start overflow [%d] for index %#x",
+		      fname, off_start, index);
+		return BLACKLIST_ERROR_ACCESS;
+	}
+	if (index < 0xffff) {
+		off_end = (buf[2] << 8) + buf[3] +
+			expected_offset(index + 1, shift, records);
+		if (off_end < off_start || (unsigned) off_end > records) {
+			error("blacklist file %s off_end overflow [%d] for index %#x",
+			      fname, off_end, index);
+			return BLACKLIST_ERROR_ACCESS;
+		}
+	} else
+		off_end = records;
+
+	if (xlseek(fname, fd,
+		   sizeof(blacklist_header) + 0x20000 + off_start * bytes))
+		return BLACKLIST_ERROR_ACCESS;
+
+	num = off_end - off_start;
+	for (i = 0; i < num; ++i) {
+		if (atomicio(read, fd, buf, bytes) != bytes) {
+			error("read blacklist file %s fingerprints failed: %m",
+			      fname);
+			return BLACKLIST_ERROR_ACCESS;
+		}
+
+		for (j = 0; j < bytes; ++j)
+			if (((c2u(s[4 + j * 2]) << 4) | c2u(s[5 + j * 2])) !=
+			    buf[j])
+				break;
+		if (j >= bytes) {
+			debug("blacklisted fingerprint: %s offset=%u, number=%u",
+			      s, off_start, i);
+			return BLACKLIST_ERROR_ALL;
+		}
+	}
+
+	debug("non-blacklisted fingerprint: %s offset=%u, number=%u",
+	      s, off_start, num);
+	return BLACKLIST_ERROR_NONE;
+}
+
+static blacklist_error_t
+blacklisted_fingerprint(const char *hex)
+{
+	int     fd = -1;
+	blacklist_error_t rc = BLACKLIST_ERROR_ACCESS;
+	const char *fname = _PATH_BLACKLIST;
+	char   *s, *p;
+
+	debug("Checking fingerprint %s using blacklist file %s", hex, fname);
+
+	s = xstrdup(hex);
+	for (p = s; *hex; ++hex)
+		if (*hex != ':')
+			*p++ = *hex;
+	*p = '\0';
+
+	if (strlen(s) != 32 || strlen(s) != strspn(s, "0123456789abcdef")) {
+		error("%s: invalid fingerprint", s);
+		goto out;
+	}
+
+	if ((fd = open(fname, O_RDONLY)) < 0) {
+		if (ENOENT == errno) {
+			rc = BLACKLIST_ERROR_MISSING;
+			verbose("open blacklist file %s failed: %m", fname);
+		} else
+			logit("open blacklist file %s failed: %m", fname);
+		goto out;
+	}
+
+	rc = check(fname, fd, s);
+
+out:
+	close(fd);
+	xfree(s);
+	return rc;
+}
+
+int
+blacklisted_key(Key *key, int hostkey)
+{
+	int     rc;
+	const char *text;
+	char   *fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
+
+	switch ((rc = blacklisted_fingerprint(fp))) {
+		case BLACKLIST_ERROR_NONE:
+			break;
+		case BLACKLIST_ERROR_ALL:
+			text = (options.ignore_blacklist_errors == rc) ?
+			       "Permitted" : "Rejected";
+			if (hostkey)
+				logit("%s blacklisted host key %s", text, fp);
+			else
+				logit("%s blacklisted public key %s from %.100s",
+				      text, fp, get_remote_ipaddr());
+			break;
+		default:
+			if (hostkey)
+				logit("Unable to check blacklist for host key %s",
+				      fp);
+			else
+				logit("Unable to check blacklist for public key %s from %.100s",
+				      fp, get_remote_ipaddr());
+	}
+
+	xfree(fp);
+	return (rc > options.ignore_blacklist_errors);
+}
new file mode 100644
--- /dev/null
+++ openssh-5.0p1/blacklist.h
@@ -0,0 +1,37 @@
+/*
+ * Support for RSA/DSA key blacklisting based on partial fingerprints,
+ * developed under Openwall Project for Owl - http://www.openwall.com/Owl/
+ *
+ * Copyright (c) 2008 Dmitry V. Levin <ldv at cvs.openwall.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef BLACKLIST_H_
+#define BLACKLIST_H_
+
+#include "key.h"
+
+int blacklisted_key(Key *, int);
+
+typedef enum
+{
+	BLACKLIST_ERROR_NONE = 0,
+	BLACKLIST_ERROR_MISSING,
+	BLACKLIST_ERROR_VERSION,
+	BLACKLIST_ERROR_FORMAT,
+	BLACKLIST_ERROR_ACCESS,
+	BLACKLIST_ERROR_ALL
+} blacklist_error_t;
+
+#endif /* BLACKLIST_H_ */
--- openssh-5.0p1/pathnames.h
+++ openssh-5.0p1/pathnames.h
@@ -43,6 +43,8 @@
 /* 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-5.0p1/servconf.c
+++ openssh-5.0p1/servconf.c
@@ -39,6 +39,7 @@
 #include "match.h"
 #include "channels.h"
 #include "groupaccess.h"
+#include "blacklist.h"
 
 static void add_listen_addr(ServerOptions *, char *, u_short);
 static void add_one_listen_addr(ServerOptions *, char *, u_short);
@@ -94,6 +95,7 @@
 	options->password_authentication = -1;
 	options->kbd_interactive_authentication = -1;
 	options->challenge_response_authentication = -1;
+	options->ignore_blacklist_errors = -1;
 	options->permit_empty_passwd = -1;
 	options->permit_user_env = -1;
 	options->use_login = -1;
@@ -213,6 +217,8 @@
 		options->kbd_interactive_authentication = 0;
 	if (options->challenge_response_authentication == -1)
 		options->challenge_response_authentication = 1;
+	if (options->ignore_blacklist_errors == -1)
+		options->ignore_blacklist_errors = BLACKLIST_ERROR_ALL; //VERSION;
 	if (options->permit_empty_passwd == -1)
 		options->permit_empty_passwd = 0;
 	if (options->permit_user_env == -1)
@@ -282,7 +299,7 @@
 	sListenAddress, sAddressFamily,
 	sPrintMotd, sPrintLastLog, sIgnoreRhosts,
 	sX11Forwarding, sX11DisplayOffset, sX11UseLocalhost,
-	sStrictModes, sEmptyPasswd, sTCPKeepAlive,
+	sStrictModes, sIgnoreBlacklistErrors, sEmptyPasswd, sTCPKeepAlive,
 	sPermitUserEnvironment, sUseLogin, sAllowTcpForwarding, sCompression,
 	sAllowUsers, sDenyUsers, sAllowGroups, sDenyGroups,
 	sIgnoreUserKnownHosts, sCiphers, sMacs, sProtocol, sPidFile,
@@ -372,6 +390,7 @@
 	{ "x11uselocalhost", sX11UseLocalhost, SSHCFG_ALL },
 	{ "xauthlocation", sXAuthLocation, SSHCFG_GLOBAL },
 	{ "strictmodes", sStrictModes, SSHCFG_GLOBAL },
+	{ "ignoreblacklisterrors", sIgnoreBlacklistErrors, SSHCFG_GLOBAL },
 	{ "permitemptypasswords", sEmptyPasswd, SSHCFG_GLOBAL },
 	{ "permituserenvironment", sPermitUserEnvironment, SSHCFG_GLOBAL },
 	{ "uselogin", sUseLogin, SSHCFG_GLOBAL },
@@ -923,6 +944,32 @@
 		intptr = &options->tcp_keep_alive;
 		goto parse_flag;
 
+	case sIgnoreBlacklistErrors:
+		intptr = &options->ignore_blacklist_errors;
+		arg = strdelim(&cp);
+		if (!arg || *arg == '\0')
+			fatal("%s line %d: missing none/missing/version/format/access/all argument.",
+			    filename, linenum);
+		value = 0;	/* silence compiler */
+		if (strcmp(arg, "none") == 0)
+			value = BLACKLIST_ERROR_NONE;
+		else if (strcmp(arg, "missing") == 0)
+			value = BLACKLIST_ERROR_MISSING;
+		else if (strcmp(arg, "version") == 0)
+			value = BLACKLIST_ERROR_VERSION;
+		else if (strcmp(arg, "format") == 0)
+			value = BLACKLIST_ERROR_FORMAT;
+		else if (strcmp(arg, "access") == 0)
+			value = BLACKLIST_ERROR_ACCESS;
+		else if (strcmp(arg, "all") == 0)
+			value = BLACKLIST_ERROR_ALL;
+		else
+			fatal("%s line %d: Bad none/missing/version/format/access/all argument: %s",
+				filename, linenum, arg);
+		if (*activep && *intptr == -1)
+			*intptr = value;
+		break;
+
 	case sEmptyPasswd:
 		intptr = &options->permit_empty_passwd;
 		goto parse_flag;
--- openssh-5.0p1/servconf.h
+++ openssh-5.0p1/servconf.h
@@ -95,6 +95,7 @@
 						 * authentication. */
 	int     kbd_interactive_authentication;	/* If true, permit */
 	int     challenge_response_authentication;
+	int     ignore_blacklist_errors;	/* none/missing/version/format/access/all */
 	int     permit_empty_passwd;	/* If false, do not permit empty
 					 * passwords. */
 	int     permit_user_env;	/* If true, read ~/.ssh/environment */
--- openssh-5.0p1/sshd.c
+++ openssh-5.0p1/sshd.c
@@ -118,6 +118,7 @@
 #include "monitor_wrap.h"
 #include "monitor_fdpass.h"
 #include "version.h"
+#include "blacklist.h"
 
 #ifdef LIBWRAP
 #include <tcpd.h>
@@ -1484,6 +1494,11 @@
 			sensitive_data.host_keys[i] = NULL;
 			continue;
 		}
+		if (blacklisted_key(key, 1)) {
+			sensitive_data.host_keys[i] = NULL;
+			key_free(key);
+			continue;
+		}
 		switch (key->type) {
 		case KEY_RSA1:
 			sensitive_data.ssh1_host_key = key;
--- openssh-5.0p1/sshd_config.5
+++ openssh-5.0p1/sshd_config.5
@@ -611,6 +611,39 @@
 Specifies whether password authentication is allowed.
 The default is
 .Dq yes .
+.It Cm IgnoreBlacklistErrors
+Specifies whether
+.Xr sshd 8
+should allow keys recorded in its blacklist of known-compromised keys.
+If
+.Dq all ,
+then attempts to authenticate with compromised keys will be logged
+but accepted.
+If
+.Dq access ,
+then attempts to authenticate with compromised keys will be rejected,
+but blacklist file access errors will be ignored.
+If
+.Dq format ,
+then attempts to authenticate with compromised keys will be rejected, but
+blacklist file access errors due to missing blacklist file or blacklist
+file unrecognized format will be ignored.
+If
+.Dq version ,
+then attempts to authenticate with compromised keys will be rejected, but
+blacklist file access errors due to missing blacklist file or blacklist
+file format version mismatch will be ignored.
+If
+.Dq missing ,
+then attempts to authenticate with compromised keys will be rejected,
+but blacklist file access errors due to missing blacklist file will
+be ignored.
+If
+.Dq none ,
+then attempts to authenticate with compromised keys, or in case of
+any blacklist file access error, will be rejected.
+The default is
+.Dq version .
 .It Cm PermitEmptyPasswords
 When password authentication is allowed, it specifies whether the
 server allows login to accounts with empty password strings.