openssh/openssh-5.5p1-authorized-keys-command.patch

diff -ruN openssh-5.5p1.orig/auth2-pubkey.c openssh-5.5p1/auth2-pubkey.c
--- openssh-5.5p1.orig/auth2-pubkey.c	2010-03-21 14:51:21.000000000 -0400
+++ openssh-5.5p1/auth2-pubkey.c	2010-07-03 20:23:43.000000000 -0400
@@ -27,6 +27,7 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 
 #include <fcntl.h>
 #include <pwd.h>
@@ -178,27 +178,15 @@
 
 /* return 1 if user allows given key */
 static int
-user_key_allowed2(struct passwd *pw, Key *key, char *file)
+user_search_key_in_file(FILE *f, char *file, Key* key, struct passwd *pw)
 {
 	char line[SSH_MAX_PUBKEY_BYTES];
 	const char *reason;
 	int found_key = 0;
-	FILE *f;
 	u_long linenum = 0;
 	Key *found;
 	char *fp;
 
-	/* Temporarily use the user's uid. */
-	temporarily_use_uid(pw);
-
-	debug("trying public key file %s", file);
-	f = auth_openkeyfile(file, pw, options.strict_modes);
-
-	if (!f) {
-		restore_uid();
-		return 0;
-	}
-
 	found_key = 0;
 	found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type);
 
@@ -273,8 +261,6 @@
 			break;
 		}
 	}
-	restore_uid();
-	fclose(f);
 	key_free(found);
 	if (!found_key)
 		debug2("key not found");
@@ -321,13 +307,191 @@
 	return ret;
 }
 
-/* check whether given key is in .ssh/authorized_keys* */
+/* return 1 if user allows given key */
+static int
+user_key_allowed2(struct passwd *pw, Key *key, char *file)
+{
+	FILE *f;
+	int found_key = 0;
+
+	/* Temporarily use the user's uid. */
+	temporarily_use_uid(pw);
+
+	debug("trying public key file %s", file);
+	f = auth_openkeyfile(file, pw, options.strict_modes);
+
+ 	if (f) {
+ 		found_key = user_search_key_in_file (f, file, key, pw);
+		fclose(f);
+	}
+
+	restore_uid();
+	return found_key;
+}
+
+#ifdef WITH_AUTHORIZED_KEYS_COMMAND
+
+#define WHITESPACE " \t\r\n"
+
+/* return 1 if user allows given key */
+static int
+user_key_via_command_allowed2(struct passwd *pw, Key *key)
+{
+	FILE *f;
+	int found_key = 0;
+	char *progname = NULL;
+	char *cp;
+	struct passwd *runas_pw;
+	struct stat st;
+	int childdescriptors[2], i;
+	pid_t pstat, pid, child;
+
+	if (options.authorized_keys_command == NULL || options.authorized_keys_command[0] != '/')
+		return -1;
+
+	/* get the run as identity from config */
+	runas_pw = (options.authorized_keys_command_runas == NULL)? pw
+	    : getpwnam (options.authorized_keys_command_runas);
+	if (!runas_pw) {
+		error("%s: getpwnam(\"%s\"): %s", __func__,
+		    options.authorized_keys_command_runas, strerror(errno));
+		return 0;
+	}
+
+	/* Temporarily use the specified uid. */
+	if (runas_pw->pw_uid != 0)
+		temporarily_use_uid(runas_pw);
+
+	progname = xstrdup(options.authorized_keys_command);
+
+	debug3("%s: checking program '%s'", __func__, progname);
+
+	if (stat (progname, &st) < 0) {
+		error("%s: stat(\"%s\"): %s", __func__,
+		    progname, strerror(errno));
+		goto go_away;
+	}
+
+	if (st.st_uid != 0 || (st.st_mode & 022) != 0) {
+		error("bad ownership or modes for AuthorizedKeysCommand \"%s\"",
+		    progname);
+		goto go_away;
+	}
+
+	if (!S_ISREG(st.st_mode)) {
+		error("AuthorizedKeysCommand \"%s\" is not a regular file",
+		    progname);
+		goto go_away;
+	}
+
+	/*
+	 * Descend the path, checking that each component is a
+	 * root-owned directory with strict permissions.
+	 */
+	do {
+		if ((cp = strrchr(progname, '/')) == NULL)
+			break;
+		else 
+			*cp = '\0';
+	
+		debug3("%s: checking component '%s'", __func__, (*progname == '\0' ? "/" : progname));
+
+		if (stat((*progname == '\0' ? "/" : progname), &st) != 0) {
+			error("%s: stat(\"%s\"): %s", __func__,
+			    progname, strerror(errno));
+			goto go_away;
+		}
+		if (st.st_uid != 0 || (st.st_mode & 022) != 0) {
+			error("bad ownership or modes for AuthorizedKeysCommand path component \"%s\"",
+			    progname);
+			goto go_away;
+		}
+		if (!S_ISDIR(st.st_mode)) {
+			error("AuthorizedKeysCommand path component \"%s\" is not a directory",
+			    progname);
+			goto go_away;
+		}
+	} while (1);
+
+	/* open the pipe and read the keys */
+	if (pipe(childdescriptors)) {
+		error("failed to pipe(2) for AuthorizedKeysCommand: %s",
+		    strerror(errno));
+		goto go_away;
+	}
+
+	child = fork();
+	if (child == -1) {
+		error("failed to fork(2) for AuthorizedKeysCommand: %s",
+		    strerror(errno));
+		goto go_away;
+	} else if (child == 0) {
+		/* we're in the child process here -- we should never return from this block. */
+		/* permanently drop privs in child process */
+		if (runas_pw->pw_uid != 0) {
+			restore_uid();
+			permanently_set_uid(runas_pw);
+	  	}
+
+		close(childdescriptors[0]);
+		/* put the write end of the pipe on stdout (FD 1) */
+		if (dup2(childdescriptors[1], 1) == -1) {
+			error("failed to dup2(2) from AuthorizedKeysCommand: %s",
+			    strerror(errno));
+			_exit(127);
+		}
+
+		debug3("about to execl() AuthorizedKeysCommand: \"%s\" \"%s\"", options.authorized_keys_command, pw->pw_name);
+		/* see session.c:child_close_fds() */
+		for (i = 3; i < 64; ++i) {
+			close(i);
+		}
+
+		execl(options.authorized_keys_command, options.authorized_keys_command, pw->pw_name, NULL);
+
+		/* if we got here, it didn't work */
+		error("failed to execl AuthorizedKeysCommand: %s", strerror(errno)); /* this won't work because we closed the fds above */
+		_exit(127);
+	}
+	
+	close(childdescriptors[1]);
+	f = fdopen(childdescriptors[0], "r");
+	if (!f) {
+		error("%s: could not buffer FDs from AuthorizedKeysCommand (\"%s\", \"r\"): %s", __func__,
+		    options.authorized_keys_command, strerror (errno));
+		goto go_away;
+	}
+
+	found_key = user_search_key_in_file (f, options.authorized_keys_command, key, pw);
+	fclose (f);
+	do {
+		pid = waitpid(child, &pstat, 0);
+	} while (pid == -1 && errno == EINTR);
+
+	/* what about the return value from the child process? */
+go_away:
+	if (progname)
+		xfree (progname);
+
+	if (runas_pw->pw_uid != 0)
+		restore_uid();
+	return found_key;
+}
+#endif
+
+/* check whether given key is in <AuthorizedKeysCommand or .ssh/authorized_keys* */
 int
 user_key_allowed(struct passwd *pw, Key *key)
 {
 	int success;
 	char *file;
 
+#ifdef WITH_AUTHORIZED_KEYS_COMMAND
+	success = user_key_via_command_allowed2(pw, key);
+	if (success > 0)
+		return success;
+#endif
+
 	if (auth_key_is_revoked(key))
 		return 0;
 	if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
diff -ruN openssh-5.5p1.orig/configure.ac openssh-5.5p1/configure.ac
--- openssh-5.5p1.orig/configure.ac	2010-04-10 08:58:01.000000000 -0400
+++ openssh-5.5p1/configure.ac	2010-07-03 19:57:42.000000000 -0400
@@ -1346,6 +1346,18 @@
 	esac ]
 )
 
+# Check whether user wants AuthorizedKeysCommand support
+AKC_MSG="no"
+AC_ARG_WITH(authorized-keys-command,
+	[  --with-authorized-keys-command      Enable AuthorizedKeysCommand support],
+	[
+		if test "x$withval" != "xno" ; then
+			AC_DEFINE([WITH_AUTHORIZED_KEYS_COMMAND], 1, [Enable AuthorizedKeysCommand support])
+			AKC_MSG="yes"
+		fi
+	]
+)
+
 dnl    Checks for library functions. Please keep in alphabetical order
 AC_CHECK_FUNCS( \
 	arc4random \
@@ -4181,6 +4193,7 @@
 echo "                 Smartcard support: $SCARD_MSG"
 echo "                     S/KEY support: $SKEY_MSG"
 echo "              TCP Wrappers support: $TCPW_MSG"
+echo "     AuthorizedKeysCommand support: $AKC_MSG"
 echo "              MD5 password support: $MD5_MSG"
 echo "                   libedit support: $LIBEDIT_MSG"
 echo "  Solaris process contract support: $SPC_MSG"
diff -ruN openssh-5.5p1.orig/servconf.c openssh-5.5p1/servconf.c
--- openssh-5.5p1.orig/servconf.c	2010-03-25 19:40:04.000000000 -0400
+++ openssh-5.5p1/servconf.c	2010-07-03 19:59:07.000000000 -0400
@@ -128,6 +128,8 @@
 	options->num_permitted_opens = -1;
 	options->adm_forced_command = NULL;
 	options->chroot_directory = NULL;
+	options->authorized_keys_command = NULL;
+	options->authorized_keys_command_runas = NULL;
 	options->zero_knowledge_password_authentication = -1;
 	options->revoked_keys_file = NULL;
 	options->trusted_user_ca_keys = NULL;
@@ -311,6 +313,7 @@
 	sUsePrivilegeSeparation, sAllowAgentForwarding,
 	sZeroKnowledgePasswordAuthentication, sHostCertificate,
 	sRevokedKeys, sTrustedUserCAKeys,
+	sAuthorizedKeysCommand, sAuthorizedKeysCommandRunAs,
 	sDeprecated, sUnsupported
 } ServerOpCodes;
 
@@ -432,6 +435,13 @@
 	{ "hostcertificate", sHostCertificate, SSHCFG_GLOBAL },
 	{ "revokedkeys", sRevokedKeys, SSHCFG_ALL },
 	{ "trustedusercakeys", sTrustedUserCAKeys, SSHCFG_ALL },
+#ifdef WITH_AUTHORIZED_KEYS_COMMAND
+	{ "authorizedkeyscommand", sAuthorizedKeysCommand, SSHCFG_ALL },
+	{ "authorizedkeyscommandrunas", sAuthorizedKeysCommandRunAs, SSHCFG_ALL },
+#else
+	{ "authorizedkeyscommand", sUnsupported, SSHCFG_ALL },
+	{ "authorizedkeyscommandrunas", sUnsupported, SSHCFG_ALL },
+#endif
 	{ NULL, sBadOption, 0 }
 };
 
@@ -1345,6 +1355,20 @@
 		charptr = &options->revoked_keys_file;
 		goto parse_filename;
 
+	case sAuthorizedKeysCommand:
+		len = strspn(cp, WHITESPACE);
+		if (*activep && options->authorized_keys_command == NULL)
+			options->authorized_keys_command = xstrdup(cp + len);
+		return 0;
+
+	case sAuthorizedKeysCommandRunAs:
+		charptr = &options->authorized_keys_command_runas;
+
+		arg = strdelim(&cp);
+		if (*activep && *charptr == NULL)
+			*charptr = xstrdup(arg);
+		break;
+
 	case sDeprecated:
 		logit("%s line %d: Deprecated option %s",
 		    filename, linenum, arg);
@@ -1438,6 +1462,8 @@
 	M_CP_INTOPT(gss_authentication);
 	M_CP_INTOPT(rsa_authentication);
 	M_CP_INTOPT(pubkey_authentication);
+	M_CP_STROPT(authorized_keys_command);
+	M_CP_STROPT(authorized_keys_command_runas);
 	M_CP_INTOPT(kerberos_authentication);
 	M_CP_INTOPT(hostbased_authentication);
 	M_CP_INTOPT(kbd_interactive_authentication);
@@ -1682,6 +1708,8 @@
 	dump_cfg_string(sChrootDirectory, o->chroot_directory);
 	dump_cfg_string(sTrustedUserCAKeys, o->trusted_user_ca_keys);
 	dump_cfg_string(sRevokedKeys, o->revoked_keys_file);
+	dump_cfg_string(sAuthorizedKeysCommand, o->authorized_keys_command);
+	dump_cfg_string(sAuthorizedKeysCommandRunAs, o->authorized_keys_command_runas);
 
 	/* string arguments requiring a lookup */
 	dump_cfg_string(sLogLevel, log_level_name(o->log_level));
diff -ruN openssh-5.5p1.orig/servconf.h openssh-5.5p1/servconf.h
--- openssh-5.5p1.orig/servconf.h	2010-03-04 05:53:35.000000000 -0500
+++ openssh-5.5p1/servconf.h	2010-07-03 19:57:42.000000000 -0400
@@ -156,6 +156,8 @@
 	char   *chroot_directory;
 	char   *revoked_keys_file;
 	char   *trusted_user_ca_keys;
+	char   *authorized_keys_command;
+	char   *authorized_keys_command_runas;
 }       ServerOptions;
 
 void	 initialize_server_options(ServerOptions *);
diff -ruN openssh-5.5p1.orig/sshd_config openssh-5.5p1/sshd_config
--- openssh-5.5p1.orig/sshd_config	2009-10-11 06:51:09.000000000 -0400
+++ openssh-5.5p1/sshd_config	2010-07-03 19:57:42.000000000 -0400
@@ -44,6 +44,8 @@
 #RSAAuthentication yes
 #PubkeyAuthentication yes
 #AuthorizedKeysFile	.ssh/authorized_keys
+#AuthorizedKeysCommand none
+#AuthorizedKeysCommandRunAs nobody
 
 # For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
 #RhostsRSAAuthentication no
diff -ruN openssh-5.5p1.orig/sshd_config.0 openssh-5.5p1/sshd_config.0
--- openssh-5.5p1.orig/sshd_config.0	2010-04-15 20:17:12.000000000 -0400
+++ openssh-5.5p1/sshd_config.0	2010-07-03 19:57:42.000000000 -0400
@@ -352,7 +352,8 @@
              KbdInteractiveAuthentication, KerberosAuthentication,
              MaxAuthTries, MaxSessions, PasswordAuthentication,
              PermitEmptyPasswords, PermitOpen, PermitRootLogin,
-             PubkeyAuthentication, RhostsRSAAuthentication, RSAAuthentication,
+             PubkeyAuthentication, AuthorizedKeysCommand, AuthorizedKeysCommandRunAs,
+             RhostsRSAAuthentication, RSAAuthentication,
              X11DisplayOffset, X11Forwarding and X11UseLocalHost.
 
      MaxAuthTries
@@ -467,6 +468,23 @@
              this file is not readable, then public key authentication will be
              refused for all users.
 
+     AuthorizedKeysCommand
+
+             Specifies a program to be used for lookup of the user's
+	      public keys.  The program will be invoked with its first
+	      argument the name of the user being authorized, and should produce 
+	      on standard output AuthorizedKeys lines (see AUTHORIZED_KEYS 
+	      in sshd(8)).  By default (or when set to the empty string) there is no
+	      AuthorizedKeysCommand run.  If the AuthorizedKeysCommand does not successfully
+	      authorize the user, authorization falls through to the
+	      AuthorizedKeysFile.  Note that this option has an effect
+	      only with PubkeyAuthentication turned on.
+
+     AuthorizedKeysCommandRunAs
+             Specifies the user under whose account the AuthorizedKeysCommand is run.
+             Empty string (the default value) means the user being authorized
+             is used.
+
      RhostsRSAAuthentication
              Specifies whether rhosts or /etc/hosts.equiv authentication to-
              gether with successful RSA host authentication is allowed.  The
diff -ruN openssh-5.5p1.orig/sshd_config.5 openssh-5.5p1/sshd_config.5
--- openssh-5.5p1.orig/sshd_config.5	2010-03-04 18:41:45.000000000 -0500
+++ openssh-5.5p1/sshd_config.5	2010-07-03 19:57:42.000000000 -0400
@@ -618,6 +618,9 @@
 .Cm KerberosAuthentication ,
 .Cm MaxAuthTries ,
 .Cm MaxSessions ,
+.Cm PubkeyAuthentication ,
+.Cm AuthorizedKeysCommand ,
+.Cm AuthorizedKeysCommandRunAs ,
 .Cm PasswordAuthentication ,
 .Cm PermitEmptyPasswords ,
 .Cm PermitOpen ,
@@ -819,6 +822,20 @@
 Keys listed in this file will be refused for public key authentication.
 Note that if this file is not readable, then public key authentication will
 be refused for all users.
+.It Cm AuthorizedKeysCommand
+Specifies a program to be used for lookup of the user's
+public keys.  The program will be invoked with its first
+argument the name of the user being authorized, and should produce 
+on standard output AuthorizedKeys lines (see AUTHORIZED_KEYS 
+in sshd(8)).  By default (or when set to the empty string) there is no
+AuthorizedKeysCommand run.  If the AuthorizedKeysCommand does not successfully
+authorize the user, authorization falls through to the
+AuthorizedKeysFile.  Note that this option has an effect
+only with PubkeyAuthentication turned on.
+.It Cm AuthorizedKeysCommandRunAs
+Specifies the user under whose account the AuthorizedKeysCommand is run. Empty
+string (the default value) means the user being authorized is used.
+.Dq 
 .It Cm RhostsRSAAuthentication
 Specifies whether rhosts or /etc/hosts.equiv authentication together
 with successful RSA host authentication is allowed.