diff -up openssh-6.1p1/auth2-pubkey.c.akc openssh-6.1p1/auth2-pubkey.c
--- openssh-6.1p1/auth2-pubkey.c.akc 2013-02-14 17:46:45.259546968 +0100
+++ openssh-6.1p1/auth2-pubkey.c 2013-02-14 17:48:19.072137541 +0100
@@ -27,9 +27,13 @@
#include <sys/types.h>
#include <sys/stat.h>
+#include <sys/wait.h>
+#include <errno.h>
#include <fcntl.h>
+#include <paths.h>
#include <pwd.h>
+#include <signal.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
@@ -260,7 +264,7 @@ match_principals_file(char *file, struct
if (strcmp(cp, cert->principals[i]) == 0) {
debug3("matched principal \"%.100s\" "
"from file \"%s\" on line %lu",
- cert->principals[i], file, linenum);
+ cert->principals[i], file, linenum);
if (auth_parse_options(pw, line_opts,
file, linenum) != 1)
continue;
@@ -273,31 +277,22 @@ match_principals_file(char *file, struct
fclose(f);
restore_uid();
return 0;
-}
+}
-/* return 1 if user allows given key */
+/*
+ * Checks whether key is allowed in authorized_keys-format file,
+ * returns 1 if the key is allowed or 0 otherwise.
+ */
static int
-user_key_allowed2(struct passwd *pw, Key *key, char *file)
+check_authkeys_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);
@@ -390,8 +385,6 @@ user_key_allowed2(struct passwd *pw, Key
break;
}
}
- restore_uid();
- fclose(f);
key_free(found);
if (!found_key)
debug2("key not found");
@@ -453,7 +446,180 @@ user_cert_trusted_ca(struct passwd *pw,
return ret;
}
-/* check whether given key is in .ssh/authorized_keys* */
+/*
+ * Checks whether key is allowed in file.
+ * returns 1 if the key is allowed or 0 otherwise.
+ */
+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);
+ if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
+ found_key = check_authkeys_file(f, file, key, pw);
+ fclose(f);
+ }
+
+ restore_uid();
+ return found_key;
+}
+
+/*
+ * Checks whether key is allowed in output of command.
+ * returns 1 if the key is allowed or 0 otherwise.
+ */
+static int
+user_key_command_allowed2(struct passwd *user_pw, Key *key)
+{
+ FILE *f;
+ int ok, found_key = 0;
+ struct passwd *pw;
+ struct stat st;
+ int status, devnull, p[2], i;
+ pid_t pid;
+ char *username, errmsg[512];
+
+ if (options.authorized_keys_command == NULL ||
+ options.authorized_keys_command[0] != '/')
+ return 0;
+
+ if (options.authorized_keys_command_user == NULL) {
+ error("No user for AuthorizedKeysCommand specified, skipping");
+ return 0;
+ }
+
+ username = percent_expand(options.authorized_keys_command_user,
+ "u", user_pw->pw_name, (char *)NULL);
+ pw = getpwnam(username);
+ if (pw == NULL) {
+ error("AuthorizedKeyCommandUser \"%s\" not found: %s",
+ username, strerror(errno));
+ free(username);
+ return 0;
+ }
+ free(username);
+
+ temporarily_use_uid(pw);
+
+ if (stat(options.authorized_keys_command, &st) < 0) {
+ error("Could not stat AuthorizedKeysCommand \"%s\": %s",
+ options.authorized_keys_command, strerror(errno));
+ goto out;
+ }
+ if (auth_secure_path(options.authorized_keys_command, &st, NULL, 0,
+ errmsg, sizeof(errmsg)) != 0) {
+ error("Unsafe AuthorizedKeysCommand: %s", errmsg);
+ goto out;
+ }
+
+ if (pipe(p) != 0) {
+ error("%s: pipe: %s", __func__, strerror(errno));
+ goto out;
+ }
+
+ debug3("Running AuthorizedKeysCommand: \"%s %s\" as \"%s\"",
+ options.authorized_keys_command, user_pw->pw_name, pw->pw_name);
+
+ /*
+ * Don't want to call this in the child, where it can fatal() and
+ * run cleanup_exit() code.
+ */
+ restore_uid();
+
+ switch ((pid = fork())) {
+ case -1: /* error */
+ error("%s: fork: %s", __func__, strerror(errno));
+ close(p[0]);
+ close(p[1]);
+ return 0;
+ case 0: /* child */
+ for (i = 0; i < NSIG; i++)
+ signal(i, SIG_DFL);
+
+ if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
+ error("%s: open %s: %s", __func__, _PATH_DEVNULL,
+ strerror(errno));
+ _exit(1);
+ }
+ /* Keep stderr around a while longer to catch errors */
+ if (dup2(devnull, STDIN_FILENO) == -1 ||
+ dup2(p[1], STDOUT_FILENO) == -1) {
+ error("%s: dup2: %s", __func__, strerror(errno));
+ _exit(1);
+ }
+ closefrom(STDERR_FILENO + 1);
+
+ /* Don't use permanently_set_uid() here to avoid fatal() */
+ if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
+ error("setresgid %u: %s", (u_int)pw->pw_gid,
+ strerror(errno));
+ _exit(1);
+ }
+ if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
+ error("setresuid %u: %s", (u_int)pw->pw_uid,
+ strerror(errno));
+ _exit(1);
+ }
+ /* stdin is pointed to /dev/null at this point */
+ if (dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
+ error("%s: dup2: %s", __func__, strerror(errno));
+ _exit(1);
+ }
+
+ execl(options.authorized_keys_command,
+ options.authorized_keys_command, user_pw->pw_name, NULL);
+
+ error("AuthorizedKeysCommand %s exec failed: %s",
+ options.authorized_keys_command, strerror(errno));
+ _exit(127);
+ default: /* parent */
+ break;
+ }
+
+ temporarily_use_uid(pw);
+
+ close(p[1]);
+ if ((f = fdopen(p[0], "r")) == NULL) {
+ error("%s: fdopen: %s", __func__, strerror(errno));
+ close(p[0]);
+ /* Don't leave zombie child */
+ kill(pid, SIGTERM);
+ while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
+ ;
+ goto out;
+ }
+ ok = check_authkeys_file(f, options.authorized_keys_command, key, pw);
+ fclose(f);
+
+ while (waitpid(pid, &status, 0) == -1) {
+ if (errno != EINTR) {
+ error("%s: waitpid: %s", __func__, strerror(errno));
+ goto out;
+ }
+ }
+ if (WIFSIGNALED(status)) {
+ error("AuthorizedKeysCommand %s exited on signal %d",
+ options.authorized_keys_command, WTERMSIG(status));
+ goto out;
+ } else if (WEXITSTATUS(status) != 0) {
+ error("AuthorizedKeysCommand %s returned status %d",
+ options.authorized_keys_command, WEXITSTATUS(status));
+ goto out;
+ }
+ found_key = ok;
+ out:
+ restore_uid();
+ return found_key;
+}
+
+/*
+ * Check whether key authenticates and authorises the user.
+ */
int
user_key_allowed(struct passwd *pw, Key *key)
{
@@ -469,9 +635,17 @@ user_key_allowed(struct passwd *pw, Key
if (success)
return success;
+ success = user_key_command_allowed2(pw, key);
+ if (success > 0)
+ return success;
+
for (i = 0; !success && i < options.num_authkeys_files; i++) {
+
+ if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
+ continue;
file = expand_authorized_keys(
options.authorized_keys_files[i], pw);
+
success = user_key_allowed2(pw, key, file);
xfree(file);
}
diff -up openssh-6.1p1/auth.c.akc openssh-6.1p1/auth.c
--- openssh-6.1p1/auth.c.akc 2013-02-14 17:46:45.189547274 +0100
+++ openssh-6.1p1/auth.c 2013-02-14 17:46:45.273546907 +0100
@@ -415,39 +415,41 @@ check_key_in_hostfiles(struct passwd *pw
/*
- * Check a given file for security. This is defined as all components
+ * Check a given path for security. This is defined as all components
* of the path to the file must be owned by either the owner of
* of the file or root and no directories must be group or world writable.
*
* XXX Should any specific check be done for sym links ?
*
- * Takes an open file descriptor, the file name, a uid and and
+ * Takes an the file name, its stat information (preferably from fstat() to
+ * avoid races), the uid of the expected owner, their home directory and an
* error buffer plus max size as arguments.
*
* Returns 0 on success and -1 on failure
*/
-static int
-secure_filename(FILE *f, const char *file, struct passwd *pw,
- char *err, size_t errlen)
+int
+auth_secure_path(const char *name, struct stat *stp, const char *pw_dir,
+ uid_t uid, char *err, size_t errlen)
{
- uid_t uid = pw->pw_uid;
char buf[MAXPATHLEN], homedir[MAXPATHLEN];
char *cp;
int comparehome = 0;
struct stat st;
- if (realpath(file, buf) == NULL) {
- snprintf(err, errlen, "realpath %s failed: %s", file,
+ if (realpath(name, buf) == NULL) {
+ snprintf(err, errlen, "realpath %s failed: %s", name,
strerror(errno));
return -1;
}
- if (realpath(pw->pw_dir, homedir) != NULL)
+ if (pw_dir != NULL && realpath(pw_dir, homedir) != NULL)
comparehome = 1;
- /* check the open file to avoid races */
- if (fstat(fileno(f), &st) < 0 ||
- (st.st_uid != 0 && st.st_uid != uid) ||
- (st.st_mode & 022) != 0) {
+ if (!S_ISREG(stp->st_mode)) {
+ snprintf(err, errlen, "%s is not a regular file", buf);
+ return -1;
+ }
+ if ((stp->st_uid != 0 && stp->st_uid != uid) ||
+ (stp->st_mode & 022) != 0) {
snprintf(err, errlen, "bad ownership or modes for file %s",
buf);
return -1;
@@ -483,6 +485,31 @@ secure_filename(FILE *f, const char *fil
return 0;
}
+/*
+ * Version of secure_path() that accepts an open file descriptor to
+ * avoid races.
+ *
+ * Returns 0 on success and -1 on failure
+ */
+static int
+secure_filename(FILE *f, const char *file, struct passwd *pw,
+ char *err, size_t errlen)
+{
+ uid_t uid = pw->pw_uid;
+ char buf[MAXPATHLEN], homedir[MAXPATHLEN];
+ char *cp;
+ int comparehome = 0;
+ struct stat st;
+
+ /* check the open file to avoid races */
+ if (fstat(fileno(f), &st) < 0) {
+ snprintf(err, errlen, "cannot stat file %s: %s",
+ buf, strerror(errno));
+ return -1;
+ }
+ return auth_secure_path(file, &st, pw->pw_dir, pw->pw_uid, err, errlen);
+}
+
static FILE *
auth_openfile(const char *file, struct passwd *pw, int strict_modes,
int log_missing, char *file_type)
diff -up openssh-6.1p1/auth.h.akc openssh-6.1p1/auth.h
--- openssh-6.1p1/auth.h.akc 2013-02-14 17:46:45.259546968 +0100
+++ openssh-6.1p1/auth.h 2013-02-14 17:46:45.274546903 +0100
@@ -125,6 +125,10 @@ int auth_rhosts_rsa_key_allowed(struct
int hostbased_key_allowed(struct passwd *, const char *, char *, Key *);
int user_key_allowed(struct passwd *, Key *);
+struct stat;
+int auth_secure_path(const char *, struct stat *, const char *, uid_t,
+ char *, size_t);
+
#ifdef KRB5
int auth_krb5(Authctxt *authctxt, krb5_data *auth, char **client, krb5_data *);
int auth_krb5_tgt(Authctxt *authctxt, krb5_data *tgt);
diff -up openssh-6.1p1/servconf.c.akc openssh-6.1p1/servconf.c
--- openssh-6.1p1/servconf.c.akc 2013-02-14 17:46:45.193547257 +0100
+++ openssh-6.1p1/servconf.c 2013-02-14 17:46:45.274546903 +0100
@@ -137,6 +137,8 @@ initialize_server_options(ServerOptions
options->num_permitted_opens = -1;
options->adm_forced_command = NULL;
options->chroot_directory = NULL;
+ options->authorized_keys_command = NULL;
+ options->authorized_keys_command_user = NULL;
options->zero_knowledge_password_authentication = -1;
options->revoked_keys_file = NULL;
options->trusted_user_ca_keys = NULL;
@@ -331,6 +333,7 @@ typedef enum {
sZeroKnowledgePasswordAuthentication, sHostCertificate,
sRevokedKeys, sTrustedUserCAKeys, sAuthorizedPrincipalsFile,
sKexAlgorithms, sIPQoS, sVersionAddendum,
+ sAuthorizedKeysCommand, sAuthorizedKeysCommandUser,
sAuthenticationMethods,
sDeprecated, sUnsupported
} ServerOpCodes;
@@ -457,6 +460,9 @@ static struct {
{ "kexalgorithms", sKexAlgorithms, SSHCFG_GLOBAL },
{ "ipqos", sIPQoS, SSHCFG_ALL },
{ "versionaddendum", sVersionAddendum, SSHCFG_GLOBAL },
+ { "authorizedkeyscommand", sAuthorizedKeysCommand, SSHCFG_ALL },
+ { "authorizedkeyscommandrunas", sAuthorizedKeysCommandUser, SSHCFG_ALL },
+ { "authorizedkeyscommanduser", sAuthorizedKeysCommandUser, SSHCFG_ALL },
{ "authenticationmethods", sAuthenticationMethods, SSHCFG_ALL },
{ NULL, sBadOption, 0 }
};
@@ -1520,6 +1526,26 @@ process_server_config_line(ServerOptions
}
return 0;
+ case sAuthorizedKeysCommand:
+ len = strspn(cp, WHITESPACE);
+ if (*activep && options->authorized_keys_command == NULL) {
+ options->authorized_keys_command = xstrdup(cp + len);
+ if (*options->authorized_keys_command != '/') {
+ fatal("%.200s line %d: AuthorizedKeysCommand "
+ "must be an absolute path",
+ filename, linenum);
+ }
+ }
+ return 0;
+
+ case sAuthorizedKeysCommandUser:
+ charptr = &options->authorized_keys_command_user;
+
+ arg = strdelim(&cp);
+ if (*activep && *charptr == NULL)
+ *charptr = xstrdup(arg);
+ break;
+
case sDeprecated:
logit("%s line %d: Deprecated option %s",
filename, linenum, arg);
@@ -1670,6 +1696,8 @@ copy_set_server_options(ServerOptions *d
M_CP_INTOPT(hostbased_uses_name_from_packet_only);
M_CP_INTOPT(kbd_interactive_authentication);
M_CP_INTOPT(zero_knowledge_password_authentication);
+ M_CP_STROPT(authorized_keys_command);
+ M_CP_STROPT(authorized_keys_command_user);
M_CP_INTOPT(permit_root_login);
M_CP_INTOPT(permit_empty_passwd);
@@ -1930,6 +1958,8 @@ dump_config(ServerOptions *o)
dump_cfg_string(sAuthorizedPrincipalsFile,
o->authorized_principals_file);
dump_cfg_string(sVersionAddendum, o->version_addendum);
+ dump_cfg_string(sAuthorizedKeysCommand, o->authorized_keys_command);
+ dump_cfg_string(sAuthorizedKeysCommandUser, o->authorized_keys_command_user);
/* string arguments requiring a lookup */
dump_cfg_string(sLogLevel, log_level_name(o->log_level));
diff -up openssh-6.1p1/servconf.h.akc openssh-6.1p1/servconf.h
--- openssh-6.1p1/servconf.h.akc 2013-02-14 17:46:45.194547252 +0100
+++ openssh-6.1p1/servconf.h 2013-02-14 17:46:45.275546898 +0100
@@ -167,6 +167,8 @@ typedef struct {
char *revoked_keys_file;
char *trusted_user_ca_keys;
char *authorized_principals_file;
+ char *authorized_keys_command;
+ char *authorized_keys_command_user;
char *version_addendum; /* Appended to SSH banner */
diff -up openssh-6.1p1/sshd.c.akc openssh-6.1p1/sshd.c
--- openssh-6.1p1/sshd.c.akc 2013-02-14 17:46:45.270546920 +0100
+++ openssh-6.1p1/sshd.c 2013-02-14 17:46:45.276546894 +0100
@@ -366,9 +366,20 @@ main_sigchld_handler(int sig)
static void
grace_alarm_handler(int sig)
{
+ pid_t pgid;
+
if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
kill(pmonitor->m_pid, SIGALRM);
+ /*
+ * Try to kill any processes that we have spawned, E.g. authorized
+ * keys command helpers.
+ */
+ if ((pgid = getpgid(0)) == getpid()) {
+ signal(SIGTERM, SIG_IGN);
+ killpg(pgid, SIGTERM);
+ }
+
/* Log error and exit. */
sigdie("Timeout before authentication for %s", get_remote_ipaddr());
}
diff -up openssh-6.1p1/sshd_config.0.akc openssh-6.1p1/sshd_config.0
--- openssh-6.1p1/sshd_config.0.akc 2012-08-29 02:53:04.000000000 +0200
+++ openssh-6.1p1/sshd_config.0 2013-02-14 17:46:45.276546894 +0100
@@ -71,6 +71,23 @@ DESCRIPTION
See PATTERNS in ssh_config(5) for more information on patterns.
+ 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.
+
AuthorizedKeysFile
Specifies the file that contains the public keys that can be used
for user authentication. The format is described in the
@@ -402,7 +419,8 @@ DESCRIPTION
Only a subset of keywords may be used on the lines following a
Match keyword. Available keywords are AcceptEnv,
AllowAgentForwarding, AllowGroups, AllowTcpForwarding,
- AllowUsers, AuthorizedKeysFile, AuthorizedPrincipalsFile, Banner,
+ AllowUsers, AuthorizedKeysFile, AuthorizedKeysCommand,
+ AuthorizedKeysCommandRunAs, AuthorizedPrincipalsFile, Banner,
ChrootDirectory, DenyGroups, DenyUsers, ForceCommand,
GatewayPorts, GSSAPIAuthentication, HostbasedAuthentication,
HostbasedUsesNameFromPacketOnly, KbdInteractiveAuthentication,
diff -up openssh-6.1p1/sshd_config.5.akc openssh-6.1p1/sshd_config.5
--- openssh-6.1p1/sshd_config.5.akc 2013-02-14 17:46:45.195547248 +0100
+++ openssh-6.1p1/sshd_config.5 2013-02-14 17:46:45.277546890 +0100
@@ -173,6 +173,20 @@ Note that each authentication method lis
in the configuration.
The default is not to require multiple authentication; successful completion
of a single authentication method is sufficient.
+.It Cm AuthorizedKeysCommand
+Specifies a program to be used for lookup of the user's public keys.
+The program will be invoked with a single argument of the username
+being authenticated, and should produce on standard output zero or
+more lines of authorized_keys output (see AUTHORIZED_KEYS in
+.Xr sshd 8 )
+If a key supplied by AuthorizedKeysCommand does not successfully authenticate
+and authorize the user then public key authentication continues using the usual
+.Cm AuthorizedKeysFile
+files.
+By default, no AuthorizedKeysCommand is run.
+.It Cm AuthorizedKeysCommandUser
+Specifies the user under whose account the AuthorizedKeysCommand is run.
+The default is the user being authenticated.
.It Cm AuthorizedKeysFile
Specifies the file that contains the public keys that can be used
for user authentication.
@@ -734,6 +748,8 @@ Available keywords are
.Cm AllowTcpForwarding ,
.Cm AllowUsers ,
.Cm AuthenticationMethods ,
+.Cm AuthorizedKeysCommand ,
+.Cm AuthorizedKeysCommandUser ,
.Cm AuthorizedKeysFile ,
.Cm AuthorizedPrincipalsFile ,
.Cm Banner ,
@@ -749,6 +765,7 @@ Available keywords are
.Cm KerberosAuthentication ,
.Cm MaxAuthTries ,
.Cm MaxSessions ,
+.Cm PubkeyAuthentication ,
.Cm PasswordAuthentication ,
.Cm PermitEmptyPasswords ,
.Cm PermitOpen ,
diff -up openssh-6.1p1/sshd_config.akc openssh-6.1p1/sshd_config
--- openssh-6.1p1/sshd_config.akc 2012-07-31 04:21:34.000000000 +0200
+++ openssh-6.1p1/sshd_config 2013-02-14 17:46:45.277546890 +0100
@@ -49,6 +49,9 @@
# but this is overridden so installations will only check .ssh/authorized_keys
AuthorizedKeysFile .ssh/authorized_keys
+#AuthorizedKeysCommand none
+#AuthorizedKeysCommandUser nobody
+
#AuthorizedPrincipalsFile none
# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts