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openssh-portable/ssh-agent.c

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/* $OpenBSD: ssh-agent.c,v 1.267 2020/11/08 22:37:24 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* The authentication agent program.
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*
* Copyright (c) 2000, 2001 Markus Friedl. 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/param.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/wait.h>
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#ifdef HAVE_SYS_UN_H
# include <sys/un.h>
#endif
#include "openbsd-compat/sys-queue.h"
#ifdef WITH_OPENSSL
#include <openssl/evp.h>
#include "openbsd-compat/openssl-compat.h"
#endif
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#ifdef HAVE_PATHS_H
# include <paths.h>
#endif
#ifdef HAVE_POLL_H
# include <poll.h>
#endif
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <unistd.h>
#ifdef HAVE_UTIL_H
# include <util.h>
#endif
#include "xmalloc.h"
#include "ssh.h"
#include "ssh2.h"
#include "sshbuf.h"
#include "sshkey.h"
#include "authfd.h"
#include "compat.h"
#include "log.h"
#include "misc.h"
#include "digest.h"
#include "ssherr.h"
#include "match.h"
#include "msg.h"
#include "ssherr.h"
#include "pathnames.h"
#include "ssh-pkcs11.h"
#include "sk-api.h"
#ifndef DEFAULT_ALLOWED_PROVIDERS
# define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/local/lib*/*"
#endif
/* Maximum accepted message length */
#define AGENT_MAX_LEN (256*1024)
/* Maximum bytes to read from client socket */
#define AGENT_RBUF_LEN (4096)
typedef enum {
AUTH_UNUSED,
AUTH_SOCKET,
AUTH_CONNECTION
} sock_type;
typedef struct {
int fd;
sock_type type;
struct sshbuf *input;
struct sshbuf *output;
struct sshbuf *request;
} SocketEntry;
u_int sockets_alloc = 0;
SocketEntry *sockets = NULL;
typedef struct identity {
TAILQ_ENTRY(identity) next;
struct sshkey *key;
char *comment;
char *provider;
time_t death;
u_int confirm;
char *sk_provider;
} Identity;
struct idtable {
int nentries;
TAILQ_HEAD(idqueue, identity) idlist;
};
/* private key table */
struct idtable *idtab;
int max_fd = 0;
/* pid of shell == parent of agent */
pid_t parent_pid = -1;
time_t parent_alive_interval = 0;
/* pid of process for which cleanup_socket is applicable */
pid_t cleanup_pid = 0;
/* pathname and directory for AUTH_SOCKET */
char socket_name[PATH_MAX];
char socket_dir[PATH_MAX];
/* Pattern-list of allowed PKCS#11/Security key paths */
static char *allowed_providers;
/* locking */
#define LOCK_SIZE 32
#define LOCK_SALT_SIZE 16
#define LOCK_ROUNDS 1
int locked = 0;
u_char lock_pwhash[LOCK_SIZE];
u_char lock_salt[LOCK_SALT_SIZE];
extern char *__progname;
/* Default lifetime in seconds (0 == forever) */
static long lifetime = 0;
static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
/* Refuse signing of non-SSH messages for web-origin FIDO keys */
static int restrict_websafe = 1;
static void
close_socket(SocketEntry *e)
{
close(e->fd);
e->fd = -1;
e->type = AUTH_UNUSED;
sshbuf_free(e->input);
sshbuf_free(e->output);
sshbuf_free(e->request);
}
static void
idtab_init(void)
{
idtab = xcalloc(1, sizeof(*idtab));
TAILQ_INIT(&idtab->idlist);
idtab->nentries = 0;
}
static void
free_identity(Identity *id)
{
sshkey_free(id->key);
free(id->provider);
free(id->comment);
free(id->sk_provider);
free(id);
}
/* return matching private key for given public key */
static Identity *
lookup_identity(struct sshkey *key)
{
Identity *id;
TAILQ_FOREACH(id, &idtab->idlist, next) {
if (sshkey_equal(key, id->key))
return (id);
}
return (NULL);
}
/* Check confirmation of keysign request */
static int
confirm_key(Identity *id)
{
char *p;
int ret = -1;
p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
if (p != NULL &&
ask_permission("Allow use of key %s?\nKey fingerprint %s.",
id->comment, p))
ret = 0;
free(p);
return (ret);
}
static void
send_status(SocketEntry *e, int success)
{
int r;
if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
(r = sshbuf_put_u8(e->output, success ?
SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
fatal_fr(r, "compose");
}
/* send list of supported public keys to 'client' */
static void
process_request_identities(SocketEntry *e)
{
Identity *id;
struct sshbuf *msg;
int r;
if ((msg = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
(r = sshbuf_put_u32(msg, idtab->nentries)) != 0)
fatal_fr(r, "compose");
TAILQ_FOREACH(id, &idtab->idlist, next) {
if ((r = sshkey_puts_opts(id->key, msg, SSHKEY_SERIALIZE_INFO))
!= 0 ||
(r = sshbuf_put_cstring(msg, id->comment)) != 0) {
error_fr(r, "compose key/comment");
continue;
}
}
if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
fatal_fr(r, "enqueue");
sshbuf_free(msg);
}
static char *
agent_decode_alg(struct sshkey *key, u_int flags)
{
if (key->type == KEY_RSA) {
if (flags & SSH_AGENT_RSA_SHA2_256)
return "rsa-sha2-256";
else if (flags & SSH_AGENT_RSA_SHA2_512)
return "rsa-sha2-512";
} else if (key->type == KEY_RSA_CERT) {
if (flags & SSH_AGENT_RSA_SHA2_256)
return "rsa-sha2-256-cert-v01@openssh.com";
else if (flags & SSH_AGENT_RSA_SHA2_512)
return "rsa-sha2-512-cert-v01@openssh.com";
}
return NULL;
}
/*
* This function inspects a message to be signed by a FIDO key that has a
* web-like application string (i.e. one that does not begin with "ssh:".
* It checks that the message is one of those expected for SSH operations
* (pubkey userauth, sshsig, CA key signing) to exclude signing challenges
* for the web.
*/
static int
check_websafe_message_contents(struct sshkey *key,
const u_char *msg, size_t len)
{
int matched = 0;
struct sshbuf *b;
u_char m, n;
char *cp1 = NULL, *cp2 = NULL;
int r;
struct sshkey *mkey = NULL;
if ((b = sshbuf_from(msg, len)) == NULL)
fatal_f("sshbuf_new");
/* SSH userauth request */
if ((r = sshbuf_get_string_direct(b, NULL, NULL)) == 0 && /* sess_id */
(r = sshbuf_get_u8(b, &m)) == 0 && /* SSH2_MSG_USERAUTH_REQUEST */
(r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* server user */
(r = sshbuf_get_cstring(b, &cp1, NULL)) == 0 && /* service */
(r = sshbuf_get_cstring(b, &cp2, NULL)) == 0 && /* method */
(r = sshbuf_get_u8(b, &n)) == 0 && /* sig-follows */
(r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* alg */
(r = sshkey_froms(b, &mkey)) == 0 && /* key */
sshbuf_len(b) == 0) {
debug_f("parsed userauth");
if (m == SSH2_MSG_USERAUTH_REQUEST && n == 1 &&
strcmp(cp1, "ssh-connection") == 0 &&
strcmp(cp2, "publickey") == 0 &&
sshkey_equal(key, mkey)) {
debug_f("well formed userauth");
matched = 1;
}
}
free(cp1);
free(cp2);
sshkey_free(mkey);
sshbuf_free(b);
if (matched)
return 1;
if ((b = sshbuf_from(msg, len)) == NULL)
fatal_f("sshbuf_new");
cp1 = cp2 = NULL;
mkey = NULL;
/* SSHSIG */
if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) == 0 &&
(r = sshbuf_consume(b, 6)) == 0 &&
(r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* namespace */
(r = sshbuf_get_string_direct(b, NULL, NULL)) == 0 && /* reserved */
(r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* hashalg */
(r = sshbuf_get_string_direct(b, NULL, NULL)) == 0 && /* H(msg) */
sshbuf_len(b) == 0) {
debug_f("parsed sshsig");
matched = 1;
}
sshbuf_free(b);
if (matched)
return 1;
/* XXX CA signature operation */
error("web-origin key attempting to sign non-SSH message");
return 0;
}
/* ssh2 only */
static void
process_sign_request2(SocketEntry *e)
{
const u_char *data;
u_char *signature = NULL;
size_t dlen, slen = 0;
u_int compat = 0, flags;
int r, ok = -1;
char *fp = NULL;
struct sshbuf *msg;
struct sshkey *key = NULL;
struct identity *id;
struct notifier_ctx *notifier = NULL;
if ((msg = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
if ((r = sshkey_froms(e->request, &key)) != 0 ||
(r = sshbuf_get_string_direct(e->request, &data, &dlen)) != 0 ||
(r = sshbuf_get_u32(e->request, &flags)) != 0) {
error_fr(r, "parse");
goto send;
}
if ((id = lookup_identity(key)) == NULL) {
verbose_f("%s key not found", sshkey_type(key));
goto send;
}
if (id->confirm && confirm_key(id) != 0) {
verbose_f("user refused key");
goto send;
}
if (sshkey_is_sk(id->key)) {
if (strncmp(id->key->sk_application, "ssh:", 4) != 0 &&
!check_websafe_message_contents(key, data, dlen)) {
/* error already logged */
goto send;
}
if ((id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD)) {
if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
SSH_FP_DEFAULT)) == NULL)
fatal_f("fingerprint failed");
notifier = notify_start(0,
"Confirm user presence for key %s %s",
sshkey_type(id->key), fp);
}
}
/* XXX support PIN required FIDO keys */
if ((r = sshkey_sign(id->key, &signature, &slen,
data, dlen, agent_decode_alg(key, flags),
id->sk_provider, NULL, compat)) != 0) {
error_fr(r, "sshkey_sign");
goto send;
}
/* Success */
ok = 0;
send:
notify_complete(notifier, "User presence confirmed");
sshkey_free(key);
free(fp);
if (ok == 0) {
if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
(r = sshbuf_put_string(msg, signature, slen)) != 0)
fatal_fr(r, "compose");
} else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
fatal_fr(r, "compose failure");
if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
fatal_fr(r, "enqueue");
sshbuf_free(msg);
free(signature);
}
/* shared */
static void
process_remove_identity(SocketEntry *e)
{
int r, success = 0;
struct sshkey *key = NULL;
Identity *id;
if ((r = sshkey_froms(e->request, &key)) != 0) {
error_fr(r, "parse key");
goto done;
}
if ((id = lookup_identity(key)) == NULL) {
debug_f("key not found");
goto done;
}
/* We have this key, free it. */
if (idtab->nentries < 1)
fatal_f("internal error: nentries %d", idtab->nentries);
TAILQ_REMOVE(&idtab->idlist, id, next);
free_identity(id);
idtab->nentries--;
sshkey_free(key);
success = 1;
done:
send_status(e, success);
}
static void
process_remove_all_identities(SocketEntry *e)
{
Identity *id;
/* Loop over all identities and clear the keys. */
for (id = TAILQ_FIRST(&idtab->idlist); id;
id = TAILQ_FIRST(&idtab->idlist)) {
TAILQ_REMOVE(&idtab->idlist, id, next);
free_identity(id);
}
/* Mark that there are no identities. */
idtab->nentries = 0;
/* Send success. */
send_status(e, 1);
}
/* removes expired keys and returns number of seconds until the next expiry */
static time_t
reaper(void)
{
time_t deadline = 0, now = monotime();
Identity *id, *nxt;
for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
nxt = TAILQ_NEXT(id, next);
if (id->death == 0)
continue;
if (now >= id->death) {
debug("expiring key '%s'", id->comment);
TAILQ_REMOVE(&idtab->idlist, id, next);
free_identity(id);
idtab->nentries--;
} else
deadline = (deadline == 0) ? id->death :
MINIMUM(deadline, id->death);
}
if (deadline == 0 || deadline <= now)
return 0;
else
return (deadline - now);
}
static void
process_add_identity(SocketEntry *e)
{
Identity *id;
int success = 0, confirm = 0;
u_int seconds = 0, maxsign;
char *fp, *comment = NULL, *ext_name = NULL, *sk_provider = NULL;
char canonical_provider[PATH_MAX];
time_t death = 0;
struct sshkey *k = NULL;
u_char ctype;
int r = SSH_ERR_INTERNAL_ERROR;
if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
k == NULL ||
(r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
error_fr(r, "parse");
goto err;
}
while (sshbuf_len(e->request)) {
if ((r = sshbuf_get_u8(e->request, &ctype)) != 0) {
error_fr(r, "parse constraint type");
goto err;
}
switch (ctype) {
case SSH_AGENT_CONSTRAIN_LIFETIME:
if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) {
error_fr(r, "parse lifetime constraint");
goto err;
}
death = monotime() + seconds;
break;
case SSH_AGENT_CONSTRAIN_CONFIRM:
confirm = 1;
break;
case SSH_AGENT_CONSTRAIN_MAXSIGN:
if ((r = sshbuf_get_u32(e->request, &maxsign)) != 0) {
error_fr(r, "parse maxsign constraint");
goto err;
}
if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
error_fr(r, "enable maxsign");
goto err;
}
break;
case SSH_AGENT_CONSTRAIN_EXTENSION:
if ((r = sshbuf_get_cstring(e->request,
&ext_name, NULL)) != 0) {
error_fr(r, "parse constraint extension");
goto err;
}
debug_f("constraint ext %s", ext_name);
if (strcmp(ext_name, "sk-provider@openssh.com") == 0) {
if (sk_provider != NULL) {
error("%s already set", ext_name);
goto err;
}
if ((r = sshbuf_get_cstring(e->request,
&sk_provider, NULL)) != 0) {
error_fr(r, "parse %s", ext_name);
goto err;
}
} else {
error_f("unsupported constraint \"%s\"",
ext_name);
goto err;
}
free(ext_name);
break;
default:
error_f("Unknown constraint %d", ctype);
err:
free(sk_provider);
free(ext_name);
sshbuf_reset(e->request);
free(comment);
sshkey_free(k);
goto send;
}
}
if (sk_provider != NULL) {
if (!sshkey_is_sk(k)) {
error("Cannot add provider: %s is not an "
"authenticator-hosted key", sshkey_type(k));
free(sk_provider);
goto send;
}
if (strcasecmp(sk_provider, "internal") == 0) {
debug_f("internal provider");
} else {
if (realpath(sk_provider, canonical_provider) == NULL) {
verbose("failed provider \"%.100s\": "
"realpath: %s", sk_provider,
strerror(errno));
free(sk_provider);
goto send;
}
free(sk_provider);
sk_provider = xstrdup(canonical_provider);
if (match_pattern_list(sk_provider,
allowed_providers, 0) != 1) {
error("Refusing add key: "
"provider %s not allowed", sk_provider);
free(sk_provider);
goto send;
}
}
}
if ((r = sshkey_shield_private(k)) != 0) {
error_fr(r, "shield private");
goto err;
}
success = 1;
if (lifetime && !death)
death = monotime() + lifetime;
if ((id = lookup_identity(k)) == NULL) {
id = xcalloc(1, sizeof(Identity));
TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
/* Increment the number of identities. */
idtab->nentries++;
} else {
/* key state might have been updated */
sshkey_free(id->key);
free(id->comment);
free(id->sk_provider);
}
id->key = k;
id->comment = comment;
id->death = death;
id->confirm = confirm;
id->sk_provider = sk_provider;
if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
SSH_FP_DEFAULT)) == NULL)
fatal_f("sshkey_fingerprint failed");
debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) "
"(provider: %s)", sshkey_ssh_name(k), fp, comment,
seconds, confirm, sk_provider == NULL ? "none" : sk_provider);
free(fp);
send:
send_status(e, success);
}
/* XXX todo: encrypt sensitive data with passphrase */
static void
process_lock_agent(SocketEntry *e, int lock)
{
int r, success = 0, delay;
char *passwd;
u_char passwdhash[LOCK_SIZE];
static u_int fail_count = 0;
size_t pwlen;
/*
* This is deliberately fatal: the user has requested that we lock,
* but we can't parse their request properly. The only safe thing to
* do is abort.
*/
if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
fatal_fr(r, "parse");
if (pwlen == 0) {
debug("empty password not supported");
} else if (locked && !lock) {
if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
fatal("bcrypt_pbkdf");
if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
debug("agent unlocked");
locked = 0;
fail_count = 0;
explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
success = 1;
} else {
/* delay in 0.1s increments up to 10s */
if (fail_count < 100)
fail_count++;
delay = 100000 * fail_count;
debug("unlock failed, delaying %0.1lf seconds",
(double)delay/1000000);
usleep(delay);
}
explicit_bzero(passwdhash, sizeof(passwdhash));
} else if (!locked && lock) {
debug("agent locked");
locked = 1;
arc4random_buf(lock_salt, sizeof(lock_salt));
if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
fatal("bcrypt_pbkdf");
success = 1;
}
freezero(passwd, pwlen);
send_status(e, success);
}
static void
no_identities(SocketEntry *e)
{
struct sshbuf *msg;
int r;
if ((msg = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
(r = sshbuf_put_u32(msg, 0)) != 0 ||
(r = sshbuf_put_stringb(e->output, msg)) != 0)
fatal_fr(r, "compose");
sshbuf_free(msg);
}
#ifdef ENABLE_PKCS11
static void
process_add_smartcard_key(SocketEntry *e)
{
char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
char **comments = NULL;
int r, i, count = 0, success = 0, confirm = 0;
u_int seconds;
time_t death = 0;
u_char type;
struct sshkey **keys = NULL, *k;
Identity *id;
if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
(r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
error_fr(r, "parse");
goto send;
}
while (sshbuf_len(e->request)) {
if ((r = sshbuf_get_u8(e->request, &type)) != 0) {
error_fr(r, "parse type");
goto send;
}
switch (type) {
case SSH_AGENT_CONSTRAIN_LIFETIME:
if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) {
error_fr(r, "parse lifetime");
goto send;
}
death = monotime() + seconds;
break;
case SSH_AGENT_CONSTRAIN_CONFIRM:
confirm = 1;
break;
default:
error_f("Unknown constraint type %d", type);
goto send;
}
}
if (realpath(provider, canonical_provider) == NULL) {
verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
provider, strerror(errno));
goto send;
}
if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
verbose("refusing PKCS#11 add of \"%.100s\": "
"provider not allowed", canonical_provider);
goto send;
}
debug_f("add %.100s", canonical_provider);
if (lifetime && !death)
death = monotime() + lifetime;
count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments);
for (i = 0; i < count; i++) {
k = keys[i];
if (lookup_identity(k) == NULL) {
id = xcalloc(1, sizeof(Identity));
id->key = k;
keys[i] = NULL; /* transferred */
id->provider = xstrdup(canonical_provider);
if (*comments[i] != '\0') {
id->comment = comments[i];
comments[i] = NULL; /* transferred */
} else {
id->comment = xstrdup(canonical_provider);
}
id->death = death;
id->confirm = confirm;
TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
idtab->nentries++;
success = 1;
}
sshkey_free(keys[i]);
free(comments[i]);
}
send:
free(pin);
free(provider);
free(keys);
free(comments);
send_status(e, success);
}
static void
process_remove_smartcard_key(SocketEntry *e)
{
char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
int r, success = 0;
Identity *id, *nxt;
if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
(r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
error_fr(r, "parse");
goto send;
}
free(pin);
if (realpath(provider, canonical_provider) == NULL) {
verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
provider, strerror(errno));
goto send;
}
debug_f("remove %.100s", canonical_provider);
for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
nxt = TAILQ_NEXT(id, next);
/* Skip file--based keys */
if (id->provider == NULL)
continue;
if (!strcmp(canonical_provider, id->provider)) {
TAILQ_REMOVE(&idtab->idlist, id, next);
free_identity(id);
idtab->nentries--;
}
}
if (pkcs11_del_provider(canonical_provider) == 0)
success = 1;
else
error_f("pkcs11_del_provider failed");
send:
free(provider);
send_status(e, success);
}
#endif /* ENABLE_PKCS11 */
/*
* dispatch incoming message.
* returns 1 on success, 0 for incomplete messages or -1 on error.
*/
static int
process_message(u_int socknum)
{
u_int msg_len;
u_char type;
const u_char *cp;
int r;
SocketEntry *e;
if (socknum >= sockets_alloc)
fatal_f("sock %u >= allocated %u", socknum, sockets_alloc);
e = &sockets[socknum];
if (sshbuf_len(e->input) < 5)
return 0; /* Incomplete message header. */
cp = sshbuf_ptr(e->input);
msg_len = PEEK_U32(cp);
if (msg_len > AGENT_MAX_LEN) {
debug_f("socket %u (fd=%d) message too long %u > %u",
socknum, e->fd, msg_len, AGENT_MAX_LEN);
return -1;
}
if (sshbuf_len(e->input) < msg_len + 4)
return 0; /* Incomplete message body. */
/* move the current input to e->request */
sshbuf_reset(e->request);
if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
(r = sshbuf_get_u8(e->request, &type)) != 0) {
if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
r == SSH_ERR_STRING_TOO_LARGE) {
error_fr(r, "parse");
return -1;
}
fatal_fr(r, "parse");
}
debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type);
/* check whether agent is locked */
if (locked && type != SSH_AGENTC_UNLOCK) {
sshbuf_reset(e->request);
switch (type) {
case SSH2_AGENTC_REQUEST_IDENTITIES:
/* send empty lists */
no_identities(e);
break;
default:
/* send a fail message for all other request types */
send_status(e, 0);
}
return 1;
}
switch (type) {
case SSH_AGENTC_LOCK:
case SSH_AGENTC_UNLOCK:
process_lock_agent(e, type == SSH_AGENTC_LOCK);
break;
case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
process_remove_all_identities(e); /* safe for !WITH_SSH1 */
break;
/* ssh2 */
case SSH2_AGENTC_SIGN_REQUEST:
process_sign_request2(e);
break;
case SSH2_AGENTC_REQUEST_IDENTITIES:
process_request_identities(e);
break;
case SSH2_AGENTC_ADD_IDENTITY:
case SSH2_AGENTC_ADD_ID_CONSTRAINED:
process_add_identity(e);
break;
case SSH2_AGENTC_REMOVE_IDENTITY:
process_remove_identity(e);
break;
case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
process_remove_all_identities(e);
break;
#ifdef ENABLE_PKCS11
case SSH_AGENTC_ADD_SMARTCARD_KEY:
case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
process_add_smartcard_key(e);
break;
case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
process_remove_smartcard_key(e);
break;
#endif /* ENABLE_PKCS11 */
default:
/* Unknown message. Respond with failure. */
error("Unknown message %d", type);
sshbuf_reset(e->request);
send_status(e, 0);
break;
}
return 1;
}
static void
new_socket(sock_type type, int fd)
{
u_int i, old_alloc, new_alloc;
set_nonblock(fd);
if (fd > max_fd)
max_fd = fd;
for (i = 0; i < sockets_alloc; i++)
if (sockets[i].type == AUTH_UNUSED) {
sockets[i].fd = fd;
if ((sockets[i].input = sshbuf_new()) == NULL ||
(sockets[i].output = sshbuf_new()) == NULL ||
(sockets[i].request = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
sockets[i].type = type;
return;
}
old_alloc = sockets_alloc;
new_alloc = sockets_alloc + 10;
sockets = xreallocarray(sockets, new_alloc, sizeof(sockets[0]));
for (i = old_alloc; i < new_alloc; i++)
sockets[i].type = AUTH_UNUSED;
sockets_alloc = new_alloc;
sockets[old_alloc].fd = fd;
if ((sockets[old_alloc].input = sshbuf_new()) == NULL ||
(sockets[old_alloc].output = sshbuf_new()) == NULL ||
(sockets[old_alloc].request = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
sockets[old_alloc].type = type;
}
static int
handle_socket_read(u_int socknum)
{
struct sockaddr_un sunaddr;
socklen_t slen;
uid_t euid;
gid_t egid;
int fd;
slen = sizeof(sunaddr);
fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
if (fd == -1) {
error("accept from AUTH_SOCKET: %s", strerror(errno));
return -1;
}
if (getpeereid(fd, &euid, &egid) == -1) {
error("getpeereid %d failed: %s", fd, strerror(errno));
close(fd);
return -1;
}
if ((euid != 0) && (getuid() != euid)) {
error("uid mismatch: peer euid %u != uid %u",
(u_int) euid, (u_int) getuid());
close(fd);
return -1;
}
new_socket(AUTH_CONNECTION, fd);
return 0;
}
static int
handle_conn_read(u_int socknum)
{
char buf[AGENT_RBUF_LEN];
ssize_t len;
int r;
if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
if (len == -1) {
if (errno == EAGAIN || errno == EINTR)
return 0;
error_f("read error on socket %u (fd %d): %s",
socknum, sockets[socknum].fd, strerror(errno));
}
return -1;
}
if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
fatal_fr(r, "compose");
explicit_bzero(buf, sizeof(buf));
for (;;) {
if ((r = process_message(socknum)) == -1)
return -1;
else if (r == 0)
break;
}
return 0;
}
static int
handle_conn_write(u_int socknum)
{
ssize_t len;
int r;
if (sshbuf_len(sockets[socknum].output) == 0)
return 0; /* shouldn't happen */
if ((len = write(sockets[socknum].fd,
sshbuf_ptr(sockets[socknum].output),
sshbuf_len(sockets[socknum].output))) <= 0) {
if (len == -1) {
if (errno == EAGAIN || errno == EINTR)
return 0;
error_f("read error on socket %u (fd %d): %s",
socknum, sockets[socknum].fd, strerror(errno));
}
return -1;
}
if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
fatal_fr(r, "consume");
return 0;
}
static void
after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds)
{
size_t i;
u_int socknum, activefds = npfd;
for (i = 0; i < npfd; i++) {
if (pfd[i].revents == 0)
continue;
/* Find sockets entry */
for (socknum = 0; socknum < sockets_alloc; socknum++) {
if (sockets[socknum].type != AUTH_SOCKET &&
sockets[socknum].type != AUTH_CONNECTION)
continue;
if (pfd[i].fd == sockets[socknum].fd)
break;
}
if (socknum >= sockets_alloc) {
error_f("no socket for fd %d", pfd[i].fd);
continue;
}
/* Process events */
switch (sockets[socknum].type) {
case AUTH_SOCKET:
if ((pfd[i].revents & (POLLIN|POLLERR)) == 0)
break;
if (npfd > maxfds) {
debug3("out of fds (active %u >= limit %u); "
"skipping accept", activefds, maxfds);
break;
}
if (handle_socket_read(socknum) == 0)
activefds++;
break;
case AUTH_CONNECTION:
if ((pfd[i].revents & (POLLIN|POLLERR)) != 0 &&
handle_conn_read(socknum) != 0) {
goto close_sock;
}
if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
handle_conn_write(socknum) != 0) {
close_sock:
if (activefds == 0)
fatal("activefds == 0 at close_sock");
close_socket(&sockets[socknum]);
activefds--;
break;
}
break;
default:
break;
}
}
}
static int
prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds)
{
struct pollfd *pfd = *pfdp;
size_t i, j, npfd = 0;
time_t deadline;
int r;
/* Count active sockets */
for (i = 0; i < sockets_alloc; i++) {
switch (sockets[i].type) {
case AUTH_SOCKET:
case AUTH_CONNECTION:
npfd++;
break;
case AUTH_UNUSED:
break;
default:
fatal("Unknown socket type %d", sockets[i].type);
break;
}
}
if (npfd != *npfdp &&
(pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
fatal_f("recallocarray failed");
*pfdp = pfd;
*npfdp = npfd;
for (i = j = 0; i < sockets_alloc; i++) {
switch (sockets[i].type) {
case AUTH_SOCKET:
if (npfd > maxfds) {
debug3("out of fds (active %zu >= limit %u); "
"skipping arming listener", npfd, maxfds);
break;
}
pfd[j].fd = sockets[i].fd;
pfd[j].revents = 0;
pfd[j].events = POLLIN;
j++;
break;
case AUTH_CONNECTION:
pfd[j].fd = sockets[i].fd;
pfd[j].revents = 0;
/*
* Only prepare to read if we can handle a full-size
* input read buffer and enqueue a max size reply..
*/
if ((r = sshbuf_check_reserve(sockets[i].input,
AGENT_RBUF_LEN)) == 0 &&
(r = sshbuf_check_reserve(sockets[i].output,
AGENT_MAX_LEN)) == 0)
pfd[j].events = POLLIN;
else if (r != SSH_ERR_NO_BUFFER_SPACE)
fatal_fr(r, "reserve");
if (sshbuf_len(sockets[i].output) > 0)
pfd[j].events |= POLLOUT;
j++;
break;
default:
break;
}
}
deadline = reaper();
if (parent_alive_interval != 0)
deadline = (deadline == 0) ? parent_alive_interval :
MINIMUM(deadline, parent_alive_interval);
if (deadline == 0) {
*timeoutp = -1; /* INFTIM */
} else {
if (deadline > INT_MAX / 1000)
*timeoutp = INT_MAX / 1000;
else
*timeoutp = deadline * 1000;
}
return (1);
}
static void
cleanup_socket(void)
{
if (cleanup_pid != 0 && getpid() != cleanup_pid)
return;
debug_f("cleanup");
if (socket_name[0])
unlink(socket_name);
if (socket_dir[0])
rmdir(socket_dir);
}
void
cleanup_exit(int i)
{
cleanup_socket();
_exit(i);
}
/*ARGSUSED*/
static void
cleanup_handler(int sig)
{
cleanup_socket();
#ifdef ENABLE_PKCS11
pkcs11_terminate();
#endif
_exit(2);
}
static void
check_parent_exists(void)
{
/*
* If our parent has exited then getppid() will return (pid_t)1,
* so testing for that should be safe.
*/
if (parent_pid != -1 && getppid() != parent_pid) {
/* printf("Parent has died - Authentication agent exiting.\n"); */
cleanup_socket();
_exit(2);
}
}
static void
usage(void)
{
fprintf(stderr,
"usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
" [-P allowed_providers] [-t life]\n"
" ssh-agent [-a bind_address] [-E fingerprint_hash] [-P allowed_providers]\n"
" [-t life] command [arg ...]\n"
" ssh-agent [-c | -s] -k\n");
exit(1);
}
int
main(int ac, char **av)
{
int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
int sock, ch, result, saved_errno;
char *shell, *format, *pidstr, *agentsocket = NULL;
#ifdef HAVE_SETRLIMIT
struct rlimit rlim;
#endif
extern int optind;
extern char *optarg;
pid_t pid;
char pidstrbuf[1 + 3 * sizeof pid];
size_t len;
mode_t prev_mask;
int timeout = -1; /* INFTIM */
struct pollfd *pfd = NULL;
size_t npfd = 0;
u_int maxfds;
/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
sanitise_stdfd();
/* drop */
setegid(getgid());
setgid(getgid());
platform_disable_tracing(0); /* strict=no */
#ifdef RLIMIT_NOFILE
if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
fatal("%s: getrlimit: %s", __progname, strerror(errno));
#endif
__progname = ssh_get_progname(av[0]);
seed_rng();
while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:")) != -1) {
switch (ch) {
case 'E':
fingerprint_hash = ssh_digest_alg_by_name(optarg);
if (fingerprint_hash == -1)
fatal("Invalid hash algorithm \"%s\"", optarg);
break;
case 'c':
if (s_flag)
usage();
c_flag++;
break;
case 'k':
k_flag++;
break;
case 'O':
if (strcmp(optarg, "no-restrict-websafe") == 0)
restrict_websafe = 0;
else
fatal("Unknown -O option");
break;
case 'P':
if (allowed_providers != NULL)
fatal("-P option already specified");
allowed_providers = xstrdup(optarg);
break;
case 's':
if (c_flag)
usage();
s_flag++;
break;
case 'd':
if (d_flag || D_flag)
usage();
d_flag++;
break;
case 'D':
if (d_flag || D_flag)
usage();
D_flag++;
break;
case 'a':
agentsocket = optarg;
break;
case 't':
if ((lifetime = convtime(optarg)) == -1) {
fprintf(stderr, "Invalid lifetime\n");
usage();
}
break;
default:
usage();
}
}
ac -= optind;
av += optind;
if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
usage();
if (allowed_providers == NULL)
allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS);
if (ac == 0 && !c_flag && !s_flag) {
shell = getenv("SHELL");
if (shell != NULL && (len = strlen(shell)) > 2 &&
strncmp(shell + len - 3, "csh", 3) == 0)
c_flag = 1;
}
if (k_flag) {
const char *errstr = NULL;
pidstr = getenv(SSH_AGENTPID_ENV_NAME);
if (pidstr == NULL) {
fprintf(stderr, "%s not set, cannot kill agent\n",
SSH_AGENTPID_ENV_NAME);
exit(1);
}
pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
if (errstr) {
fprintf(stderr,
"%s=\"%s\", which is not a good PID: %s\n",
SSH_AGENTPID_ENV_NAME, pidstr, errstr);
exit(1);
}
if (kill(pid, SIGTERM) == -1) {
perror("kill");
exit(1);
}
format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
printf(format, SSH_AUTHSOCKET_ENV_NAME);
printf(format, SSH_AGENTPID_ENV_NAME);
printf("echo Agent pid %ld killed;\n", (long)pid);
exit(0);
}
/*
* Minimum file descriptors:
* stdio (3) + listener (1) + syslog (1 maybe) + connection (1) +
* a few spare for libc / stack protectors / sanitisers, etc.
*/
#define SSH_AGENT_MIN_FDS (3+1+1+1+4)
if (rlim.rlim_cur < SSH_AGENT_MIN_FDS)
fatal("%s: file descriptor rlimit %lld too low (minimum %u)",
__progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS);
maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS;
parent_pid = getpid();
if (agentsocket == NULL) {
/* Create private directory for agent socket */
mktemp_proto(socket_dir, sizeof(socket_dir));
if (mkdtemp(socket_dir) == NULL) {
perror("mkdtemp: private socket dir");
exit(1);
}
snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
(long)parent_pid);
} else {
/* Try to use specified agent socket */
socket_dir[0] = '\0';
strlcpy(socket_name, agentsocket, sizeof socket_name);
}
/*
* Create socket early so it will exist before command gets run from
* the parent.
*/
prev_mask = umask(0177);
sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
if (sock < 0) {
/* XXX - unix_listener() calls error() not perror() */
*socket_name = '\0'; /* Don't unlink any existing file */
cleanup_exit(1);
}
umask(prev_mask);
/*
* Fork, and have the parent execute the command, if any, or present
* the socket data. The child continues as the authentication agent.
*/
if (D_flag || d_flag) {
log_init(__progname,
d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
SYSLOG_FACILITY_AUTH, 1);
format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
SSH_AUTHSOCKET_ENV_NAME);
printf("echo Agent pid %ld;\n", (long)parent_pid);
fflush(stdout);
goto skip;
}
pid = fork();
if (pid == -1) {
perror("fork");
cleanup_exit(1);
}
if (pid != 0) { /* Parent - execute the given command. */
close(sock);
snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
if (ac == 0) {
format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
SSH_AUTHSOCKET_ENV_NAME);
printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
SSH_AGENTPID_ENV_NAME);
printf("echo Agent pid %ld;\n", (long)pid);
exit(0);
}
if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
perror("setenv");
exit(1);
}
execvp(av[0], av);
perror(av[0]);
exit(1);
}
/* child */
log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
if (setsid() == -1) {
error("setsid: %s", strerror(errno));
cleanup_exit(1);
}
(void)chdir("/");
if (stdfd_devnull(1, 1, 1) == -1)
error_f("stdfd_devnull failed");
#ifdef HAVE_SETRLIMIT
/* deny core dumps, since memory contains unencrypted private keys */
rlim.rlim_cur = rlim.rlim_max = 0;
if (setrlimit(RLIMIT_CORE, &rlim) == -1) {
error("setrlimit RLIMIT_CORE: %s", strerror(errno));
cleanup_exit(1);
}
#endif
skip:
cleanup_pid = getpid();
#ifdef ENABLE_PKCS11
pkcs11_init(0);
#endif
new_socket(AUTH_SOCKET, sock);
if (ac > 0)
parent_alive_interval = 10;
idtab_init();
ssh_signal(SIGPIPE, SIG_IGN);
ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
ssh_signal(SIGHUP, cleanup_handler);
ssh_signal(SIGTERM, cleanup_handler);
if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
fatal("%s: pledge: %s", __progname, strerror(errno));
platform_pledge_agent();
while (1) {
prepare_poll(&pfd, &npfd, &timeout, maxfds);
result = poll(pfd, npfd, timeout);
saved_errno = errno;
if (parent_alive_interval != 0)
check_parent_exists();
(void) reaper(); /* remove expired keys */
if (result == -1) {
if (saved_errno == EINTR)
continue;
fatal("poll: %s", strerror(saved_errno));
} else if (result > 0)
after_poll(pfd, npfd, maxfds);
}
/* NOTREACHED */
}
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