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Diffstat (limited to '')
| -rw-r--r-- | ssh-agent.c | 1339 |
1 files changed, 1339 insertions, 0 deletions
diff --git a/ssh-agent.c b/ssh-agent.c new file mode 100644 index 0000000..d8a8260 --- /dev/null +++ b/ssh-agent.c @@ -0,0 +1,1339 @@ +/* $OpenBSD: ssh-agent.c,v 1.231 2018/05/11 03:38:51 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> +#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 "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" + +#ifdef ENABLE_PKCS11 +#include "ssh-pkcs11.h" +#endif + +#ifndef DEFAULT_PKCS11_WHITELIST +# define DEFAULT_PKCS11_WHITELIST "/usr/lib*/*,/usr/local/lib*/*" +#endif + +/* Maximum accepted message length */ +#define AGENT_MAX_LEN (256*1024) + +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; +} 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]; + +/* PKCS#11 path whitelist */ +static char *pkcs11_whitelist; + +/* 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; + +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); +} + +/* 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("%s: buffer error: %s", __func__, ssh_err(r)); +} + +/* 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("%s: sshbuf_new failed", __func__); + if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || + (r = sshbuf_put_u32(msg, idtab->nentries)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + 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("%s: put key/comment: %s", __func__, + ssh_err(r)); + continue; + } + } + if ((r = sshbuf_put_stringb(e->output, msg)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + 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"; + } + return NULL; +} + +/* 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; + struct sshbuf *msg; + struct sshkey *key = NULL; + struct identity *id; + + if ((msg = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __func__); + 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("%s: couldn't parse request: %s", __func__, ssh_err(r)); + goto send; + } + + if ((id = lookup_identity(key)) == NULL) { + verbose("%s: %s key not found", __func__, sshkey_type(key)); + goto send; + } + if (id->confirm && confirm_key(id) != 0) { + verbose("%s: user refused key", __func__); + goto send; + } + if ((r = sshkey_sign(id->key, &signature, &slen, + data, dlen, agent_decode_alg(key, flags), compat)) != 0) { + error("%s: sshkey_sign: %s", __func__, ssh_err(r)); + goto send; + } + /* Success */ + ok = 0; + send: + sshkey_free(key); + if (ok == 0) { + if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 || + (r = sshbuf_put_string(msg, signature, slen)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + + if ((r = sshbuf_put_stringb(e->output, msg)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + + 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("%s: get key: %s", __func__, ssh_err(r)); + goto done; + } + if ((id = lookup_identity(key)) == NULL) { + debug("%s: key not found", __func__); + goto done; + } + /* We have this key, free it. */ + if (idtab->nentries < 1) + fatal("%s: internal error: nentries %d", + __func__, 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, maxsign; + char *comment = NULL; + 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("%s: decode private key: %s", __func__, ssh_err(r)); + goto err; + } + + while (sshbuf_len(e->request)) { + if ((r = sshbuf_get_u8(e->request, &ctype)) != 0) { + error("%s: buffer error: %s", __func__, ssh_err(r)); + goto err; + } + switch (ctype) { + case SSH_AGENT_CONSTRAIN_LIFETIME: + if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) { + error("%s: bad lifetime constraint: %s", + __func__, ssh_err(r)); + 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("%s: bad maxsign constraint: %s", + __func__, ssh_err(r)); + goto err; + } + if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) { + error("%s: cannot enable maxsign: %s", + __func__, ssh_err(r)); + goto err; + } + break; + default: + error("%s: Unknown constraint %d", __func__, ctype); + err: + sshbuf_reset(e->request); + free(comment); + sshkey_free(k); + goto send; + } + } + + 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); + } + id->key = k; + id->comment = comment; + id->death = death; + id->confirm = confirm; +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("%s: buffer error: %s", __func__, ssh_err(r)); + 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; + } + explicit_bzero(passwd, pwlen); + free(passwd); + send_status(e, success); +} + +static void +no_identities(SocketEntry *e) +{ + struct sshbuf *msg; + int r; + + if ((msg = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __func__); + 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("%s: buffer error: %s", __func__, ssh_err(r)); + sshbuf_free(msg); +} + +#ifdef ENABLE_PKCS11 +static void +process_add_smartcard_key(SocketEntry *e) +{ + char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; + 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("%s: buffer error: %s", __func__, ssh_err(r)); + goto send; + } + + while (sshbuf_len(e->request)) { + if ((r = sshbuf_get_u8(e->request, &type)) != 0) { + error("%s: buffer error: %s", __func__, ssh_err(r)); + goto send; + } + switch (type) { + case SSH_AGENT_CONSTRAIN_LIFETIME: + if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) { + error("%s: buffer error: %s", + __func__, ssh_err(r)); + goto send; + } + death = monotime() + seconds; + break; + case SSH_AGENT_CONSTRAIN_CONFIRM: + confirm = 1; + break; + default: + error("%s: Unknown constraint type %d", __func__, 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, pkcs11_whitelist, 0) != 1) { + verbose("refusing PKCS#11 add of \"%.100s\": " + "provider not whitelisted", canonical_provider); + goto send; + } + debug("%s: add %.100s", __func__, canonical_provider); + if (lifetime && !death) + death = monotime() + lifetime; + + count = pkcs11_add_provider(canonical_provider, pin, &keys); + for (i = 0; i < count; i++) { + k = keys[i]; + if (lookup_identity(k) == NULL) { + id = xcalloc(1, sizeof(Identity)); + id->key = k; + id->provider = xstrdup(canonical_provider); + id->comment = xstrdup(canonical_provider); /* XXX */ + id->death = death; + id->confirm = confirm; + TAILQ_INSERT_TAIL(&idtab->idlist, id, next); + idtab->nentries++; + success = 1; + } else { + sshkey_free(k); + } + keys[i] = NULL; + } +send: + free(pin); + free(provider); + free(keys); + 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("%s: buffer error: %s", __func__, ssh_err(r)); + 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("%s: remove %.100s", __func__, 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("%s: pkcs11_del_provider failed", __func__); +send: + free(provider); + send_status(e, success); +} +#endif /* ENABLE_PKCS11 */ + +/* dispatch incoming messages */ + +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("%s: socket number %u >= allocated %u", + __func__, 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("%s: socket %u (fd=%d) message too long %u > %u", + __func__, 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) { + debug("%s: buffer error: %s", __func__, ssh_err(r)); + return -1; + } + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + } + + debug("%s: socket %u (fd=%d) type %d", __func__, 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 0; + } + + 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 0; +} + +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) + fatal("%s: sshbuf_new failed", __func__); + if ((sockets[i].output = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __func__); + if ((sockets[i].request = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __func__); + 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) + fatal("%s: sshbuf_new failed", __func__); + if ((sockets[old_alloc].output = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __func__); + if ((sockets[old_alloc].request = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __func__); + 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 < 0) { + error("accept from AUTH_SOCKET: %s", strerror(errno)); + return -1; + } + if (getpeereid(fd, &euid, &egid) < 0) { + 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[1024]; + 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("%s: read error on socket %u (fd %d): %s", + __func__, socknum, sockets[socknum].fd, + strerror(errno)); + } + return -1; + } + if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + explicit_bzero(buf, sizeof(buf)); + process_message(socknum); + 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("%s: read error on socket %u (fd %d): %s", + __func__, socknum, sockets[socknum].fd, + strerror(errno)); + } + return -1; + } + if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + 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("%s: no socket for fd %d", __func__, 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; + + /* 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("%s: recallocarray failed", __func__); + *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; + /* XXX backoff when input buffer full */ + pfd[j].events = POLLIN; + 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("%s: cleanup", __func__); + 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 pkcs11_whitelist] [-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, fd, 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; + + ssh_malloc_init(); /* must be called before any mallocs */ + /* 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 */ + + if (getrlimit(RLIMIT_NOFILE, &rlim) == -1) + fatal("%s: getrlimit: %s", __progname, strerror(errno)); + +#ifdef WITH_OPENSSL + OpenSSL_add_all_algorithms(); +#endif + + __progname = ssh_get_progname(av[0]); + seed_rng(); + + while ((ch = getopt(ac, av, "cDdksE:a: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 'P': + if (pkcs11_whitelist != NULL) + fatal("-P option already specified"); + pkcs11_whitelist = 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 (pkcs11_whitelist == NULL) + pkcs11_whitelist = xstrdup(DEFAULT_PKCS11_WHITELIST); + + 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 descriptior 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 ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { + /* XXX might close listen socket */ + (void)dup2(fd, STDIN_FILENO); + (void)dup2(fd, STDOUT_FILENO); + (void)dup2(fd, STDERR_FILENO); + if (fd > 2) + close(fd); + } + +#ifdef HAVE_SETRLIMIT + /* deny core dumps, since memory contains unencrypted private keys */ + rlim.rlim_cur = rlim.rlim_max = 0; + if (setrlimit(RLIMIT_CORE, &rlim) < 0) { + 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(); + signal(SIGPIPE, SIG_IGN); + signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN); + signal(SIGHUP, cleanup_handler); + 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 < 0) { + if (saved_errno == EINTR) + continue; + fatal("poll: %s", strerror(saved_errno)); + } else if (result > 0) + after_poll(pfd, npfd, maxfds); + } + /* NOTREACHED */ +} |