Edit
IABSD.fr/src/usr.bin/ssh/ssh-agent.c
djm
- usr.bin/ssh/ssh-agent.c
-
/* $OpenBSD: ssh-agent.c,v 1.262 2020/07/05 23:59:45 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 <sys/types.h> #include <sys/time.h> #include <sys/queue.h> #include <sys/resource.h> #include <sys/socket.h> #include <sys/stat.h> #include <sys/un.h> #include <sys/wait.h> #ifdef WITH_OPENSSL #include <openssl/evp.h> #endif #include <errno.h> #include <fcntl.h> #include <paths.h> #include <poll.h> #include <signal.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <stdarg.h> #include <limits.h> #include <time.h> #include <unistd.h> #include <util.h> #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("%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"; } 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("%s: sshbuf_new", __func__); /* 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("%s: parsed userauth", __func__); if (m == SSH2_MSG_USERAUTH_REQUEST && n == 1 && strcmp(cp1, "ssh-connection") == 0 && strcmp(cp2, "publickey") == 0 && sshkey_equal(key, mkey)) { debug("%s: well formed userauth", __func__); matched = 1; } } free(cp1); free(cp2); sshkey_free(mkey); sshbuf_free(b); if (matched) return 1; if ((b = sshbuf_from(msg, len)) == NULL) fatal("%s: sshbuf_new", __func__); 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("%s: parsed sshsig", __func__); 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("%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 (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("%s: fingerprint failed", __func__); notifier = notify_start(0, "Confirm user presence for key %s %s", sshkey_type(id->key), fp); } } if ((r = sshkey_sign(id->key, &signature, &slen, data, dlen, agent_decode_alg(key, flags), id->sk_provider, compat)) != 0) { error("%s: sshkey_sign: %s", __func__, ssh_err(r)); goto send; } /* Success */ ok = 0; send: notify_complete(notifier); 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("%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 = 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("%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; case SSH_AGENT_CONSTRAIN_EXTENSION: if ((r = sshbuf_get_cstring(e->request, &ext_name, NULL)) != 0) { error("%s: cannot parse extension: %s", __func__, ssh_err(r)); goto err; } debug("%s: constraint ext %s", __func__, 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("%s: cannot parse %s: %s", __func__, ext_name, ssh_err(r)); goto err; } } else { error("%s: unsupported constraint \"%s\"", __func__, ext_name); goto err; } free(ext_name); break; default: error("%s: Unknown constraint %d", __func__, 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("%s: internal provider", __func__); } 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("%s: shield private key: %s", __func__, ssh_err(r)); 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("%s: sshkey_fingerprint failed", __func__); debug("%s: add %s %s \"%.100s\" (life: %u) (confirm: %u) " "(provider: %s)", __func__, 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("%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; } freezero(passwd, pwlen); 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]; 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("%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, allowed_providers, 0) != 1) { verbose("refusing PKCS#11 add of \"%.100s\": " "provider not allowed", 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, &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("%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 == -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("%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; 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("%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; /* * 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("%s: buffer error: %s", __func__, ssh_err(r)); } 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 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, fd, ch, result, saved_errno; char *shell, *format, *pidstr, *agentsocket = NULL; struct rlimit rlim; 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()); if (getrlimit(RLIMIT_NOFILE, &rlim) == -1) fatal("%s: getrlimit: %s", __progname, strerror(errno)); #ifdef WITH_OPENSSL OpenSSL_add_all_algorithms(); #endif 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 ((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); } /* 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); } 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)); 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 */ }