/* $OpenBSD: ssh-agent.c,v 1.308 2024/10/24 03:15:47 djm Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , 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 #include #include #include #include #include #include #include #ifdef WITH_OPENSSL #include #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #include "xmalloc.h" #include "ssh.h" #include "ssh2.h" #include "sshbuf.h" #include "sshkey.h" #include "authfd.h" #include "log.h" #include "misc.h" #include "digest.h" #include "ssherr.h" #include "match.h" #include "msg.h" #include "pathnames.h" #include "ssh-pkcs11.h" #include "sk-api.h" #include "myproposal.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) /* Maximum number of recorded session IDs/hostkeys per connection */ #define AGENT_MAX_SESSION_IDS 16 /* Maximum size of session ID */ #define AGENT_MAX_SID_LEN 128 /* Maximum number of destination constraints to accept on a key */ #define AGENT_MAX_DEST_CONSTRAINTS 1024 /* Maximum number of associated certificate constraints to accept on a key */ #define AGENT_MAX_EXT_CERTS 1024 /* XXX store hostkey_sid in a refcounted tree */ typedef enum { AUTH_UNUSED = 0, AUTH_SOCKET = 1, AUTH_CONNECTION = 2, } sock_type; struct hostkey_sid { struct sshkey *key; struct sshbuf *sid; int forwarded; }; typedef struct socket_entry { int fd; sock_type type; struct sshbuf *input; struct sshbuf *output; struct sshbuf *request; size_t nsession_ids; struct hostkey_sid *session_ids; int session_bind_attempted; } 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; struct dest_constraint *dest_constraints; size_t ndest_constraints; } 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; static sig_atomic_t signalled_exit; static sig_atomic_t signalled_keydrop; /* 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; /* * Allows PKCS11 providers or SK keys that use non-internal providers to * be added over a remote connection (identified by session-bind@openssh.com). */ static int remote_add_provider; /* 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 int 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) { size_t i; close(e->fd); sshbuf_free(e->input); sshbuf_free(e->output); sshbuf_free(e->request); for (i = 0; i < e->nsession_ids; i++) { sshkey_free(e->session_ids[i].key); sshbuf_free(e->session_ids[i].sid); } free(e->session_ids); memset(e, '\0', sizeof(*e)); e->fd = -1; e->type = AUTH_UNUSED; } static void idtab_init(void) { idtab = xcalloc(1, sizeof(*idtab)); TAILQ_INIT(&idtab->idlist); idtab->nentries = 0; } static void free_dest_constraint_hop(struct dest_constraint_hop *dch) { u_int i; if (dch == NULL) return; free(dch->user); free(dch->hostname); for (i = 0; i < dch->nkeys; i++) sshkey_free(dch->keys[i]); free(dch->keys); free(dch->key_is_ca); } static void free_dest_constraints(struct dest_constraint *dcs, size_t ndcs) { size_t i; for (i = 0; i < ndcs; i++) { free_dest_constraint_hop(&dcs[i].from); free_dest_constraint_hop(&dcs[i].to); } free(dcs); } #ifdef ENABLE_PKCS11 static void dup_dest_constraint_hop(const struct dest_constraint_hop *dch, struct dest_constraint_hop *out) { u_int i; int r; out->user = dch->user == NULL ? NULL : xstrdup(dch->user); out->hostname = dch->hostname == NULL ? NULL : xstrdup(dch->hostname); out->is_ca = dch->is_ca; out->nkeys = dch->nkeys; out->keys = out->nkeys == 0 ? NULL : xcalloc(out->nkeys, sizeof(*out->keys)); out->key_is_ca = out->nkeys == 0 ? NULL : xcalloc(out->nkeys, sizeof(*out->key_is_ca)); for (i = 0; i < dch->nkeys; i++) { if (dch->keys[i] != NULL && (r = sshkey_from_private(dch->keys[i], &(out->keys[i]))) != 0) fatal_fr(r, "copy key"); out->key_is_ca[i] = dch->key_is_ca[i]; } } static struct dest_constraint * dup_dest_constraints(const struct dest_constraint *dcs, size_t ndcs) { size_t i; struct dest_constraint *ret; if (ndcs == 0) return NULL; ret = xcalloc(ndcs, sizeof(*ret)); for (i = 0; i < ndcs; i++) { dup_dest_constraint_hop(&dcs[i].from, &ret[i].from); dup_dest_constraint_hop(&dcs[i].to, &ret[i].to); } return ret; } #endif /* ENABLE_PKCS11 */ #ifdef DEBUG_CONSTRAINTS static void dump_dest_constraint_hop(const struct dest_constraint_hop *dch) { u_int i; char *fp; debug_f("user %s hostname %s is_ca %d nkeys %u", dch->user == NULL ? "(null)" : dch->user, dch->hostname == NULL ? "(null)" : dch->hostname, dch->is_ca, dch->nkeys); for (i = 0; i < dch->nkeys; i++) { fp = NULL; if (dch->keys[i] != NULL && (fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) fatal_f("fingerprint failed"); debug_f("key %u/%u: %s%s%s key_is_ca %d", i, dch->nkeys, dch->keys[i] == NULL ? "" : sshkey_ssh_name(dch->keys[i]), dch->keys[i] == NULL ? "" : " ", dch->keys[i] == NULL ? "none" : fp, dch->key_is_ca[i]); free(fp); } } #endif /* DEBUG_CONSTRAINTS */ static void dump_dest_constraints(const char *context, const struct dest_constraint *dcs, size_t ndcs) { #ifdef DEBUG_CONSTRAINTS size_t i; debug_f("%s: %zu constraints", context, ndcs); for (i = 0; i < ndcs; i++) { debug_f("constraint %zu / %zu: from: ", i, ndcs); dump_dest_constraint_hop(&dcs[i].from); debug_f("constraint %zu / %zu: to: ", i, ndcs); dump_dest_constraint_hop(&dcs[i].to); } debug_f("done for %s", context); #endif /* DEBUG_CONSTRAINTS */ } static void free_identity(Identity *id) { sshkey_free(id->key); free(id->provider); free(id->comment); free(id->sk_provider); free_dest_constraints(id->dest_constraints, id->ndest_constraints); free(id); } /* * Match 'key' against the key/CA list in a destination constraint hop * Returns 0 on success or -1 otherwise. */ static int match_key_hop(const char *tag, const struct sshkey *key, const struct dest_constraint_hop *dch) { const char *reason = NULL; const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)"; u_int i; char *fp; if (key == NULL) return -1; /* XXX logspam */ if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) fatal_f("fingerprint failed"); debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail", tag, hostname, sshkey_type(key), fp, dch->nkeys); free(fp); for (i = 0; i < dch->nkeys; i++) { if (dch->keys[i] == NULL) return -1; /* XXX logspam */ if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) fatal_f("fingerprint failed"); debug3_f("%s: key %u: %s%s %s", tag, i, dch->key_is_ca[i] ? "CA " : "", sshkey_type(dch->keys[i]), fp); free(fp); if (!sshkey_is_cert(key)) { /* plain key */ if (dch->key_is_ca[i] || !sshkey_equal(key, dch->keys[i])) continue; return 0; } /* certificate */ if (!dch->key_is_ca[i]) continue; if (key->cert == NULL || key->cert->signature_key == NULL) return -1; /* shouldn't happen */ if (!sshkey_equal(key->cert->signature_key, dch->keys[i])) continue; if (sshkey_cert_check_host(key, hostname, 1, SSH_ALLOWED_CA_SIGALGS, &reason) != 0) { debug_f("cert %s / hostname %s rejected: %s", key->cert->key_id, hostname, reason); continue; } return 0; } return -1; } /* Check destination constraints on an identity against the hostkey/user */ static int permitted_by_dest_constraints(const struct sshkey *fromkey, const struct sshkey *tokey, Identity *id, const char *user, const char **hostnamep) { size_t i; struct dest_constraint *d; if (hostnamep != NULL) *hostnamep = NULL; for (i = 0; i < id->ndest_constraints; i++) { d = id->dest_constraints + i; /* XXX remove logspam */ debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)", i, d->from.user ? d->from.user : "", d->from.user ? "@" : "", d->from.hostname ? d->from.hostname : "(ORIGIN)", d->from.nkeys, d->to.user ? d->to.user : "", d->to.user ? "@" : "", d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys); /* Match 'from' key */ if (fromkey == NULL) { /* We are matching the first hop */ if (d->from.hostname != NULL || d->from.nkeys != 0) continue; } else if (match_key_hop("from", fromkey, &d->from) != 0) continue; /* Match 'to' key */ if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0) continue; /* Match user if specified */ if (d->to.user != NULL && user != NULL && !match_pattern(user, d->to.user)) continue; /* successfully matched this constraint */ if (hostnamep != NULL) *hostnamep = d->to.hostname; debug2_f("allowed for hostname %s", d->to.hostname == NULL ? "*" : d->to.hostname); return 0; } /* no match */ debug2_f("%s identity \"%s\" not permitted for this destination", sshkey_type(id->key), id->comment); return -1; } /* * Check whether hostkeys on a SocketEntry and the optionally specified user * are permitted by the destination constraints on the Identity. * Returns 0 on success or -1 otherwise. */ static int identity_permitted(Identity *id, SocketEntry *e, char *user, const char **forward_hostnamep, const char **last_hostnamep) { size_t i; const char **hp; struct hostkey_sid *hks; const struct sshkey *fromkey = NULL; const char *test_user; char *fp1, *fp2; /* XXX remove logspam */ debug3_f("entering: key %s comment \"%s\", %zu socket bindings, " "%zu constraints", sshkey_type(id->key), id->comment, e->nsession_ids, id->ndest_constraints); if (id->ndest_constraints == 0) return 0; /* unconstrained */ if (e->session_bind_attempted && e->nsession_ids == 0) { error_f("previous session bind failed on socket"); return -1; } if (e->nsession_ids == 0) return 0; /* local use */ /* * Walk through the hops recorded by session_id and try to find a * constraint that satisfies each. */ for (i = 0; i < e->nsession_ids; i++) { hks = e->session_ids + i; if (hks->key == NULL) fatal_f("internal error: no bound key"); /* XXX remove logspam */ fp1 = fp2 = NULL; if (fromkey != NULL && (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) fatal_f("fingerprint failed"); if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) fatal_f("fingerprint failed"); debug3_f("socketentry fd=%d, entry %zu %s, " "from hostkey %s %s to user %s hostkey %s %s", e->fd, i, hks->forwarded ? "FORWARD" : "AUTH", fromkey ? sshkey_type(fromkey) : "(ORIGIN)", fromkey ? fp1 : "", user ? user : "(ANY)", sshkey_type(hks->key), fp2); free(fp1); free(fp2); /* * Record the hostnames for the initial forwarding and * the final destination. */ hp = NULL; if (i == e->nsession_ids - 1) hp = last_hostnamep; else if (i == 0) hp = forward_hostnamep; /* Special handling for final recorded binding */ test_user = NULL; if (i == e->nsession_ids - 1) { /* Can only check user at final hop */ test_user = user; /* * user is only presented for signature requests. * If this is the case, make sure last binding is not * for a forwarding. */ if (hks->forwarded && user != NULL) { error_f("tried to sign on forwarding hop"); return -1; } } else if (!hks->forwarded) { error_f("tried to forward though signing bind"); return -1; } if (permitted_by_dest_constraints(fromkey, hks->key, id, test_user, hp) != 0) return -1; fromkey = hks->key; } /* * Another special case: if the last bound session ID was for a * forwarding, and this function is not being called to check a sign * request (i.e. no 'user' supplied), then only permit the key if * there is a permission that would allow it to be used at another * destination. This hides keys that are allowed to be used to * authenticate *to* a host but not permitted for *use* beyond it. */ hks = &e->session_ids[e->nsession_ids - 1]; if (hks->forwarded && user == NULL && permitted_by_dest_constraints(hks->key, NULL, id, NULL, NULL) != 0) { debug3_f("key permitted at host but not after"); return -1; } /* success */ return 0; } static int socket_is_remote(SocketEntry *e) { return e->session_bind_attempted || (e->nsession_ids != 0); } /* 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, const char *extra) { 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.%s%s", id->comment, p, extra == NULL ? "" : "\n", extra == NULL ? "" : extra)) 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, *keys; int r; u_int i = 0, nentries = 0; char *fp; debug2_f("entering"); if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL) fatal_f("sshbuf_new failed"); TAILQ_FOREACH(id, &idtab->idlist, next) { if ((fp = sshkey_fingerprint(id->key, SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) fatal_f("fingerprint failed"); debug_f("key %u / %u: %s %s", i++, idtab->nentries, sshkey_ssh_name(id->key), fp); dump_dest_constraints(__func__, id->dest_constraints, id->ndest_constraints); free(fp); /* identity not visible, don't include in response */ if (identity_permitted(id, e, NULL, NULL, NULL) != 0) continue; if ((r = sshkey_puts_opts(id->key, keys, SSHKEY_SERIALIZE_INFO)) != 0 || (r = sshbuf_put_cstring(keys, id->comment)) != 0) { error_fr(r, "compose key/comment"); continue; } nentries++; } debug2_f("replying with %u allowed of %u available keys", nentries, idtab->nentries); if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || (r = sshbuf_put_u32(msg, nentries)) != 0 || (r = sshbuf_putb(msg, keys)) != 0) fatal_fr(r, "compose"); if ((r = sshbuf_put_stringb(e->output, msg)) != 0) fatal_fr(r, "enqueue"); sshbuf_free(msg); sshbuf_free(keys); } 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; } /* * Attempt to parse the contents of a buffer as a SSH publickey userauth * request, checking its contents for consistency and matching the embedded * key against the one that is being used for signing. * Note: does not modify msg buffer. * Optionally extract the username, session ID and/or hostkey from the request. */ static int parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key, char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp) { struct sshbuf *b = NULL, *sess_id = NULL; char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL; int r; u_char t, sig_follows; struct sshkey *mkey = NULL, *hostkey = NULL; if (userp != NULL) *userp = NULL; if (sess_idp != NULL) *sess_idp = NULL; if (hostkeyp != NULL) *hostkeyp = NULL; if ((b = sshbuf_fromb(msg)) == NULL) fatal_f("sshbuf_fromb"); /* SSH userauth request */ if ((r = sshbuf_froms(b, &sess_id)) != 0) goto out; if (sshbuf_len(sess_id) == 0) { r = SSH_ERR_INVALID_FORMAT; goto out; } if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */ (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */ (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */ (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */ (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */ (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */ (r = sshkey_froms(b, &mkey)) != 0) /* key */ goto out; if (t != SSH2_MSG_USERAUTH_REQUEST || sig_follows != 1 || strcmp(service, "ssh-connection") != 0 || !sshkey_equal(expected_key, mkey) || sshkey_type_from_name(pkalg) != expected_key->type) { r = SSH_ERR_INVALID_FORMAT; goto out; } if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) { if ((r = sshkey_froms(b, &hostkey)) != 0) goto out; } else if (strcmp(method, "publickey") != 0) { r = SSH_ERR_INVALID_FORMAT; goto out; } if (sshbuf_len(b) != 0) { r = SSH_ERR_INVALID_FORMAT; goto out; } /* success */ r = 0; debug3_f("well formed userauth"); if (userp != NULL) { *userp = user; user = NULL; } if (sess_idp != NULL) { *sess_idp = sess_id; sess_id = NULL; } if (hostkeyp != NULL) { *hostkeyp = hostkey; hostkey = NULL; } out: sshbuf_free(b); sshbuf_free(sess_id); free(user); free(service); free(method); free(pkalg); sshkey_free(mkey); sshkey_free(hostkey); return r; } /* * Attempt to parse the contents of a buffer as a SSHSIG signature request. * Note: does not modify buffer. */ static int parse_sshsig_request(struct sshbuf *msg) { int r; struct sshbuf *b; if ((b = sshbuf_fromb(msg)) == NULL) fatal_f("sshbuf_fromb"); 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) */ goto out; if (sshbuf_len(b) != 0) { r = SSH_ERR_INVALID_FORMAT; goto out; } /* success */ r = 0; out: sshbuf_free(b); return r; } /* * 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, struct sshbuf *data) { if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) { debug_f("signed data matches public key userauth request"); return 1; } if (parse_sshsig_request(data) == 0) { debug_f("signed data matches SSHSIG signature request"); return 1; } /* XXX check CA signature operation */ error("web-origin key attempting to sign non-SSH message"); return 0; } static int buf_equal(const struct sshbuf *a, const struct sshbuf *b) { if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL) return SSH_ERR_INVALID_ARGUMENT; if (sshbuf_len(a) != sshbuf_len(b)) return SSH_ERR_INVALID_FORMAT; if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0) return SSH_ERR_INVALID_FORMAT; return 0; } /* ssh2 only */ static void process_sign_request2(SocketEntry *e) { u_char *signature = NULL; size_t slen = 0; u_int compat = 0, flags; int r, ok = -1, retried = 0; char *fp = NULL, *pin = NULL, *prompt = NULL; char *user = NULL, *sig_dest = NULL; const char *fwd_host = NULL, *dest_host = NULL; struct sshbuf *msg = NULL, *data = NULL, *sid = NULL; struct sshkey *key = NULL, *hostkey = NULL; struct identity *id; struct notifier_ctx *notifier = NULL; debug_f("entering"); if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL) fatal_f("sshbuf_new failed"); if ((r = sshkey_froms(e->request, &key)) != 0 || (r = sshbuf_get_stringb(e->request, data)) != 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 ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) fatal_f("fingerprint failed"); if (id->ndest_constraints != 0) { if (e->nsession_ids == 0) { logit_f("refusing use of destination-constrained key " "to sign on unbound connection"); goto send; } if (parse_userauth_request(data, key, &user, &sid, &hostkey) != 0) { logit_f("refusing use of destination-constrained key " "to sign an unidentified signature"); goto send; } /* XXX logspam */ debug_f("user=%s", user); if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0) goto send; /* XXX display fwd_host/dest_host in askpass UI */ /* * Ensure that the session ID is the most recent one * registered on the socket - it should have been bound by * ssh immediately before userauth. */ if (buf_equal(sid, e->session_ids[e->nsession_ids - 1].sid) != 0) { error_f("unexpected session ID (%zu listed) on " "signature request for target user %s with " "key %s %s", e->nsession_ids, user, sshkey_type(id->key), fp); goto send; } /* * Ensure that the hostkey embedded in the signature matches * the one most recently bound to the socket. An exception is * made for the initial forwarding hop. */ if (e->nsession_ids > 1 && hostkey == NULL) { error_f("refusing use of destination-constrained key: " "no hostkey recorded in signature for forwarded " "connection"); goto send; } if (hostkey != NULL && !sshkey_equal(hostkey, e->session_ids[e->nsession_ids - 1].key)) { error_f("refusing use of destination-constrained key: " "mismatch between hostkey in request and most " "recently bound session"); goto send; } xasprintf(&sig_dest, "public key authentication request for " "user \"%s\" to listed host", user); } if (id->confirm && confirm_key(id, sig_dest) != 0) { verbose_f("user refused key"); goto send; } if (sshkey_is_sk(id->key)) { if (restrict_websafe && strncmp(id->key->sk_application, "ssh:", 4) != 0 && !check_websafe_message_contents(key, data)) { /* error already logged */ goto send; } if (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { notifier = notify_start(0, "Confirm user presence for key %s %s%s%s", sshkey_type(id->key), fp, sig_dest == NULL ? "" : "\n", sig_dest == NULL ? "" : sig_dest); } } retry_pin: if ((r = sshkey_sign(id->key, &signature, &slen, sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags), id->sk_provider, pin, compat)) != 0) { debug_fr(r, "sshkey_sign"); if (pin == NULL && !retried && sshkey_is_sk(id->key) && r == SSH_ERR_KEY_WRONG_PASSPHRASE) { notify_complete(notifier, NULL); notifier = NULL; /* XXX include sig_dest */ xasprintf(&prompt, "Enter PIN%sfor %s key %s: ", (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ? " and confirm user presence " : " ", sshkey_type(id->key), fp); pin = read_passphrase(prompt, RP_USE_ASKPASS); retried = 1; goto retry_pin; } error_fr(r, "sshkey_sign"); goto send; } /* Success */ ok = 0; debug_f("good signature"); send: notify_complete(notifier, "User presence confirmed"); 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(sid); sshbuf_free(data); sshbuf_free(msg); sshkey_free(key); sshkey_free(hostkey); free(fp); free(signature); free(sig_dest); free(user); free(prompt); if (pin != NULL) freezero(pin, strlen(pin)); } /* shared */ static void process_remove_identity(SocketEntry *e) { int r, success = 0; struct sshkey *key = NULL; Identity *id; debug2_f("entering"); 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; } /* identity not visible, cannot be removed */ if (identity_permitted(id, e, NULL, NULL, NULL) != 0) goto done; /* error already logged */ /* 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--; success = 1; done: sshkey_free(key); send_status(e, success); } static void remove_all_identities(void) { Identity *id; debug2_f("entering"); /* 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; } static void process_remove_all_identities(SocketEntry *e) { remove_all_identities(); /* 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 int parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch) { u_char key_is_ca; size_t elen = 0; int r; struct sshkey *k = NULL; char *fp; memset(dch, '\0', sizeof(*dch)); if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 || (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 || (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { error_fr(r, "parse"); goto out; } if (elen != 0) { error_f("unsupported extensions (len %zu)", elen); r = SSH_ERR_FEATURE_UNSUPPORTED; goto out; } if (*dch->hostname == '\0') { free(dch->hostname); dch->hostname = NULL; } if (*dch->user == '\0') { free(dch->user); dch->user = NULL; } while (sshbuf_len(b) != 0) { dch->keys = xrecallocarray(dch->keys, dch->nkeys, dch->nkeys + 1, sizeof(*dch->keys)); dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys, dch->nkeys + 1, sizeof(*dch->key_is_ca)); if ((r = sshkey_froms(b, &k)) != 0 || (r = sshbuf_get_u8(b, &key_is_ca)) != 0) goto out; if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) fatal_f("fingerprint failed"); debug3_f("%s%s%s: adding %skey %s %s", dch->user == NULL ? "" : dch->user, dch->user == NULL ? "" : "@", dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp); free(fp); dch->keys[dch->nkeys] = k; dch->key_is_ca[dch->nkeys] = key_is_ca != 0; dch->nkeys++; k = NULL; /* transferred */ } /* success */ r = 0; out: sshkey_free(k); return r; } static int parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc) { struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL; int r; size_t elen = 0; debug3_f("entering"); memset(dc, '\0', sizeof(*dc)); if ((r = sshbuf_froms(m, &b)) != 0 || (r = sshbuf_froms(b, &frombuf)) != 0 || (r = sshbuf_froms(b, &tobuf)) != 0 || (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { error_fr(r, "parse"); goto out; } if ((r = parse_dest_constraint_hop(frombuf, &dc->from)) != 0 || (r = parse_dest_constraint_hop(tobuf, &dc->to)) != 0) goto out; /* already logged */ if (elen != 0) { error_f("unsupported extensions (len %zu)", elen); r = SSH_ERR_FEATURE_UNSUPPORTED; goto out; } debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)", dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys, dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "", dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys); /* check consistency */ if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) || dc->from.user != NULL) { error_f("inconsistent \"from\" specification"); r = SSH_ERR_INVALID_FORMAT; goto out; } if (dc->to.hostname == NULL || dc->to.nkeys == 0) { error_f("incomplete \"to\" specification"); r = SSH_ERR_INVALID_FORMAT; goto out; } /* success */ r = 0; out: sshbuf_free(b); sshbuf_free(frombuf); sshbuf_free(tobuf); return r; } static int parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp, struct dest_constraint **dcsp, size_t *ndcsp, int *cert_onlyp, struct sshkey ***certs, size_t *ncerts) { char *ext_name = NULL; int r; struct sshbuf *b = NULL; u_char v; struct sshkey *k; if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) { error_fr(r, "parse constraint extension"); goto out; } debug_f("constraint ext %s", ext_name); if (strcmp(ext_name, "sk-provider@openssh.com") == 0) { if (sk_providerp == NULL) { error_f("%s not valid here", ext_name); r = SSH_ERR_INVALID_FORMAT; goto out; } if (*sk_providerp != NULL) { error_f("%s already set", ext_name); r = SSH_ERR_INVALID_FORMAT; goto out; } if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) { error_fr(r, "parse %s", ext_name); goto out; } } else if (strcmp(ext_name, "restrict-destination-v00@openssh.com") == 0) { if (*dcsp != NULL) { error_f("%s already set", ext_name); goto out; } if ((r = sshbuf_froms(m, &b)) != 0) { error_fr(r, "parse %s outer", ext_name); goto out; } while (sshbuf_len(b) != 0) { if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) { error_f("too many %s constraints", ext_name); goto out; } *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1, sizeof(**dcsp)); if ((r = parse_dest_constraint(b, *dcsp + (*ndcsp)++)) != 0) goto out; /* error already logged */ } } else if (strcmp(ext_name, "associated-certs-v00@openssh.com") == 0) { if (certs == NULL || ncerts == NULL || cert_onlyp == NULL) { error_f("%s not valid here", ext_name); r = SSH_ERR_INVALID_FORMAT; goto out; } if (*certs != NULL) { error_f("%s already set", ext_name); goto out; } if ((r = sshbuf_get_u8(m, &v)) != 0 || (r = sshbuf_froms(m, &b)) != 0) { error_fr(r, "parse %s", ext_name); goto out; } *cert_onlyp = v != 0; while (sshbuf_len(b) != 0) { if (*ncerts >= AGENT_MAX_EXT_CERTS) { error_f("too many %s constraints", ext_name); goto out; } *certs = xrecallocarray(*certs, *ncerts, *ncerts + 1, sizeof(**certs)); if ((r = sshkey_froms(b, &k)) != 0) { error_fr(r, "parse key"); goto out; } (*certs)[(*ncerts)++] = k; } } else { error_f("unsupported constraint \"%s\"", ext_name); r = SSH_ERR_FEATURE_UNSUPPORTED; goto out; } /* success */ r = 0; out: free(ext_name); sshbuf_free(b); return r; } static int parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp, u_int *secondsp, int *confirmp, char **sk_providerp, struct dest_constraint **dcsp, size_t *ndcsp, int *cert_onlyp, size_t *ncerts, struct sshkey ***certs) { u_char ctype; int r; u_int seconds, maxsign = 0; while (sshbuf_len(m)) { if ((r = sshbuf_get_u8(m, &ctype)) != 0) { error_fr(r, "parse constraint type"); goto out; } switch (ctype) { case SSH_AGENT_CONSTRAIN_LIFETIME: if (*deathp != 0) { error_f("lifetime already set"); r = SSH_ERR_INVALID_FORMAT; goto out; } if ((r = sshbuf_get_u32(m, &seconds)) != 0) { error_fr(r, "parse lifetime constraint"); goto out; } *deathp = monotime() + seconds; *secondsp = seconds; break; case SSH_AGENT_CONSTRAIN_CONFIRM: if (*confirmp != 0) { error_f("confirm already set"); r = SSH_ERR_INVALID_FORMAT; goto out; } *confirmp = 1; break; case SSH_AGENT_CONSTRAIN_MAXSIGN: if (k == NULL) { error_f("maxsign not valid here"); r = SSH_ERR_INVALID_FORMAT; goto out; } if (maxsign != 0) { error_f("maxsign already set"); r = SSH_ERR_INVALID_FORMAT; goto out; } if ((r = sshbuf_get_u32(m, &maxsign)) != 0) { error_fr(r, "parse maxsign constraint"); goto out; } if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) { error_fr(r, "enable maxsign"); goto out; } break; case SSH_AGENT_CONSTRAIN_EXTENSION: if ((r = parse_key_constraint_extension(m, sk_providerp, dcsp, ndcsp, cert_onlyp, certs, ncerts)) != 0) goto out; /* error already logged */ break; default: error_f("Unknown constraint %d", ctype); r = SSH_ERR_FEATURE_UNSUPPORTED; goto out; } } /* success */ r = 0; out: return r; } static void process_add_identity(SocketEntry *e) { Identity *id; int success = 0, confirm = 0; char *fp, *comment = NULL, *sk_provider = NULL; char canonical_provider[PATH_MAX]; time_t death = 0; u_int seconds = 0; struct dest_constraint *dest_constraints = NULL; size_t ndest_constraints = 0; struct sshkey *k = NULL; int r = SSH_ERR_INTERNAL_ERROR; debug2_f("entering"); 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 out; } if (parse_key_constraints(e->request, k, &death, &seconds, &confirm, &sk_provider, &dest_constraints, &ndest_constraints, NULL, NULL, NULL) != 0) { error_f("failed to parse constraints"); sshbuf_reset(e->request); goto out; } dump_dest_constraints(__func__, dest_constraints, ndest_constraints); if (sk_provider != NULL) { if (!sshkey_is_sk(k)) { error("Cannot add provider: %s is not an " "authenticator-hosted key", sshkey_type(k)); goto out; } if (strcasecmp(sk_provider, "internal") == 0) { debug_f("internal provider"); } else { if (socket_is_remote(e) && !remote_add_provider) { verbose("failed add of SK provider \"%.100s\": " "remote addition of providers is disabled", sk_provider); goto out; } if (realpath(sk_provider, canonical_provider) == NULL) { verbose("failed provider \"%.100s\": " "realpath: %s", sk_provider, strerror(errno)); goto out; } 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); goto out; } } } if ((r = sshkey_shield_private(k)) != 0) { error_fr(r, "shield private"); goto out; } 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 { /* identity not visible, do not update */ if (identity_permitted(id, e, NULL, NULL, NULL) != 0) goto out; /* error already logged */ /* key state might have been updated */ sshkey_free(id->key); free(id->comment); free(id->sk_provider); free_dest_constraints(id->dest_constraints, id->ndest_constraints); } /* success */ id->key = k; id->comment = comment; id->death = death; id->confirm = confirm; id->sk_provider = sk_provider; id->dest_constraints = dest_constraints; id->ndest_constraints = ndest_constraints; 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) (destination constraints: %zu)", sshkey_ssh_name(k), fp, comment, seconds, confirm, sk_provider == NULL ? "none" : sk_provider, ndest_constraints); free(fp); /* transferred */ k = NULL; comment = NULL; sk_provider = NULL; dest_constraints = NULL; ndest_constraints = 0; success = 1; out: free(sk_provider); free(comment); sshkey_free(k); free_dest_constraints(dest_constraints, ndest_constraints); 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; debug2_f("entering"); /* * 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 /* Add an identity to idlist; takes ownership of 'key' and 'comment' */ static void add_p11_identity(struct sshkey *key, char *comment, const char *provider, time_t death, u_int confirm, struct dest_constraint *dest_constraints, size_t ndest_constraints) { Identity *id; if (lookup_identity(key) != NULL) { sshkey_free(key); free(comment); return; } id = xcalloc(1, sizeof(Identity)); id->key = key; id->comment = comment; id->provider = xstrdup(provider); id->death = death; id->confirm = confirm; id->dest_constraints = dup_dest_constraints(dest_constraints, ndest_constraints); id->ndest_constraints = ndest_constraints; TAILQ_INSERT_TAIL(&idtab->idlist, id, next); idtab->nentries++; } 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 = 0; time_t death = 0; struct sshkey **keys = NULL, *k; struct dest_constraint *dest_constraints = NULL; size_t j, ndest_constraints = 0, ncerts = 0; struct sshkey **certs = NULL; int cert_only = 0; debug2_f("entering"); 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; } if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm, NULL, &dest_constraints, &ndest_constraints, &cert_only, &ncerts, &certs) != 0) { error_f("failed to parse constraints"); goto send; } dump_dest_constraints(__func__, dest_constraints, ndest_constraints); if (socket_is_remote(e) && !remote_add_provider) { verbose("failed PKCS#11 add of \"%.100s\": remote addition of " "providers is disabled", provider); 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++) { if (comments[i] == NULL || comments[i][0] == '\0') { free(comments[i]); comments[i] = xstrdup(canonical_provider); } for (j = 0; j < ncerts; j++) { if (!sshkey_is_cert(certs[j])) continue; if (!sshkey_equal_public(keys[i], certs[j])) continue; if (pkcs11_make_cert(keys[i], certs[j], &k) != 0) continue; add_p11_identity(k, xstrdup(comments[i]), canonical_provider, death, confirm, dest_constraints, ndest_constraints); success = 1; } if (!cert_only && lookup_identity(keys[i]) == NULL) { add_p11_identity(keys[i], comments[i], canonical_provider, death, confirm, dest_constraints, ndest_constraints); keys[i] = NULL; /* transferred */ comments[i] = NULL; /* transferred */ success = 1; } /* XXX update constraints for existing keys */ sshkey_free(keys[i]); free(comments[i]); } send: free(pin); free(provider); free(keys); free(comments); free_dest_constraints(dest_constraints, ndest_constraints); for (j = 0; j < ncerts; j++) sshkey_free(certs[j]); free(certs); 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; debug2_f("entering"); 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 */ static int process_ext_session_bind(SocketEntry *e) { int r, sid_match, key_match; struct sshkey *key = NULL; struct sshbuf *sid = NULL, *sig = NULL; char *fp = NULL; size_t i; u_char fwd = 0; debug2_f("entering"); e->session_bind_attempted = 1; if ((r = sshkey_froms(e->request, &key)) != 0 || (r = sshbuf_froms(e->request, &sid)) != 0 || (r = sshbuf_froms(e->request, &sig)) != 0 || (r = sshbuf_get_u8(e->request, &fwd)) != 0) { error_fr(r, "parse"); goto out; } if (sshbuf_len(sid) > AGENT_MAX_SID_LEN) { error_f("session ID too long"); goto out; } if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) fatal_f("fingerprint failed"); /* check signature with hostkey on session ID */ if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig), sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) { error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp); goto out; } /* check whether sid/key already recorded */ for (i = 0; i < e->nsession_ids; i++) { if (!e->session_ids[i].forwarded) { error_f("attempt to bind session ID to socket " "previously bound for authentication attempt"); r = -1; goto out; } sid_match = buf_equal(sid, e->session_ids[i].sid) == 0; key_match = sshkey_equal(key, e->session_ids[i].key); if (sid_match && key_match) { debug_f("session ID already recorded for %s %s", sshkey_type(key), fp); r = 0; goto out; } else if (sid_match) { error_f("session ID recorded against different key " "for %s %s", sshkey_type(key), fp); r = -1; goto out; } /* * new sid with previously-seen key can happen, e.g. multiple * connections to the same host. */ } /* record new key/sid */ if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) { error_f("too many session IDs recorded"); goto out; } e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids, e->nsession_ids + 1, sizeof(*e->session_ids)); i = e->nsession_ids++; debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i, AGENT_MAX_SESSION_IDS); e->session_ids[i].key = key; e->session_ids[i].forwarded = fwd != 0; key = NULL; /* transferred */ /* can't transfer sid; it's refcounted and scoped to request's life */ if ((e->session_ids[i].sid = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0) fatal_fr(r, "sshbuf_putb session ID"); /* success */ r = 0; out: free(fp); sshkey_free(key); sshbuf_free(sid); sshbuf_free(sig); return r == 0 ? 1 : 0; } static void process_extension(SocketEntry *e) { int r, success = 0; char *name; debug2_f("entering"); if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) { error_fr(r, "parse"); goto send; } if (strcmp(name, "session-bind@openssh.com") == 0) success = process_ext_session_bind(e); else debug_f("unsupported extension \"%s\"", name); free(name); send: send_status(e, success); } /* * 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 */ case SSH_AGENTC_EXTENSION: process_extension(e); break; 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; debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" : (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN")); 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 = xrecallocarray(sockets, old_alloc, 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|POLLHUP|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, struct timespec *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) ptimeout_deadline_sec(timeoutp, deadline); 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(); #ifdef ENABLE_PKCS11 pkcs11_terminate(); #endif _exit(i); } static void cleanup_handler(int sig) { signalled_exit = sig; } static void keydrop_handler(int sig) { signalled_keydrop = sig; } 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" " [-O option] [-P allowed_providers] [-t life]\n" " ssh-agent [-a bind_address] [-E fingerprint_hash] [-O option]\n" " [-P allowed_providers] [-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; 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; struct timespec timeout; struct pollfd *pfd = NULL; size_t npfd = 0; u_int maxfds; sigset_t nsigset, osigset; /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ sanitise_stdfd(); /* drop */ (void)setegid(getgid()); (void)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 if (strcmp(optarg, "allow-remote-pkcs11") == 0) remote_add_provider = 1; 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"); /* 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); ssh_signal(SIGUSR1, keydrop_handler); sigemptyset(&nsigset); sigaddset(&nsigset, SIGINT); sigaddset(&nsigset, SIGHUP); sigaddset(&nsigset, SIGTERM); sigaddset(&nsigset, SIGUSR1); if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1) fatal("%s: pledge: %s", __progname, strerror(errno)); while (1) { sigprocmask(SIG_BLOCK, &nsigset, &osigset); if (signalled_exit != 0) { logit("exiting on signal %d", (int)signalled_exit); cleanup_exit(2); } if (signalled_keydrop) { logit("signal %d received; removing all keys", signalled_keydrop); remove_all_identities(); signalled_keydrop = 0; } ptimeout_init(&timeout); prepare_poll(&pfd, &npfd, &timeout, maxfds); result = ppoll(pfd, npfd, ptimeout_get_tsp(&timeout), &osigset); sigprocmask(SIG_SETMASK, &osigset, NULL); 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 */ }