diff options
Diffstat (limited to 'auth2-pubkey.c')
| -rw-r--r-- | auth2-pubkey.c | 815 |
1 files changed, 815 insertions, 0 deletions
diff --git a/auth2-pubkey.c b/auth2-pubkey.c new file mode 100644 index 0000000..5d59feb --- /dev/null +++ b/auth2-pubkey.c @@ -0,0 +1,815 @@ +/* $OpenBSD: auth2-pubkey.c,v 1.117 2022/09/17 10:34:29 djm Exp $ */ +/* + * Copyright (c) 2000 Markus Friedl. All rights reserved. + * Copyright (c) 2010 Damien Miller. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "includes.h" + +#include <sys/types.h> + +#include <stdlib.h> +#include <errno.h> +#ifdef HAVE_PATHS_H +# include <paths.h> +#endif +#include <pwd.h> +#include <signal.h> +#include <stdio.h> +#include <stdarg.h> +#include <string.h> +#include <time.h> +#include <unistd.h> +#include <limits.h> + +#include "xmalloc.h" +#include "ssh.h" +#include "ssh2.h" +#include "packet.h" +#include "kex.h" +#include "sshbuf.h" +#include "log.h" +#include "misc.h" +#include "servconf.h" +#include "compat.h" +#include "sshkey.h" +#include "hostfile.h" +#include "auth.h" +#include "pathnames.h" +#include "uidswap.h" +#include "auth-options.h" +#include "canohost.h" +#ifdef GSSAPI +#include "ssh-gss.h" +#endif +#include "monitor_wrap.h" +#include "authfile.h" +#include "match.h" +#include "ssherr.h" +#include "channels.h" /* XXX for session.h */ +#include "session.h" /* XXX for child_set_env(); refactor? */ +#include "sk-api.h" + +/* import */ +extern ServerOptions options; + +static char * +format_key(const struct sshkey *key) +{ + char *ret, *fp = sshkey_fingerprint(key, + options.fingerprint_hash, SSH_FP_DEFAULT); + + xasprintf(&ret, "%s %s", sshkey_type(key), fp); + free(fp); + return ret; +} + +static int +userauth_pubkey(struct ssh *ssh, const char *method) +{ + Authctxt *authctxt = ssh->authctxt; + struct passwd *pw = authctxt->pw; + struct sshbuf *b = NULL; + struct sshkey *key = NULL, *hostkey = NULL; + char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL; + u_char *pkblob = NULL, *sig = NULL, have_sig; + size_t blen, slen; + int hostbound, r, pktype; + int req_presence = 0, req_verify = 0, authenticated = 0; + struct sshauthopt *authopts = NULL; + struct sshkey_sig_details *sig_details = NULL; + + hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0; + + if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 || + (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 || + (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0) + fatal_fr(r, "parse %s packet", method); + + /* hostbound auth includes the hostkey offered at initial KEX */ + if (hostbound) { + if ((r = sshpkt_getb_froms(ssh, &b)) != 0 || + (r = sshkey_fromb(b, &hostkey)) != 0) + fatal_fr(r, "parse %s hostkey", method); + if (ssh->kex->initial_hostkey == NULL) + fatal_f("internal error: initial hostkey not recorded"); + if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey)) + fatal_f("%s packet contained wrong host key", method); + sshbuf_free(b); + b = NULL; + } + + if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) { + char *keystring; + struct sshbuf *pkbuf; + + if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL) + fatal_f("sshbuf_from failed"); + if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL) + fatal_f("sshbuf_dtob64 failed"); + debug2_f("%s user %s %s public key %s %s", + authctxt->valid ? "valid" : "invalid", authctxt->user, + have_sig ? "attempting" : "querying", pkalg, keystring); + sshbuf_free(pkbuf); + free(keystring); + } + + pktype = sshkey_type_from_name(pkalg); + if (pktype == KEY_UNSPEC) { + /* this is perfectly legal */ + verbose_f("unsupported public key algorithm: %s", pkalg); + goto done; + } + if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { + error_fr(r, "parse key"); + goto done; + } + if (key == NULL) { + error_f("cannot decode key: %s", pkalg); + goto done; + } + if (key->type != pktype) { + error_f("type mismatch for decoded key " + "(received %d, expected %d)", key->type, pktype); + goto done; + } + if (sshkey_type_plain(key->type) == KEY_RSA && + (ssh->compat & SSH_BUG_RSASIGMD5) != 0) { + logit("Refusing RSA key because client uses unsafe " + "signature scheme"); + goto done; + } + if (auth2_key_already_used(authctxt, key)) { + logit("refusing previously-used %s key", sshkey_type(key)); + goto done; + } + if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) { + logit_f("signature algorithm %s not in " + "PubkeyAcceptedAlgorithms", pkalg); + goto done; + } + if ((r = sshkey_check_cert_sigtype(key, + options.ca_sign_algorithms)) != 0) { + logit_fr(r, "certificate signature algorithm %s", + (key->cert == NULL || key->cert->signature_type == NULL) ? + "(null)" : key->cert->signature_type); + goto done; + } + if ((r = sshkey_check_rsa_length(key, + options.required_rsa_size)) != 0) { + logit_r(r, "refusing %s key", sshkey_type(key)); + goto done; + } + key_s = format_key(key); + if (sshkey_is_cert(key)) + ca_s = format_key(key->cert->signature_key); + + if (have_sig) { + debug3_f("%s have %s signature for %s%s%s", + method, pkalg, key_s, + ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); + if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + fatal_fr(r, "parse signature packet"); + if ((b = sshbuf_new()) == NULL) + fatal_f("sshbuf_new failed"); + if (ssh->compat & SSH_OLD_SESSIONID) { + if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0) + fatal_fr(r, "put old session id"); + } else { + if ((r = sshbuf_put_stringb(b, + ssh->kex->session_id)) != 0) + fatal_fr(r, "put session id"); + } + if (!authctxt->valid || authctxt->user == NULL) { + debug2_f("disabled because of invalid user"); + goto done; + } + /* reconstruct packet */ + xasprintf(&userstyle, "%s%s%s", authctxt->user, + authctxt->style ? ":" : "", + authctxt->style ? authctxt->style : ""); + if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || + (r = sshbuf_put_cstring(b, userstyle)) != 0 || + (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || + (r = sshbuf_put_cstring(b, method)) != 0 || + (r = sshbuf_put_u8(b, have_sig)) != 0 || + (r = sshbuf_put_cstring(b, pkalg)) != 0 || + (r = sshbuf_put_string(b, pkblob, blen)) != 0) + fatal_fr(r, "reconstruct %s packet", method); + if (hostbound && + (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0) + fatal_fr(r, "reconstruct %s packet", method); +#ifdef DEBUG_PK + sshbuf_dump(b, stderr); +#endif + /* test for correct signature */ + authenticated = 0; + if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) && + PRIVSEP(sshkey_verify(key, sig, slen, + sshbuf_ptr(b), sshbuf_len(b), + (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL, + ssh->compat, &sig_details)) == 0) { + authenticated = 1; + } + if (authenticated == 1 && sig_details != NULL) { + auth2_record_info(authctxt, "signature count = %u", + sig_details->sk_counter); + debug_f("sk_counter = %u, sk_flags = 0x%02x", + sig_details->sk_counter, sig_details->sk_flags); + req_presence = (options.pubkey_auth_options & + PUBKEYAUTH_TOUCH_REQUIRED) || + !authopts->no_require_user_presence; + if (req_presence && (sig_details->sk_flags & + SSH_SK_USER_PRESENCE_REQD) == 0) { + error("public key %s signature for %s%s from " + "%.128s port %d rejected: user presence " + "(authenticator touch) requirement " + "not met ", key_s, + authctxt->valid ? "" : "invalid user ", + authctxt->user, ssh_remote_ipaddr(ssh), + ssh_remote_port(ssh)); + authenticated = 0; + goto done; + } + req_verify = (options.pubkey_auth_options & + PUBKEYAUTH_VERIFY_REQUIRED) || + authopts->require_verify; + if (req_verify && (sig_details->sk_flags & + SSH_SK_USER_VERIFICATION_REQD) == 0) { + error("public key %s signature for %s%s from " + "%.128s port %d rejected: user " + "verification requirement not met ", key_s, + authctxt->valid ? "" : "invalid user ", + authctxt->user, ssh_remote_ipaddr(ssh), + ssh_remote_port(ssh)); + authenticated = 0; + goto done; + } + } + auth2_record_key(authctxt, authenticated, key); + } else { + debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s, + ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); + + if ((r = sshpkt_get_end(ssh)) != 0) + fatal_fr(r, "parse packet"); + + if (!authctxt->valid || authctxt->user == NULL) { + debug2_f("disabled because of invalid user"); + goto done; + } + /* XXX fake reply and always send PK_OK ? */ + /* + * XXX this allows testing whether a user is allowed + * to login: if you happen to have a valid pubkey this + * message is sent. the message is NEVER sent at all + * if a user is not allowed to login. is this an + * issue? -markus + */ + if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) { + if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) + != 0 || + (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || + (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || + (r = sshpkt_send(ssh)) != 0 || + (r = ssh_packet_write_wait(ssh)) != 0) + fatal_fr(r, "send packet"); + authctxt->postponed = 1; + } + } +done: + if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) { + debug_f("key options inconsistent with existing"); + authenticated = 0; + } + debug2_f("authenticated %d pkalg %s", authenticated, pkalg); + + sshbuf_free(b); + sshauthopt_free(authopts); + sshkey_free(key); + sshkey_free(hostkey); + free(userstyle); + free(pkalg); + free(pkblob); + free(key_s); + free(ca_s); + free(sig); + sshkey_sig_details_free(sig_details); + return authenticated; +} + +static int +match_principals_file(struct passwd *pw, char *file, + struct sshkey_cert *cert, struct sshauthopt **authoptsp) +{ + FILE *f; + int success; + + if (authoptsp != NULL) + *authoptsp = NULL; + + temporarily_use_uid(pw); + debug("trying authorized principals file %s", file); + if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { + restore_uid(); + return 0; + } + success = auth_process_principals(f, file, cert, authoptsp); + fclose(f); + restore_uid(); + return success; +} + +/* + * Checks whether principal is allowed in output of command. + * returns 1 if the principal is allowed or 0 otherwise. + */ +static int +match_principals_command(struct passwd *user_pw, + const struct sshkey *key, struct sshauthopt **authoptsp) +{ + struct passwd *runas_pw = NULL; + const struct sshkey_cert *cert = key->cert; + FILE *f = NULL; + int r, ok, found_principal = 0; + int i, ac = 0, uid_swapped = 0; + pid_t pid; + char *tmp, *username = NULL, *command = NULL, **av = NULL; + char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; + char serial_s[32], uidstr[32]; + void (*osigchld)(int); + + if (authoptsp != NULL) + *authoptsp = NULL; + if (options.authorized_principals_command == NULL) + return 0; + if (options.authorized_principals_command_user == NULL) { + error("No user for AuthorizedPrincipalsCommand specified, " + "skipping"); + return 0; + } + + /* + * NB. all returns later this function should go via "out" to + * ensure the original SIGCHLD handler is restored properly. + */ + osigchld = ssh_signal(SIGCHLD, SIG_DFL); + + /* Prepare and verify the user for the command */ + username = percent_expand(options.authorized_principals_command_user, + "u", user_pw->pw_name, (char *)NULL); + runas_pw = getpwnam(username); + if (runas_pw == NULL) { + error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", + username, strerror(errno)); + goto out; + } + + /* Turn the command into an argument vector */ + if (argv_split(options.authorized_principals_command, + &ac, &av, 0) != 0) { + error("AuthorizedPrincipalsCommand \"%s\" contains " + "invalid quotes", options.authorized_principals_command); + goto out; + } + if (ac == 0) { + error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", + options.authorized_principals_command); + goto out; + } + if ((ca_fp = sshkey_fingerprint(cert->signature_key, + options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { + error_f("sshkey_fingerprint failed"); + goto out; + } + if ((key_fp = sshkey_fingerprint(key, + options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { + error_f("sshkey_fingerprint failed"); + goto out; + } + if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { + error_fr(r, "sshkey_to_base64 failed"); + goto out; + } + if ((r = sshkey_to_base64(key, &keytext)) != 0) { + error_fr(r, "sshkey_to_base64 failed"); + goto out; + } + snprintf(serial_s, sizeof(serial_s), "%llu", + (unsigned long long)cert->serial); + snprintf(uidstr, sizeof(uidstr), "%llu", + (unsigned long long)user_pw->pw_uid); + for (i = 1; i < ac; i++) { + tmp = percent_expand(av[i], + "U", uidstr, + "u", user_pw->pw_name, + "h", user_pw->pw_dir, + "t", sshkey_ssh_name(key), + "T", sshkey_ssh_name(cert->signature_key), + "f", key_fp, + "F", ca_fp, + "k", keytext, + "K", catext, + "i", cert->key_id, + "s", serial_s, + (char *)NULL); + if (tmp == NULL) + fatal_f("percent_expand failed"); + free(av[i]); + av[i] = tmp; + } + /* Prepare a printable command for logs, etc. */ + command = argv_assemble(ac, av); + + if ((pid = subprocess("AuthorizedPrincipalsCommand", command, + ac, av, &f, + SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, + runas_pw, temporarily_use_uid, restore_uid)) == 0) + goto out; + + uid_swapped = 1; + temporarily_use_uid(runas_pw); + + ok = auth_process_principals(f, "(command)", cert, authoptsp); + + fclose(f); + f = NULL; + + if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) + goto out; + + /* Read completed successfully */ + found_principal = ok; + out: + if (f != NULL) + fclose(f); + ssh_signal(SIGCHLD, osigchld); + for (i = 0; i < ac; i++) + free(av[i]); + free(av); + if (uid_swapped) + restore_uid(); + free(command); + free(username); + free(ca_fp); + free(key_fp); + free(catext); + free(keytext); + return found_principal; +} + +/* Authenticate a certificate key against TrustedUserCAKeys */ +static int +user_cert_trusted_ca(struct passwd *pw, struct sshkey *key, + const char *remote_ip, const char *remote_host, + struct sshauthopt **authoptsp) +{ + char *ca_fp, *principals_file = NULL; + const char *reason; + struct sshauthopt *principals_opts = NULL, *cert_opts = NULL; + struct sshauthopt *final_opts = NULL; + int r, ret = 0, found_principal = 0, use_authorized_principals; + + if (authoptsp != NULL) + *authoptsp = NULL; + + if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) + return 0; + + if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, + options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) + return 0; + + if ((r = sshkey_in_file(key->cert->signature_key, + options.trusted_user_ca_keys, 1, 0)) != 0) { + debug2_fr(r, "CA %s %s is not listed in %s", + sshkey_type(key->cert->signature_key), ca_fp, + options.trusted_user_ca_keys); + goto out; + } + /* + * If AuthorizedPrincipals is in use, then compare the certificate + * principals against the names in that file rather than matching + * against the username. + */ + if ((principals_file = authorized_principals_file(pw)) != NULL) { + if (match_principals_file(pw, principals_file, + key->cert, &principals_opts)) + found_principal = 1; + } + /* Try querying command if specified */ + if (!found_principal && match_principals_command(pw, key, + &principals_opts)) + found_principal = 1; + /* If principals file or command is specified, then require a match */ + use_authorized_principals = principals_file != NULL || + options.authorized_principals_command != NULL; + if (!found_principal && use_authorized_principals) { + reason = "Certificate does not contain an authorized principal"; + goto fail_reason; + } + if (use_authorized_principals && principals_opts == NULL) + fatal_f("internal error: missing principals_opts"); + if (sshkey_cert_check_authority_now(key, 0, 1, 0, + use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) + goto fail_reason; + + /* Check authority from options in key and from principals file/cmd */ + if ((cert_opts = sshauthopt_from_cert(key)) == NULL) { + reason = "Invalid certificate options"; + goto fail_reason; + } + if (auth_authorise_keyopts(pw, cert_opts, 0, + remote_ip, remote_host, "cert") != 0) { + reason = "Refused by certificate options"; + goto fail_reason; + } + if (principals_opts == NULL) { + final_opts = cert_opts; + cert_opts = NULL; + } else { + if (auth_authorise_keyopts(pw, principals_opts, 0, + remote_ip, remote_host, "principals") != 0) { + reason = "Refused by certificate principals options"; + goto fail_reason; + } + if ((final_opts = sshauthopt_merge(principals_opts, + cert_opts, &reason)) == NULL) { + fail_reason: + error("%s", reason); + auth_debug_add("%s", reason); + goto out; + } + } + + /* Success */ + verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " + "%s CA %s via %s", key->cert->key_id, + (unsigned long long)key->cert->serial, + sshkey_type(key->cert->signature_key), ca_fp, + options.trusted_user_ca_keys); + if (authoptsp != NULL) { + *authoptsp = final_opts; + final_opts = NULL; + } + ret = 1; + out: + sshauthopt_free(principals_opts); + sshauthopt_free(cert_opts); + sshauthopt_free(final_opts); + free(principals_file); + free(ca_fp); + return ret; +} + +/* + * Checks whether key is allowed in file. + * returns 1 if the key is allowed or 0 otherwise. + */ +static int +user_key_allowed2(struct passwd *pw, struct sshkey *key, + char *file, const char *remote_ip, const char *remote_host, + struct sshauthopt **authoptsp) +{ + FILE *f; + int found_key = 0; + + if (authoptsp != NULL) + *authoptsp = NULL; + + /* Temporarily use the user's uid. */ + temporarily_use_uid(pw); + + debug("trying public key file %s", file); + if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { + found_key = auth_check_authkeys_file(pw, f, file, + key, remote_ip, remote_host, authoptsp); + fclose(f); + } + + restore_uid(); + return found_key; +} + +/* + * Checks whether key is allowed in output of command. + * returns 1 if the key is allowed or 0 otherwise. + */ +static int +user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key, + const char *remote_ip, const char *remote_host, + struct sshauthopt **authoptsp) +{ + struct passwd *runas_pw = NULL; + FILE *f = NULL; + int r, ok, found_key = 0; + int i, uid_swapped = 0, ac = 0; + pid_t pid; + char *username = NULL, *key_fp = NULL, *keytext = NULL; + char uidstr[32], *tmp, *command = NULL, **av = NULL; + void (*osigchld)(int); + + if (authoptsp != NULL) + *authoptsp = NULL; + if (options.authorized_keys_command == NULL) + return 0; + if (options.authorized_keys_command_user == NULL) { + error("No user for AuthorizedKeysCommand specified, skipping"); + return 0; + } + + /* + * NB. all returns later this function should go via "out" to + * ensure the original SIGCHLD handler is restored properly. + */ + osigchld = ssh_signal(SIGCHLD, SIG_DFL); + + /* Prepare and verify the user for the command */ + username = percent_expand(options.authorized_keys_command_user, + "u", user_pw->pw_name, (char *)NULL); + runas_pw = getpwnam(username); + if (runas_pw == NULL) { + error("AuthorizedKeysCommandUser \"%s\" not found: %s", + username, strerror(errno)); + goto out; + } + + /* Prepare AuthorizedKeysCommand */ + if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, + SSH_FP_DEFAULT)) == NULL) { + error_f("sshkey_fingerprint failed"); + goto out; + } + if ((r = sshkey_to_base64(key, &keytext)) != 0) { + error_fr(r, "sshkey_to_base64 failed"); + goto out; + } + + /* Turn the command into an argument vector */ + if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) { + error("AuthorizedKeysCommand \"%s\" contains invalid quotes", + options.authorized_keys_command); + goto out; + } + if (ac == 0) { + error("AuthorizedKeysCommand \"%s\" yielded no arguments", + options.authorized_keys_command); + goto out; + } + snprintf(uidstr, sizeof(uidstr), "%llu", + (unsigned long long)user_pw->pw_uid); + for (i = 1; i < ac; i++) { + tmp = percent_expand(av[i], + "U", uidstr, + "u", user_pw->pw_name, + "h", user_pw->pw_dir, + "t", sshkey_ssh_name(key), + "f", key_fp, + "k", keytext, + (char *)NULL); + if (tmp == NULL) + fatal_f("percent_expand failed"); + free(av[i]); + av[i] = tmp; + } + /* Prepare a printable command for logs, etc. */ + command = argv_assemble(ac, av); + + /* + * If AuthorizedKeysCommand was run without arguments + * then fall back to the old behaviour of passing the + * target username as a single argument. + */ + if (ac == 1) { + av = xreallocarray(av, ac + 2, sizeof(*av)); + av[1] = xstrdup(user_pw->pw_name); + av[2] = NULL; + /* Fix up command too, since it is used in log messages */ + free(command); + xasprintf(&command, "%s %s", av[0], av[1]); + } + + if ((pid = subprocess("AuthorizedKeysCommand", command, + ac, av, &f, + SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, + runas_pw, temporarily_use_uid, restore_uid)) == 0) + goto out; + + uid_swapped = 1; + temporarily_use_uid(runas_pw); + + ok = auth_check_authkeys_file(user_pw, f, + options.authorized_keys_command, key, remote_ip, + remote_host, authoptsp); + + fclose(f); + f = NULL; + + if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) + goto out; + + /* Read completed successfully */ + found_key = ok; + out: + if (f != NULL) + fclose(f); + ssh_signal(SIGCHLD, osigchld); + for (i = 0; i < ac; i++) + free(av[i]); + free(av); + if (uid_swapped) + restore_uid(); + free(command); + free(username); + free(key_fp); + free(keytext); + return found_key; +} + +/* + * Check whether key authenticates and authorises the user. + */ +int +user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, + int auth_attempt, struct sshauthopt **authoptsp) +{ + u_int success = 0, i; + char *file; + struct sshauthopt *opts = NULL; + const char *remote_ip = ssh_remote_ipaddr(ssh); + const char *remote_host = auth_get_canonical_hostname(ssh, + options.use_dns); + + if (authoptsp != NULL) + *authoptsp = NULL; + + if (auth_key_is_revoked(key)) + return 0; + if (sshkey_is_cert(key) && + auth_key_is_revoked(key->cert->signature_key)) + return 0; + + for (i = 0; !success && i < options.num_authkeys_files; i++) { + if (strcasecmp(options.authorized_keys_files[i], "none") == 0) + continue; + file = expand_authorized_keys( + options.authorized_keys_files[i], pw); + success = user_key_allowed2(pw, key, file, + remote_ip, remote_host, &opts); + free(file); + if (!success) { + sshauthopt_free(opts); + opts = NULL; + } + } + if (success) + goto out; + + if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host, + &opts)) != 0) + goto out; + sshauthopt_free(opts); + opts = NULL; + + if ((success = user_key_command_allowed2(pw, key, remote_ip, + remote_host, &opts)) != 0) + goto out; + sshauthopt_free(opts); + opts = NULL; + + out: + if (success && authoptsp != NULL) { + *authoptsp = opts; + opts = NULL; + } + sshauthopt_free(opts); + return success; +} + +Authmethod method_pubkey = { + "publickey", + "publickey-hostbound-v00@openssh.com", + userauth_pubkey, + &options.pubkey_authentication +}; |