Edit
IABSD.fr/src/usr.bin/ssh/auth2-pubkey.c
djm
- usr.bin/ssh/auth2-pubkey.c
-
/* $OpenBSD: auth2-pubkey.c,v 1.110 2021/09/29 01:33:32 djm Exp $ */ /* * Copyright (c) 2000 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/stat.h> #include <stdlib.h> #include <errno.h> #include <fcntl.h> #include <paths.h> #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) { Authctxt *authctxt = ssh->authctxt; struct passwd *pw = authctxt->pw; struct sshbuf *b = NULL; struct sshkey *key = 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 r, pktype; int req_presence = 0, req_verify = 0, authenticated = 0; struct sshauthopt *authopts = NULL; struct sshkey_sig_details *sig_details = NULL; 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 packet"); 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("key type %s not in PubkeyAcceptedAlgorithms", sshkey_ssh_name(key)); 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; } key_s = format_key(key); if (sshkey_is_cert(key)) ca_s = format_key(key->cert->signature_key); if (have_sig) { debug3_f("have %s signature for %s%s%s", 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, "publickey")) != 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 packet"); #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("test pkalg %s pkblob %s%s%s", 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); 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_option(const char *principal_list, struct sshkey_cert *cert) { char *result; u_int i; /* XXX percent_expand() sequences for authorized_principals? */ for (i = 0; i < cert->nprincipals; i++) { if ((result = match_list(cert->principals[i], principal_list, NULL)) != NULL) { debug3("matched principal from key options \"%.100s\"", result); free(result); return 1; } } return 0; } /* * Process a single authorized_principals format line. Returns 0 and sets * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a * log preamble for file/line information. */ static int check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert, const char *loc, struct sshauthopt **authoptsp) { u_int i, found = 0; char *ep, *line_opts; const char *reason = NULL; struct sshauthopt *opts = NULL; if (authoptsp != NULL) *authoptsp = NULL; /* Trim trailing whitespace. */ ep = cp + strlen(cp) - 1; while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t')) *ep-- = '\0'; /* * If the line has internal whitespace then assume it has * key options. */ line_opts = NULL; if ((ep = strrchr(cp, ' ')) != NULL || (ep = strrchr(cp, '\t')) != NULL) { for (; *ep == ' ' || *ep == '\t'; ep++) ; line_opts = cp; cp = ep; } if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) { debug("%s: bad principals options: %s", loc, reason); auth_debug_add("%s: bad principals options: %s", loc, reason); return -1; } /* Check principals in cert against those on line */ for (i = 0; i < cert->nprincipals; i++) { if (strcmp(cp, cert->principals[i]) != 0) continue; debug3("%s: matched principal \"%.100s\"", loc, cert->principals[i]); found = 1; } if (found && authoptsp != NULL) { *authoptsp = opts; opts = NULL; } sshauthopt_free(opts); return found ? 0 : -1; } static int process_principals(struct ssh *ssh, FILE *f, const char *file, const struct sshkey_cert *cert, struct sshauthopt **authoptsp) { char loc[256], *line = NULL, *cp, *ep; size_t linesize = 0; u_long linenum = 0, nonblank = 0; u_int found_principal = 0; if (authoptsp != NULL) *authoptsp = NULL; while (getline(&line, &linesize, f) != -1) { linenum++; /* Always consume entire input */ if (found_principal) continue; /* Skip leading whitespace. */ for (cp = line; *cp == ' ' || *cp == '\t'; cp++) ; /* Skip blank and comment lines. */ if ((ep = strchr(cp, '#')) != NULL) *ep = '\0'; if (!*cp || *cp == '\n') continue; nonblank++; snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum); if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0) found_principal = 1; } debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum); free(line); return found_principal; } /* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */ static int match_principals_file(struct ssh *ssh, 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 = process_principals(ssh, 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 ssh *ssh, 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 = process_principals(ssh, 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; } /* * Check a single line of an authorized_keys-format file. Returns 0 if key * matches, -1 otherwise. Will return key/cert options via *authoptsp * on success. "loc" is used as file/line location in log messages. */ static int check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key, char *cp, const char *loc, struct sshauthopt **authoptsp) { int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type; struct sshkey *found = NULL; struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL; char *key_options = NULL, *fp = NULL; const char *reason = NULL; int ret = -1; if (authoptsp != NULL) *authoptsp = NULL; if ((found = sshkey_new(want_keytype)) == NULL) { debug3_f("keytype %d failed", want_keytype); goto out; } /* XXX djm: peek at key type in line and skip if unwanted */ if (sshkey_read(found, &cp) != 0) { /* no key? check for options */ debug2("%s: check options: '%s'", loc, cp); key_options = cp; if (sshkey_advance_past_options(&cp) != 0) { reason = "invalid key option string"; goto fail_reason; } skip_space(&cp); if (sshkey_read(found, &cp) != 0) { /* still no key? advance to next line*/ debug2("%s: advance: '%s'", loc, cp); goto out; } } /* Parse key options now; we need to know if this is a CA key */ if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) { debug("%s: bad key options: %s", loc, reason); auth_debug_add("%s: bad key options: %s", loc, reason); goto out; } /* Ignore keys that don't match or incorrectly marked as CAs */ if (sshkey_is_cert(key)) { /* Certificate; check signature key against CA */ if (!sshkey_equal(found, key->cert->signature_key) || !keyopts->cert_authority) goto out; } else { /* Plain key: check it against key found in file */ if (!sshkey_equal(found, key) || keyopts->cert_authority) goto out; } /* We have a candidate key, perform authorisation checks */ if ((fp = sshkey_fingerprint(found, options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) fatal_f("fingerprint failed"); debug("%s: matching %s found: %s %s", loc, sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp); if (auth_authorise_keyopts(ssh, pw, keyopts, sshkey_is_cert(key), loc) != 0) { reason = "Refused by key options"; goto fail_reason; } /* That's all we need for plain keys. */ if (!sshkey_is_cert(key)) { verbose("Accepted key %s %s found at %s", sshkey_type(found), fp, loc); finalopts = keyopts; keyopts = NULL; goto success; } /* * Additional authorisation for certificates. */ /* Parse and check options present in certificate */ if ((certopts = sshauthopt_from_cert(key)) == NULL) { reason = "Invalid certificate options"; goto fail_reason; } if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) { reason = "Refused by certificate options"; goto fail_reason; } if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL) goto fail_reason; /* * If the user has specified a list of principals as * a key option, then prefer that list to matching * their username in the certificate principals list. */ if (keyopts->cert_principals != NULL && !match_principals_option(keyopts->cert_principals, key->cert)) { reason = "Certificate does not contain an authorized principal"; goto fail_reason; } if (sshkey_cert_check_authority_now(key, 0, 0, 0, keyopts->cert_principals == NULL ? pw->pw_name : NULL, &reason) != 0) goto fail_reason; verbose("Accepted certificate ID \"%s\" (serial %llu) " "signed by CA %s %s found at %s", key->cert->key_id, (unsigned long long)key->cert->serial, sshkey_type(found), fp, loc); success: if (finalopts == NULL) fatal_f("internal error: missing options"); if (authoptsp != NULL) { *authoptsp = finalopts; finalopts = NULL; } /* success */ ret = 0; goto out; fail_reason: error("%s", reason); auth_debug_add("%s", reason); out: free(fp); sshauthopt_free(keyopts); sshauthopt_free(certopts); sshauthopt_free(finalopts); sshkey_free(found); return ret; } /* * Checks whether key is allowed in authorized_keys-format file, * returns 1 if the key is allowed or 0 otherwise. */ static int check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f, char *file, struct sshkey *key, struct sshauthopt **authoptsp) { char *cp, *line = NULL, loc[256]; size_t linesize = 0; int found_key = 0; u_long linenum = 0, nonblank = 0; if (authoptsp != NULL) *authoptsp = NULL; while (getline(&line, &linesize, f) != -1) { linenum++; /* Always consume entire file */ if (found_key) continue; /* Skip leading whitespace, empty and comment lines. */ cp = line; skip_space(&cp); if (!*cp || *cp == '\n' || *cp == '#') continue; nonblank++; snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum); if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0) found_key = 1; } free(line); debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum); return found_key; } /* Authenticate a certificate key against TrustedUserCAKeys */ static int user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 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(ssh, pw, principals_file, key->cert, &principals_opts)) found_principal = 1; } /* Try querying command if specified */ if (!found_principal && match_principals_command(ssh, 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(ssh, pw, cert_opts, 0, "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(ssh, pw, principals_opts, 0, "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 ssh *ssh, struct passwd *pw, struct sshkey *key, char *file, 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 = check_authkeys_file(ssh, pw, f, file, key, 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 ssh *ssh, struct passwd *user_pw, struct sshkey *key, 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 = check_authkeys_file(ssh, user_pw, f, options.authorized_keys_command, key, 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; 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(ssh, pw, key, file, &opts); free(file); if (!success) { sshauthopt_free(opts); opts = NULL; } } if (success) goto out; if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0) goto out; sshauthopt_free(opts); opts = NULL; if ((success = user_key_command_allowed2(ssh, pw, key, &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", userauth_pubkey, &options.pubkey_authentication };