From 25505898530a333011f4fd5cbc841ad6b26c089c Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 16:40:04 +0200 Subject: Adding upstream version 1:9.2p1. Signed-off-by: Daniel Baumann --- auth2-pubkeyfile.c | 501 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 501 insertions(+) create mode 100644 auth2-pubkeyfile.c (limited to 'auth2-pubkeyfile.c') diff --git a/auth2-pubkeyfile.c b/auth2-pubkeyfile.c new file mode 100644 index 0000000..0cfacac --- /dev/null +++ b/auth2-pubkeyfile.c @@ -0,0 +1,501 @@ +/* $OpenBSD: auth2-pubkeyfile.c,v 1.3 2022/07/01 03:52:57 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 +#include + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "ssh.h" +#include "log.h" +#include "misc.h" +#include "compat.h" +#include "sshkey.h" +#include "digest.h" +#include "hostfile.h" +#include "auth.h" +#include "auth-options.h" +#include "authfile.h" +#include "match.h" +#include "ssherr.h" + +int +auth_authorise_keyopts(struct passwd *pw, struct sshauthopt *opts, + int allow_cert_authority, const char *remote_ip, const char *remote_host, + const char *loc) +{ + time_t now = time(NULL); + char buf[64]; + + /* + * Check keys/principals file expiry time. + * NB. validity interval in certificate is handled elsewhere. + */ + if (opts->valid_before && now > 0 && + opts->valid_before < (uint64_t)now) { + format_absolute_time(opts->valid_before, buf, sizeof(buf)); + debug("%s: entry expired at %s", loc, buf); + auth_debug_add("%s: entry expired at %s", loc, buf); + return -1; + } + /* Consistency checks */ + if (opts->cert_principals != NULL && !opts->cert_authority) { + debug("%s: principals on non-CA key", loc); + auth_debug_add("%s: principals on non-CA key", loc); + /* deny access */ + return -1; + } + /* cert-authority flag isn't valid in authorized_principals files */ + if (!allow_cert_authority && opts->cert_authority) { + debug("%s: cert-authority flag invalid here", loc); + auth_debug_add("%s: cert-authority flag invalid here", loc); + /* deny access */ + return -1; + } + + /* Perform from= checks */ + if (opts->required_from_host_keys != NULL) { + switch (match_host_and_ip(remote_host, remote_ip, + opts->required_from_host_keys )) { + case 1: + /* Host name matches. */ + break; + case -1: + default: + debug("%s: invalid from criteria", loc); + auth_debug_add("%s: invalid from criteria", loc); + /* FALLTHROUGH */ + case 0: + logit("%s: Authentication tried for %.100s with " + "correct key but not from a permitted " + "host (host=%.200s, ip=%.200s, required=%.200s).", + loc, pw->pw_name, remote_host, remote_ip, + opts->required_from_host_keys); + auth_debug_add("%s: Your host '%.200s' is not " + "permitted to use this key for login.", + loc, remote_host); + /* deny access */ + return -1; + } + } + /* Check source-address restriction from certificate */ + if (opts->required_from_host_cert != NULL) { + switch (addr_match_cidr_list(remote_ip, + opts->required_from_host_cert)) { + case 1: + /* accepted */ + break; + case -1: + default: + /* invalid */ + error("%s: Certificate source-address invalid", loc); + /* FALLTHROUGH */ + case 0: + logit("%s: Authentication tried for %.100s with valid " + "certificate but not from a permitted source " + "address (%.200s).", loc, pw->pw_name, remote_ip); + auth_debug_add("%s: Your address '%.200s' is not " + "permitted to use this certificate for login.", + loc, remote_ip); + return -1; + } + } + /* + * + * XXX this is spammy. We should report remotely only for keys + * that are successful in actual auth attempts, and not PK_OK + * tests. + */ + auth_log_authopts(loc, opts, 1); + + return 0; +} + +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. + */ +int +auth_check_principals_line(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; +} + +int +auth_process_principals(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 (auth_check_principals_line(cp, cert, loc, authoptsp) == 0) + found_principal = 1; + } + debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum); + free(line); + 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. + */ +int +auth_check_authkey_line(struct passwd *pw, struct sshkey *key, + char *cp, const char *remote_ip, const char *remote_host, 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, + SSH_FP_HASH_DEFAULT, 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(pw, keyopts, + sshkey_is_cert(key), remote_ip, remote_host, 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(pw, certopts, 0, + remote_ip, remote_host, 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. + */ +int +auth_check_authkeys_file(struct passwd *pw, FILE *f, char *file, + struct sshkey *key, const char *remote_ip, + const char *remote_host, 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 (auth_check_authkey_line(pw, key, cp, + remote_ip, remote_host, loc, authoptsp) == 0) + found_key = 1; + } + free(line); + debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum); + return found_key; +} + +static FILE * +auth_openfile(const char *file, struct passwd *pw, int strict_modes, + int log_missing, char *file_type) +{ + char line[1024]; + struct stat st; + int fd; + FILE *f; + + if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { + if (errno != ENOENT) { + logit("Could not open user '%s' %s '%s': %s", + pw->pw_name, file_type, file, strerror(errno)); + } else if (log_missing) { + debug("Could not open user '%s' %s '%s': %s", + pw->pw_name, file_type, file, strerror(errno)); + } + return NULL; + } + + if (fstat(fd, &st) == -1) { + close(fd); + return NULL; + } + if (!S_ISREG(st.st_mode)) { + logit("User '%s' %s '%s' is not a regular file", + pw->pw_name, file_type, file); + close(fd); + return NULL; + } + unset_nonblock(fd); + if ((f = fdopen(fd, "r")) == NULL) { + close(fd); + return NULL; + } + if (strict_modes && + safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { + fclose(f); + logit("Authentication refused: %s", line); + auth_debug_add("Ignored %s: %s", file_type, line); + return NULL; + } + + return f; +} + + +FILE * +auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) +{ + return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); +} + +FILE * +auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) +{ + return auth_openfile(file, pw, strict_modes, 0, + "authorized principals"); +} + -- cgit v1.2.3