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Diffstat (limited to 'auth.c')
| -rw-r--r-- | auth.c | 1191 |
1 files changed, 1191 insertions, 0 deletions
@@ -0,0 +1,1191 @@ +/* $OpenBSD: auth.c,v 1.147 2020/08/27 01:07:09 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 "includes.h" + +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/socket.h> +#include <sys/wait.h> + +#include <netinet/in.h> + +#include <stdlib.h> +#include <errno.h> +#include <fcntl.h> +#ifdef HAVE_PATHS_H +# include <paths.h> +#endif +#include <pwd.h> +#ifdef HAVE_LOGIN_H +#include <login.h> +#endif +#ifdef USE_SHADOW +#include <shadow.h> +#endif +#include <stdarg.h> +#include <stdio.h> +#include <string.h> +#include <unistd.h> +#include <limits.h> +#include <netdb.h> +#include <time.h> + +#include "xmalloc.h" +#include "match.h" +#include "groupaccess.h" +#include "log.h" +#include "sshbuf.h" +#include "misc.h" +#include "servconf.h" +#include "sshkey.h" +#include "hostfile.h" +#include "auth.h" +#include "auth-options.h" +#include "canohost.h" +#include "uidswap.h" +#include "packet.h" +#include "loginrec.h" +#ifdef GSSAPI +#include "ssh-gss.h" +#endif +#include "authfile.h" +#include "monitor_wrap.h" +#include "ssherr.h" +#include "compat.h" +#include "channels.h" + +/* import */ +extern ServerOptions options; +extern struct include_list includes; +extern int use_privsep; +extern struct sshbuf *loginmsg; +extern struct passwd *privsep_pw; +extern struct sshauthopt *auth_opts; + +/* Debugging messages */ +static struct sshbuf *auth_debug; + +/* + * Check if the user is allowed to log in via ssh. If user is listed + * in DenyUsers or one of user's groups is listed in DenyGroups, false + * will be returned. If AllowUsers isn't empty and user isn't listed + * there, or if AllowGroups isn't empty and one of user's groups isn't + * listed there, false will be returned. + * If the user's shell is not executable, false will be returned. + * Otherwise true is returned. + */ +int +allowed_user(struct ssh *ssh, struct passwd * pw) +{ + struct stat st; + const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; + u_int i; + int r; +#ifdef USE_SHADOW + struct spwd *spw = NULL; +#endif + + /* Shouldn't be called if pw is NULL, but better safe than sorry... */ + if (!pw || !pw->pw_name) + return 0; + +#ifdef USE_SHADOW + if (!options.use_pam) + spw = getspnam(pw->pw_name); +#ifdef HAS_SHADOW_EXPIRE + if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) + return 0; +#endif /* HAS_SHADOW_EXPIRE */ +#endif /* USE_SHADOW */ + + /* grab passwd field for locked account check */ + passwd = pw->pw_passwd; +#ifdef USE_SHADOW + if (spw != NULL) +#ifdef USE_LIBIAF + passwd = get_iaf_password(pw); +#else + passwd = spw->sp_pwdp; +#endif /* USE_LIBIAF */ +#endif + + /* check for locked account */ + if (!options.use_pam && passwd && *passwd) { + int locked = 0; + +#ifdef LOCKED_PASSWD_STRING + if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) + locked = 1; +#endif +#ifdef LOCKED_PASSWD_PREFIX + if (strncmp(passwd, LOCKED_PASSWD_PREFIX, + strlen(LOCKED_PASSWD_PREFIX)) == 0) + locked = 1; +#endif +#ifdef LOCKED_PASSWD_SUBSTR + if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) + locked = 1; +#endif +#ifdef USE_LIBIAF + free((void *) passwd); +#endif /* USE_LIBIAF */ + if (locked) { + logit("User %.100s not allowed because account is locked", + pw->pw_name); + return 0; + } + } + + /* + * Deny if shell does not exist or is not executable unless we + * are chrooting. + */ + if (options.chroot_directory == NULL || + strcasecmp(options.chroot_directory, "none") == 0) { + char *shell = xstrdup((pw->pw_shell[0] == '\0') ? + _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ + + if (stat(shell, &st) == -1) { + logit("User %.100s not allowed because shell %.100s " + "does not exist", pw->pw_name, shell); + free(shell); + return 0; + } + if (S_ISREG(st.st_mode) == 0 || + (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { + logit("User %.100s not allowed because shell %.100s " + "is not executable", pw->pw_name, shell); + free(shell); + return 0; + } + free(shell); + } + + if (options.num_deny_users > 0 || options.num_allow_users > 0 || + options.num_deny_groups > 0 || options.num_allow_groups > 0) { + hostname = auth_get_canonical_hostname(ssh, options.use_dns); + ipaddr = ssh_remote_ipaddr(ssh); + } + + /* Return false if user is listed in DenyUsers */ + if (options.num_deny_users > 0) { + for (i = 0; i < options.num_deny_users; i++) { + r = match_user(pw->pw_name, hostname, ipaddr, + options.deny_users[i]); + if (r < 0) { + fatal("Invalid DenyUsers pattern \"%.100s\"", + options.deny_users[i]); + } else if (r != 0) { + logit("User %.100s from %.100s not allowed " + "because listed in DenyUsers", + pw->pw_name, hostname); + return 0; + } + } + } + /* Return false if AllowUsers isn't empty and user isn't listed there */ + if (options.num_allow_users > 0) { + for (i = 0; i < options.num_allow_users; i++) { + r = match_user(pw->pw_name, hostname, ipaddr, + options.allow_users[i]); + if (r < 0) { + fatal("Invalid AllowUsers pattern \"%.100s\"", + options.allow_users[i]); + } else if (r == 1) + break; + } + /* i < options.num_allow_users iff we break for loop */ + if (i >= options.num_allow_users) { + logit("User %.100s from %.100s not allowed because " + "not listed in AllowUsers", pw->pw_name, hostname); + return 0; + } + } + if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { + /* Get the user's group access list (primary and supplementary) */ + if (ga_init(pw->pw_name, pw->pw_gid) == 0) { + logit("User %.100s from %.100s not allowed because " + "not in any group", pw->pw_name, hostname); + return 0; + } + + /* Return false if one of user's groups is listed in DenyGroups */ + if (options.num_deny_groups > 0) + if (ga_match(options.deny_groups, + options.num_deny_groups)) { + ga_free(); + logit("User %.100s from %.100s not allowed " + "because a group is listed in DenyGroups", + pw->pw_name, hostname); + return 0; + } + /* + * Return false if AllowGroups isn't empty and one of user's groups + * isn't listed there + */ + if (options.num_allow_groups > 0) + if (!ga_match(options.allow_groups, + options.num_allow_groups)) { + ga_free(); + logit("User %.100s from %.100s not allowed " + "because none of user's groups are listed " + "in AllowGroups", pw->pw_name, hostname); + return 0; + } + ga_free(); + } + +#ifdef CUSTOM_SYS_AUTH_ALLOWED_USER + if (!sys_auth_allowed_user(pw, loginmsg)) + return 0; +#endif + + /* We found no reason not to let this user try to log on... */ + return 1; +} + +/* + * Formats any key left in authctxt->auth_method_key for inclusion in + * auth_log()'s message. Also includes authxtct->auth_method_info if present. + */ +static char * +format_method_key(Authctxt *authctxt) +{ + const struct sshkey *key = authctxt->auth_method_key; + const char *methinfo = authctxt->auth_method_info; + char *fp, *cafp, *ret = NULL; + + if (key == NULL) + return NULL; + + if (sshkey_is_cert(key)) { + fp = sshkey_fingerprint(key, + options.fingerprint_hash, SSH_FP_DEFAULT); + cafp = sshkey_fingerprint(key->cert->signature_key, + options.fingerprint_hash, SSH_FP_DEFAULT); + xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s", + sshkey_type(key), fp == NULL ? "(null)" : fp, + key->cert->key_id, + (unsigned long long)key->cert->serial, + sshkey_type(key->cert->signature_key), + cafp == NULL ? "(null)" : cafp, + methinfo == NULL ? "" : ", ", + methinfo == NULL ? "" : methinfo); + free(fp); + free(cafp); + } else { + fp = sshkey_fingerprint(key, options.fingerprint_hash, + SSH_FP_DEFAULT); + xasprintf(&ret, "%s %s%s%s", sshkey_type(key), + fp == NULL ? "(null)" : fp, + methinfo == NULL ? "" : ", ", + methinfo == NULL ? "" : methinfo); + free(fp); + } + return ret; +} + +void +auth_log(struct ssh *ssh, int authenticated, int partial, + const char *method, const char *submethod) +{ + Authctxt *authctxt = (Authctxt *)ssh->authctxt; + int level = SYSLOG_LEVEL_VERBOSE; + const char *authmsg; + char *extra = NULL; + + if (use_privsep && !mm_is_monitor() && !authctxt->postponed) + return; + + /* Raise logging level */ + if (authenticated == 1 || + !authctxt->valid || + authctxt->failures >= options.max_authtries / 2 || + strcmp(method, "password") == 0) + level = SYSLOG_LEVEL_INFO; + + if (authctxt->postponed) + authmsg = "Postponed"; + else if (partial) + authmsg = "Partial"; + else + authmsg = authenticated ? "Accepted" : "Failed"; + + if ((extra = format_method_key(authctxt)) == NULL) { + if (authctxt->auth_method_info != NULL) + extra = xstrdup(authctxt->auth_method_info); + } + + do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", + authmsg, + method, + submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, + authctxt->valid ? "" : "invalid user ", + authctxt->user, + ssh_remote_ipaddr(ssh), + ssh_remote_port(ssh), + extra != NULL ? ": " : "", + extra != NULL ? extra : ""); + + free(extra); + +#ifdef CUSTOM_FAILED_LOGIN + if (authenticated == 0 && !authctxt->postponed && + (strcmp(method, "password") == 0 || + strncmp(method, "keyboard-interactive", 20) == 0 || + strcmp(method, "challenge-response") == 0)) + record_failed_login(ssh, authctxt->user, + auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); +# ifdef WITH_AIXAUTHENTICATE + if (authenticated) + sys_auth_record_login(authctxt->user, + auth_get_canonical_hostname(ssh, options.use_dns), "ssh", + loginmsg); +# endif +#endif +#ifdef SSH_AUDIT_EVENTS + if (authenticated == 0 && !authctxt->postponed) + audit_event(ssh, audit_classify_auth(method)); +#endif +} + + +void +auth_maxtries_exceeded(struct ssh *ssh) +{ + Authctxt *authctxt = (Authctxt *)ssh->authctxt; + + error("maximum authentication attempts exceeded for " + "%s%.100s from %.200s port %d ssh2", + authctxt->valid ? "" : "invalid user ", + authctxt->user, + ssh_remote_ipaddr(ssh), + ssh_remote_port(ssh)); + ssh_packet_disconnect(ssh, "Too many authentication failures"); + /* NOTREACHED */ +} + +/* + * Check whether root logins are disallowed. + */ +int +auth_root_allowed(struct ssh *ssh, const char *method) +{ + switch (options.permit_root_login) { + case PERMIT_YES: + return 1; + case PERMIT_NO_PASSWD: + if (strcmp(method, "publickey") == 0 || + strcmp(method, "hostbased") == 0 || + strcmp(method, "gssapi-with-mic") == 0) + return 1; + break; + case PERMIT_FORCED_ONLY: + if (auth_opts->force_command != NULL) { + logit("Root login accepted for forced command."); + return 1; + } + break; + } + logit("ROOT LOGIN REFUSED FROM %.200s port %d", + ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); + return 0; +} + + +/* + * Given a template and a passwd structure, build a filename + * by substituting % tokenised options. Currently, %% becomes '%', + * %h becomes the home directory and %u the username. + * + * This returns a buffer allocated by xmalloc. + */ +char * +expand_authorized_keys(const char *filename, struct passwd *pw) +{ + char *file, uidstr[32], ret[PATH_MAX]; + int i; + + snprintf(uidstr, sizeof(uidstr), "%llu", + (unsigned long long)pw->pw_uid); + file = percent_expand(filename, "h", pw->pw_dir, + "u", pw->pw_name, "U", uidstr, (char *)NULL); + + /* + * Ensure that filename starts anchored. If not, be backward + * compatible and prepend the '%h/' + */ + if (path_absolute(file)) + return (file); + + i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); + if (i < 0 || (size_t)i >= sizeof(ret)) + fatal("expand_authorized_keys: path too long"); + free(file); + return (xstrdup(ret)); +} + +char * +authorized_principals_file(struct passwd *pw) +{ + if (options.authorized_principals_file == NULL) + return NULL; + return expand_authorized_keys(options.authorized_principals_file, pw); +} + +/* return ok if key exists in sysfile or userfile */ +HostStatus +check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, + const char *sysfile, const char *userfile) +{ + char *user_hostfile; + struct stat st; + HostStatus host_status; + struct hostkeys *hostkeys; + const struct hostkey_entry *found; + + hostkeys = init_hostkeys(); + load_hostkeys(hostkeys, host, sysfile); + if (userfile != NULL) { + user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); + if (options.strict_modes && + (stat(user_hostfile, &st) == 0) && + ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || + (st.st_mode & 022) != 0)) { + logit("Authentication refused for %.100s: " + "bad owner or modes for %.200s", + pw->pw_name, user_hostfile); + auth_debug_add("Ignored %.200s: bad ownership or modes", + user_hostfile); + } else { + temporarily_use_uid(pw); + load_hostkeys(hostkeys, host, user_hostfile); + restore_uid(); + } + free(user_hostfile); + } + host_status = check_key_in_hostkeys(hostkeys, key, &found); + if (host_status == HOST_REVOKED) + error("WARNING: revoked key for %s attempted authentication", + host); + else if (host_status == HOST_OK) + debug("%s: key for %s found at %s:%ld", __func__, + found->host, found->file, found->line); + else + debug("%s: key for host %s not found", __func__, host); + + free_hostkeys(hostkeys); + + return host_status; +} + +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 (log_missing || errno != ENOENT) + debug("Could not open %s '%s': %s", 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"); +} + +struct passwd * +getpwnamallow(struct ssh *ssh, const char *user) +{ +#ifdef HAVE_LOGIN_CAP + extern login_cap_t *lc; +#ifdef BSD_AUTH + auth_session_t *as; +#endif +#endif + struct passwd *pw; + struct connection_info *ci; + + ci = get_connection_info(ssh, 1, options.use_dns); + ci->user = user; + parse_server_match_config(&options, &includes, ci); + log_change_level(options.log_level); + process_permitopen(ssh, &options); + +#if defined(_AIX) && defined(HAVE_SETAUTHDB) + aix_setauthdb(user); +#endif + + pw = getpwnam(user); + +#if defined(_AIX) && defined(HAVE_SETAUTHDB) + aix_restoreauthdb(); +#endif + if (pw == NULL) { + logit("Invalid user %.100s from %.100s port %d", + user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); +#ifdef CUSTOM_FAILED_LOGIN + record_failed_login(ssh, user, + auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); +#endif +#ifdef SSH_AUDIT_EVENTS + audit_event(ssh, SSH_INVALID_USER); +#endif /* SSH_AUDIT_EVENTS */ + return (NULL); + } + if (!allowed_user(ssh, pw)) + return (NULL); +#ifdef HAVE_LOGIN_CAP + if ((lc = login_getclass(pw->pw_class)) == NULL) { + debug("unable to get login class: %s", user); + return (NULL); + } +#ifdef BSD_AUTH + if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || + auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { + debug("Approval failure for %s", user); + pw = NULL; + } + if (as != NULL) + auth_close(as); +#endif +#endif + if (pw != NULL) + return (pwcopy(pw)); + return (NULL); +} + +/* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ +int +auth_key_is_revoked(struct sshkey *key) +{ + char *fp = NULL; + int r; + + if (options.revoked_keys_file == NULL) + return 0; + if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, + SSH_FP_DEFAULT)) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + error("%s: fingerprint key: %s", __func__, ssh_err(r)); + goto out; + } + + r = sshkey_check_revoked(key, options.revoked_keys_file); + switch (r) { + case 0: + break; /* not revoked */ + case SSH_ERR_KEY_REVOKED: + error("Authentication key %s %s revoked by file %s", + sshkey_type(key), fp, options.revoked_keys_file); + goto out; + default: + error("Error checking authentication key %s %s in " + "revoked keys file %s: %s", sshkey_type(key), fp, + options.revoked_keys_file, ssh_err(r)); + goto out; + } + + /* Success */ + r = 0; + + out: + free(fp); + return r == 0 ? 0 : 1; +} + +void +auth_debug_add(const char *fmt,...) +{ + char buf[1024]; + va_list args; + int r; + + if (auth_debug == NULL) + return; + + va_start(args, fmt); + vsnprintf(buf, sizeof(buf), fmt, args); + va_end(args); + if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0) + fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r)); +} + +void +auth_debug_send(struct ssh *ssh) +{ + char *msg; + int r; + + if (auth_debug == NULL) + return; + while (sshbuf_len(auth_debug) != 0) { + if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0) + fatal("%s: sshbuf_get_cstring: %s", + __func__, ssh_err(r)); + ssh_packet_send_debug(ssh, "%s", msg); + free(msg); + } +} + +void +auth_debug_reset(void) +{ + if (auth_debug != NULL) + sshbuf_reset(auth_debug); + else if ((auth_debug = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __func__); +} + +struct passwd * +fakepw(void) +{ + static struct passwd fake; + + memset(&fake, 0, sizeof(fake)); + fake.pw_name = "NOUSER"; + fake.pw_passwd = + "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; +#ifdef HAVE_STRUCT_PASSWD_PW_GECOS + fake.pw_gecos = "NOUSER"; +#endif + fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; + fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; +#ifdef HAVE_STRUCT_PASSWD_PW_CLASS + fake.pw_class = ""; +#endif + fake.pw_dir = "/nonexist"; + fake.pw_shell = "/nonexist"; + + return (&fake); +} + +/* + * Returns the remote DNS hostname as a string. The returned string must not + * be freed. NB. this will usually trigger a DNS query the first time it is + * called. + * This function does additional checks on the hostname to mitigate some + * attacks on legacy rhosts-style authentication. + * XXX is RhostsRSAAuthentication vulnerable to these? + * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) + */ + +static char * +remote_hostname(struct ssh *ssh) +{ + struct sockaddr_storage from; + socklen_t fromlen; + struct addrinfo hints, *ai, *aitop; + char name[NI_MAXHOST], ntop2[NI_MAXHOST]; + const char *ntop = ssh_remote_ipaddr(ssh); + + /* Get IP address of client. */ + fromlen = sizeof(from); + memset(&from, 0, sizeof(from)); + if (getpeername(ssh_packet_get_connection_in(ssh), + (struct sockaddr *)&from, &fromlen) == -1) { + debug("getpeername failed: %.100s", strerror(errno)); + return xstrdup(ntop); + } + + ipv64_normalise_mapped(&from, &fromlen); + if (from.ss_family == AF_INET6) + fromlen = sizeof(struct sockaddr_in6); + + debug3("Trying to reverse map address %.100s.", ntop); + /* Map the IP address to a host name. */ + if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), + NULL, 0, NI_NAMEREQD) != 0) { + /* Host name not found. Use ip address. */ + return xstrdup(ntop); + } + + /* + * if reverse lookup result looks like a numeric hostname, + * someone is trying to trick us by PTR record like following: + * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 + */ + memset(&hints, 0, sizeof(hints)); + hints.ai_socktype = SOCK_DGRAM; /*dummy*/ + hints.ai_flags = AI_NUMERICHOST; + if (getaddrinfo(name, NULL, &hints, &ai) == 0) { + logit("Nasty PTR record \"%s\" is set up for %s, ignoring", + name, ntop); + freeaddrinfo(ai); + return xstrdup(ntop); + } + + /* Names are stored in lowercase. */ + lowercase(name); + + /* + * Map it back to an IP address and check that the given + * address actually is an address of this host. This is + * necessary because anyone with access to a name server can + * define arbitrary names for an IP address. Mapping from + * name to IP address can be trusted better (but can still be + * fooled if the intruder has access to the name server of + * the domain). + */ + memset(&hints, 0, sizeof(hints)); + hints.ai_family = from.ss_family; + hints.ai_socktype = SOCK_STREAM; + if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { + logit("reverse mapping checking getaddrinfo for %.700s " + "[%s] failed.", name, ntop); + return xstrdup(ntop); + } + /* Look for the address from the list of addresses. */ + for (ai = aitop; ai; ai = ai->ai_next) { + if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, + sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && + (strcmp(ntop, ntop2) == 0)) + break; + } + freeaddrinfo(aitop); + /* If we reached the end of the list, the address was not there. */ + if (ai == NULL) { + /* Address not found for the host name. */ + logit("Address %.100s maps to %.600s, but this does not " + "map back to the address.", ntop, name); + return xstrdup(ntop); + } + return xstrdup(name); +} + +/* + * Return the canonical name of the host in the other side of the current + * connection. The host name is cached, so it is efficient to call this + * several times. + */ + +const char * +auth_get_canonical_hostname(struct ssh *ssh, int use_dns) +{ + static char *dnsname; + + if (!use_dns) + return ssh_remote_ipaddr(ssh); + else if (dnsname != NULL) + return dnsname; + else { + dnsname = remote_hostname(ssh); + return dnsname; + } +} + +/* + * Runs command in a subprocess with a minimal environment. + * Returns pid on success, 0 on failure. + * The child stdout and stderr maybe captured, left attached or sent to + * /dev/null depending on the contents of flags. + * "tag" is prepended to log messages. + * NB. "command" is only used for logging; the actual command executed is + * av[0]. + */ +pid_t +subprocess(const char *tag, struct passwd *pw, const char *command, + int ac, char **av, FILE **child, u_int flags) +{ + FILE *f = NULL; + struct stat st; + int fd, devnull, p[2], i; + pid_t pid; + char *cp, errmsg[512]; + u_int envsize; + char **child_env; + + if (child != NULL) + *child = NULL; + + debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__, + tag, command, pw->pw_name, flags); + + /* Check consistency */ + if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && + (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) { + error("%s: inconsistent flags", __func__); + return 0; + } + if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) { + error("%s: inconsistent flags/output", __func__); + return 0; + } + + /* + * If executing an explicit binary, then verify the it exists + * and appears safe-ish to execute + */ + if (!path_absolute(av[0])) { + error("%s path is not absolute", tag); + return 0; + } + temporarily_use_uid(pw); + if (stat(av[0], &st) == -1) { + error("Could not stat %s \"%s\": %s", tag, + av[0], strerror(errno)); + restore_uid(); + return 0; + } + if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) { + error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); + restore_uid(); + return 0; + } + /* Prepare to keep the child's stdout if requested */ + if (pipe(p) == -1) { + error("%s: pipe: %s", tag, strerror(errno)); + restore_uid(); + return 0; + } + restore_uid(); + + switch ((pid = fork())) { + case -1: /* error */ + error("%s: fork: %s", tag, strerror(errno)); + close(p[0]); + close(p[1]); + return 0; + case 0: /* child */ + /* Prepare a minimal environment for the child. */ + envsize = 5; + child_env = xcalloc(sizeof(*child_env), envsize); + child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH); + child_set_env(&child_env, &envsize, "USER", pw->pw_name); + child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name); + child_set_env(&child_env, &envsize, "HOME", pw->pw_dir); + if ((cp = getenv("LANG")) != NULL) + child_set_env(&child_env, &envsize, "LANG", cp); + + for (i = 0; i < NSIG; i++) + ssh_signal(i, SIG_DFL); + + if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { + error("%s: open %s: %s", tag, _PATH_DEVNULL, + strerror(errno)); + _exit(1); + } + if (dup2(devnull, STDIN_FILENO) == -1) { + error("%s: dup2: %s", tag, strerror(errno)); + _exit(1); + } + + /* Set up stdout as requested; leave stderr in place for now. */ + fd = -1; + if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) + fd = p[1]; + else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0) + fd = devnull; + if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) { + error("%s: dup2: %s", tag, strerror(errno)); + _exit(1); + } + closefrom(STDERR_FILENO + 1); + + /* Don't use permanently_set_uid() here to avoid fatal() */ + if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) { + error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid, + strerror(errno)); + _exit(1); + } + if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1) { + error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid, + strerror(errno)); + _exit(1); + } + /* stdin is pointed to /dev/null at this point */ + if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && + dup2(STDIN_FILENO, STDERR_FILENO) == -1) { + error("%s: dup2: %s", tag, strerror(errno)); + _exit(1); + } + + execve(av[0], av, child_env); + error("%s exec \"%s\": %s", tag, command, strerror(errno)); + _exit(127); + default: /* parent */ + break; + } + + close(p[1]); + if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) + close(p[0]); + else if ((f = fdopen(p[0], "r")) == NULL) { + error("%s: fdopen: %s", tag, strerror(errno)); + close(p[0]); + /* Don't leave zombie child */ + kill(pid, SIGTERM); + while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) + ; + return 0; + } + /* Success */ + debug3("%s: %s pid %ld", __func__, tag, (long)pid); + if (child != NULL) + *child = f; + return pid; +} + +/* These functions link key/cert options to the auth framework */ + +/* Log sshauthopt options locally and (optionally) for remote transmission */ +void +auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote) +{ + int do_env = options.permit_user_env && opts->nenv > 0; + int do_permitopen = opts->npermitopen > 0 && + (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0; + int do_permitlisten = opts->npermitlisten > 0 && + (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0; + size_t i; + char msg[1024], buf[64]; + + snprintf(buf, sizeof(buf), "%d", opts->force_tun_device); + /* Try to keep this alphabetically sorted */ + snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s", + opts->permit_agent_forwarding_flag ? " agent-forwarding" : "", + opts->force_command == NULL ? "" : " command", + do_env ? " environment" : "", + opts->valid_before == 0 ? "" : "expires", + opts->no_require_user_presence ? " no-touch-required" : "", + do_permitopen ? " permitopen" : "", + do_permitlisten ? " permitlisten" : "", + opts->permit_port_forwarding_flag ? " port-forwarding" : "", + opts->cert_principals == NULL ? "" : " principals", + opts->permit_pty_flag ? " pty" : "", + opts->require_verify ? " uv" : "", + opts->force_tun_device == -1 ? "" : " tun=", + opts->force_tun_device == -1 ? "" : buf, + opts->permit_user_rc ? " user-rc" : "", + opts->permit_x11_forwarding_flag ? " x11-forwarding" : ""); + + debug("%s: %s", loc, msg); + if (do_remote) + auth_debug_add("%s: %s", loc, msg); + + if (options.permit_user_env) { + for (i = 0; i < opts->nenv; i++) { + debug("%s: environment: %s", loc, opts->env[i]); + if (do_remote) { + auth_debug_add("%s: environment: %s", + loc, opts->env[i]); + } + } + } + + /* Go into a little more details for the local logs. */ + if (opts->valid_before != 0) { + format_absolute_time(opts->valid_before, buf, sizeof(buf)); + debug("%s: expires at %s", loc, buf); + } + if (opts->cert_principals != NULL) { + debug("%s: authorized principals: \"%s\"", + loc, opts->cert_principals); + } + if (opts->force_command != NULL) + debug("%s: forced command: \"%s\"", loc, opts->force_command); + if (do_permitopen) { + for (i = 0; i < opts->npermitopen; i++) { + debug("%s: permitted open: %s", + loc, opts->permitopen[i]); + } + } + if (do_permitlisten) { + for (i = 0; i < opts->npermitlisten; i++) { + debug("%s: permitted listen: %s", + loc, opts->permitlisten[i]); + } + } +} + +/* Activate a new set of key/cert options; merging with what is there. */ +int +auth_activate_options(struct ssh *ssh, struct sshauthopt *opts) +{ + struct sshauthopt *old = auth_opts; + const char *emsg = NULL; + + debug("%s: setting new authentication options", __func__); + if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) { + error("Inconsistent authentication options: %s", emsg); + return -1; + } + return 0; +} + +/* Disable forwarding, etc for the session */ +void +auth_restrict_session(struct ssh *ssh) +{ + struct sshauthopt *restricted; + + debug("%s: restricting session", __func__); + + /* A blank sshauthopt defaults to permitting nothing */ + restricted = sshauthopt_new(); + restricted->permit_pty_flag = 1; + restricted->restricted = 1; + + if (auth_activate_options(ssh, restricted) != 0) + fatal("%s: failed to restrict session", __func__); + sshauthopt_free(restricted); +} + +int +auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw, + struct sshauthopt *opts, int allow_cert_authority, const char *loc) +{ + const char *remote_ip = ssh_remote_ipaddr(ssh); + const char *remote_host = auth_get_canonical_hostname(ssh, + options.use_dns); + 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; +} |