X-Git-Url: http://andersk.mit.edu/gitweb/openssh.git/blobdiff_plain/c1ef833349a77ca330c4a3ba40eb5e155fbcaa92..5486a45797557bd2ffca421ca5e7ad2441f4db59:/auth.c diff --git a/auth.c b/auth.c index c3063e42..c6e7c21c 100644 --- a/auth.c +++ b/auth.c @@ -1,45 +1,71 @@ /* - * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland - * All rights reserved - * Copyright (c) 2000 Markus Friedl. All rights reserved. + * 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" -RCSID("$OpenBSD: auth.c,v 1.6 2000/04/26 21:28:31 markus Exp $"); +RCSID("$OpenBSD: auth.c,v 1.51 2003/11/21 11:57:02 djm Exp $"); -#include "xmalloc.h" -#include "rsa.h" -#include "ssh.h" -#include "pty.h" -#include "packet.h" -#include "buffer.h" -#include "cipher.h" -#include "mpaux.h" -#include "servconf.h" -#include "compat.h" -#include "channels.h" -#include "match.h" #ifdef HAVE_LOGIN_H #include #endif +#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) +#include +#endif /* defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) */ -#include "bufaux.h" -#include "ssh2.h" -#include "auth.h" -#include "session.h" -#include "dispatch.h" +#ifdef HAVE_LIBGEN_H +#include +#endif +#include "xmalloc.h" +#include "match.h" +#include "groupaccess.h" +#include "log.h" +#include "servconf.h" +#include "auth.h" +#include "auth-options.h" +#include "canohost.h" +#include "buffer.h" +#include "bufaux.h" +#include "uidswap.h" +#include "tildexpand.h" +#include "misc.h" +#include "bufaux.h" +#include "packet.h" /* import */ extern ServerOptions options; -extern char *forced_command; +extern Buffer loginmsg; + +/* Debugging messages */ +Buffer auth_debug; +int auth_debug_init; /* - * Check if the user is allowed to log in via ssh. If user is listed in - * DenyUsers or user's primary group 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 user isn't listed there, false will be - * returned. + * 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. */ @@ -47,89 +73,520 @@ int allowed_user(struct passwd * pw) { struct stat st; - struct group *grp; + const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; + char *shell; int i; -#ifdef WITH_AIXAUTHENTICATE - char *loginmsg; -#endif /* WITH_AIXAUTHENTICATE */ +#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) + struct spwd *spw = NULL; +#endif /* Shouldn't be called if pw is NULL, but better safe than sorry... */ - if (!pw) + if (!pw || !pw->pw_name) return 0; +#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) + if (!options.use_pam) + spw = getspnam(pw->pw_name); +#ifdef HAS_SHADOW_EXPIRE +#define DAY (24L * 60 * 60) /* 1 day in seconds */ + if (!options.use_pam && spw != NULL) { + int disabled = 0; + time_t today; + + today = time(NULL) / DAY; + debug3("allowed_user: today %d sp_expire %d sp_lstchg %d" + " sp_max %d", (int)today, (int)spw->sp_expire, + (int)spw->sp_lstchg, (int)spw->sp_max); + + /* + * We assume account and password expiration occurs the + * day after the day specified. + */ + if (spw->sp_expire != -1 && today > spw->sp_expire) { + logit("Account %.100s has expired", pw->pw_name); + return 0; + } + } +#endif /* HAS_SHADOW_EXPIRE */ +#endif /* defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) */ + + /* grab passwd field for locked account check */ +#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) + if (spw != NULL) + passwd = spw->sp_pwdp; +#else + passwd = pw->pw_passwd; +#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 + if (locked) { + logit("User %.100s not allowed because account is locked", + pw->pw_name); + return 0; + } + } + + /* + * Get the shell from the password data. An empty shell field is + * legal, and means /bin/sh. + */ + shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; + /* deny if shell does not exists or is not executable */ - if (stat(pw->pw_shell, &st) != 0) + if (stat(shell, &st) != 0) { + logit("User %.100s not allowed because shell %.100s does not exist", + pw->pw_name, shell); return 0; - if (!((st.st_mode & S_IFREG) && (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)))) + } + 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); return 0; + } + + if (options.num_deny_users > 0 || options.num_allow_users > 0) { + hostname = get_canonical_hostname(options.use_dns); + ipaddr = get_remote_ipaddr(); + } /* Return false if user is listed in DenyUsers */ if (options.num_deny_users > 0) { - if (!pw->pw_name) - return 0; for (i = 0; i < options.num_deny_users; i++) - if (match_pattern(pw->pw_name, options.deny_users[i])) + if (match_user(pw->pw_name, hostname, ipaddr, + options.deny_users[i])) { + logit("User %.100s not allowed because listed in DenyUsers", + pw->pw_name); return 0; + } } /* Return false if AllowUsers isn't empty and user isn't listed there */ if (options.num_allow_users > 0) { - if (!pw->pw_name) - return 0; for (i = 0; i < options.num_allow_users; i++) - if (match_pattern(pw->pw_name, options.allow_users[i])) + if (match_user(pw->pw_name, hostname, ipaddr, + options.allow_users[i])) break; /* i < options.num_allow_users iff we break for loop */ - if (i >= options.num_allow_users) + if (i >= options.num_allow_users) { + logit("User %.100s not allowed because not listed in AllowUsers", + pw->pw_name); return 0; + } } - /* Get the primary group name if we need it. Return false if it fails */ if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { - grp = getgrgid(pw->pw_gid); - if (!grp) + /* Get the user's group access list (primary and supplementary) */ + if (ga_init(pw->pw_name, pw->pw_gid) == 0) { + logit("User %.100s not allowed because not in any group", + pw->pw_name); return 0; + } - /* Return false if user's group is listed in DenyGroups */ - if (options.num_deny_groups > 0) { - if (!grp->gr_name) + /* 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 not allowed because a group is listed in DenyGroups", + pw->pw_name); return 0; - for (i = 0; i < options.num_deny_groups; i++) - if (match_pattern(grp->gr_name, options.deny_groups[i])) - return 0; - } + } /* - * Return false if AllowGroups isn't empty and user's group + * Return false if AllowGroups isn't empty and one of user's groups * isn't listed there */ - if (options.num_allow_groups > 0) { - if (!grp->gr_name) + if (options.num_allow_groups > 0) + if (!ga_match(options.allow_groups, + options.num_allow_groups)) { + ga_free(); + logit("User %.100s not allowed because none of user's groups are listed in AllowGroups", + pw->pw_name); return 0; - for (i = 0; i < options.num_allow_groups; i++) - if (match_pattern(grp->gr_name, options.allow_groups[i])) - break; - /* i < options.num_allow_groups iff we break for - loop */ - if (i >= options.num_allow_groups) - return 0; - } + } + ga_free(); } #ifdef WITH_AIXAUTHENTICATE - if (loginrestrictions(pw->pw_name,S_RLOGIN,NULL,&loginmsg) != 0) { - if (loginmsg && *loginmsg) { - /* Remove embedded newlines (if any) */ - char *p; - for (p = loginmsg; *p; p++) - if (*p == '\n') - *p = ' '; - /* Remove trailing newline */ - *--p = '\0'; - log("Login restricted for %s: %.100s", - pw->pw_name, loginmsg); + /* + * Don't check loginrestrictions() for root account (use + * PermitRootLogin to control logins via ssh), or if running as + * non-root user (since loginrestrictions will always fail). + */ + if ((pw->pw_uid != 0) && (geteuid() == 0)) { + char *msg; + + if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &msg) != 0) { + int loginrestrict_errno = errno; + + if (msg && *msg) { + buffer_append(&loginmsg, msg, strlen(msg)); + aix_remove_embedded_newlines(msg); + logit("Login restricted for %s: %.100s", + pw->pw_name, msg); + } + /* Don't fail if /etc/nologin set */ + if (!(loginrestrict_errno == EPERM && + stat(_PATH_NOLOGIN, &st) == 0)) + return 0; } - return 0; } #endif /* WITH_AIXAUTHENTICATE */ /* We found no reason not to let this user try to log on... */ return 1; } + +void +auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) +{ + void (*authlog) (const char *fmt,...) = verbose; + char *authmsg; + + /* Raise logging level */ + if (authenticated == 1 || + !authctxt->valid || + authctxt->failures >= AUTH_FAIL_LOG || + strcmp(method, "password") == 0) + authlog = logit; + + if (authctxt->postponed) + authmsg = "Postponed"; + else + authmsg = authenticated ? "Accepted" : "Failed"; + + authlog("%s %s for %s%.100s from %.200s port %d%s", + authmsg, + method, + authctxt->valid ? "" : "illegal user ", + authctxt->user, + get_remote_ipaddr(), + get_remote_port(), + info); + +#ifdef CUSTOM_FAILED_LOGIN + if (authenticated == 0 && strcmp(method, "password") == 0) + record_failed_login(authctxt->user, "ssh"); +#endif +} + +/* + * Check whether root logins are disallowed. + */ +int +auth_root_allowed(char *method) +{ + switch (options.permit_root_login) { + case PERMIT_YES: + return 1; + break; + case PERMIT_NO_PASSWD: + if (strcmp(method, "password") != 0) + return 1; + break; + case PERMIT_FORCED_ONLY: + if (forced_command) { + logit("Root login accepted for forced command."); + return 1; + } + break; + } + logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); + 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_filename(const char *filename, struct passwd *pw) +{ + Buffer buffer; + char *file; + const char *cp; + + /* + * Build the filename string in the buffer by making the appropriate + * substitutions to the given file name. + */ + buffer_init(&buffer); + for (cp = filename; *cp; cp++) { + if (cp[0] == '%' && cp[1] == '%') { + buffer_append(&buffer, "%", 1); + cp++; + continue; + } + if (cp[0] == '%' && cp[1] == 'h') { + buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); + cp++; + continue; + } + if (cp[0] == '%' && cp[1] == 'u') { + buffer_append(&buffer, pw->pw_name, + strlen(pw->pw_name)); + cp++; + continue; + } + buffer_append(&buffer, cp, 1); + } + buffer_append(&buffer, "\0", 1); + + /* + * Ensure that filename starts anchored. If not, be backward + * compatible and prepend the '%h/' + */ + file = xmalloc(MAXPATHLEN); + cp = buffer_ptr(&buffer); + if (*cp != '/') + snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); + else + strlcpy(file, cp, MAXPATHLEN); + + buffer_free(&buffer); + return file; +} + +char * +authorized_keys_file(struct passwd *pw) +{ + return expand_filename(options.authorized_keys_file, pw); +} + +char * +authorized_keys_file2(struct passwd *pw) +{ + return expand_filename(options.authorized_keys_file2, pw); +} + +/* return ok if key exists in sysfile or userfile */ +HostStatus +check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, + const char *sysfile, const char *userfile) +{ + Key *found; + char *user_hostfile; + struct stat st; + HostStatus host_status; + + /* Check if we know the host and its host key. */ + found = key_new(key->type); + host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); + + if (host_status != HOST_OK && 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); + } else { + temporarily_use_uid(pw); + host_status = check_host_in_hostfile(user_hostfile, + host, key, found, NULL); + restore_uid(); + } + xfree(user_hostfile); + } + key_free(found); + + debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? + "ok" : "not found", host); + return host_status; +} + + +/* + * Check a given file for security. This is defined as all components + * of the path to the file must be owned by either the owner of + * of the file or root and no directories must be group or world writable. + * + * XXX Should any specific check be done for sym links ? + * + * Takes an open file descriptor, the file name, a uid and and + * error buffer plus max size as arguments. + * + * Returns 0 on success and -1 on failure + */ +int +secure_filename(FILE *f, const char *file, struct passwd *pw, + char *err, size_t errlen) +{ + uid_t uid = pw->pw_uid; + char buf[MAXPATHLEN], homedir[MAXPATHLEN]; + char *cp; + int comparehome = 0; + struct stat st; + + if (realpath(file, buf) == NULL) { + snprintf(err, errlen, "realpath %s failed: %s", file, + strerror(errno)); + return -1; + } + if (realpath(pw->pw_dir, homedir) != NULL) + comparehome = 1; + + /* check the open file to avoid races */ + if (fstat(fileno(f), &st) < 0 || + (st.st_uid != 0 && st.st_uid != uid) || + (st.st_mode & 022) != 0) { + snprintf(err, errlen, "bad ownership or modes for file %s", + buf); + return -1; + } + + /* for each component of the canonical path, walking upwards */ + for (;;) { + if ((cp = dirname(buf)) == NULL) { + snprintf(err, errlen, "dirname() failed"); + return -1; + } + strlcpy(buf, cp, sizeof(buf)); + + debug3("secure_filename: checking '%s'", buf); + if (stat(buf, &st) < 0 || + (st.st_uid != 0 && st.st_uid != uid) || + (st.st_mode & 022) != 0) { + snprintf(err, errlen, + "bad ownership or modes for directory %s", buf); + return -1; + } + + /* If are passed the homedir then we can stop */ + if (comparehome && strcmp(homedir, buf) == 0) { + debug3("secure_filename: terminating check at '%s'", + buf); + break; + } + /* + * dirname should always complete with a "/" path, + * but we can be paranoid and check for "." too + */ + if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) + break; + } + return 0; +} + +struct passwd * +getpwnamallow(const char *user) +{ +#ifdef HAVE_LOGIN_CAP + extern login_cap_t *lc; +#ifdef BSD_AUTH + auth_session_t *as; +#endif +#endif + struct passwd *pw; + + pw = getpwnam(user); + if (pw == NULL) { + logit("Illegal user %.100s from %.100s", + user, get_remote_ipaddr()); +#ifdef CUSTOM_FAILED_LOGIN + record_failed_login(user, "ssh"); +#endif + return (NULL); + } + if (!allowed_user(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); +} + +void +auth_debug_add(const char *fmt,...) +{ + char buf[1024]; + va_list args; + + if (!auth_debug_init) + return; + + va_start(args, fmt); + vsnprintf(buf, sizeof(buf), fmt, args); + va_end(args); + buffer_put_cstring(&auth_debug, buf); +} + +void +auth_debug_send(void) +{ + char *msg; + + if (!auth_debug_init) + return; + while (buffer_len(&auth_debug)) { + msg = buffer_get_string(&auth_debug, NULL); + packet_send_debug("%s", msg); + xfree(msg); + } +} + +void +auth_debug_reset(void) +{ + if (auth_debug_init) + buffer_clear(&auth_debug); + else { + buffer_init(&auth_debug); + auth_debug_init = 1; + } +} + +struct passwd * +fakepw(void) +{ + static struct passwd fake; + + memset(&fake, 0, sizeof(fake)); + fake.pw_name = "NOUSER"; + fake.pw_passwd = + "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; + fake.pw_gecos = "NOUSER"; + fake.pw_uid = -1; + fake.pw_gid = -1; +#ifdef HAVE_PW_CLASS_IN_PASSWD + fake.pw_class = ""; +#endif + fake.pw_dir = "/nonexist"; + fake.pw_shell = "/nonexist"; + + return (&fake); +}