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Diffstat (limited to '')
| -rw-r--r-- | auth-pam.c | 1391 |
1 files changed, 1391 insertions, 0 deletions
diff --git a/auth-pam.c b/auth-pam.c new file mode 100644 index 0000000..8323821 --- /dev/null +++ b/auth-pam.c @@ -0,0 +1,1391 @@ +/*- + * Copyright (c) 2002 Networks Associates Technology, Inc. + * All rights reserved. + * + * This software was developed for the FreeBSD Project by ThinkSec AS and + * NAI Labs, the Security Research Division of Network Associates, Inc. + * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the + * DARPA CHATS research program. + * + * 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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. + */ +/* + * Copyright (c) 2003,2004 Damien Miller <djm@mindrot.org> + * Copyright (c) 2003,2004 Darren Tucker <dtucker@zip.com.au> + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +/* Based on FreeBSD: src/crypto/openssh/auth2-pam-freebsd.c,v 1.11 2003/03/31 13:48:18 des */ + +#include "includes.h" + +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/wait.h> + +#include <errno.h> +#include <signal.h> +#include <stdarg.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#ifdef USE_PAM +#if defined(HAVE_SECURITY_PAM_APPL_H) +#include <security/pam_appl.h> +#elif defined (HAVE_PAM_PAM_APPL_H) +#include <pam/pam_appl.h> +#endif + +#if !defined(SSHD_PAM_SERVICE) +extern char *__progname; +# define SSHD_PAM_SERVICE __progname +#endif + +/* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */ +#ifdef PAM_SUN_CODEBASE +# define sshpam_const /* Solaris, HP-UX, SunOS */ +#else +# define sshpam_const const /* LinuxPAM, OpenPAM, AIX */ +#endif + +/* Ambiguity in spec: is it an array of pointers or a pointer to an array? */ +#ifdef PAM_SUN_CODEBASE +# define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member) +#else +# define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member) +#endif + +#include "xmalloc.h" +#include "sshbuf.h" +#include "ssherr.h" +#include "hostfile.h" +#include "auth.h" +#include "auth-pam.h" +#include "canohost.h" +#include "log.h" +#include "msg.h" +#include "packet.h" +#include "misc.h" +#include "servconf.h" +#include "ssh2.h" +#include "auth-options.h" +#include "misc.h" +#ifdef GSSAPI +#include "ssh-gss.h" +#endif +#include "monitor_wrap.h" + +extern ServerOptions options; +extern struct sshbuf *loginmsg; +extern u_int utmp_len; + +/* so we don't silently change behaviour */ +#ifdef USE_POSIX_THREADS +# error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK" +#endif + +/* + * Formerly known as USE_POSIX_THREADS, using this is completely unsupported + * and generally a bad idea. Use at own risk and do not expect support if + * this breaks. + */ +#ifdef UNSUPPORTED_POSIX_THREADS_HACK +#include <pthread.h> +/* + * Avoid namespace clash when *not* using pthreads for systems *with* + * pthreads, which unconditionally define pthread_t via sys/types.h + * (e.g. Linux) + */ +typedef pthread_t sp_pthread_t; +#else +typedef pid_t sp_pthread_t; +#define pthread_exit fake_pthread_exit +#define pthread_create fake_pthread_create +#define pthread_cancel fake_pthread_cancel +#define pthread_join fake_pthread_join +#endif + +struct pam_ctxt { + sp_pthread_t pam_thread; + int pam_psock; + int pam_csock; + int pam_done; +}; + +static void sshpam_free_ctx(void *); +static struct pam_ctxt *cleanup_ctxt; + +#ifndef UNSUPPORTED_POSIX_THREADS_HACK +/* + * Simulate threads with processes. + */ + +static int sshpam_thread_status = -1; +static sshsig_t sshpam_oldsig; + +static void +sshpam_sigchld_handler(int sig) +{ + ssh_signal(SIGCHLD, SIG_DFL); + if (cleanup_ctxt == NULL) + return; /* handler called after PAM cleanup, shouldn't happen */ + if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG) + <= 0) { + /* PAM thread has not exitted, privsep slave must have */ + kill(cleanup_ctxt->pam_thread, SIGTERM); + while (waitpid(cleanup_ctxt->pam_thread, + &sshpam_thread_status, 0) == -1) { + if (errno == EINTR) + continue; + return; + } + } + if (WIFSIGNALED(sshpam_thread_status) && + WTERMSIG(sshpam_thread_status) == SIGTERM) + return; /* terminated by pthread_cancel */ + if (!WIFEXITED(sshpam_thread_status)) + sigdie("PAM: authentication thread exited unexpectedly"); + if (WEXITSTATUS(sshpam_thread_status) != 0) + sigdie("PAM: authentication thread exited uncleanly"); +} + +/* ARGSUSED */ +static void +pthread_exit(void *value) +{ + _exit(0); +} + +/* ARGSUSED */ +static int +pthread_create(sp_pthread_t *thread, const void *attr, + void *(*thread_start)(void *), void *arg) +{ + pid_t pid; + struct pam_ctxt *ctx = arg; + + sshpam_thread_status = -1; + switch ((pid = fork())) { + case -1: + error("fork(): %s", strerror(errno)); + return errno; + case 0: + close(ctx->pam_psock); + ctx->pam_psock = -1; + thread_start(arg); + _exit(1); + default: + *thread = pid; + close(ctx->pam_csock); + ctx->pam_csock = -1; + sshpam_oldsig = ssh_signal(SIGCHLD, sshpam_sigchld_handler); + return (0); + } +} + +static int +pthread_cancel(sp_pthread_t thread) +{ + ssh_signal(SIGCHLD, sshpam_oldsig); + return (kill(thread, SIGTERM)); +} + +/* ARGSUSED */ +static int +pthread_join(sp_pthread_t thread, void **value) +{ + int status; + + if (sshpam_thread_status != -1) + return (sshpam_thread_status); + ssh_signal(SIGCHLD, sshpam_oldsig); + while (waitpid(thread, &status, 0) == -1) { + if (errno == EINTR) + continue; + fatal("%s: waitpid: %s", __func__, strerror(errno)); + } + return (status); +} +#endif + + +static pam_handle_t *sshpam_handle = NULL; +static int sshpam_err = 0; +static int sshpam_authenticated = 0; +static int sshpam_session_open = 0; +static int sshpam_cred_established = 0; +static int sshpam_account_status = -1; +static int sshpam_maxtries_reached = 0; +static char **sshpam_env = NULL; +static Authctxt *sshpam_authctxt = NULL; +static const char *sshpam_password = NULL; +static char *sshpam_rhost = NULL; +static char *sshpam_laddr = NULL; +static char *sshpam_conninfo = NULL; + +/* Some PAM implementations don't implement this */ +#ifndef HAVE_PAM_GETENVLIST +static char ** +pam_getenvlist(pam_handle_t *pamh) +{ + /* + * XXX - If necessary, we can still support environment passing + * for platforms without pam_getenvlist by searching for known + * env vars (e.g. KRB5CCNAME) from the PAM environment. + */ + return NULL; +} +#endif + +#ifndef HAVE_PAM_PUTENV +static int +pam_putenv(pam_handle_t *pamh, const char *name_value) +{ + return PAM_SUCCESS; +} +#endif /* HAVE_PAM_PUTENV */ + +/* + * Some platforms, notably Solaris, do not enforce password complexity + * rules during pam_chauthtok() if the real uid of the calling process + * is 0, on the assumption that it's being called by "passwd" run by root. + * This wraps pam_chauthtok and sets/restore the real uid so PAM will do + * the right thing. + */ +#ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID +static int +sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags) +{ + int result; + + if (sshpam_authctxt == NULL) + fatal("PAM: sshpam_authctxt not initialized"); + if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1) + fatal("%s: setreuid failed: %s", __func__, strerror(errno)); + result = pam_chauthtok(pamh, flags); + if (setreuid(0, -1) == -1) + fatal("%s: setreuid failed: %s", __func__, strerror(errno)); + return result; +} +# define pam_chauthtok(a,b) (sshpam_chauthtok_ruid((a), (b))) +#endif + +static void +sshpam_password_change_required(int reqd) +{ + extern struct sshauthopt *auth_opts; + static int saved_port, saved_agent, saved_x11; + + debug3("%s %d", __func__, reqd); + if (sshpam_authctxt == NULL) + fatal("%s: PAM authctxt not initialized", __func__); + sshpam_authctxt->force_pwchange = reqd; + if (reqd) { + saved_port = auth_opts->permit_port_forwarding_flag; + saved_agent = auth_opts->permit_agent_forwarding_flag; + saved_x11 = auth_opts->permit_x11_forwarding_flag; + auth_opts->permit_port_forwarding_flag = 0; + auth_opts->permit_agent_forwarding_flag = 0; + auth_opts->permit_x11_forwarding_flag = 0; + } else { + if (saved_port) + auth_opts->permit_port_forwarding_flag = saved_port; + if (saved_agent) + auth_opts->permit_agent_forwarding_flag = saved_agent; + if (saved_x11) + auth_opts->permit_x11_forwarding_flag = saved_x11; + } +} + +/* Import regular and PAM environment from subprocess */ +static void +import_environments(struct sshbuf *b) +{ + char *env; + u_int n, i, num_env; + int r; + + debug3("PAM: %s entering", __func__); + +#ifndef UNSUPPORTED_POSIX_THREADS_HACK + /* Import variables set by do_pam_account */ + if ((r = sshbuf_get_u32(b, &n)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + if (n > INT_MAX) + fatal("%s: invalid PAM account status %u", __func__, n); + sshpam_account_status = (int)n; + if ((r = sshbuf_get_u32(b, &n)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + sshpam_password_change_required(n != 0); + + /* Import environment from subprocess */ + if ((r = sshbuf_get_u32(b, &num_env)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + if (num_env > 1024) + fatal("%s: received %u environment variables, expected <= 1024", + __func__, num_env); + sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env)); + debug3("PAM: num env strings %d", num_env); + for(i = 0; i < num_env; i++) { + if ((r = sshbuf_get_cstring(b, &(sshpam_env[i]), NULL)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + } + sshpam_env[num_env] = NULL; + + /* Import PAM environment from subprocess */ + if ((r = sshbuf_get_u32(b, &num_env)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + debug("PAM: num PAM env strings %d", num_env); + for (i = 0; i < num_env; i++) { + if ((r = sshbuf_get_cstring(b, &env, NULL)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + /* Errors are not fatal here */ + if ((r = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) { + error("PAM: pam_putenv: %s", + pam_strerror(sshpam_handle, r)); + } + /* + * XXX this possibly leaks env because it is not documented + * what pam_putenv() does with it. Does it copy it? Does it + * take ownweship? We don't know, so it's safest just to leak. + */ + } +#endif +} + +/* + * Conversation function for authentication thread. + */ +static int +sshpam_thread_conv(int n, sshpam_const struct pam_message **msg, + struct pam_response **resp, void *data) +{ + struct sshbuf *buffer; + struct pam_ctxt *ctxt; + struct pam_response *reply; + int r, i; + u_char status; + + debug3("PAM: %s entering, %d messages", __func__, n); + *resp = NULL; + + if (data == NULL) { + error("PAM: conversation function passed a null context"); + return (PAM_CONV_ERR); + } + ctxt = data; + if (n <= 0 || n > PAM_MAX_NUM_MSG) + return (PAM_CONV_ERR); + + if ((reply = calloc(n, sizeof(*reply))) == NULL) + return PAM_CONV_ERR; + if ((buffer = sshbuf_new()) == NULL) { + free(reply); + return PAM_CONV_ERR; + } + + for (i = 0; i < n; ++i) { + switch (PAM_MSG_MEMBER(msg, i, msg_style)) { + case PAM_PROMPT_ECHO_OFF: + case PAM_PROMPT_ECHO_ON: + if ((r = sshbuf_put_cstring(buffer, + PAM_MSG_MEMBER(msg, i, msg))) != 0) + fatal("%s: buffer error: %s", + __func__, ssh_err(r)); + if (ssh_msg_send(ctxt->pam_csock, + PAM_MSG_MEMBER(msg, i, msg_style), buffer) == -1) + goto fail; + + if (ssh_msg_recv(ctxt->pam_csock, buffer) == -1) + goto fail; + if ((r = sshbuf_get_u8(buffer, &status)) != 0) + fatal("%s: buffer error: %s", + __func__, ssh_err(r)); + if (status != PAM_AUTHTOK) + goto fail; + if ((r = sshbuf_get_cstring(buffer, + &reply[i].resp, NULL)) != 0) + fatal("%s: buffer error: %s", + __func__, ssh_err(r)); + break; + case PAM_ERROR_MSG: + case PAM_TEXT_INFO: + if ((r = sshbuf_put_cstring(buffer, + PAM_MSG_MEMBER(msg, i, msg))) != 0) + fatal("%s: buffer error: %s", + __func__, ssh_err(r)); + if (ssh_msg_send(ctxt->pam_csock, + PAM_MSG_MEMBER(msg, i, msg_style), buffer) == -1) + goto fail; + break; + default: + goto fail; + } + sshbuf_reset(buffer); + } + sshbuf_free(buffer); + *resp = reply; + return (PAM_SUCCESS); + + fail: + for(i = 0; i < n; i++) { + free(reply[i].resp); + } + free(reply); + sshbuf_free(buffer); + return (PAM_CONV_ERR); +} + +/* + * Authentication thread. + */ +static void * +sshpam_thread(void *ctxtp) +{ + struct pam_ctxt *ctxt = ctxtp; + struct sshbuf *buffer = NULL; + struct pam_conv sshpam_conv; + int r, flags = (options.permit_empty_passwd == 0 ? + PAM_DISALLOW_NULL_AUTHTOK : 0); +#ifndef UNSUPPORTED_POSIX_THREADS_HACK + extern char **environ; + char **env_from_pam; + u_int i; + const char *pam_user; + const char **ptr_pam_user = &pam_user; + char *tz = getenv("TZ"); + + sshpam_err = pam_get_item(sshpam_handle, PAM_USER, + (sshpam_const void **)ptr_pam_user); + if (sshpam_err != PAM_SUCCESS) + goto auth_fail; + + environ[0] = NULL; + if (tz != NULL) + if (setenv("TZ", tz, 1) == -1) + error("PAM: could not set TZ environment: %s", + strerror(errno)); + + if (sshpam_authctxt != NULL) { + setproctitle("%s [pam]", + sshpam_authctxt->valid ? pam_user : "unknown"); + } +#endif + + sshpam_conv.conv = sshpam_thread_conv; + sshpam_conv.appdata_ptr = ctxt; + + if (sshpam_authctxt == NULL) + fatal("%s: PAM authctxt not initialized", __func__); + + if ((buffer = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __func__); + + sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, + (const void *)&sshpam_conv); + if (sshpam_err != PAM_SUCCESS) + goto auth_fail; + sshpam_err = pam_authenticate(sshpam_handle, flags); + if (sshpam_err == PAM_MAXTRIES) + sshpam_set_maxtries_reached(1); + if (sshpam_err != PAM_SUCCESS) + goto auth_fail; + + if (!do_pam_account()) { + sshpam_err = PAM_ACCT_EXPIRED; + goto auth_fail; + } + if (sshpam_authctxt->force_pwchange) { + sshpam_err = pam_chauthtok(sshpam_handle, + PAM_CHANGE_EXPIRED_AUTHTOK); + if (sshpam_err != PAM_SUCCESS) + goto auth_fail; + sshpam_password_change_required(0); + } + + if ((r = sshbuf_put_cstring(buffer, "OK")) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + +#ifndef UNSUPPORTED_POSIX_THREADS_HACK + /* Export variables set by do_pam_account */ + if ((r = sshbuf_put_u32(buffer, sshpam_account_status)) != 0 || + (r = sshbuf_put_u32(buffer, sshpam_authctxt->force_pwchange)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + + /* Export any environment strings set in child */ + for (i = 0; environ[i] != NULL; i++) { + /* Count */ + if (i > INT_MAX) + fatal("%s: too many environment strings", __func__); + } + if ((r = sshbuf_put_u32(buffer, i)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + for (i = 0; environ[i] != NULL; i++) { + if ((r = sshbuf_put_cstring(buffer, environ[i])) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + } + /* Export any environment strings set by PAM in child */ + env_from_pam = pam_getenvlist(sshpam_handle); + for (i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) { + /* Count */ + if (i > INT_MAX) + fatal("%s: too many PAM environment strings", __func__); + } + if ((r = sshbuf_put_u32(buffer, i)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + for (i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) { + if ((r = sshbuf_put_cstring(buffer, env_from_pam[i])) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + } +#endif /* UNSUPPORTED_POSIX_THREADS_HACK */ + + /* XXX - can't do much about an error here */ + ssh_msg_send(ctxt->pam_csock, sshpam_err, buffer); + sshbuf_free(buffer); + pthread_exit(NULL); + + auth_fail: + if ((r = sshbuf_put_cstring(buffer, + pam_strerror(sshpam_handle, sshpam_err))) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + /* XXX - can't do much about an error here */ + if (sshpam_err == PAM_ACCT_EXPIRED) + ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, buffer); + else if (sshpam_maxtries_reached) + ssh_msg_send(ctxt->pam_csock, PAM_MAXTRIES, buffer); + else + ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, buffer); + sshbuf_free(buffer); + pthread_exit(NULL); + + return (NULL); /* Avoid warning for non-pthread case */ +} + +void +sshpam_thread_cleanup(void) +{ + struct pam_ctxt *ctxt = cleanup_ctxt; + + debug3("PAM: %s entering", __func__); + if (ctxt != NULL && ctxt->pam_thread != 0) { + pthread_cancel(ctxt->pam_thread); + pthread_join(ctxt->pam_thread, NULL); + close(ctxt->pam_psock); + close(ctxt->pam_csock); + memset(ctxt, 0, sizeof(*ctxt)); + cleanup_ctxt = NULL; + } +} + +static int +sshpam_null_conv(int n, sshpam_const struct pam_message **msg, + struct pam_response **resp, void *data) +{ + debug3("PAM: %s entering, %d messages", __func__, n); + return (PAM_CONV_ERR); +} + +static struct pam_conv null_conv = { sshpam_null_conv, NULL }; + +static int +sshpam_store_conv(int n, sshpam_const struct pam_message **msg, + struct pam_response **resp, void *data) +{ + struct pam_response *reply; + int r, i; + + debug3("PAM: %s called with %d messages", __func__, n); + *resp = NULL; + + if (n <= 0 || n > PAM_MAX_NUM_MSG) + return (PAM_CONV_ERR); + + if ((reply = calloc(n, sizeof(*reply))) == NULL) + return (PAM_CONV_ERR); + + for (i = 0; i < n; ++i) { + switch (PAM_MSG_MEMBER(msg, i, msg_style)) { + case PAM_ERROR_MSG: + case PAM_TEXT_INFO: + if ((r = sshbuf_putf(loginmsg, "%s\n", + PAM_MSG_MEMBER(msg, i, msg))) != 0) + fatal("%s: buffer error: %s", + __func__, ssh_err(r)); + reply[i].resp_retcode = PAM_SUCCESS; + break; + default: + goto fail; + } + } + *resp = reply; + return (PAM_SUCCESS); + + fail: + for(i = 0; i < n; i++) { + free(reply[i].resp); + } + free(reply); + return (PAM_CONV_ERR); +} + +static struct pam_conv store_conv = { sshpam_store_conv, NULL }; + +void +sshpam_cleanup(void) +{ + if (sshpam_handle == NULL || (use_privsep && !mm_is_monitor())) + return; + debug("PAM: cleanup"); + pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv); + if (sshpam_session_open) { + debug("PAM: closing session"); + pam_close_session(sshpam_handle, PAM_SILENT); + sshpam_session_open = 0; + } + if (sshpam_cred_established) { + debug("PAM: deleting credentials"); + pam_setcred(sshpam_handle, PAM_DELETE_CRED); + sshpam_cred_established = 0; + } + sshpam_authenticated = 0; + pam_end(sshpam_handle, sshpam_err); + sshpam_handle = NULL; +} + +static int +sshpam_init(struct ssh *ssh, Authctxt *authctxt) +{ + const char *pam_user, *user = authctxt->user; + const char **ptr_pam_user = &pam_user; + + if (sshpam_handle == NULL) { + if (ssh == NULL) { + fatal("%s: called initially with no " + "packet context", __func__); + } + } if (sshpam_handle != NULL) { + /* We already have a PAM context; check if the user matches */ + sshpam_err = pam_get_item(sshpam_handle, + PAM_USER, (sshpam_const void **)ptr_pam_user); + if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0) + return (0); + pam_end(sshpam_handle, sshpam_err); + sshpam_handle = NULL; + } + debug("PAM: initializing for \"%s\"", user); + sshpam_err = + pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle); + sshpam_authctxt = authctxt; + + if (sshpam_err != PAM_SUCCESS) { + pam_end(sshpam_handle, sshpam_err); + sshpam_handle = NULL; + return (-1); + } + + if (ssh != NULL && sshpam_rhost == NULL) { + /* + * We need to cache these as we don't have packet context + * during the kbdint flow. + */ + sshpam_rhost = xstrdup(auth_get_canonical_hostname(ssh, + options.use_dns)); + sshpam_laddr = get_local_ipaddr( + ssh_packet_get_connection_in(ssh)); + xasprintf(&sshpam_conninfo, "SSH_CONNECTION=%.50s %d %.50s %d", + ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), + sshpam_laddr, ssh_local_port(ssh)); + } + if (sshpam_rhost != NULL) { + debug("PAM: setting PAM_RHOST to \"%s\"", sshpam_rhost); + sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, + sshpam_rhost); + if (sshpam_err != PAM_SUCCESS) { + pam_end(sshpam_handle, sshpam_err); + sshpam_handle = NULL; + return (-1); + } + /* Put SSH_CONNECTION in the PAM environment too */ + pam_putenv(sshpam_handle, sshpam_conninfo); + } + +#ifdef PAM_TTY_KLUDGE + /* + * Some silly PAM modules (e.g. pam_time) require a TTY to operate. + * sshd doesn't set the tty until too late in the auth process and + * may not even set one (for tty-less connections) + */ + debug("PAM: setting PAM_TTY to \"ssh\""); + sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh"); + if (sshpam_err != PAM_SUCCESS) { + pam_end(sshpam_handle, sshpam_err); + sshpam_handle = NULL; + return (-1); + } +#endif + return (0); +} + +static void +expose_authinfo(const char *caller) +{ + char *auth_info; + + /* + * Expose authentication information to PAM. + * The environment variable is versioned. Please increment the + * version suffix if the format of session_info changes. + */ + if (sshpam_authctxt->session_info == NULL) + auth_info = xstrdup(""); + else if ((auth_info = sshbuf_dup_string( + sshpam_authctxt->session_info)) == NULL) + fatal("%s: sshbuf_dup_string failed", __func__); + + debug2("%s: auth information in SSH_AUTH_INFO_0", caller); + do_pam_putenv("SSH_AUTH_INFO_0", auth_info); + free(auth_info); +} + +static void * +sshpam_init_ctx(Authctxt *authctxt) +{ + struct pam_ctxt *ctxt; + int result, socks[2]; + + debug3("PAM: %s entering", __func__); + /* + * Refuse to start if we don't have PAM enabled or do_pam_account + * has previously failed. + */ + if (!options.use_pam || sshpam_account_status == 0) + return NULL; + + /* Initialize PAM */ + if (sshpam_init(NULL, authctxt) == -1) { + error("PAM: initialization failed"); + return (NULL); + } + + expose_authinfo(__func__); + ctxt = xcalloc(1, sizeof *ctxt); + + /* Start the authentication thread */ + if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) { + error("PAM: failed create sockets: %s", strerror(errno)); + free(ctxt); + return (NULL); + } + ctxt->pam_psock = socks[0]; + ctxt->pam_csock = socks[1]; + result = pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt); + if (result != 0) { + error("PAM: failed to start authentication thread: %s", + strerror(result)); + close(socks[0]); + close(socks[1]); + free(ctxt); + return (NULL); + } + cleanup_ctxt = ctxt; + return (ctxt); +} + +static int +sshpam_query(void *ctx, char **name, char **info, + u_int *num, char ***prompts, u_int **echo_on) +{ + struct sshbuf *buffer; + struct pam_ctxt *ctxt = ctx; + size_t plen; + u_char type; + char *msg; + size_t len, mlen; + int r; + + debug3("PAM: %s entering", __func__); + if ((buffer = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __func__); + *name = xstrdup(""); + *info = xstrdup(""); + *prompts = xmalloc(sizeof(char *)); + **prompts = NULL; + plen = 0; + *echo_on = xmalloc(sizeof(u_int)); + while (ssh_msg_recv(ctxt->pam_psock, buffer) == 0) { + if ((r = sshbuf_get_u8(buffer, &type)) != 0 || + (r = sshbuf_get_cstring(buffer, &msg, &mlen)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + switch (type) { + case PAM_PROMPT_ECHO_ON: + case PAM_PROMPT_ECHO_OFF: + *num = 1; + len = plen + mlen + 1; + **prompts = xreallocarray(**prompts, 1, len); + strlcpy(**prompts + plen, msg, len - plen); + plen += mlen; + **echo_on = (type == PAM_PROMPT_ECHO_ON); + free(msg); + sshbuf_free(buffer); + return (0); + case PAM_ERROR_MSG: + case PAM_TEXT_INFO: + /* accumulate messages */ + len = plen + mlen + 2; + **prompts = xreallocarray(**prompts, 1, len); + strlcpy(**prompts + plen, msg, len - plen); + plen += mlen; + strlcat(**prompts + plen, "\n", len - plen); + plen++; + free(msg); + break; + case PAM_ACCT_EXPIRED: + case PAM_MAXTRIES: + if (type == PAM_ACCT_EXPIRED) + sshpam_account_status = 0; + if (type == PAM_MAXTRIES) + sshpam_set_maxtries_reached(1); + /* FALLTHROUGH */ + case PAM_AUTH_ERR: + debug3("PAM: %s", pam_strerror(sshpam_handle, type)); + if (**prompts != NULL && strlen(**prompts) != 0) { + *info = **prompts; + **prompts = NULL; + *num = 0; + **echo_on = 0; + ctxt->pam_done = -1; + free(msg); + sshbuf_free(buffer); + return 0; + } + /* FALLTHROUGH */ + case PAM_SUCCESS: + if (**prompts != NULL) { + /* drain any accumulated messages */ + debug("PAM: %s", **prompts); + if ((r = sshbuf_put(loginmsg, **prompts, + strlen(**prompts))) != 0) + fatal("%s: buffer error: %s", + __func__, ssh_err(r)); + free(**prompts); + **prompts = NULL; + } + if (type == PAM_SUCCESS) { + if (!sshpam_authctxt->valid || + (sshpam_authctxt->pw->pw_uid == 0 && + options.permit_root_login != PERMIT_YES)) + fatal("Internal error: PAM auth " + "succeeded when it should have " + "failed"); + import_environments(buffer); + *num = 0; + **echo_on = 0; + ctxt->pam_done = 1; + free(msg); + sshbuf_free(buffer); + return (0); + } + error("PAM: %s for %s%.100s from %.100s", msg, + sshpam_authctxt->valid ? "" : "illegal user ", + sshpam_authctxt->user, sshpam_rhost); + /* FALLTHROUGH */ + default: + *num = 0; + **echo_on = 0; + free(msg); + ctxt->pam_done = -1; + sshbuf_free(buffer); + return (-1); + } + } + sshbuf_free(buffer); + return (-1); +} + +/* + * Returns a junk password of identical length to that the user supplied. + * Used to mitigate timing attacks against crypt(3)/PAM stacks that + * vary processing time in proportion to password length. + */ +static char * +fake_password(const char *wire_password) +{ + const char junk[] = "\b\n\r\177INCORRECT"; + char *ret = NULL; + size_t i, l = wire_password != NULL ? strlen(wire_password) : 0; + + if (l >= INT_MAX) + fatal("%s: password length too long: %zu", __func__, l); + + ret = malloc(l + 1); + if (ret == NULL) + return NULL; + for (i = 0; i < l; i++) + ret[i] = junk[i % (sizeof(junk) - 1)]; + ret[i] = '\0'; + return ret; +} + +/* XXX - see also comment in auth-chall.c:verify_response */ +static int +sshpam_respond(void *ctx, u_int num, char **resp) +{ + struct sshbuf *buffer; + struct pam_ctxt *ctxt = ctx; + char *fake; + int r; + + debug2("PAM: %s entering, %u responses", __func__, num); + switch (ctxt->pam_done) { + case 1: + sshpam_authenticated = 1; + return (0); + case 0: + break; + default: + return (-1); + } + if (num != 1) { + error("PAM: expected one response, got %u", num); + return (-1); + } + if ((buffer = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __func__); + if (sshpam_authctxt->valid && + (sshpam_authctxt->pw->pw_uid != 0 || + options.permit_root_login == PERMIT_YES)) { + if ((r = sshbuf_put_cstring(buffer, *resp)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + } else { + fake = fake_password(*resp); + if ((r = sshbuf_put_cstring(buffer, fake)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + free(fake); + } + if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, buffer) == -1) { + sshbuf_free(buffer); + return (-1); + } + sshbuf_free(buffer); + return (1); +} + +static void +sshpam_free_ctx(void *ctxtp) +{ + struct pam_ctxt *ctxt = ctxtp; + + debug3("PAM: %s entering", __func__); + sshpam_thread_cleanup(); + free(ctxt); + /* + * We don't call sshpam_cleanup() here because we may need the PAM + * handle at a later stage, e.g. when setting up a session. It's + * still on the cleanup list, so pam_end() *will* be called before + * the server process terminates. + */ +} + +KbdintDevice sshpam_device = { + "pam", + sshpam_init_ctx, + sshpam_query, + sshpam_respond, + sshpam_free_ctx +}; + +KbdintDevice mm_sshpam_device = { + "pam", + mm_sshpam_init_ctx, + mm_sshpam_query, + mm_sshpam_respond, + mm_sshpam_free_ctx +}; + +/* + * This replaces auth-pam.c + */ +void +start_pam(struct ssh *ssh) +{ + Authctxt *authctxt = (Authctxt *)ssh->authctxt; + + if (!options.use_pam) + fatal("PAM: initialisation requested when UsePAM=no"); + + if (sshpam_init(ssh, authctxt) == -1) + fatal("PAM: initialisation failed"); +} + +void +finish_pam(void) +{ + sshpam_cleanup(); +} + + +u_int +do_pam_account(void) +{ + debug("%s: called", __func__); + if (sshpam_account_status != -1) + return (sshpam_account_status); + + expose_authinfo(__func__); + + sshpam_err = pam_acct_mgmt(sshpam_handle, 0); + debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err, + pam_strerror(sshpam_handle, sshpam_err)); + + if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) { + sshpam_account_status = 0; + return (sshpam_account_status); + } + + if (sshpam_err == PAM_NEW_AUTHTOK_REQD) + sshpam_password_change_required(1); + + sshpam_account_status = 1; + return (sshpam_account_status); +} + +void +do_pam_setcred(int init) +{ + sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, + (const void *)&store_conv); + if (sshpam_err != PAM_SUCCESS) + fatal("PAM: failed to set PAM_CONV: %s", + pam_strerror(sshpam_handle, sshpam_err)); + if (init) { + debug("PAM: establishing credentials"); + sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED); + } else { + debug("PAM: reinitializing credentials"); + sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED); + } + if (sshpam_err == PAM_SUCCESS) { + sshpam_cred_established = 1; + return; + } + if (sshpam_authenticated) + fatal("PAM: pam_setcred(): %s", + pam_strerror(sshpam_handle, sshpam_err)); + else + debug("PAM: pam_setcred(): %s", + pam_strerror(sshpam_handle, sshpam_err)); +} + +static int +sshpam_tty_conv(int n, sshpam_const struct pam_message **msg, + struct pam_response **resp, void *data) +{ + char input[PAM_MAX_MSG_SIZE]; + struct pam_response *reply; + int i; + + debug3("PAM: %s called with %d messages", __func__, n); + + *resp = NULL; + + if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO)) + return (PAM_CONV_ERR); + + if ((reply = calloc(n, sizeof(*reply))) == NULL) + return (PAM_CONV_ERR); + + for (i = 0; i < n; ++i) { + switch (PAM_MSG_MEMBER(msg, i, msg_style)) { + case PAM_PROMPT_ECHO_OFF: + reply[i].resp = + read_passphrase(PAM_MSG_MEMBER(msg, i, msg), + RP_ALLOW_STDIN); + reply[i].resp_retcode = PAM_SUCCESS; + break; + case PAM_PROMPT_ECHO_ON: + fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg)); + if (fgets(input, sizeof input, stdin) == NULL) + input[0] = '\0'; + if ((reply[i].resp = strdup(input)) == NULL) + goto fail; + reply[i].resp_retcode = PAM_SUCCESS; + break; + case PAM_ERROR_MSG: + case PAM_TEXT_INFO: + fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg)); + reply[i].resp_retcode = PAM_SUCCESS; + break; + default: + goto fail; + } + } + *resp = reply; + return (PAM_SUCCESS); + + fail: + for(i = 0; i < n; i++) { + free(reply[i].resp); + } + free(reply); + return (PAM_CONV_ERR); +} + +static struct pam_conv tty_conv = { sshpam_tty_conv, NULL }; + +/* + * XXX this should be done in the authentication phase, but ssh1 doesn't + * support that + */ +void +do_pam_chauthtok(void) +{ + if (use_privsep) + fatal("Password expired (unable to change with privsep)"); + sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, + (const void *)&tty_conv); + if (sshpam_err != PAM_SUCCESS) + fatal("PAM: failed to set PAM_CONV: %s", + pam_strerror(sshpam_handle, sshpam_err)); + debug("PAM: changing password"); + sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK); + if (sshpam_err != PAM_SUCCESS) + fatal("PAM: pam_chauthtok(): %s", + pam_strerror(sshpam_handle, sshpam_err)); +} + +void +do_pam_session(struct ssh *ssh) +{ + debug3("PAM: opening session"); + + expose_authinfo(__func__); + + sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, + (const void *)&store_conv); + if (sshpam_err != PAM_SUCCESS) + fatal("PAM: failed to set PAM_CONV: %s", + pam_strerror(sshpam_handle, sshpam_err)); + sshpam_err = pam_open_session(sshpam_handle, 0); + if (sshpam_err == PAM_SUCCESS) + sshpam_session_open = 1; + else { + sshpam_session_open = 0; + auth_restrict_session(ssh); + error("PAM: pam_open_session(): %s", + pam_strerror(sshpam_handle, sshpam_err)); + } + +} + +int +is_pam_session_open(void) +{ + return sshpam_session_open; +} + +/* + * Set a PAM environment string. We need to do this so that the session + * modules can handle things like Kerberos/GSI credentials that appear + * during the ssh authentication process. + */ +int +do_pam_putenv(char *name, char *value) +{ + int ret = 1; + char *compound; + size_t len; + + len = strlen(name) + strlen(value) + 2; + compound = xmalloc(len); + + snprintf(compound, len, "%s=%s", name, value); + ret = pam_putenv(sshpam_handle, compound); + free(compound); + + return (ret); +} + +char ** +fetch_pam_child_environment(void) +{ + return sshpam_env; +} + +char ** +fetch_pam_environment(void) +{ + return (pam_getenvlist(sshpam_handle)); +} + +void +free_pam_environment(char **env) +{ + char **envp; + + if (env == NULL) + return; + + for (envp = env; *envp; envp++) + free(*envp); + free(env); +} + +/* + * "Blind" conversation function for password authentication. Assumes that + * echo-off prompts are for the password and stores messages for later + * display. + */ +static int +sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg, + struct pam_response **resp, void *data) +{ + struct pam_response *reply; + int r, i; + size_t len; + + debug3("PAM: %s called with %d messages", __func__, n); + + *resp = NULL; + + if (n <= 0 || n > PAM_MAX_NUM_MSG) + return (PAM_CONV_ERR); + + if ((reply = calloc(n, sizeof(*reply))) == NULL) + return (PAM_CONV_ERR); + + for (i = 0; i < n; ++i) { + switch (PAM_MSG_MEMBER(msg, i, msg_style)) { + case PAM_PROMPT_ECHO_OFF: + if (sshpam_password == NULL) + goto fail; + if ((reply[i].resp = strdup(sshpam_password)) == NULL) + goto fail; + reply[i].resp_retcode = PAM_SUCCESS; + break; + case PAM_ERROR_MSG: + case PAM_TEXT_INFO: + len = strlen(PAM_MSG_MEMBER(msg, i, msg)); + if (len > 0) { + if ((r = sshbuf_putf(loginmsg, "%s\n", + PAM_MSG_MEMBER(msg, i, msg))) != 0) + fatal("%s: buffer error: %s", + __func__, ssh_err(r)); + } + if ((reply[i].resp = strdup("")) == NULL) + goto fail; + reply[i].resp_retcode = PAM_SUCCESS; + break; + default: + goto fail; + } + } + *resp = reply; + return (PAM_SUCCESS); + + fail: + for(i = 0; i < n; i++) { + free(reply[i].resp); + } + free(reply); + return (PAM_CONV_ERR); +} + +static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL }; + +/* + * Attempt password authentication via PAM + */ +int +sshpam_auth_passwd(Authctxt *authctxt, const char *password) +{ + int flags = (options.permit_empty_passwd == 0 ? + PAM_DISALLOW_NULL_AUTHTOK : 0); + char *fake = NULL; + + if (!options.use_pam || sshpam_handle == NULL) + fatal("PAM: %s called when PAM disabled or failed to " + "initialise.", __func__); + + sshpam_password = password; + sshpam_authctxt = authctxt; + + /* + * If the user logging in is invalid, or is root but is not permitted + * by PermitRootLogin, use an invalid password to prevent leaking + * information via timing (eg if the PAM config has a delay on fail). + */ + if (!authctxt->valid || (authctxt->pw->pw_uid == 0 && + options.permit_root_login != PERMIT_YES)) + sshpam_password = fake = fake_password(password); + + sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, + (const void *)&passwd_conv); + if (sshpam_err != PAM_SUCCESS) + fatal("PAM: %s: failed to set PAM_CONV: %s", __func__, + pam_strerror(sshpam_handle, sshpam_err)); + + sshpam_err = pam_authenticate(sshpam_handle, flags); + sshpam_password = NULL; + free(fake); + if (sshpam_err == PAM_MAXTRIES) + sshpam_set_maxtries_reached(1); + if (sshpam_err == PAM_SUCCESS && authctxt->valid) { + debug("PAM: password authentication accepted for %.100s", + authctxt->user); + return 1; + } else { + debug("PAM: password authentication failed for %.100s: %s", + authctxt->valid ? authctxt->user : "an illegal user", + pam_strerror(sshpam_handle, sshpam_err)); + return 0; + } +} + +int +sshpam_get_maxtries_reached(void) +{ + return sshpam_maxtries_reached; +} + +void +sshpam_set_maxtries_reached(int reached) +{ + if (reached == 0 || sshpam_maxtries_reached) + return; + sshpam_maxtries_reached = 1; + options.password_authentication = 0; + options.kbd_interactive_authentication = 0; + options.challenge_response_authentication = 0; +} +#endif /* USE_PAM */ |