/* $NetBSD: auth-pam.c,v 1.20.2.1 2023/11/02 22:15:21 sborrill Exp $ */ /*- * 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 * Copyright (c) 2003,2004 Darren Tucker * * 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" /* * NetBSD local changes */ __RCSID("$NetBSD: auth-pam.c,v 1.20.2.1 2023/11/02 22:15:21 sborrill Exp $"); #define _LIB_PTHREAD_H #undef USE_POSIX_THREADS /* Not yet */ #define HAVE_SECURITY_PAM_APPL_H #define HAVE_PAM_GETENVLIST #define HAVE_PAM_PUTENV #define sshpam_const const /* LinuxPAM, OpenPAM */ #define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member) #define SSHD_PAM_SERVICE getprogname() /* end NetBSD local changes */ #include #include #include #include #include #include #include #include #include #include #include #ifdef USE_PAM #if defined(HAVE_SECURITY_PAM_APPL_H) #include #elif defined (HAVE_PAM_PAM_APPL_H) #include #endif #if !defined(SSHD_PAM_SERVICE) extern char *__progname; # define SSHD_PAM_SERVICE __progname #endif #ifndef __NetBSD__ /* 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 #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" #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 #error "foo" #include /* * 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 */ __dead 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; /* 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_f("received %u environment variables, expected <= 1024", num_env); } sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env)); debug3("PAM: num env strings %u", 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)); if (num_env > 1024) { fatal_f("received %u PAM env variables, expected <= 1024", num_env); } debug("PAM: num PAM env strings %u", 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)); #ifdef HAVE_PAM_PUTENV /* Errors are not fatal here */ if ((r = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) { error("PAM: pam_putenv: %s", pam_strerror(sshpam_handle, r)); } #endif /* * 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; int r; #if defined(PAM_SUN_CODEBASE) && defined(PAM_MAX_RESP_SIZE) /* Protect buggy PAM implementations from excessively long usernames */ if (strlen(user) >= PAM_MAX_RESP_SIZE) fatal("Username too long from %s port %d", ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); #endif 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)); } 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); } } if (ssh != NULL && sshpam_laddr != NULL) { char *conninfo; /* Put SSH_CONNECTION in the PAM environment too */ xasprintf(&conninfo, "SSH_CONNECTION=%.50s %d %.50s %d", ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), sshpam_laddr, ssh_local_port(ssh)); if ((r = pam_putenv(sshpam_handle, conninfo)) != PAM_SUCCESS) logit("pam_putenv: %s", pam_strerror(sshpam_handle, r)); free(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, nmesg = 0; 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 (++nmesg > PAM_MAX_NUM_MSG) fatal_f("too many query messages"); 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) { free(*info); *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(const char *name, char *value) { int ret = 1; #ifdef HAVE_PAM_PUTENV 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); #endif 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; } #endif /* USE_PAM */