/* * Copyright (c) 2000 Damien Miller. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include "includes.h" #ifdef USE_PAM #include #include "ssh.h" #include "xmalloc.h" #include "servconf.h" RCSID("$FreeBSD$"); #define NEW_AUTHTOK_MSG \ "Warning: Your password has expired, please change it now" #define SSHD_PAM_SERVICE "sshd" #define PAM_STRERROR(a, b) pam_strerror((a), (b)) /* Callbacks */ static int pamconv(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *appdata_ptr); void pam_cleanup_proc(void *context); void pam_msg_cat(const char *msg); /* module-local variables */ static struct pam_conv conv = { pamconv, NULL }; static pam_handle_t *pamh = NULL; static const char *pampasswd = NULL; static char *pam_msg = NULL; /* states for pamconv() */ typedef enum { INITIAL_LOGIN, OTHER } pamstates; static pamstates pamstate = INITIAL_LOGIN; /* remember whether pam_acct_mgmt() returned PAM_NEWAUTHTOK_REQD */ static int password_change_required = 0; /* * PAM conversation function. * There are two states this can run in. * * INITIAL_LOGIN mode simply feeds the password from the client into * PAM in response to PAM_PROMPT_ECHO_OFF, and collects output * messages with pam_msg_cat(). This is used during initial * authentication to bypass the normal PAM password prompt. * * OTHER mode handles PAM_PROMPT_ECHO_OFF with read_passphrase(prompt, 1) * and outputs messages to stderr. This mode is used if pam_chauthtok() * is called to update expired passwords. */ static int pamconv(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *appdata_ptr) { struct pam_response *reply; int count; char buf[1024]; /* PAM will free this later */ reply = malloc(num_msg * sizeof(*reply)); if (reply == NULL) return PAM_CONV_ERR; for (count = 0; count < num_msg; count++) { switch ((*msg)[count].msg_style) { case PAM_PROMPT_ECHO_ON: if (pamstate == INITIAL_LOGIN) { free(reply); return PAM_CONV_ERR; } else { fputs((*msg)[count].msg, stderr); fgets(buf, sizeof(buf), stdin); reply[count].resp = xstrdup(buf); reply[count].resp_retcode = PAM_SUCCESS; break; } case PAM_PROMPT_ECHO_OFF: if (pamstate == INITIAL_LOGIN) { if (pampasswd == NULL) { free(reply); return PAM_CONV_ERR; } reply[count].resp = xstrdup(pampasswd); } else { reply[count].resp = xstrdup(read_passphrase((*msg)[count].msg, 1)); } reply[count].resp_retcode = PAM_SUCCESS; break; case PAM_ERROR_MSG: case PAM_TEXT_INFO: if ((*msg)[count].msg != NULL) { if (pamstate == INITIAL_LOGIN) pam_msg_cat((*msg)[count].msg); else { fputs((*msg)[count].msg, stderr); fputs("\n", stderr); } } reply[count].resp = xstrdup(""); reply[count].resp_retcode = PAM_SUCCESS; break; default: free(reply); return PAM_CONV_ERR; } } *resp = reply; return PAM_SUCCESS; } /* Called at exit to cleanly shutdown PAM */ void pam_cleanup_proc(void *context) { int pam_retval; if (pamh != NULL) { pam_retval = pam_close_session(pamh, 0); if (pam_retval != PAM_SUCCESS) { log("Cannot close PAM session[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } pam_retval = pam_setcred(pamh, PAM_DELETE_CRED); if (pam_retval != PAM_SUCCESS) { debug("Cannot delete credentials[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } pam_retval = pam_end(pamh, pam_retval); if (pam_retval != PAM_SUCCESS) { log("Cannot release PAM authentication[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } } } /* Attempt password authentation using PAM */ int auth_pam_password(struct passwd *pw, const char *password) { extern ServerOptions options; int pam_retval; /* deny if no user. */ if (pw == NULL) return 0; if (pw->pw_uid == 0 && options.permit_root_login == 2) return 0; if (*password == '\0' && options.permit_empty_passwd == 0) return 0; pampasswd = password; pamstate = INITIAL_LOGIN; pam_retval = pam_authenticate(pamh, 0); if (pam_retval == PAM_SUCCESS) { debug("PAM Password authentication accepted for user \"%.100s\"", pw->pw_name); return 1; } else { debug("PAM Password authentication for \"%.100s\" failed[%d]: %s", pw->pw_name, pam_retval, PAM_STRERROR(pamh, pam_retval)); return 0; } } /* Do account management using PAM */ int do_pam_account(char *username, char *remote_user) { int pam_retval; debug("PAM setting rhost to \"%.200s\"", get_canonical_hostname()); pam_retval = pam_set_item(pamh, PAM_RHOST, get_canonical_hostname()); if (pam_retval != PAM_SUCCESS) { fatal("PAM set rhost failed[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } if (remote_user != NULL) { debug("PAM setting ruser to \"%.200s\"", remote_user); pam_retval = pam_set_item(pamh, PAM_RUSER, remote_user); if (pam_retval != PAM_SUCCESS) { fatal("PAM set ruser failed[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } } pam_retval = pam_acct_mgmt(pamh, 0); switch (pam_retval) { case PAM_SUCCESS: /* This is what we want */ break; case PAM_NEW_AUTHTOK_REQD: pam_msg_cat(NEW_AUTHTOK_MSG); /* flag that password change is necessary */ password_change_required = 1; break; default: log("PAM rejected by account configuration[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); return(0); } return(1); } /* Do PAM-specific session initialisation */ void do_pam_session(char *username, const char *ttyname) { int pam_retval; if (ttyname != NULL) { debug("PAM setting tty to \"%.200s\"", ttyname); pam_retval = pam_set_item(pamh, PAM_TTY, ttyname); if (pam_retval != PAM_SUCCESS) { fatal("PAM set tty failed[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } } debug("do_pam_session: euid %u, uid %u", geteuid(), getuid()); pam_retval = pam_open_session(pamh, 0); if (pam_retval != PAM_SUCCESS) { fatal("PAM session setup failed[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } } /* Set PAM credentials */ void do_pam_setcred(void) { int pam_retval; debug("PAM establishing creds"); pam_retval = pam_setcred(pamh, PAM_ESTABLISH_CRED); if (pam_retval != PAM_SUCCESS) { fatal("PAM setcred failed[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } } /* accessor function for file scope static variable */ int pam_password_change_required(void) { return password_change_required; } /* * Have user change authentication token if pam_acct_mgmt() indicated * it was expired. This needs to be called after an interactive * session is established and the user's pty is connected to * stdin/stout/stderr. */ void do_pam_chauthtok(void) { int pam_retval; if (password_change_required) { pamstate = OTHER; /* * XXX: should we really loop forever? */ do { pam_retval = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK); if (pam_retval != PAM_SUCCESS) { log("PAM pam_chauthtok failed[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } } while (pam_retval != PAM_SUCCESS); } } /* Cleanly shutdown PAM */ void finish_pam(void) { pam_cleanup_proc(NULL); fatal_remove_cleanup(&pam_cleanup_proc, NULL); } /* Start PAM authentication for specified account */ void start_pam(struct passwd *pw) { int pam_retval; debug("Starting up PAM with username \"%.200s\"", pw->pw_name); pam_retval = pam_start(SSHD_PAM_SERVICE, pw->pw_name, &conv, &pamh); if (pam_retval != PAM_SUCCESS) { fatal("PAM initialisation failed[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } #ifdef PAM_TTY_KLUDGE /* * Some PAM modules (e.g. pam_time) require a TTY to operate, * and will fail in various stupid ways if they don't get one. * sshd doesn't set the tty until too late in the auth process and may * not even need one (for tty-less connections) * Kludge: Set a fake PAM_TTY */ pam_retval = pam_set_item(pamh, PAM_TTY, "ssh"); if (pam_retval != PAM_SUCCESS) { fatal("PAM set tty failed[%d]: %.200s", pam_retval, PAM_STRERROR(pamh, pam_retval)); } #endif /* PAM_TTY_KLUDGE */ fatal_add_cleanup(&pam_cleanup_proc, NULL); } /* Return list of PAM enviornment strings */ char **fetch_pam_environment(void) { #ifdef HAVE_PAM_GETENVLIST return(pam_getenvlist(pamh)); #else /* HAVE_PAM_GETENVLIST */ return(NULL); #endif /* HAVE_PAM_GETENVLIST */ } /* Print any messages that have been generated during authentication */ /* or account checking to stderr */ void print_pam_messages(void) { if (pam_msg != NULL) fputs(pam_msg, stderr); } /* Append a message to the PAM message buffer */ void pam_msg_cat(const char *msg) { char *p; size_t new_msg_len; size_t pam_msg_len; new_msg_len = strlen(msg); if (pam_msg) { pam_msg_len = strlen(pam_msg); pam_msg = xrealloc(pam_msg, new_msg_len + pam_msg_len + 2); p = pam_msg + pam_msg_len; } else { pam_msg = p = xmalloc(new_msg_len + 2); } memcpy(p, msg, new_msg_len); p[new_msg_len] = '\n'; p[new_msg_len + 1] = '\0'; } struct inverted_pam_userdata { /* * Pipe for telling whether we are doing conversation or sending * authentication results. */ int statefd[2]; int challengefd[2]; int responsefd[2]; /* Whether we have sent off our challenge */ int state; }; #define STATE_CONV 1 #define STATE_AUTH_OK 2 #define STATE_AUTH_FAIL 3 int ssh_conv(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *userdata) { int i; FILE *reader; char buf[1024]; struct pam_response *reply = NULL; char state_to_write = STATE_CONV; /* One char to write */ struct inverted_pam_userdata *ud = userdata; char *response = NULL; /* The stdio functions are more convenient for the read half */ reader = fdopen(ud->responsefd[0], "rb"); if (reader == NULL) goto protocol_failure; reply = malloc(num_msg * sizeof(struct pam_response)); if (reply == NULL) return PAM_CONV_ERR; if (write(ud->statefd[1], &state_to_write, 1) != 1) goto protocol_failure; /* * Re-package our data and send it off to our better half (the actual SSH * process) */ if (write(ud->challengefd[1], buf, sprintf(buf, "%d\n", num_msg)) == -1) goto protocol_failure; for (i = 0; i < num_msg; i++) { if (write(ud->challengefd[1], buf, sprintf(buf, "%d\n", msg[i]->msg_style)) == -1) goto protocol_failure; if (write(ud->challengefd[1], buf, sprintf(buf, "%d\n", strlen(msg[i]->msg))) == -1) goto protocol_failure; if (write(ud->challengefd[1], msg[i]->msg, strlen(msg[i]->msg)) == -1) goto protocol_failure; } /* * Read back responses. These may not be as nice as we want, as the SSH * protocol isn't exactly a perfect fit with PAM. */ for (i = 0; i < num_msg; i++) { char buf[1024]; char *endptr; size_t len; /* Length of the response */ switch (msg[i]->msg_style) { case PAM_PROMPT_ECHO_OFF: case PAM_PROMPT_ECHO_ON: if (fgets(buf, sizeof(buf), reader) == NULL) goto protocol_failure; len = (size_t)strtoul(buf, &endptr, 10); /* The length is supposed to stand on a line by itself */ if (endptr == NULL || *endptr != '\n') goto protocol_failure; response = malloc(len+1); if (response == NULL) goto protocol_failure; if (fread(response, len, 1, reader) != 1) goto protocol_failure; response[len] = '\0'; reply[i].resp = response; response = NULL; break; default: reply[i].resp = NULL; break; } } *resp = reply; return PAM_SUCCESS; protocol_failure: free(reply); return PAM_CONV_ERR; } void ipam_free_cookie(struct inverted_pam_cookie *cookie) { struct inverted_pam_userdata *ud; int i; if (cookie == NULL) return; ud = cookie->userdata; cookie->userdata = NULL; /* Free userdata if allocated */ if (ud) { /* Close any opened file descriptors */ if (ud->statefd[0] != -1) close(ud->statefd[0]); if (ud->statefd[1] != -1) close(ud->statefd[1]); if (ud->challengefd[0] != -1) close(ud->challengefd[0]); if (ud->challengefd[1] != -1) close(ud->challengefd[1]); if (ud->responsefd[0] != -1) close(ud->responsefd[0]); if (ud->responsefd[1] != -1) close(ud->responsefd[1]); free(ud); ud = NULL; } /* Now free the normal cookie */ if (cookie->pid != 0 && cookie->pid != -1) { int status; /* XXX Use different signal? */ kill(cookie->pid, SIGKILL); waitpid(cookie->pid, &status, 0); } for (i = 0; i < cookie->num_msg; i++) { if (cookie->resp && cookie->resp[i]) { free(cookie->resp[i]->resp); free(cookie->resp[i]); } if (cookie->msg && cookie->msg[i]) { free((void *)cookie->msg[i]->msg); free(cookie->msg[i]); } } free(cookie->msg); free(cookie->resp); free(cookie); } /* * Do first half of PAM authentication - this comes to the point where * you get a message to send to the user. */ struct inverted_pam_cookie * ipam_start_auth(const char *service, const char *username) { struct inverted_pam_cookie *cookie; struct inverted_pam_userdata *ud; static struct pam_conv conv = { ssh_conv, NULL }; cookie = malloc(sizeof(*cookie)); if (cookie == NULL) return NULL; cookie->state = 0; /* Set up the cookie so ipam_freecookie can be used on it */ cookie->num_msg = 0; cookie->msg = NULL; cookie->resp = NULL; cookie->pid = -1; ud = calloc(sizeof(*ud), 1); if (ud == NULL) { free(cookie); return NULL; } cookie->userdata = ud; ud->statefd[0] = ud->statefd[1] = -1; ud->challengefd[0] = ud->challengefd[1] = -1; ud->responsefd[0] = ud->responsefd[1] = -1; if (pipe(ud->statefd) != 0) { ud->statefd[0] = ud->statefd[1] = -1; ipam_free_cookie(cookie); return NULL; } if (pipe(ud->challengefd) != 0) { ud->challengefd[0] = ud->challengefd[1] = -1; ipam_free_cookie(cookie); return NULL; } if (pipe(ud->responsefd) != 0) { ud->responsefd[0] = ud->responsefd[1] = -1; ipam_free_cookie(cookie); return NULL; } cookie->pid = fork(); if (cookie->pid == -1) { ipam_free_cookie(cookie); return NULL; } else if (cookie->pid != 0) { int num_msgs; /* Number of messages from PAM */ char *endptr; char buf[1024]; FILE *reader; size_t num_msg; int i; char state; /* Which state did the connection just enter? */ /* We are the parent - wait for a call to the communications function to turn up, or the challenge to be finished */ if (read(ud->statefd[0], &state, 1) != 1) { ipam_free_cookie(cookie); return NULL; } cookie->state = state; switch (state) { case STATE_CONV: /* We are running the conversation function */ /* The stdio functions are more convenient for read */ reader = fdopen(ud->challengefd[0], "r"); if (reader == NULL) { ipam_free_cookie(cookie); return NULL; } if (fgets(buf, 4, reader) == NULL) { fclose(reader); ipam_free_cookie(cookie); return NULL; } num_msg = (size_t)strtoul(buf, &endptr, 10); /* The length is supposed to stand on a line by itself */ if (endptr == NULL || *endptr != '\n') { fclose(reader); ipam_free_cookie(cookie); return NULL; } cookie->msg = malloc(sizeof(struct pam_message *) * num_msg); cookie->resp = malloc(sizeof(struct pam_response *) * num_msg); if (cookie->msg == NULL || cookie->resp == NULL) { fclose(reader); ipam_free_cookie(cookie); return NULL; } for (i = 0; i < num_msg; i++) { cookie->msg[i] = malloc(sizeof(struct pam_message)); cookie->resp[i] = malloc(sizeof(struct pam_response)); if (cookie->msg[i] == NULL || cookie->resp[i] == NULL) { for (;;) { free(cookie->msg[i]); free(cookie->resp[i]); if (i == 0) break; i--; } fclose(reader); ipam_free_cookie(cookie); return NULL; } cookie->msg[i]->msg = NULL; cookie->resp[i]->resp = NULL; cookie->resp[i]->resp_retcode = 0; } /* Set up so the above will be freed on failure */ cookie->num_msg = num_msg; /* * We have a an allocated response and message for * each of the entries in the PAM structure - transfer * the data sent to the conversation function over. */ for (i = 0; i < num_msg; i++) { size_t len; if (fgets(buf, sizeof(buf), reader) == NULL) { fclose(reader); ipam_free_cookie(cookie); return NULL; } cookie->msg[i]->msg_style = (size_t)strtoul(buf, &endptr, 10); if (endptr == NULL || *endptr != '\n') { fclose(reader); ipam_free_cookie(cookie); return NULL; } if (fgets(buf, sizeof(buf), reader) == NULL) { fclose(reader); ipam_free_cookie(cookie); return NULL; } len = (size_t)strtoul(buf, &endptr, 10); if (endptr == NULL || *endptr != '\n') { fclose(reader); ipam_free_cookie(cookie); return NULL; } cookie->msg[i]->msg = malloc(len + 1); if (cookie->msg[i]->msg == NULL) { fclose(reader); ipam_free_cookie(cookie); return NULL; } if (fread((char *)cookie->msg[i]->msg, len, 1, reader) != 1) { fclose(reader); ipam_free_cookie(cookie); return NULL; } *(char *)&(cookie->msg[i]->msg[len]) = '\0'; } break; case STATE_AUTH_OK: case STATE_AUTH_FAIL: break; default: /* Internal failure, somehow */ fclose(reader); ipam_free_cookie(cookie); return NULL; } return cookie; } else { /* We are the child */ pam_handle_t *pamh=NULL; int retval; char state; conv.appdata_ptr = ud; retval = pam_start(service, username, &conv, &pamh); /* Is user really user? */ if (retval == PAM_SUCCESS) retval = pam_authenticate(pamh, 0); /* permitted access? */ if (retval == PAM_SUCCESS) retval = pam_acct_mgmt(pamh, 0); /* This is where we have been authorized or not. */ /* Be conservative - flag as auth failure if we can't close */ /* * XXX This is based on example code from Linux-PAM - * but can it really be correct to pam_end if * pam_start failed? */ if (pam_end(pamh, retval) != PAM_SUCCESS) retval = PAM_AUTH_ERR; /* Message to parent */ state = retval == PAM_SUCCESS ? STATE_AUTH_OK : STATE_AUTH_FAIL; if (write(ud->statefd[1], &state, 1) != 1) { _exit(1); } /* FDs will be closed, so further communication will stop */ _exit(0); } } /* * Do second half of PAM authentication - cookie should now be filled * in with the response to the challenge. */ int ipam_complete_auth(struct inverted_pam_cookie *cookie) { int i; char buf[1024]; struct inverted_pam_userdata *ud = cookie->userdata; char state; /* Send over our responses */ for (i = 0; i < cookie->num_msg; i++) { if (cookie->msg[i]->msg_style != PAM_PROMPT_ECHO_ON && cookie->msg[i]->msg_style != PAM_PROMPT_ECHO_OFF) continue; if (write(ud->responsefd[1], buf, sprintf(buf, "%d\n", strlen(cookie->resp[i]->resp))) == -1) { ipam_free_cookie(cookie); return 0; } if (write(ud->responsefd[1], cookie->resp[i]->resp, strlen(cookie->resp[i]->resp)) == -1) { ipam_free_cookie(cookie); return 0; } } /* Find out what state we are changing to */ if (read(ud->statefd[0], &state, 1) != 1) { ipam_free_cookie(cookie); return 0; } return state == STATE_AUTH_OK ? 1 : 0; } #endif /* USE_PAM */