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/*
* Copyright © 2012 Canonical Ltd.
*
* This program is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 3, as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranties of
* MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
* PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Author: Ted Gould <ted@canonical.com>
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/un.h>
#include <pwd.h>
#include <grp.h>
#include <errno.h>
#include <security/pam_modules.h>
#include <security/pam_modutil.h>
#include <security/pam_appl.h>
#define PAM_TYPE_DOMAIN 1234
#define ALL_GOOD_SIGNAL "Ar, ready to authenticate cap'n"
static int unpriveleged_kill (struct passwd * pwdent);
static char * global_domain = NULL;
/* FIXME? This is a work around to the fact that PAM seems to be clearing
the auth token between authorize and open_session. Which then requires
us to save it. Seems like we're the wrong people to do it, but we have
no choice */
static char * global_password = NULL;
/* Either grab a value or prompt for it */
static char *
get_item (pam_handle_t * pamh, int type)
{
/* Check to see if we just have the value. If we do, great
let's dup it some we're consitently allocating memory */
if (type != PAM_TYPE_DOMAIN) {
/* If it's not a domain we can use the PAM functions because the PAM
functions don't support the domain */
char * value = NULL;
if (pam_get_item(pamh, type, (const void **)&value) == PAM_SUCCESS && value != NULL) {
return value;
}
if (type == PAM_AUTHTOK && global_password != NULL) {
/* If we're looking for a password, we didn't get one, before
prompting see if we've got a global one. */
return global_password;
}
} else {
/* Here we only have domains, so we can see if the global domain is
useful for us, if we have it */
if (global_domain != NULL) {
return global_domain;
}
}
/* Now we need to prompt */
/* Build up the message we're prompting for */
struct pam_message message;
const struct pam_message * pmessage = &message;
message.msg = NULL;
message.msg_style = PAM_PROMPT_ECHO_ON;
switch (type) {
case PAM_USER:
message.msg = "login:";
break;
case PAM_RUSER:
message.msg = "remote login:";
break;
case PAM_RHOST:
message.msg = "remote host:";
break;
case PAM_AUTHTOK:
message.msg = "password:";
message.msg_style = PAM_PROMPT_ECHO_OFF;
break;
case PAM_TYPE_DOMAIN:
message.msg = "domain:";
break;
default:
return NULL;
}
struct pam_conv * conv = NULL;
if (pam_get_item(pamh, PAM_CONV, (const void **)&conv) != PAM_SUCCESS || conv == NULL || conv->conv == NULL) {
return NULL;
}
struct pam_response * responses = NULL;
if (conv->conv(1, &pmessage, &responses, conv->appdata_ptr) != PAM_SUCCESS || responses == NULL) {
return NULL;
}
char * promptval = responses->resp;
free(responses);
/* If we didn't get anything, just move on */
if (promptval == NULL) {
return NULL;
}
if (type == PAM_AUTHTOK) {
if (mlock(promptval, strlen(promptval) + 1) != 0) {
free(promptval);
return NULL;
}
}
if (type == PAM_RHOST) {
char * subloc = strstr(promptval, "://");
if (subloc != NULL) {
char * original = promptval;
char * newish = subloc + strlen("://");
char * endslash = strstr(newish, "/");
if (endslash != NULL) {
endslash[0] = '\0';
}
promptval = strdup(newish);
free(original);
}
}
char * retval = NULL;
if (promptval != NULL) { /* Can't believe it really would be at this point, but let's be sure */
if (type != PAM_TYPE_DOMAIN) {
/* We can only use the PAM functions if it's not the domain */
pam_set_item(pamh, type, (const void *)promptval);
/* We're returning the value saved by PAM so we can clear promptval */
pam_get_item(pamh, type, (const void **)&retval);
}
if (type == PAM_TYPE_DOMAIN) {
/* The domain can be saved globally so we can use it for open */
if (global_domain != NULL) {
free(global_domain);
}
global_domain = strdup(promptval);
retval = global_domain;
}
if (type == PAM_AUTHTOK) {
/* We also save the password globally if we've got one */
if (global_password != NULL) {
memset(global_password, 0, strlen(global_password));
munlock(global_password, strlen(global_password) + 1);
free(global_password);
}
global_password = strdup(promptval);
if (mlock(global_password, strlen(global_password) + 1) != 0) {
/* Woah, can't lock it. Can't keep it. */
free(global_password);
global_password = NULL;
} else {
retval = global_password;
}
}
if (type == PAM_AUTHTOK) {
memset(promptval, 0, strlen(promptval) + 1);
munlock(promptval, strlen(promptval) + 1);
}
free(promptval);
}
return retval;
}
#define GET_ITEM(val, type) \
if ((val = get_item(pamh, type)) == NULL) { \
retval = PAM_AUTH_ERR; \
goto done; \
}
/* Authenticate. We need to make sure we have a user account, that
there are remote accounts and then verify them with FreeRDP */
PAM_EXTERN int
pam_sm_authenticate (pam_handle_t *pamh, int flags, int argc, const char **argv)
{
char * username = NULL;
char * password = NULL;
char * ruser = NULL;
char * rhost = NULL;
char * rdomain = NULL;
int retval = PAM_IGNORE;
/* Get all the values, or prompt for them, or return with
an auth error */
GET_ITEM(username, PAM_USER);
GET_ITEM(ruser, PAM_RUSER);
GET_ITEM(rhost, PAM_RHOST);
GET_ITEM(rdomain, PAM_TYPE_DOMAIN);
GET_ITEM(password, PAM_AUTHTOK);
int stdinpipe[2];
if (pipe(stdinpipe) != 0) {
retval = PAM_SYSTEM_ERR;
goto done;
}
/* At this point we should have the values, let's check the auth */
pid_t pid;
switch (pid = fork()) {
case 0: { /* child */
dup2(stdinpipe[0], 0);
char * args[5];
args[0] = AUTH_CHECK;
args[1] = rhost;
args[2] = ruser;
args[3] = rdomain;
args[4] = NULL;
struct passwd * pwdent = getpwnam(username);
if (pwdent == NULL) {
_exit(EXIT_FAILURE);
}
/* Setting groups, but allowing EPERM as if we're not 100% root
we might not be able to do this */
if (setgroups(1, &pwdent->pw_gid) != 0 && errno != EPERM) {
_exit(EXIT_FAILURE);
}
if (setgid(pwdent->pw_gid) < 0 || setuid(pwdent->pw_uid) < 0 ||
setegid(pwdent->pw_gid) < 0 || seteuid(pwdent->pw_uid) < 0) {
_exit(EXIT_FAILURE);
}
if (clearenv() != 0) {
_exit(EXIT_FAILURE);
}
if (chdir(pwdent->pw_dir) != 0) {
_exit(EXIT_FAILURE);
}
setenv("HOME", pwdent->pw_dir, 1);
execvp(args[0], args);
_exit(EXIT_FAILURE);
break;
}
case -1: { /* fork'n error! */
retval = PAM_SYSTEM_ERR;
break;
}
default: {
int forkret = 0;
int bytesout = 0;
bytesout += write(stdinpipe[1], password, strlen(password));
bytesout += write(stdinpipe[1], "\n", 1);
close(stdinpipe[1]);
if (waitpid(pid, &forkret, 0) < 0 || bytesout == 0) {
retval = PAM_SYSTEM_ERR;
} else if (forkret == 0) {
retval = PAM_SUCCESS;
} else {
retval = PAM_AUTH_ERR;
}
}
}
/* Return our status */
done:
return retval;
}
static int
session_socket_handler (struct passwd * pwdent, int readypipe, const char * ruser, const char * rhost, const char * rdomain, const char * password)
{
/* Socket stuff */
int socketfd = 0;
struct sockaddr_un socket_addr;
/* Connected user */
socklen_t connected_addr_size;
int connectfd = 0;
struct sockaddr_un connected_addr;
/* Our buffer */
char * buffer = NULL;
int buffer_len = 0;
int buffer_fill = 0;
/* Track write out */
int writedata = 0;
/* Track ready writing */
int readywrite = 0;
/* Setting groups, but allowing EPERM as if we're not 100% root
we might not be able to do this */
if (setgroups(1, &pwdent->pw_gid) != 0 && errno != EPERM) {
_exit(EXIT_FAILURE);
}
if (setgid(pwdent->pw_gid) < 0 || setuid(pwdent->pw_uid) < 0 ||
setegid(pwdent->pw_gid) < 0 || seteuid(pwdent->pw_uid) < 0) {
/* Don't need to clean up yet */
return EXIT_FAILURE;
}
if (clearenv() != 0) {
/* Don't need to clean up yet */
return EXIT_FAILURE;
}
if (chdir(pwdent->pw_dir) != 0) {
/* Don't need to clean up yet */
return EXIT_FAILURE;
}
if (rdomain[0] == '\0') {
rdomain = ".";
}
/* Build this up as a buffer so we can just write it and see that
very, very clearly */
buffer_len += strlen(ruser) + 1; /* Add one for the space */
buffer_len += strlen(rhost) + 1; /* Add one for the space */
buffer_len += strlen(rdomain) + 1; /* Add one for the space */
buffer_len += strlen(password) + 1; /* Add one for the NULL */
if (buffer_len < 5) {
/* Don't need to clean up yet */
return EXIT_FAILURE;
}
buffer = malloc(buffer_len);
if (buffer == NULL) {
/* Don't need to clean up yet */
return EXIT_FAILURE;
}
/* Lock the buffer before writing */
if (mlock(buffer, buffer_len) != 0) {
/* We can't lock, we go home */
goto cleanup;
}
buffer_fill = snprintf(buffer, buffer_len, "%s %s %s %s", ruser, password, rdomain, rhost);
if (buffer_fill > buffer_len) {
/* This really shouldn't happen, but if for some reason we have an
difference between they way that the lengths are calculated we want
to catch that. */
goto cleanup;
}
/* Make our socket and bind it */
socketfd = socket(AF_UNIX, SOCK_STREAM, 0);
if (socketfd < 0) {
goto cleanup;
}
memset(&socket_addr, 0, sizeof(struct sockaddr_un));
socket_addr.sun_family = AF_UNIX;
strncpy(socket_addr.sun_path, pwdent->pw_dir, sizeof(socket_addr.sun_path) - 1);
strncpy(socket_addr.sun_path + strlen(pwdent->pw_dir), "/.freerdp-socket", (sizeof(socket_addr.sun_path) - strlen(pwdent->pw_dir)) - 1);
/* We bind the socket before forking so that we ensure that
there isn't a race condition to get to it. Things will block
otherwise. */
if (bind(socketfd, (struct sockaddr *)&socket_addr, sizeof(struct sockaddr_un)) < 0) {
goto cleanup;
}
/* Set the socket file permissions to be 600 and the user and group
to be the guest user. NOTE: This won't protect on BSD */
if (chmod(socket_addr.sun_path, S_IRUSR | S_IWUSR) != 0 ||
chown(socket_addr.sun_path, pwdent->pw_uid, pwdent->pw_gid) != 0) {
goto cleanup;
}
if (listen(socketfd, 1) < 0) {
goto cleanup;
}
readywrite = write(readypipe, ALL_GOOD_SIGNAL, strlen(ALL_GOOD_SIGNAL) + 1);
if (readywrite != strlen(ALL_GOOD_SIGNAL) + 1) {
goto cleanup;
}
connected_addr_size = sizeof(struct sockaddr_un);
connectfd = accept(socketfd, (struct sockaddr *)&connected_addr, &connected_addr_size);
if (connectfd < 0) {
goto cleanup;
}
writedata = write(connectfd, buffer, buffer_len);
cleanup:
if (socketfd != 0) {
close(socketfd);
}
if (connectfd != 0) {
close(connectfd);
}
if (buffer != NULL) {
memset(buffer, 0, buffer_len);
munlock(buffer, buffer_len);
free(buffer);
buffer = NULL;
}
/* This should be only true on the write, so we can use this to check
out as writedata is init to 0 */
if (writedata == buffer_len) {
return 0;
}
return EXIT_FAILURE;
}
pid_t session_pid = 0;
/* Open Session. Here we need to fork a little process so that we can
give the credentials to the session itself so that it can startup the
xfreerdp viewer for the login */
PAM_EXTERN int
pam_sm_open_session (pam_handle_t *pamh, int flags, int argc, const char ** argv)
{
char * username = NULL;
char * password = NULL;
char * ruser = NULL;
char * rhost = NULL;
char * rdomain = NULL;
int retval = PAM_SUCCESS;
/* Get all the values, or prompt for them, or return with
an auth error */
GET_ITEM(username, PAM_USER);
GET_ITEM(ruser, PAM_RUSER);
GET_ITEM(rhost, PAM_RHOST);
GET_ITEM(rdomain, PAM_TYPE_DOMAIN);
GET_ITEM(password, PAM_AUTHTOK);
struct passwd * pwdent = getpwnam(username);
if (pwdent == NULL) {
retval = PAM_SYSTEM_ERR;
goto done;
}
if (session_pid != 0) {
unpriveleged_kill(pwdent);
}
int sessionready[2];
if (pipe(sessionready) != 0) {
retval = PAM_SYSTEM_ERR;
goto done;
}
pid_t pid = fork();
if (pid == 0) {
int retval = 0;
retval = session_socket_handler(pwdent, sessionready[1], ruser, rhost, rdomain, password);
close(sessionready[1]);
_exit(retval);
} else if (pid < 0) {
close(sessionready[0]);
close(sessionready[1]);
retval = PAM_SYSTEM_ERR;
} else {
char readbuffer[strlen(ALL_GOOD_SIGNAL) + 1];
int readlen = 0;
readlen = read(sessionready[0], readbuffer, strlen(ALL_GOOD_SIGNAL) + 1);
close(sessionready[0]);
if (readlen == strlen(ALL_GOOD_SIGNAL) + 1) {
session_pid = pid;
} else {
retval = PAM_SYSTEM_ERR;
}
}
done:
return retval;
}
/* Close Session. Make sure our little guy has died so he doesn't become
a zombie and eat things. */
PAM_EXTERN int
pam_sm_close_session (pam_handle_t *pamh, int flags, int argc, const char **argv)
{
if (session_pid == 0) {
return PAM_IGNORE;
}
char * username = NULL;
int retval = PAM_SUCCESS;
GET_ITEM(username, PAM_USER);
struct passwd * pwdent = getpwnam(username);
if (pwdent == NULL) {
retval = PAM_SYSTEM_ERR;
goto done;
}
retval = unpriveleged_kill(pwdent);
done:
return retval;
}
/* Drop privs and try to kill the process with the PID of session_pid.
This ensures that we don't kill something important if there is PID wrap
around. */
static int
unpriveleged_kill (struct passwd * pwdent)
{
int retval = PAM_SUCCESS;
pid_t pid = fork();
if (pid == 0) {
/* Setting groups, but allowing EPERM as if we're not 100% root
we might not be able to do this */
if (setgroups(1, &pwdent->pw_gid) != 0 && errno != EPERM) {
_exit(EXIT_FAILURE);
}
if (setgid(pwdent->pw_gid) < 0 || setuid(pwdent->pw_uid) < 0 ||
setegid(pwdent->pw_gid) < 0 || seteuid(pwdent->pw_uid) < 0) {
_exit(EXIT_FAILURE);
}
if (clearenv() != 0) {
_exit(EXIT_FAILURE);
}
int killval = kill(session_pid, SIGKILL);
session_pid = 0;
if (killval != 0) {
printf("Unable to kill\n");
}
/* NOTE: We're ignoring whether we could kill it or not. It'd be nice to
track that but there are a lot of reason that we could fail there and
it's not a bad thing. Really we're attempting a best effort to clean up
we won't be able to gaurantee it. */
_exit(EXIT_SUCCESS);
} else if (pid < 0) {
retval = PAM_SYSTEM_ERR;
} else {
int forkret = 0;
if (waitpid(pid, &forkret, 0) < 0) {
retval = PAM_SYSTEM_ERR;
}
}
/* We reset this no matter. If we error'd trying to do it, we don't
want to try again. We'll just return the error for this time. */
session_pid = 0;
return retval;
}
/* LightDM likes to have this function around, but we don't need it as we
don't have a token hanging around. */
PAM_EXTERN int
pam_sm_setcred (pam_handle_t *pamh, int flags, int argc, const char ** argv)
{
return PAM_SUCCESS;
}
#ifdef PAM_STATIC
struct pam_module _pam_freerdp_modstruct = {
"pam_freerdp",
pam_sm_authenticate,
pam_sm_setcred,
NULL,
pam_sm_open_session,
pam_sm_close_session,
NULL,
};
#endif
|