freebsd-dev/crypto/openssh/pam_ssh/pam_ssh.c
Brian Feldman 0e17bca17c Upgrade to the pam_ssh module, version 1.1..
(From the author:)
Primarily, I have added built-in functions for manipulating the
environment, so putenv() is no longer used.  XDM and its variants
should now work without modification.  Note that the new code uses
the macros in <sys/queue.h>.

Submitted by:	Andrew J. Korty <ajk@iu.edu>
1999-12-28 05:32:54 +00:00

490 lines
12 KiB
C

/*-
* Copyright (c) 1999 Andrew J. Korty
* 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 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.
*
* $FreeBSD$
*
*/
#include <sys/param.h>
#include <sys/queue.h>
#include <fcntl.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define PAM_SM_AUTH
#define PAM_SM_SESSION
#include <security/pam_modules.h>
#include <security/pam_mod_misc.h>
#include "includes.h"
#include "rsa.h"
#include "ssh.h"
#include "authfd.h"
#define MODULE_NAME "pam_ssh"
#define NEED_PASSPHRASE "Need passphrase for %s (%s).\nEnter passphrase: "
#define PATH_SSH_AGENT "__PREFIX__/bin/ssh-agent"
void
rsa_cleanup(pam_handle_t *pamh, void *data, int error_status)
{
if (data)
RSA_free(data);
}
void
ssh_cleanup(pam_handle_t *pamh, void *data, int error_status)
{
if (data)
free(data);
}
/*
* The following set of functions allow the module to manipulate the
* environment without calling the putenv() or setenv() stdlib functions.
* At least one version of these functions, on the first call, copies
* the environment into dynamically-allocated memory and then augments
* it. On subsequent calls, the realloc() call is used to grow the
* previously allocated buffer. Problems arise when the "environ"
* variable is changed to point to static memory after putenv()/setenv()
* have been called.
*
* We don't use putenv() or setenv() in case the application subsequently
* manipulates environ, (e.g., to clear the environment by pointing
* environ at an array of one element equal to NULL).
*/
SLIST_HEAD(env_head, env_entry);
struct env_entry {
char *ee_env;
SLIST_ENTRY(env_entry) ee_entries;
};
typedef struct env {
char **e_environ_orig;
char **e_environ_new;
int e_count;
struct env_head e_head;
int e_committed;
} ENV;
extern char **environ;
static ENV *
env_new(void)
{
ENV *self;
if (!(self = malloc(sizeof (ENV)))) {
syslog(LOG_CRIT, "%m");
return NULL;
}
SLIST_INIT(&self->e_head);
self->e_count = 0;
self->e_committed = 0;
return self;
}
static int
env_put(ENV *self, char *s)
{
struct env_entry *env;
if (!(env = malloc(sizeof (struct env_entry))) ||
!(env->ee_env = strdup(s))) {
syslog(LOG_CRIT, "%m");
return PAM_SERVICE_ERR;
}
SLIST_INSERT_HEAD(&self->e_head, env, ee_entries);
++self->e_count;
return PAM_SUCCESS;
}
static void
env_swap(ENV *self, int which)
{
environ = which ? self->e_environ_new : self->e_environ_orig;
}
static int
env_commit(ENV *self)
{
int n;
struct env_entry *p;
char **v;
for (v = environ, n = 0; v && *v; v++, n++)
;
if (!(v = malloc((n + self->e_count + 1) * sizeof (char *)))) {
syslog(LOG_CRIT, "%m");
return PAM_SERVICE_ERR;
}
self->e_committed = 1;
(void)memcpy(v, environ, n * sizeof (char *));
SLIST_FOREACH(p, &self->e_head, ee_entries)
v[n++] = p->ee_env;
v[n] = NULL;
self->e_environ_orig = environ;
self->e_environ_new = v;
env_swap(self, 1);
return PAM_SUCCESS;
}
static void
env_destroy(ENV *self)
{
struct env_entry *p;
env_swap(self, 0);
SLIST_FOREACH(p, &self->e_head, ee_entries) {
free(p->ee_env);
free(p);
}
if (self->e_committed)
free(self->e_environ_new);
free(self);
}
void
env_cleanup(pam_handle_t *pamh, void *data, int error_status)
{
if (data)
env_destroy(data);
}
typedef struct passwd PASSWD;
PAM_EXTERN int
pam_sm_authenticate(
pam_handle_t *pamh,
int flags,
int argc,
const char **argv)
{
char *comment_priv; /* on private key */
char *comment_pub; /* on public key */
char *identity; /* user's identity file */
RSA *key; /* user's private key */
int options; /* module options */
const char *pass; /* passphrase */
char *prompt; /* passphrase prompt */
RSA *public_key; /* user's public key */
const PASSWD *pwent; /* user's passwd entry */
PASSWD *pwent_keep; /* our own copy */
int retval; /* from calls */
uid_t saved_uid; /* caller's uid */
const char *user; /* username */
options = 0;
while (argc--)
pam_std_option(&options, *argv++);
if ((retval = pam_get_user(pamh, &user, NULL)) != PAM_SUCCESS)
return retval;
if (!((pwent = getpwnam(user)) && pwent->pw_dir)) {
/* delay? */
return PAM_AUTH_ERR;
}
/* locate the user's private key file */
if (!asprintf(&identity, "%s/%s", pwent->pw_dir,
SSH_CLIENT_IDENTITY)) {
syslog(LOG_CRIT, "%s: %m", MODULE_NAME);
return PAM_SERVICE_ERR;
}
/*
* Fail unless we can load the public key. Change to the
* owner's UID to appease load_public_key().
*/
key = RSA_new();
public_key = RSA_new();
saved_uid = getuid();
(void)setreuid(pwent->pw_uid, saved_uid);
retval = load_public_key(identity, public_key, &comment_pub);
(void)setuid(saved_uid);
if (!retval) {
free(identity);
return PAM_AUTH_ERR;
}
RSA_free(public_key);
/* build the passphrase prompt */
retval = asprintf(&prompt, NEED_PASSPHRASE, identity, comment_pub);
free(comment_pub);
if (!retval) {
syslog(LOG_CRIT, "%s: %m", MODULE_NAME);
free(identity);
return PAM_SERVICE_ERR;
}
/* pass prompt message to application and receive passphrase */
retval = pam_get_pass(pamh, &pass, prompt, options);
free(prompt);
if (retval != PAM_SUCCESS) {
free(identity);
return retval;
}
/*
* Try to decrypt the private key with the passphrase provided.
* If success, the user is authenticated.
*/
(void)setreuid(pwent->pw_uid, saved_uid);
retval = load_private_key(identity, pass, key, &comment_priv);
free(identity);
(void)setuid(saved_uid);
if (!retval)
return PAM_AUTH_ERR;
/*
* Save the key and comment to pass to ssh-agent in the session
* phase.
*/
if ((retval = pam_set_data(pamh, "ssh_private_key", key,
rsa_cleanup)) != PAM_SUCCESS) {
RSA_free(key);
free(comment_priv);
return retval;
}
if ((retval = pam_set_data(pamh, "ssh_key_comment", comment_priv,
ssh_cleanup)) != PAM_SUCCESS) {
free(comment_priv);
return retval;
}
/*
* Copy the passwd entry (in case successive calls are made)
* and save it for the session phase.
*/
if (!(pwent_keep = malloc(sizeof *pwent))) {
syslog(LOG_CRIT, "%m");
return PAM_SERVICE_ERR;
}
(void)memcpy(pwent_keep, pwent, sizeof *pwent_keep);
if ((retval = pam_set_data(pamh, "ssh_passwd_entry", pwent_keep,
ssh_cleanup)) != PAM_SUCCESS) {
free(pwent_keep);
return retval;
}
return PAM_SUCCESS;
}
PAM_EXTERN int
pam_sm_setcred(
pam_handle_t *pamh,
int flags,
int argc,
const char **argv)
{
return PAM_SUCCESS;
}
typedef AuthenticationConnection AC;
PAM_EXTERN int
pam_sm_open_session(
pam_handle_t *pamh,
int flags,
int argc,
const char **argv)
{
AC *ac; /* to ssh-agent */
char *comment; /* on private key */
char *env_end; /* end of env */
char *env_file; /* to store env */
FILE *env_fp; /* env_file handle */
RSA *key; /* user's private key */
FILE *pipe; /* ssh-agent handle */
const PASSWD *pwent; /* user's passwd entry */
int retval; /* from calls */
uid_t saved_uid; /* caller's uid */
ENV *ssh_env; /* env handle */
const char *tty; /* tty or display name */
char hname[MAXHOSTNAMELEN]; /* local hostname */
char parse[BUFSIZ]; /* commands output */
/* dump output of ssh-agent in ~/.ssh */
if ((retval = pam_get_data(pamh, "ssh_passwd_entry",
(const void **)&pwent)) != PAM_SUCCESS)
return retval;
/* use the tty or X display name in the filename */
if ((retval = pam_get_item(pamh, PAM_TTY, (const void **)&tty))
!= PAM_SUCCESS)
return retval;
if (*tty == ':' && gethostname(hname, sizeof hname) == 0) {
if (asprintf(&env_file, "%s/.ssh/agent-%s%s",
pwent->pw_dir, hname, tty) == -1) {
syslog(LOG_CRIT, "%s: %m", MODULE_NAME);
return PAM_SERVICE_ERR;
}
} else if (asprintf(&env_file, "%s/.ssh/agent-%s", pwent->pw_dir,
tty) == -1) {
syslog(LOG_CRIT, "%s: %m", MODULE_NAME);
return PAM_SERVICE_ERR;
}
/* save the filename so we can delete the file on session close */
if ((retval = pam_set_data(pamh, "ssh_agent_env", env_file,
ssh_cleanup)) != PAM_SUCCESS) {
free(env_file);
return retval;
}
/* start the agent as the user */
saved_uid = geteuid();
(void)seteuid(pwent->pw_uid);
env_fp = fopen(env_file, "w");
pipe = popen(PATH_SSH_AGENT, "r");
(void)seteuid(saved_uid);
if (!pipe) {
syslog(LOG_ERR, "%s: %s: %m", MODULE_NAME, PATH_SSH_AGENT);
if (env_fp)
(void)fclose(env_fp);
return PAM_SESSION_ERR;
}
if (!(ssh_env = env_new()))
return PAM_SESSION_ERR;
if ((retval = pam_set_data(pamh, "ssh_env_handle", ssh_env,
env_cleanup)) != PAM_SUCCESS)
return retval;
while (fgets(parse, sizeof parse, pipe)) {
if (env_fp)
(void)fputs(parse, env_fp);
/*
* Save environment for application with pam_putenv()
* but also with env_* functions for our own call to
* ssh_get_authentication_connection().
*/
if (strchr(parse, '=') && (env_end = strchr(parse, ';'))) {
*env_end = '\0';
/* pass to the application ... */
if (!((retval = pam_putenv(pamh, parse)) ==
PAM_SUCCESS)) {
(void)pclose(pipe);
if (env_fp)
(void)fclose(env_fp);
env_destroy(ssh_env);
return PAM_SERVICE_ERR;
}
env_put(ssh_env, parse);
}
}
if (env_fp)
(void)fclose(env_fp);
switch (retval = pclose(pipe)) {
case -1:
syslog(LOG_ERR, "%s: %s: %m", MODULE_NAME, PATH_SSH_AGENT);
env_destroy(ssh_env);
return PAM_SESSION_ERR;
case 0:
break;
case 127:
syslog(LOG_ERR, "%s: cannot execute %s", MODULE_NAME,
PATH_SSH_AGENT);
env_destroy(ssh_env);
return PAM_SESSION_ERR;
default:
syslog(LOG_ERR, "%s: %s exited with status %d",
MODULE_NAME, PATH_SSH_AGENT, WEXITSTATUS(retval));
env_destroy(ssh_env);
return PAM_SESSION_ERR;
}
/* connect to the agent and hand off the private key */
if ((retval = pam_get_data(pamh, "ssh_private_key",
(const void **)&key)) != PAM_SUCCESS ||
(retval = pam_get_data(pamh, "ssh_key_comment",
(const void **)&comment)) != PAM_SUCCESS ||
(retval = env_commit(ssh_env)) != PAM_SUCCESS) {
env_destroy(ssh_env);
return retval;
}
if (!(ac = ssh_get_authentication_connection())) {
syslog(LOG_ERR, "%s: could not connect to agent",
MODULE_NAME);
env_destroy(ssh_env);
return PAM_SESSION_ERR;
}
retval = ssh_add_identity(ac, key, comment);
ssh_close_authentication_connection(ac);
env_swap(ssh_env, 0);
return retval ? PAM_SUCCESS : PAM_SESSION_ERR;
}
PAM_EXTERN int
pam_sm_close_session(
pam_handle_t *pamh,
int flags,
int argc,
const char **argv)
{
const char *env_file; /* ssh-agent environment */
int retval; /* from calls */
ENV *ssh_env; /* env handle */
if ((retval = pam_get_data(pamh, "ssh_env_handle",
(const void **)&ssh_env)) != PAM_SUCCESS)
return retval;
env_swap(ssh_env, 1);
/* kill the agent */
retval = system(PATH_SSH_AGENT " -k");
env_destroy(ssh_env);
switch (retval) {
case -1:
syslog(LOG_ERR, "%s: %s -k: %m", MODULE_NAME,
PATH_SSH_AGENT);
return PAM_SESSION_ERR;
case 0:
break;
case 127:
syslog(LOG_ERR, "%s: cannot execute %s -k", MODULE_NAME,
PATH_SSH_AGENT);
return PAM_SESSION_ERR;
default:
syslog(LOG_ERR, "%s: %s -k exited with status %d",
MODULE_NAME, PATH_SSH_AGENT, WEXITSTATUS(retval));
return PAM_SESSION_ERR;
}
/* retrieve environment filename, then remove the file */
if ((retval = pam_get_data(pamh, "ssh_agent_env",
(const void **)&env_file)) != PAM_SUCCESS)
return retval;
(void)unlink(env_file);
return PAM_SUCCESS;
}
PAM_MODULE_ENTRY(MODULE_NAME);