1 files changed, 424 insertions, 0 deletions
diff --git a/lib/libpam/modules/pam_ssh/pam_ssh.c b/lib/libpam/modules/pam_ssh/pam_ssh.c
new file mode 100644
index 0000000..11ebfe8
--- /dev/null
+++ b/lib/libpam/modules/pam_ssh/pam_ssh.c
@@ -0,0 +1,424 @@
+/*-
+ * Copyright (c) 2003 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.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * 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.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/wait.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <paths.h>
+#include <pwd.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#define PAM_SM_AUTH
+#define PAM_SM_SESSION
+
+#include <security/pam_appl.h>
+#include <security/pam_modules.h>
+#include <security/openpam.h>
+
+#include <openssl/evp.h>
+
+#include "key.h"
+#include "authfd.h"
+#include "authfile.h"
+
+extern char **environ;
+
+struct pam_ssh_key {
+	Key	*key;
+	char	*comment;
+};
+
+static const char *pam_ssh_prompt = "SSH passphrase: ";
+static const char *pam_ssh_have_keys = "pam_ssh_have_keys";
+
+static const char *pam_ssh_keyfiles[] = {
+	".ssh/identity",	/* SSH1 RSA key */
+	".ssh/id_rsa",		/* SSH2 RSA key */
+	".ssh/id_dsa",		/* SSH2 DSA key */
+	NULL
+};
+
+static const char *pam_ssh_agent = "/usr/bin/ssh-agent";
+static char *const pam_ssh_agent_argv[] = { "ssh_agent", "-s", NULL };
+static char *const pam_ssh_agent_envp[] = { NULL };
+
+/*
+ * Attempts to load a private key from the specified file in the specified
+ * directory, using the specified passphrase.  If successful, returns a
+ * struct pam_ssh_key containing the key and its comment.
+ */
+static struct pam_ssh_key *
+pam_ssh_load_key(const char *dir, const char *kfn, const char *passphrase)
+{
+	struct pam_ssh_key *psk;
+	char fn[PATH_MAX];
+	char *comment;
+	Key *key;
+
+	if (snprintf(fn, sizeof(fn), "%s/%s", dir, kfn) > (int)sizeof(fn))
+		return (NULL);
+	comment = NULL;
+	key = key_load_private(fn, passphrase, &comment);
+	if (key == NULL) {
+		openpam_log(PAM_LOG_DEBUG, "failed to load key from %s\n", fn);
+		return (NULL);
+	}
+
+	openpam_log(PAM_LOG_DEBUG, "loaded '%s' from %s\n", comment, fn);
+	if ((psk = malloc(sizeof(*psk))) == NULL) {
+		key_free(key);
+		free(comment);
+		return (NULL);
+	}
+	psk->key = key;
+	psk->comment = comment;
+	return (psk);
+}
+
+/*
+ * Wipes a private key and frees the associated resources.
+ */
+static void
+pam_ssh_free_key(pam_handle_t *pamh __unused,
+    void *data, int pam_err __unused)
+{
+	struct pam_ssh_key *psk;
+
+	psk = data;
+	key_free(psk->key);
+	free(psk->comment);
+	free(psk);
+}
+
+PAM_EXTERN int
+pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
+    int argc __unused, const char *argv[] __unused)
+{
+	const char **kfn, *passphrase, *user;
+	const void *item;
+	struct passwd *pwd;
+	struct pam_ssh_key *psk;
+	int nkeys, nullok, pam_err, pass;
+
+	nullok = (openpam_get_option(pamh, "nullok") != NULL);
+
+	/* PEM is not loaded by default */
+	OpenSSL_add_all_algorithms();
+
+	/* get user name and home directory */
+	pam_err = pam_get_user(pamh, &user, NULL);
+	if (pam_err != PAM_SUCCESS)
+		return (pam_err);
+	pwd = getpwnam(user);
+	if (pwd == NULL)
+		return (PAM_USER_UNKNOWN);
+	if (pwd->pw_dir == NULL)
+		return (PAM_AUTH_ERR);
+
+	nkeys = 0;
+	pass = (pam_get_item(pamh, PAM_AUTHTOK, &item) == PAM_SUCCESS &&
+	    item != NULL);
+ load_keys:
+	/* get passphrase */
+	pam_err = pam_get_authtok(pamh, PAM_AUTHTOK,
+	    &passphrase, pam_ssh_prompt);
+	if (pam_err != PAM_SUCCESS)
+		return (pam_err);
+
+	if (*passphrase == '\0' && !nullok)
+		goto skip_keys;
+
+	/* switch to user credentials */
+	pam_err = openpam_borrow_cred(pamh, pwd);
+	if (pam_err != PAM_SUCCESS)
+		return (pam_err);
+
+	/* try to load keys from all keyfiles we know of */
+	for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
+		psk = pam_ssh_load_key(pwd->pw_dir, *kfn, passphrase);
+		if (psk != NULL) {
+			pam_set_data(pamh, *kfn, psk, pam_ssh_free_key);
+			++nkeys;
+		}
+	}
+
+	/* switch back to arbitrator credentials */
+	openpam_restore_cred(pamh);
+
+ skip_keys:
+	/*
+	 * If we tried an old token and didn't get anything, and
+	 * try_first_pass was specified, try again after prompting the
+	 * user for a new passphrase.
+	 */
+	if (nkeys == 0 && pass == 1 &&
+	    openpam_get_option(pamh, "try_first_pass") != NULL) {
+		pam_set_item(pamh, PAM_AUTHTOK, NULL);
+		pass = 0;
+		goto load_keys;
+	}
+
+	/* no keys? */
+	if (nkeys == 0)
+		return (PAM_AUTH_ERR);
+
+	pam_set_data(pamh, pam_ssh_have_keys, NULL, NULL);
+	return (PAM_SUCCESS);
+}
+
+PAM_EXTERN int
+pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused,
+    int argc __unused, const char *argv[] __unused)
+{
+
+	return (PAM_SUCCESS);
+}
+
+/*
+ * Parses a line from ssh-agent's output.
+ */
+static void
+pam_ssh_process_agent_output(pam_handle_t *pamh, FILE *f)
+{
+	char *line, *p, *key, *val;
+	size_t len;
+
+	while ((line = fgetln(f, &len)) != NULL) {
+		if (len < 4 || strncmp(line, "SSH_", 4) != 0)
+			continue;
+
+		/* find equal sign at end of key */
+		for (p = key = line; p < line + len; ++p)
+			if (*p == '=')
+				break;
+		if (p == line + len || *p != '=')
+			continue;
+		*p = '\0';
+
+		/* find semicolon at end of value */
+		for (val = ++p; p < line + len; ++p)
+			if (*p == ';')
+				break;
+		if (p == line + len || *p != ';')
+			continue;
+		*p = '\0';
+
+		/* store key-value pair in environment */
+		openpam_log(PAM_LOG_DEBUG, "got %s: %s", key, val);
+		pam_setenv(pamh, key, val, 1);
+	}
+}
+
+/*
+ * Starts an ssh agent and stores the environment variables derived from
+ * its output.
+ */
+static int
+pam_ssh_start_agent(pam_handle_t *pamh)
+{
+	int agent_pipe[2];
+	pid_t pid;
+	FILE *f;
+
+	/* get a pipe which we will use to read the agent's output */
+	if (pipe(agent_pipe) == -1)
+		return (PAM_SYSTEM_ERR);
+
+	/* start the agent */
+	openpam_log(PAM_LOG_DEBUG, "starting an ssh agent");
+	pid = fork();
+	if (pid == (pid_t)-1) {
+		/* failed */
+		close(agent_pipe[0]);
+		close(agent_pipe[1]);
+		return (PAM_SYSTEM_ERR);
+	}
+	if (pid == 0) {
+		int fd;
+
+		/* child: drop privs, close fds and start agent */
+		setgid(getegid());
+		setuid(geteuid());
+		close(STDIN_FILENO);
+		open(_PATH_DEVNULL, O_RDONLY);
+		dup2(agent_pipe[1], STDOUT_FILENO);
+		dup2(agent_pipe[1], STDERR_FILENO);
+		for (fd = 3; fd < getdtablesize(); ++fd)
+			close(fd);
+		execve(pam_ssh_agent, pam_ssh_agent_argv, pam_ssh_agent_envp);
+		_exit(127);
+	}
+
+	/* parent */
+	close(agent_pipe[1]);
+	if ((f = fdopen(agent_pipe[0], "r")) == NULL)
+		return (PAM_SYSTEM_ERR);
+	pam_ssh_process_agent_output(pamh, f);
+	fclose(f);
+
+	return (PAM_SUCCESS);
+}
+
+/*
+ * Adds previously stored keys to a running agent.
+ */
+static int
+pam_ssh_add_keys_to_agent(pam_handle_t *pamh)
+{
+	AuthenticationConnection *ac;
+	struct pam_ssh_key *psk;
+	const char **kfn;
+	void *item;
+	char **envlist, **env;
+	int pam_err;
+
+	/* switch to PAM environment */
+	envlist = environ;
+	if ((environ = pam_getenvlist(pamh)) == NULL) {
+		environ = envlist;
+		return (PAM_SYSTEM_ERR);
+	}
+
+	/* get a connection to the agent */
+	if ((ac = ssh_get_authentication_connection()) == NULL) {
+		pam_err = PAM_SYSTEM_ERR;
+		goto end;
+	}
+
+	/* look for keys to add to it */
+	for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
+		pam_err = pam_get_data(pamh, *kfn, &item);
+		if (pam_err == PAM_SUCCESS && item != NULL) {
+			psk = item;
+			if (ssh_add_identity(ac, psk->key, psk->comment))
+				openpam_log(PAM_LOG_DEBUG,
+				    "added %s to ssh agent", psk->comment);
+			else
+				openpam_log(PAM_LOG_DEBUG, "failed "
+				    "to add %s to ssh agent", psk->comment);
+			/* we won't need the key again, so wipe it */
+			pam_set_data(pamh, *kfn, NULL, NULL);
+		}
+	}
+	pam_err = PAM_SUCCESS;
+ end:
+	/* disconnect from agent */
+	if (ac != NULL)
+		ssh_close_authentication_connection(ac);
+
+	/* switch back to original environment */
+	for (env = environ; *env != NULL; ++env)
+		free(*env);
+	free(environ);
+	environ = envlist;
+
+	return (pam_err);
+}
+
+PAM_EXTERN int
+pam_sm_open_session(pam_handle_t *pamh, int flags __unused,
+    int argc __unused, const char *argv[] __unused)
+{
+	struct passwd *pwd;
+	const char *user;
+	void *data;
+	int pam_err;
+
+	/* no keys, no work */
+	if (pam_get_data(pamh, pam_ssh_have_keys, &data) != PAM_SUCCESS &&
+	    openpam_get_option(pamh, "want_agent") == NULL)
+		return (PAM_SUCCESS);
+
+	/* switch to user credentials */
+	pam_err = pam_get_user(pamh, &user, NULL);
+	if (pam_err != PAM_SUCCESS)
+		return (pam_err);
+	pwd = getpwnam(user);
+	if (pwd == NULL)
+		return (PAM_USER_UNKNOWN);
+	pam_err = openpam_borrow_cred(pamh, pwd);
+	if (pam_err != PAM_SUCCESS)
+		return (pam_err);
+
+	/* start the agent */
+	pam_err = pam_ssh_start_agent(pamh);
+	if (pam_err != PAM_SUCCESS) {
+		openpam_restore_cred(pamh);
+		return (pam_err);
+	}
+
+	/* we have an agent, see if we can add any keys to it */
+	pam_err = pam_ssh_add_keys_to_agent(pamh);
+	if (pam_err != PAM_SUCCESS) {
+		/* XXX ignore failures */
+	}
+
+	openpam_restore_cred(pamh);
+	return (PAM_SUCCESS);
+}
+
+PAM_EXTERN int
+pam_sm_close_session(pam_handle_t *pamh, int flags __unused,
+    int argc __unused, const char *argv[] __unused)
+{
+	const char *ssh_agent_pid;
+	char *end;
+	int status;
+	pid_t pid;
+
+	if ((ssh_agent_pid = pam_getenv(pamh, "SSH_AGENT_PID")) == NULL) {
+		openpam_log(PAM_LOG_DEBUG, "no ssh agent");
+		return (PAM_SUCCESS);
+	}
+	pid = (pid_t)strtol(ssh_agent_pid, &end, 10);
+	if (*ssh_agent_pid == '\0' || *end != '\0') {
+		openpam_log(PAM_LOG_DEBUG, "invalid ssh agent pid");
+		return (PAM_SESSION_ERR);
+	}
+	openpam_log(PAM_LOG_DEBUG, "killing ssh agent %d", (int)pid);
+	if (kill(pid, SIGTERM) == -1 ||
+	    (waitpid(pid, &status, 0) == -1 && errno != ECHILD))
+		return (PAM_SYSTEM_ERR);
+	return (PAM_SUCCESS);
+}
+
+PAM_MODULE_ENTRY("pam_ssh");