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-rw-r--r--plugin/auth-pam/auth-pam.c755
1 files changed, 755 insertions, 0 deletions
diff --git a/plugin/auth-pam/auth-pam.c b/plugin/auth-pam/auth-pam.c
new file mode 100644
index 0000000..5047b34
--- /dev/null
+++ b/plugin/auth-pam/auth-pam.c
@@ -0,0 +1,755 @@
+/*
+ * OpenVPN -- An application to securely tunnel IP networks
+ * over a single TCP/UDP port, with support for SSL/TLS-based
+ * session authentication and key exchange,
+ * packet encryption, packet authentication, and
+ * packet compression.
+ *
+ * Copyright (C) 2002-2005 OpenVPN Solutions LLC <info@openvpn.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * 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 warranty of
+ * MERCHANTABILITY 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 (see the file COPYING included with this
+ * distribution); if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+/*
+ * OpenVPN plugin module to do PAM authentication using a split
+ * privilege model.
+ */
+
+#if DLOPEN_PAM
+#include <dlfcn.h>
+#include "pamdl.h"
+#else
+#include <security/pam_appl.h>
+#endif
+
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <syslog.h>
+
+#include "openvpn-plugin.h"
+
+#define DEBUG(verb) ((verb) >= 7)
+
+/* Command codes for foreground -> background communication */
+#define COMMAND_VERIFY 0
+#define COMMAND_EXIT 1
+
+/* Response codes for background -> foreground communication */
+#define RESPONSE_INIT_SUCCEEDED 10
+#define RESPONSE_INIT_FAILED 11
+#define RESPONSE_VERIFY_SUCCEEDED 12
+#define RESPONSE_VERIFY_FAILED 13
+
+/*
+ * Plugin state, used by foreground
+ */
+struct auth_pam_context
+{
+ /* Foreground's socket to background process */
+ int foreground_fd;
+
+ /* Process ID of background process */
+ pid_t background_pid;
+
+ /* Verbosity level of OpenVPN */
+ int verb;
+};
+
+/*
+ * Name/Value pairs for conversation function.
+ * Special Values:
+ *
+ * "USERNAME" -- substitute client-supplied username
+ * "PASSWORD" -- substitute client-specified password
+ */
+
+#define N_NAME_VALUE 16
+
+struct name_value {
+ const char *name;
+ const char *value;
+};
+
+struct name_value_list {
+ int len;
+ struct name_value data[N_NAME_VALUE];
+};
+
+/*
+ * Used to pass the username/password
+ * to the PAM conversation function.
+ */
+struct user_pass {
+ int verb;
+
+ char username[128];
+ char password[128];
+
+ const struct name_value_list *name_value_list;
+};
+
+/* Background process function */
+static void pam_server (int fd, const char *service, int verb, const struct name_value_list *name_value_list);
+
+/*
+ * Given an environmental variable name, search
+ * the envp array for its value, returning it
+ * if found or NULL otherwise.
+ */
+static const char *
+get_env (const char *name, const char *envp[])
+{
+ if (envp)
+ {
+ int i;
+ const int namelen = strlen (name);
+ for (i = 0; envp[i]; ++i)
+ {
+ if (!strncmp (envp[i], name, namelen))
+ {
+ const char *cp = envp[i] + namelen;
+ if (*cp == '=')
+ return cp + 1;
+ }
+ }
+ }
+ return NULL;
+}
+
+/*
+ * Return the length of a string array
+ */
+static int
+string_array_len (const char *array[])
+{
+ int i = 0;
+ if (array)
+ {
+ while (array[i])
+ ++i;
+ }
+ return i;
+}
+
+/*
+ * Socket read/write functions.
+ */
+
+static int
+recv_control (int fd)
+{
+ unsigned char c;
+ const ssize_t size = read (fd, &c, sizeof (c));
+ if (size == sizeof (c))
+ return c;
+ else
+ {
+ /*fprintf (stderr, "AUTH-PAM: DEBUG recv_control.read=%d\n", (int)size);*/
+ return -1;
+ }
+}
+
+static int
+send_control (int fd, int code)
+{
+ unsigned char c = (unsigned char) code;
+ const ssize_t size = write (fd, &c, sizeof (c));
+ if (size == sizeof (c))
+ return (int) size;
+ else
+ return -1;
+}
+
+static int
+recv_string (int fd, char *buffer, int len)
+{
+ if (len > 0)
+ {
+ ssize_t size;
+ memset (buffer, 0, len);
+ size = read (fd, buffer, len);
+ buffer[len-1] = 0;
+ if (size >= 1)
+ return (int)size;
+ }
+ return -1;
+}
+
+static int
+send_string (int fd, const char *string)
+{
+ const int len = strlen (string) + 1;
+ const ssize_t size = write (fd, string, len);
+ if (size == len)
+ return (int) size;
+ else
+ return -1;
+}
+
+/*
+ * Daemonize if "daemon" env var is true.
+ * Preserve stderr across daemonization if
+ * "daemon_log_redirect" env var is true.
+ */
+static void
+daemonize (const char *envp[])
+{
+ const char *daemon_string = get_env ("daemon", envp);
+ if (daemon_string && daemon_string[0] == '1')
+ {
+ const char *log_redirect = get_env ("daemon_log_redirect", envp);
+ int fd = -1;
+ if (log_redirect && log_redirect[0] == '1')
+ fd = dup (2);
+ if (daemon (0, 0) < 0)
+ {
+ fprintf (stderr, "AUTH-PAM: daemonization failed\n");
+ }
+ else if (fd >= 3)
+ {
+ dup2 (fd, 2);
+ close (fd);
+ }
+ }
+}
+
+/*
+ * Close most of parent's fds.
+ * Keep stdin/stdout/stderr, plus one
+ * other fd which is presumed to be
+ * our pipe back to parent.
+ * Admittedly, a bit of a kludge,
+ * but posix doesn't give us a kind
+ * of FD_CLOEXEC which will stop
+ * fds from crossing a fork().
+ */
+static void
+close_fds_except (int keep)
+{
+ int i;
+ closelog ();
+ for (i = 3; i <= 100; ++i)
+ {
+ if (i != keep)
+ close (i);
+ }
+}
+
+/*
+ * Usually we ignore signals, because our parent will
+ * deal with them.
+ */
+static void
+set_signals (void)
+{
+ signal (SIGTERM, SIG_DFL);
+
+ signal (SIGINT, SIG_IGN);
+ signal (SIGHUP, SIG_IGN);
+ signal (SIGUSR1, SIG_IGN);
+ signal (SIGUSR2, SIG_IGN);
+ signal (SIGPIPE, SIG_IGN);
+}
+
+/*
+ * Return 1 if query matches match.
+ */
+static int
+name_value_match (const char *query, const char *match)
+{
+ while (!isalnum (*query))
+ {
+ if (*query == '\0')
+ return 0;
+ ++query;
+ }
+ return strncasecmp (match, query, strlen (match)) == 0;
+}
+
+OPENVPN_EXPORT openvpn_plugin_handle_t
+openvpn_plugin_open_v1 (unsigned int *type_mask, const char *argv[], const char *envp[])
+{
+ pid_t pid;
+ int fd[2];
+
+ struct auth_pam_context *context;
+ struct name_value_list name_value_list;
+
+ const int base_parms = 2;
+
+ /*
+ * Allocate our context
+ */
+ context = (struct auth_pam_context *) calloc (1, sizeof (struct auth_pam_context));
+ context->foreground_fd = -1;
+
+ /*
+ * Intercept the --auth-user-pass-verify callback.
+ */
+ *type_mask = OPENVPN_PLUGIN_MASK (OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY);
+
+ /*
+ * Make sure we have two string arguments: the first is the .so name,
+ * the second is the PAM service type.
+ */
+ if (string_array_len (argv) < base_parms)
+ {
+ fprintf (stderr, "AUTH-PAM: need PAM service parameter\n");
+ goto error;
+ }
+
+ /*
+ * See if we have optional name/value pairs to match against
+ * PAM module queried fields in the conversation function.
+ */
+ name_value_list.len = 0;
+ if (string_array_len (argv) > base_parms)
+ {
+ const int nv_len = string_array_len (argv) - base_parms;
+ int i;
+
+ if ((nv_len & 1) == 1 || (nv_len / 2) > N_NAME_VALUE)
+ {
+ fprintf (stderr, "AUTH-PAM: bad name/value list length\n");
+ goto error;
+ }
+
+ name_value_list.len = nv_len / 2;
+ for (i = 0; i < name_value_list.len; ++i)
+ {
+ const int base = base_parms + i * 2;
+ name_value_list.data[i].name = argv[base];
+ name_value_list.data[i].value = argv[base+1];
+ }
+ }
+
+ /*
+ * Get verbosity level from environment
+ */
+ {
+ const char *verb_string = get_env ("verb", envp);
+ if (verb_string)
+ context->verb = atoi (verb_string);
+ }
+
+ /*
+ * Make a socket for foreground and background processes
+ * to communicate.
+ */
+ if (socketpair (PF_UNIX, SOCK_DGRAM, 0, fd) == -1)
+ {
+ fprintf (stderr, "AUTH-PAM: socketpair call failed\n");
+ goto error;
+ }
+
+ /*
+ * Fork off the privileged process. It will remain privileged
+ * even after the foreground process drops its privileges.
+ */
+ pid = fork ();
+
+ if (pid)
+ {
+ int status;
+
+ /*
+ * Foreground Process
+ */
+
+ context->background_pid = pid;
+
+ /* close our copy of child's socket */
+ close (fd[1]);
+
+ /* don't let future subprocesses inherit child socket */
+ if (fcntl (fd[0], F_SETFD, FD_CLOEXEC) < 0)
+ fprintf (stderr, "AUTH-PAM: Set FD_CLOEXEC flag on socket file descriptor failed\n");
+
+ /* wait for background child process to initialize */
+ status = recv_control (fd[0]);
+ if (status == RESPONSE_INIT_SUCCEEDED)
+ {
+ context->foreground_fd = fd[0];
+ return (openvpn_plugin_handle_t) context;
+ }
+ }
+ else
+ {
+ /*
+ * Background Process
+ */
+
+ /* close all parent fds except our socket back to parent */
+ close_fds_except (fd[1]);
+
+ /* Ignore most signals (the parent will receive them) */
+ set_signals ();
+
+ /* Daemonize if --daemon option is set. */
+ daemonize (envp);
+
+ /* execute the event loop */
+ pam_server (fd[1], argv[1], context->verb, &name_value_list);
+
+ close (fd[1]);
+
+ exit (0);
+ return 0; /* NOTREACHED */
+ }
+
+ error:
+ if (context)
+ free (context);
+ return NULL;
+}
+
+OPENVPN_EXPORT int
+openvpn_plugin_func_v1 (openvpn_plugin_handle_t handle, const int type, const char *argv[], const char *envp[])
+{
+ struct auth_pam_context *context = (struct auth_pam_context *) handle;
+
+ if (type == OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY && context->foreground_fd >= 0)
+ {
+ /* get username/password from envp string array */
+ const char *username = get_env ("username", envp);
+ const char *password = get_env ("password", envp);
+
+ if (username && strlen (username) > 0 && password)
+ {
+ if (send_control (context->foreground_fd, COMMAND_VERIFY) == -1
+ || send_string (context->foreground_fd, username) == -1
+ || send_string (context->foreground_fd, password) == -1)
+ {
+ fprintf (stderr, "AUTH-PAM: Error sending auth info to background process\n");
+ }
+ else
+ {
+ const int status = recv_control (context->foreground_fd);
+ if (status == RESPONSE_VERIFY_SUCCEEDED)
+ return OPENVPN_PLUGIN_FUNC_SUCCESS;
+ if (status == -1)
+ fprintf (stderr, "AUTH-PAM: Error receiving auth confirmation from background process\n");
+ }
+ }
+ }
+ return OPENVPN_PLUGIN_FUNC_ERROR;
+}
+
+OPENVPN_EXPORT void
+openvpn_plugin_close_v1 (openvpn_plugin_handle_t handle)
+{
+ struct auth_pam_context *context = (struct auth_pam_context *) handle;
+
+ if (DEBUG (context->verb))
+ fprintf (stderr, "AUTH-PAM: close\n");
+
+ if (context->foreground_fd >= 0)
+ {
+ /* tell background process to exit */
+ if (send_control (context->foreground_fd, COMMAND_EXIT) == -1)
+ fprintf (stderr, "AUTH-PAM: Error signaling background process to exit\n");
+
+ /* wait for background process to exit */
+ if (context->background_pid > 0)
+ waitpid (context->background_pid, NULL, 0);
+
+ close (context->foreground_fd);
+ context->foreground_fd = -1;
+ }
+
+ free (context);
+}
+
+OPENVPN_EXPORT void
+openvpn_plugin_abort_v1 (openvpn_plugin_handle_t handle)
+{
+ struct auth_pam_context *context = (struct auth_pam_context *) handle;
+
+ /* tell background process to exit */
+ if (context->foreground_fd >= 0)
+ {
+ send_control (context->foreground_fd, COMMAND_EXIT);
+ close (context->foreground_fd);
+ context->foreground_fd = -1;
+ }
+}
+
+/*
+ * PAM conversation function
+ */
+static int
+my_conv (int n, const struct pam_message **msg_array,
+ struct pam_response **response_array, void *appdata_ptr)
+{
+ const struct user_pass *up = ( const struct user_pass *) appdata_ptr;
+ struct pam_response *aresp;
+ int i;
+ int ret = PAM_SUCCESS;
+
+ *response_array = NULL;
+
+ if (n <= 0 || n > PAM_MAX_NUM_MSG)
+ return (PAM_CONV_ERR);
+ if ((aresp = calloc (n, sizeof *aresp)) == NULL)
+ return (PAM_BUF_ERR);
+
+ /* loop through each PAM-module query */
+ for (i = 0; i < n; ++i)
+ {
+ const struct pam_message *msg = msg_array[i];
+ aresp[i].resp_retcode = 0;
+ aresp[i].resp = NULL;
+
+ if (DEBUG (up->verb))
+ {
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: my_conv[%d] query='%s' style=%d\n",
+ i,
+ msg->msg ? msg->msg : "NULL",
+ msg->msg_style);
+ }
+
+ if (up->name_value_list && up->name_value_list->len > 0)
+ {
+ /* use name/value list match method */
+ const struct name_value_list *list = up->name_value_list;
+ int j;
+
+ /* loop through name/value pairs */
+ for (j = 0; j < list->len; ++j)
+ {
+ const char *match_name = list->data[j].name;
+ const char *match_value = list->data[j].value;
+
+ if (name_value_match (msg->msg, match_name))
+ {
+ /* found name/value match */
+ const char *return_value = NULL;
+
+ if (DEBUG (up->verb))
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: name match found, query/match-string ['%s', '%s'] = '%s'\n",
+ msg->msg,
+ match_name,
+ match_value);
+
+ if (!strcmp (match_value, "USERNAME"))
+ return_value = up->username;
+ else if (!strcmp (match_value, "PASSWORD"))
+ return_value = up->password;
+ else
+ return_value = match_value;
+
+ aresp[i].resp = strdup (return_value);
+ if (aresp[i].resp == NULL)
+ ret = PAM_CONV_ERR;
+ break;
+ }
+ }
+
+ if (j == list->len)
+ ret = PAM_CONV_ERR;
+ }
+ else
+ {
+ /* use PAM_PROMPT_ECHO_x hints */
+ switch (msg->msg_style)
+ {
+ case PAM_PROMPT_ECHO_OFF:
+ aresp[i].resp = strdup (up->password);
+ if (aresp[i].resp == NULL)
+ ret = PAM_CONV_ERR;
+ break;
+
+ case PAM_PROMPT_ECHO_ON:
+ aresp[i].resp = strdup (up->username);
+ if (aresp[i].resp == NULL)
+ ret = PAM_CONV_ERR;
+ break;
+
+ case PAM_ERROR_MSG:
+ case PAM_TEXT_INFO:
+ break;
+
+ default:
+ ret = PAM_CONV_ERR;
+ break;
+ }
+ }
+ }
+
+ if (ret == PAM_SUCCESS)
+ *response_array = aresp;
+ return ret;
+}
+
+/*
+ * Return 1 if authenticated and 0 if failed.
+ * Called once for every username/password
+ * to be authenticated.
+ */
+static int
+pam_auth (const char *service, const struct user_pass *up)
+{
+ struct pam_conv conv;
+ pam_handle_t *pamh = NULL;
+ int status = PAM_SUCCESS;
+ int ret = 0;
+ const int name_value_list_provided = (up->name_value_list && up->name_value_list->len > 0);
+
+ /* Initialize PAM */
+ conv.conv = my_conv;
+ conv.appdata_ptr = (void *)up;
+ status = pam_start (service, name_value_list_provided ? NULL : up->username, &conv, &pamh);
+ if (status == PAM_SUCCESS)
+ {
+ /* Call PAM to verify username/password */
+ status = pam_authenticate(pamh, 0);
+ if (status == PAM_SUCCESS)
+ status = pam_acct_mgmt (pamh, 0);
+ if (status == PAM_SUCCESS)
+ ret = 1;
+
+ /* Output error message if failed */
+ if (!ret)
+ {
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: user '%s' failed to authenticate: %s\n",
+ up->username,
+ pam_strerror (pamh, status));
+ }
+
+ /* Close PAM */
+ pam_end (pamh, status);
+ }
+
+ return ret;
+}
+
+/*
+ * Background process -- runs with privilege.
+ */
+static void
+pam_server (int fd, const char *service, int verb, const struct name_value_list *name_value_list)
+{
+ struct user_pass up;
+ int command;
+#if DLOPEN_PAM
+ static const char pam_so[] = "libpam.so";
+#endif
+
+ /*
+ * Do initialization
+ */
+ if (DEBUG (verb))
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: INIT service='%s'\n", service);
+
+#if DLOPEN_PAM
+ /*
+ * Load PAM shared object
+ */
+ if (!dlopen_pam (pam_so))
+ {
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: could not load PAM lib %s: %s\n", pam_so, dlerror());
+ send_control (fd, RESPONSE_INIT_FAILED);
+ goto done;
+ }
+#endif
+
+ /*
+ * Tell foreground that we initialized successfully
+ */
+ if (send_control (fd, RESPONSE_INIT_SUCCEEDED) == -1)
+ {
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: write error on response socket [1]\n");
+ goto done;
+ }
+
+ /*
+ * Event loop
+ */
+ while (1)
+ {
+ memset (&up, 0, sizeof (up));
+ up.verb = verb;
+ up.name_value_list = name_value_list;
+
+ /* get a command from foreground process */
+ command = recv_control (fd);
+
+ if (DEBUG (verb))
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: received command code: %d\n", command);
+
+ switch (command)
+ {
+ case COMMAND_VERIFY:
+ if (recv_string (fd, up.username, sizeof (up.username)) == -1
+ || recv_string (fd, up.password, sizeof (up.password)) == -1)
+ {
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: read error on command channel: code=%d, exiting\n",
+ command);
+ goto done;
+ }
+
+ if (DEBUG (verb))
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: USER/PASS: %s/%s\n",
+ up.username, up.password);
+
+ if (pam_auth (service, &up)) /* Succeeded */
+ {
+ if (send_control (fd, RESPONSE_VERIFY_SUCCEEDED) == -1)
+ {
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: write error on response socket [2]\n");
+ goto done;
+ }
+ }
+ else /* Failed */
+ {
+ if (send_control (fd, RESPONSE_VERIFY_FAILED) == -1)
+ {
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: write error on response socket [3]\n");
+ goto done;
+ }
+ }
+ break;
+
+ case COMMAND_EXIT:
+ goto done;
+
+ case -1:
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: read error on command channel\n");
+ goto done;
+
+ default:
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: unknown command code: code=%d, exiting\n",
+ command);
+ goto done;
+ }
+ }
+ done:
+
+#if DLOPEN_PAM
+ dlclose_pam ();
+#endif
+ if (DEBUG (verb))
+ fprintf (stderr, "AUTH-PAM: BACKGROUND: EXIT\n");
+
+ return;
+}
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