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systemd-stable/src/login/pam_systemd.c
David Tardon f369f47c26 be consistent about sun_path length 
Most places use the whole buffer for name, without leaving extra space
for the trailing NUL.
2018-10-12 12:38:49 +02:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <security/_pam_macros.h>
#include <security/pam_ext.h>
#include <security/pam_misc.h>
#include <security/pam_modules.h>
#include <security/pam_modutil.h>
#include <sys/file.h>
#include "alloc-util.h"
#include "audit-util.h"
#include "bus-common-errors.h"
#include "bus-error.h"
#include "bus-util.h"
#include "cgroup-util.h"
#include "def.h"
#include "fd-util.h"
#include "fileio.h"
#include "format-util.h"
#include "hostname-util.h"
#include "login-util.h"
#include "macro.h"
#include "parse-util.h"
#include "path-util.h"
#include "process-util.h"
#include "socket-util.h"
#include "strv.h"
#include "terminal-util.h"
#include "util.h"
static int parse_argv(
pam_handle_t *handle,
int argc, const char **argv,
const char **class,
const char **type,
const char **desktop,
bool *debug) {
unsigned i;
assert(argc >= 0);
assert(argc == 0 || argv);
for (i = 0; i < (unsigned) argc; i++) {
if (startswith(argv[i], "class=")) {
if (class)
*class = argv[i] + 6;
} else if (startswith(argv[i], "type=")) {
if (type)
*type = argv[i] + 5;
} else if (startswith(argv[i], "desktop=")) {
if (desktop)
*desktop = argv[i] + 8;
} else if (streq(argv[i], "debug")) {
if (debug)
*debug = true;
} else if (startswith(argv[i], "debug=")) {
int k;
k = parse_boolean(argv[i] + 6);
if (k < 0)
pam_syslog(handle, LOG_WARNING, "Failed to parse debug= argument, ignoring.");
else if (debug)
*debug = k;
} else
pam_syslog(handle, LOG_WARNING, "Unknown parameter '%s', ignoring", argv[i]);
}
return 0;
}
static int get_user_data(
pam_handle_t *handle,
const char **ret_username,
struct passwd **ret_pw) {
const char *username = NULL;
struct passwd *pw = NULL;
int r;
assert(handle);
assert(ret_username);
assert(ret_pw);
r = pam_get_user(handle, &username, NULL);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to get user name.");
return r;
}
if (isempty(username)) {
pam_syslog(handle, LOG_ERR, "User name not valid.");
return PAM_AUTH_ERR;
}
pw = pam_modutil_getpwnam(handle, username);
if (!pw) {
pam_syslog(handle, LOG_ERR, "Failed to get user data.");
return PAM_USER_UNKNOWN;
}
*ret_pw = pw;
*ret_username = username;
return PAM_SUCCESS;
}
static int socket_from_display(const char *display, char **path) {
size_t k;
char *f, *c;
assert(display);
assert(path);
if (!display_is_local(display))
return -EINVAL;
k = strspn(display+1, "0123456789");
f = new(char, STRLEN("/tmp/.X11-unix/X") + k + 1);
if (!f)
return -ENOMEM;
c = stpcpy(f, "/tmp/.X11-unix/X");
memcpy(c, display+1, k);
c[k] = 0;
*path = f;
return 0;
}
static int get_seat_from_display(const char *display, const char **seat, uint32_t *vtnr) {
union sockaddr_union sa = {
.un.sun_family = AF_UNIX,
};
_cleanup_free_ char *p = NULL, *tty = NULL;
_cleanup_close_ int fd = -1;
struct ucred ucred;
int v, r;
assert(display);
assert(vtnr);
/* We deduce the X11 socket from the display name, then use
* SO_PEERCRED to determine the X11 server process, ask for
* the controlling tty of that and if it's a VC then we know
* the seat and the virtual terminal. Sounds ugly, is only
* semi-ugly. */
r = socket_from_display(display, &p);
if (r < 0)
return r;
strncpy(sa.un.sun_path, p, sizeof(sa.un.sun_path));
fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
if (fd < 0)
return -errno;
if (connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
return -errno;
r = getpeercred(fd, &ucred);
if (r < 0)
return r;
r = get_ctty(ucred.pid, NULL, &tty);
if (r < 0)
return r;
v = vtnr_from_tty(tty);
if (v < 0)
return v;
else if (v == 0)
return -ENOENT;
if (seat)
*seat = "seat0";
*vtnr = (uint32_t) v;
return 0;
}
static int append_session_memory_max(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
uint64_t val;
int r;
if (isempty(limit))
return 0;
if (streq(limit, "infinity")) {
r = sd_bus_message_append(m, "(sv)", "MemoryMax", "t", (uint64_t)-1);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
return r;
}
} else {
r = parse_permille(limit);
if (r >= 0) {
r = sd_bus_message_append(m, "(sv)", "MemoryMaxScale", "u", (uint32_t) (((uint64_t) r * UINT32_MAX) / 1000U));
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
return r;
}
} else {
r = parse_size(limit, 1024, &val);
if (r >= 0) {
r = sd_bus_message_append(m, "(sv)", "MemoryMax", "t", val);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
return r;
}
} else
pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.limit: %s, ignoring.", limit);
}
}
return 0;
}
static int append_session_tasks_max(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
uint64_t val;
int r;
/* No need to parse "infinity" here, it will be set unconditionally later in manager_start_scope() */
if (isempty(limit) || streq(limit, "infinity"))
return 0;
r = safe_atou64(limit, &val);
if (r >= 0) {
r = sd_bus_message_append(m, "(sv)", "TasksMax", "t", val);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
return r;
}
} else
pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.limit: %s, ignoring.", limit);
return 0;
}
static int append_session_cg_weight(pam_handle_t *handle, sd_bus_message *m, const char *limit, const char *field) {
uint64_t val;
int r;
if (isempty(limit))
return 0;
r = cg_weight_parse(limit, &val);
if (r >= 0) {
r = sd_bus_message_append(m, "(sv)", field, "t", val);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
return r;
}
} else if (streq(field, "CPUWeight"))
pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.cpu_weight: %s, ignoring.", limit);
else
pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.io_weight: %s, ignoring.", limit);
return 0;
}
static const char* getenv_harder(pam_handle_t *handle, const char *key, const char *fallback) {
const char *v;
assert(handle);
assert(key);
/* Looks for an environment variable, preferrably in the environment block associated with the specified PAM
* handle, falling back to the process' block instead. */
v = pam_getenv(handle, key);
if (!isempty(v))
return v;
v = getenv(key);
if (!isempty(v))
return v;
return fallback;
}
static int update_environment(pam_handle_t *handle, const char *key, const char *value) {
int r;
assert(handle);
assert(key);
/* Updates the environment, but only if there's actually a value set. Also, log about errors */
if (isempty(value))
return PAM_SUCCESS;
r = pam_misc_setenv(handle, key, value, 0);
if (r != PAM_SUCCESS)
pam_syslog(handle, LOG_ERR, "Failed to set environment variable %s.", key);
return r;
}
_public_ PAM_EXTERN int pam_sm_open_session(
pam_handle_t *handle,
int flags,
int argc, const char **argv) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL, *reply = NULL;
const char
*username, *id, *object_path, *runtime_path,
*service = NULL,
*tty = NULL, *display = NULL,
*remote_user = NULL, *remote_host = NULL,
*seat = NULL,
*type = NULL, *class = NULL,
*class_pam = NULL, *type_pam = NULL, *cvtnr = NULL, *desktop = NULL, *desktop_pam = NULL,
*memory_max = NULL, *tasks_max = NULL, *cpu_weight = NULL, *io_weight = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
int session_fd = -1, existing, r;
bool debug = false, remote;
struct passwd *pw;
uint32_t vtnr = 0;
uid_t original_uid;
assert(handle);
/* Make this a NOP on non-logind systems */
if (!logind_running())
return PAM_SUCCESS;
if (parse_argv(handle,
argc, argv,
&class_pam,
&type_pam,
&desktop_pam,
&debug) < 0)
return PAM_SESSION_ERR;
if (debug)
pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing");
r = get_user_data(handle, &username, &pw);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to get user data.");
return r;
}
/* Make sure we don't enter a loop by talking to
* systemd-logind when it is actually waiting for the
* background to finish start-up. If the service is
* "systemd-user" we simply set XDG_RUNTIME_DIR and
* leave. */
pam_get_item(handle, PAM_SERVICE, (const void**) &service);
if (streq_ptr(service, "systemd-user")) {
_cleanup_free_ char *rt = NULL;
if (asprintf(&rt, "/run/user/"UID_FMT, pw->pw_uid) < 0)
return PAM_BUF_ERR;
r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", rt, 0);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
return r;
}
return PAM_SUCCESS;
}
/* Otherwise, we ask logind to create a session for us */
pam_get_item(handle, PAM_XDISPLAY, (const void**) &display);
pam_get_item(handle, PAM_TTY, (const void**) &tty);
pam_get_item(handle, PAM_RUSER, (const void**) &remote_user);
pam_get_item(handle, PAM_RHOST, (const void**) &remote_host);
seat = getenv_harder(handle, "XDG_SEAT", NULL);
cvtnr = getenv_harder(handle, "XDG_VTNR", NULL);
type = getenv_harder(handle, "XDG_SESSION_TYPE", type_pam);
class = getenv_harder(handle, "XDG_SESSION_CLASS", class_pam);
desktop = getenv_harder(handle, "XDG_SESSION_DESKTOP", desktop_pam);
tty = strempty(tty);
if (strchr(tty, ':')) {
/* A tty with a colon is usually an X11 display, placed there to show up in utmp. We rearrange things
* and don't pretend that an X display was a tty. */
if (isempty(display))
display = tty;
tty = NULL;
} else if (streq(tty, "cron")) {
/* cron is setting PAM_TTY to "cron" for some reason (the commit carries no information why, but
* probably because it wants to set it to something as pam_time/pam_access/… require PAM_TTY to be set
* (as they otherwise even try to update it!) — but cron doesn't actually allocate a TTY for its forked
* off processes.) */
type = "unspecified";
class = "background";
tty = NULL;
} else if (streq(tty, "ssh")) {
/* ssh has been setting PAM_TTY to "ssh" (for the same reason as cron does this, see above. For further
* details look for "PAM_TTY_KLUDGE" in the openssh sources). */
type ="tty";
class = "user";
tty = NULL; /* This one is particularly sad, as this means that ssh sessions — even though usually
* associated with a pty — won't be tracked by their tty in logind. This is because ssh
* does the PAM session registration early for new connections, and registers a pty only
* much later (this is because it doesn't know yet if it needs one at all, as whether to
* register a pty or not is negotiated much later in the protocol). */
} else
/* Chop off leading /dev prefix that some clients specify, but others do not. */
tty = skip_dev_prefix(tty);
/* If this fails vtnr will be 0, that's intended */
if (!isempty(cvtnr))
(void) safe_atou32(cvtnr, &vtnr);
if (!isempty(display) && !vtnr) {
if (isempty(seat))
(void) get_seat_from_display(display, &seat, &vtnr);
else if (streq(seat, "seat0"))
(void) get_seat_from_display(display, NULL, &vtnr);
}
if (seat && !streq(seat, "seat0") && vtnr != 0) {
pam_syslog(handle, LOG_DEBUG, "Ignoring vtnr %"PRIu32" for %s which is not seat0", vtnr, seat);
vtnr = 0;
}
if (isempty(type))
type = !isempty(display) ? "x11" :
!isempty(tty) ? "tty" : "unspecified";
if (isempty(class))
class = streq(type, "unspecified") ? "background" : "user";
remote = !isempty(remote_host) && !is_localhost(remote_host);
(void) pam_get_data(handle, "systemd.memory_max", (const void **)&memory_max);
(void) pam_get_data(handle, "systemd.tasks_max", (const void **)&tasks_max);
(void) pam_get_data(handle, "systemd.cpu_weight", (const void **)&cpu_weight);
(void) pam_get_data(handle, "systemd.io_weight", (const void **)&io_weight);
/* Talk to logind over the message bus */
r = sd_bus_open_system(&bus);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
return PAM_SESSION_ERR;
}
if (debug) {
pam_syslog(handle, LOG_DEBUG, "Asking logind to create session: "
"uid="UID_FMT" pid="PID_FMT" service=%s type=%s class=%s desktop=%s seat=%s vtnr=%"PRIu32" tty=%s display=%s remote=%s remote_user=%s remote_host=%s",
pw->pw_uid, getpid_cached(),
strempty(service),
type, class, strempty(desktop),
strempty(seat), vtnr, strempty(tty), strempty(display),
yes_no(remote), strempty(remote_user), strempty(remote_host));
pam_syslog(handle, LOG_DEBUG, "Session limits: "
"memory_max=%s tasks_max=%s cpu_weight=%s io_weight=%s",
strna(memory_max), strna(tasks_max), strna(cpu_weight), strna(io_weight));
}
r = sd_bus_message_new_method_call(
bus,
&m,
"org.freedesktop.login1",
"/org/freedesktop/login1",
"org.freedesktop.login1.Manager",
"CreateSession");
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to create CreateSession method call: %s", strerror(-r));
return PAM_SESSION_ERR;
}
r = sd_bus_message_append(m, "uusssssussbss",
(uint32_t) pw->pw_uid,
0,
service,
type,
class,
desktop,
seat,
vtnr,
tty,
display,
remote,
remote_user,
remote_host);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
return PAM_SESSION_ERR;
}
r = sd_bus_message_open_container(m, 'a', "(sv)");
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to open message container: %s", strerror(-r));
return PAM_SYSTEM_ERR;
}
r = append_session_memory_max(handle, m, memory_max);
if (r < 0)
return PAM_SESSION_ERR;
r = append_session_tasks_max(handle, m, tasks_max);
if (r < 0)
return PAM_SESSION_ERR;
r = append_session_cg_weight(handle, m, cpu_weight, "CPUWeight");
if (r < 0)
return PAM_SESSION_ERR;
r = append_session_cg_weight(handle, m, io_weight, "IOWeight");
if (r < 0)
return PAM_SESSION_ERR;
r = sd_bus_message_close_container(m);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to close message container: %s", strerror(-r));
return PAM_SYSTEM_ERR;
}
r = sd_bus_call(bus, m, 0, &error, &reply);
if (r < 0) {
if (sd_bus_error_has_name(&error, BUS_ERROR_SESSION_BUSY)) {
pam_syslog(handle, LOG_DEBUG, "Cannot create session: %s", bus_error_message(&error, r));
return PAM_SUCCESS;
} else {
pam_syslog(handle, LOG_ERR, "Failed to create session: %s", bus_error_message(&error, r));
return PAM_SYSTEM_ERR;
}
}
r = sd_bus_message_read(reply,
"soshusub",
&id,
&object_path,
&runtime_path,
&session_fd,
&original_uid,
&seat,
&vtnr,
&existing);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to parse message: %s", strerror(-r));
return PAM_SESSION_ERR;
}
if (debug)
pam_syslog(handle, LOG_DEBUG, "Reply from logind: "
"id=%s object_path=%s runtime_path=%s session_fd=%d seat=%s vtnr=%u original_uid=%u",
id, object_path, runtime_path, session_fd, seat, vtnr, original_uid);
r = update_environment(handle, "XDG_SESSION_ID", id);
if (r != PAM_SUCCESS)
return r;
if (original_uid == pw->pw_uid) {
/* Don't set $XDG_RUNTIME_DIR if the user we now
* authenticated for does not match the original user
* of the session. We do this in order not to result
* in privileged apps clobbering the runtime directory
* unnecessarily. */
r = update_environment(handle, "XDG_RUNTIME_DIR", runtime_path);
if (r != PAM_SUCCESS)
return r;
}
/* Most likely we got the session/type/class from environment variables, but might have gotten the data
* somewhere else (for example PAM module parameters). Let's now update the environment variables, so that this
* data is inherited into the session processes, and programs can rely on them to be initialized. */
r = update_environment(handle, "XDG_SESSION_TYPE", type);
if (r != PAM_SUCCESS)
return r;
r = update_environment(handle, "XDG_SESSION_CLASS", class);
if (r != PAM_SUCCESS)
return r;
r = update_environment(handle, "XDG_SESSION_DESKTOP", desktop);
if (r != PAM_SUCCESS)
return r;
r = update_environment(handle, "XDG_SEAT", seat);
if (r != PAM_SUCCESS)
return r;
if (vtnr > 0) {
char buf[DECIMAL_STR_MAX(vtnr)];
sprintf(buf, "%u", vtnr);
r = update_environment(handle, "XDG_VTNR", buf);
if (r != PAM_SUCCESS)
return r;
}
r = pam_set_data(handle, "systemd.existing", INT_TO_PTR(!!existing), NULL);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to install existing flag.");
return r;
}
if (session_fd >= 0) {
session_fd = fcntl(session_fd, F_DUPFD_CLOEXEC, 3);
if (session_fd < 0) {
pam_syslog(handle, LOG_ERR, "Failed to dup session fd: %m");
return PAM_SESSION_ERR;
}
r = pam_set_data(handle, "systemd.session-fd", FD_TO_PTR(session_fd), NULL);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to install session fd.");
safe_close(session_fd);
return r;
}
}
return PAM_SUCCESS;
}
_public_ PAM_EXTERN int pam_sm_close_session(
pam_handle_t *handle,
int flags,
int argc, const char **argv) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
const void *existing = NULL;
const char *id;
int r;
assert(handle);
/* Only release session if it wasn't pre-existing when we
* tried to create it */
(void) pam_get_data(handle, "systemd.existing", &existing);
id = pam_getenv(handle, "XDG_SESSION_ID");
if (id && !existing) {
/* Before we go and close the FIFO we need to tell
* logind that this is a clean session shutdown, so
* that it doesn't just go and slaughter us
* immediately after closing the fd */
r = sd_bus_open_system(&bus);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
return PAM_SESSION_ERR;
}
r = sd_bus_call_method(bus,
"org.freedesktop.login1",
"/org/freedesktop/login1",
"org.freedesktop.login1.Manager",
"ReleaseSession",
&error,
NULL,
"s",
id);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to release session: %s", bus_error_message(&error, r));
return PAM_SESSION_ERR;
}
}
/* Note that we are knowingly leaking the FIFO fd here. This
* way, logind can watch us die. If we closed it here it would
* not have any clue when that is completed. Given that one
* cannot really have multiple PAM sessions open from the same
* process this means we will leak one FD at max. */
return PAM_SUCCESS;
}
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