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Merge pull request #7148 from keszybz/dynamic-user-use-gid

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Use gid for static dynamic users
This commit is contained in:
Lennart Poettering 2017-10-24 09:38:01 +02:00 committed by GitHub
parent 195b943d4e c2983a7fdd
commit b88d48c2ca
1 changed files with 74 additions and 55 deletions
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129
src/core/dynamic-user.c
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@ -421,31 +421,55 @@ static void unlink_uid_lock(int lock_fd, uid_t uid, const char *name) {
(void) make_uid_symlinks(uid, name, false); /* remove direct lookup symlinks */
}
static int dynamic_user_realize(DynamicUser *d, char **suggested_dirs, uid_t *ret, bool is_user) {
static int lockfp(int fd, int *fd_lock) {
if (lockf(fd, F_LOCK, 0) < 0)
return -errno;
*fd_lock = fd;
return 0;
}
_cleanup_close_ int etc_passwd_lock_fd = -1, uid_lock_fd = -1;
uid_t uid = UID_INVALID;
static void unlockfp(int *fd_lock) {
if (*fd_lock < 0)
return;
lockf(*fd_lock, F_ULOCK, 0);
*fd_lock = -1;
}
static int dynamic_user_realize(
DynamicUser *d,
char **suggested_dirs,
uid_t *ret_uid, gid_t *ret_gid,
bool is_user) {
_cleanup_(unlockfp) int storage_socket0_lock = -1;
_cleanup_close_ int uid_lock_fd = -1;
_cleanup_close_ int etc_passwd_lock_fd = -1;
uid_t num = UID_INVALID; /* a uid if is_user, and a gid otherwise */
gid_t gid = GID_INVALID; /* a gid if is_user, ignored otherwise */
int r;
assert(d);
assert(is_user == !!ret_uid);
assert(ret_gid);
/* Acquire a UID for the user name. This will allocate a UID for the user name if the user doesn't exist
* yet. If it already exists its existing UID/GID will be reused. */
if (lockf(d->storage_socket[0], F_LOCK, 0) < 0)
return -errno;
r = lockfp(d->storage_socket[0], &storage_socket0_lock);
if (r < 0)
return r;
r = dynamic_user_pop(d, &uid, &uid_lock_fd);
r = dynamic_user_pop(d, &num, &uid_lock_fd);
if (r < 0) {
int new_uid_lock_fd;
uid_t new_uid;
if (r != -EAGAIN)
goto finish;
return r;
/* OK, nothing stored yet, let's try to find something useful. While we are working on this release the
* lock however, so that nobody else blocks on our NSS lookups. */
(void) lockf(d->storage_socket[0], F_ULOCK, 0);
unlockfp(&storage_socket0_lock);
/* Let's see if a proper, static user or group by this name exists. Try to take the lock on
* /etc/passwd, if that fails with EROFS then /etc is read-only. In that case it's fine if we don't
@ -455,7 +479,7 @@ static int dynamic_user_realize(DynamicUser *d, char **suggested_dirs, uid_t *re
return etc_passwd_lock_fd;
/* First, let's parse this as numeric UID */
r = parse_uid(d->name, &uid);
r = parse_uid(d->name, &num);
if (r < 0) {
struct passwd *p;
struct group *g;
@ -463,9 +487,10 @@ static int dynamic_user_realize(DynamicUser *d, char **suggested_dirs, uid_t *re
if (is_user) {
/* OK, this is not a numeric UID. Let's see if there's a user by this name */
p = getpwnam(d->name);
if (p)
uid = p->pw_uid;
else {
if (p) {
num = p->pw_uid;
gid = p->pw_gid;
} else {
/* if the user does not exist but the group with the same name exists, refuse operation */
g = getgrnam(d->name);
if (g)
@ -475,7 +500,7 @@ static int dynamic_user_realize(DynamicUser *d, char **suggested_dirs, uid_t *re
/* Let's see if there's a group by this name */
g = getgrnam(d->name);
if (g)
uid = (uid_t) g->gr_gid;
num = (uid_t) g->gr_gid;
else {
/* if the group does not exist but the user with the same name exists, refuse operation */
p = getpwnam(d->name);
@ -485,26 +510,27 @@ static int dynamic_user_realize(DynamicUser *d, char **suggested_dirs, uid_t *re
}
}
if (uid == UID_INVALID) {
if (num == UID_INVALID) {
/* No static UID assigned yet, excellent. Let's pick a new dynamic one, and lock it. */
uid_lock_fd = pick_uid(suggested_dirs, d->name, &uid);
uid_lock_fd = pick_uid(suggested_dirs, d->name, &num);
if (uid_lock_fd < 0)
return uid_lock_fd;
}
/* So, we found a working UID/lock combination. Let's see if we actually still need it. */
if (lockf(d->storage_socket[0], F_LOCK, 0) < 0) {
unlink_uid_lock(uid_lock_fd, uid, d->name);
return -errno;
r = lockfp(d->storage_socket[0], &storage_socket0_lock);
if (r < 0) {
unlink_uid_lock(uid_lock_fd, num, d->name);
return r;
}
r = dynamic_user_pop(d, &new_uid, &new_uid_lock_fd);
if (r < 0) {
if (r != -EAGAIN) {
/* OK, something bad happened, let's get rid of the bits we acquired. */
unlink_uid_lock(uid_lock_fd, uid, d->name);
goto finish;
unlink_uid_lock(uid_lock_fd, num, d->name);
return r;
}
/* Great! Nothing is stored here, still. Store our newly acquired data. */
@ -512,10 +538,10 @@ static int dynamic_user_realize(DynamicUser *d, char **suggested_dirs, uid_t *re
/* Hmm, so as it appears there's now something stored in the storage socket. Throw away what we
* acquired, and use what's stored now. */
unlink_uid_lock(uid_lock_fd, uid, d->name);
unlink_uid_lock(uid_lock_fd, num, d->name);
safe_close(uid_lock_fd);
uid = new_uid;
num = new_uid;
uid_lock_fd = new_uid_lock_fd;
}
}
@ -523,19 +549,21 @@ static int dynamic_user_realize(DynamicUser *d, char **suggested_dirs, uid_t *re
/* If the UID/GID was already allocated dynamically, push the data we popped out back in. If it was already
* allocated statically, push the UID back too, but do not push the lock fd in. If we allocated the UID
* dynamically right here, push that in along with the lock fd for it. */
r = dynamic_user_push(d, uid, uid_lock_fd);
r = dynamic_user_push(d, num, uid_lock_fd);
if (r < 0)
goto finish;
return r;
*ret = uid;
r = 0;
if (is_user) {
*ret_uid = num;
*ret_gid = gid != GID_INVALID ? gid : num;
} else
*ret_gid = num;
finish:
(void) lockf(d->storage_socket[0], F_ULOCK, 0);
return r;
return 0;
}
static int dynamic_user_current(DynamicUser *d, uid_t *ret) {
_cleanup_(unlockfp) int storage_socket0_lock = -1;
_cleanup_close_ int lock_fd = -1;
uid_t uid;
int r;
@ -545,23 +573,20 @@ static int dynamic_user_current(DynamicUser *d, uid_t *ret) {
/* Get the currently assigned UID for the user, if there's any. This simply pops the data from the storage socket, and pushes it back in right-away. */
if (lockf(d->storage_socket[0], F_LOCK, 0) < 0)
return -errno;
r = lockfp(d->storage_socket[0], &storage_socket0_lock);
if (r < 0)
return r;
r = dynamic_user_pop(d, &uid, &lock_fd);
if (r < 0)
goto finish;
return r;
r = dynamic_user_push(d, uid, lock_fd);
if (r < 0)
goto finish;
return r;
*ret = uid;
r = 0;
finish:
(void) lockf(d->storage_socket[0], F_ULOCK, 0);
return r;
return 0;
}
static DynamicUser* dynamic_user_ref(DynamicUser *d) {
@ -589,6 +614,7 @@ static DynamicUser* dynamic_user_unref(DynamicUser *d) {
}
static int dynamic_user_close(DynamicUser *d) {
_cleanup_(unlockfp) int storage_socket0_lock = -1;
_cleanup_close_ int lock_fd = -1;
uid_t uid;
int r;
@ -596,25 +622,20 @@ static int dynamic_user_close(DynamicUser *d) {
/* Release the user ID, by releasing the lock on it, and emptying the storage socket. After this the user is
* unrealized again, much like it was after it the DynamicUser object was first allocated. */
if (lockf(d->storage_socket[0], F_LOCK, 0) < 0)
return -errno;
r = lockfp(d->storage_socket[0], &storage_socket0_lock);
if (r < 0)
return r;
r = dynamic_user_pop(d, &uid, &lock_fd);
if (r == -EAGAIN) {
if (r == -EAGAIN)
/* User wasn't realized yet, nothing to do. */
r = 0;
goto finish;
}
return 0;
if (r < 0)
goto finish;
return r;
/* This dynamic user was realized and dynamically allocated. In this case, let's remove the lock file. */
unlink_uid_lock(lock_fd, uid, d->name);
r = 1;
finish:
(void) lockf(d->storage_socket[0], F_ULOCK, 0);
return r;
return 1;
}
static DynamicUser* dynamic_user_destroy(DynamicUser *d) {
@ -823,21 +844,19 @@ int dynamic_creds_realize(DynamicCreds *creds, char **suggested_paths, uid_t *ui
/* Realize both the referenced user and group */
if (creds->user) {
r = dynamic_user_realize(creds->user, suggested_paths, &u, true);
r = dynamic_user_realize(creds->user, suggested_paths, &u, &g, true);
if (r < 0)
return r;
}
if (creds->group && creds->group != creds->user) {
r = dynamic_user_realize(creds->group, suggested_paths, &g, false);
r = dynamic_user_realize(creds->group, suggested_paths, NULL, &g, false);
if (r < 0)
return r;
} else
g = u;
}
*uid = u;
*gid = g;
return 0;
}