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firstboot: follow lock protocol when changing /etc/shadow

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This commit is contained in:
Lennart Poettering 2014-07-07 18:57:09 +02:00
parent 30f10abf42
commit 45035609fc
4 changed files with 51 additions and 38 deletions
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9
src/firstboot/firstboot.c
View file

@ -530,7 +530,6 @@ static int write_root_shadow(const char *path, const struct spwd *p) {
assert(path);
assert(p);
mkdir_parents(path, 0755);
RUN_WITH_UMASK(0777)
f = fopen(path, "wex");
if (!f)
@ -560,6 +559,8 @@ static int process_root_password(void) {
.sp_expire = -1,
.sp_flag = (unsigned long) -1, /* this appears to be what everybody does ... */
};
_cleanup_close_ int lock = -1;
char salt[3+16+1+1];
uint8_t raw[16];
unsigned i;
@ -572,6 +573,12 @@ static int process_root_password(void) {
if (faccessat(AT_FDCWD, etc_shadow, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
return 0;
mkdir_parents(etc_shadow, 0755);
lock = take_password_lock(arg_root);
if (lock < 0)
return lock;
if (arg_copy_root_password && arg_root) {
struct spwd *p;

40
src/shared/util.c
View file

@ -6823,3 +6823,43 @@ bool is_localhost(const char *hostname) {
endswith(hostname, ".localdomain") ||
endswith(hostname, ".localdomain.");
}
int take_password_lock(const char *root) {
struct flock flock = {
.l_type = F_WRLCK,
.l_whence = SEEK_SET,
.l_start = 0,
.l_len = 0,
};
const char *path;
int fd, r;
/* This is roughly the same as lckpwdf(), but not as awful. We
* don't want to use alarm() and signals, hence we implement
* our own trivial version of this.
*
* Note that shadow-utils also takes per-database locks in
* addition to lckpwdf(). However, we don't given that they
* are redundant as they they invoke lckpwdf() first and keep
* it during everything they do. The per-database locks are
* awfully racy, and thus we just won't do them. */
if (root)
path = strappenda(root, "/etc/.pwd.lock");
else
path = "/etc/.pwd.lock";
fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600);
if (fd < 0)
return -errno;
r = fcntl(fd, F_SETLKW, &flock);
if (r < 0) {
safe_close(fd);
return -errno;
}
return fd;
}

2
src/shared/util.h
View file

@ -964,3 +964,5 @@ char *tempfn_xxxxxx(const char *p);
char *tempfn_random(const char *p);
bool is_localhost(const char *hostname);
int take_password_lock(const char *root);

38
src/sysusers/sysusers.c
View file

@ -1379,42 +1379,6 @@ static int read_config_file(const char *fn, bool ignore_enoent) {
return r;
}
static int take_lock(void) {
struct flock flock = {
.l_type = F_WRLCK,
.l_whence = SEEK_SET,
.l_start = 0,
.l_len = 0,
};
const char *path;
int fd, r;
/* This is roughly the same as lckpwdf(), but not as awful. We
* don't want to use alarm() and signals, hence we implement
* our own trivial version of this.
*
* Note that shadow-utils also takes per-database locks in
* addition to lckpwdf(). However, we don't given that they
* are redundant as they they invoke lckpwdf() first and keep
* it during everything they do. The per-database locks are
* awfully racy, and thus we just won't do them. */
path = fix_root("/etc/.pwd.lock");
fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600);
if (fd < 0)
return -errno;
r = fcntl(fd, F_SETLKW, &flock);
if (r < 0) {
safe_close(fd);
return -errno;
}
return fd;
}
static void free_database(Hashmap *by_name, Hashmap *by_id) {
char *name;
@ -1548,7 +1512,7 @@ int main(int argc, char *argv[]) {
if (r < 0)
goto finish;
lock = take_lock();
lock = take_password_lock(arg_root);
if (lock < 0) {
log_error("Failed to take lock: %s", strerror(-lock));
goto finish;