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authorLennart Poettering <lennart@poettering.net>2014-07-07 18:57:09 +0200
committerLennart Poettering <lennart@poettering.net>2014-07-07 18:57:09 +0200
commit45035609fcfc3fe09324988c4929a3c147171c23 (patch)
tree17968a9f24515cef3f744eda4cb933778029f2ce /src/shared
parent30f10abf42f9e4d251a0b45b07812aafdef6be7c (diff)
firstboot: follow lock protocol when changing /etc/shadow
Diffstat (limited to 'src/shared')
-rw-r--r--src/shared/util.c40
-rw-r--r--src/shared/util.h2
2 files changed, 42 insertions, 0 deletions
diff --git a/src/shared/util.c b/src/shared/util.c
index bef87304e6..88511b69c0 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -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;
+}
diff --git a/src/shared/util.h b/src/shared/util.h
index 7c9842b3e6..fb852d6973 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -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);