diff options
| -rw-r--r-- | src/pam-module.c | 37 |
1 files changed, 33 insertions, 4 deletions
diff --git a/src/pam-module.c b/src/pam-module.c index 08de006f68..1834dd92e6 100644 --- a/src/pam-module.c +++ b/src/pam-module.c @@ -97,16 +97,30 @@ static int open_file_and_lock(const char *fn) { if ((fd = open(fn, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_CREAT, 0600)) < 0) return -errno; + /* The BSD socket semantics are a lot nicer than those of + * POSIX locks. Which is why we use flock() here. BSD locking + * does not work across NFS which however is not needed here + * as the filesystems in question should be local, and only + * locally accessible, and most likely even tmpfs. */ + if (flock(fd, LOCK_EX) < 0) return -errno; return fd; } -static uint64_t get_session_id(void) { +enum { + SESSION_ID_AUDIT = 'a', + SESSION_ID_COUNTER = 'c', + SESSION_ID_RANDOM = 'r' +}; + +static uint64_t get_session_id(int *mode) { char *s; int fd; + assert(mode); + /* First attempt: let's use the session ID of the audit * system, if it is available. */ if (read_one_line_file("/proc/self/sessionid", &s) >= 0) { @@ -116,8 +130,10 @@ static uint64_t get_session_id(void) { r = safe_atou32(s, &u); free(s); - if (r >= 0 && u != (uint32_t) -1) + if (r >= 0 && u != (uint32_t) -1) { + *mode = SESSION_ID_AUDIT; return (uint64_t) u; + } } /* Second attempt, use our own counter. */ @@ -149,10 +165,14 @@ static uint64_t get_session_id(void) { close_nointr_nofail(fd); - if (r >= 0) + if (r >= 0) { + *mode = SESSION_ID_COUNTER; return counter; + } } + *mode = SESSION_ID_RANDOM; + /* Last attempt, pick a random value */ return (uint64_t) random_ull(); } @@ -283,12 +303,21 @@ _public_ PAM_EXTERN int pam_sm_open_session( /* Reuse or create XDG session ID */ if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) { + int mode; - if (asprintf(&buf, "%llu", (unsigned long long) get_session_id()) < 0) { + if (asprintf(&buf, "%llux", (unsigned long long) get_session_id(&mode)) < 0) { r = PAM_BUF_ERR; goto finish; } + /* To avoid id clashes we add the session id + * source to our session ids. Note that the + * session id source might change during + * runtime, because a filesystem became + * writable or the system reconfigured. */ + buf[strlen(buf)-1] = + mode != SESSION_ID_AUDIT ? (char) mode : 0; + if ((r = pam_misc_setenv(handle, "XDG_SESSION_ID", buf, 0)) != PAM_SUCCESS) { pam_syslog(handle, LOG_ERR, "Failed to set session id."); goto finish; |