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shared/pam-util: add pam_syslog_errno() wrapper that sets errno

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So far our pam code was using strerror_safe(). But that's not a good approach,
because strerror_safe() is not thread-safe, and the pam code is "library code"
that should be thread-safe. In fact, the whole effort to use strerror() is
unnecessary, because pam_syslog() is documented to support %m. The
implementation in linux-pam simply uses vasprintf(). If we use %m too, we get
rid of the issue. The wrapper sets errno temporarily from the argument.

Apparently some PAM consumers run multiple PAM stacks in threads, so we should
avoid non-thread-safe code.

The new helper returns PAM_BUF_ERR for ENOMEM, and PAM_SERVICE_ERR in other
cases. This may change the returned code in some cases, but I think a) it
doesn't matter much, b) it's probably for the better. E.g. we might now return
PAM_SERVICE_ERR if the dbus message is borked, and PAM_SERVICE_ERR seems
appropriate.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2022-10-04 14:19:12 +02:00
parent 50c5b991df
commit b1eff892bb
2 changed files with 26 additions and 21 deletions
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28
src/shared/pam-util.c
View File

@ -9,22 +9,16 @@
#include "macro.h"
#include "pam-util.h"
int pam_log_oom(pam_handle_t *handle) {
/* This is like log_oom(), but uses PAM logging */
pam_syslog(handle, LOG_ERR, "Out of memory.");
return PAM_BUF_ERR;
}
int pam_syslog_errno(pam_handle_t *handle, int level, int error, const char *format, ...) {
va_list ap;
int pam_bus_log_create_error(pam_handle_t *handle, int r) {
/* This is like bus_log_create_error(), but uses PAM logging */
pam_syslog(handle, LOG_ERR, "Failed to create bus message: %s", strerror_safe(r));
return PAM_BUF_ERR;
}
LOCAL_ERRNO(error);
int pam_bus_log_parse_error(pam_handle_t *handle, int r) {
/* This is like bus_log_parse_error(), but uses PAM logging */
pam_syslog(handle, LOG_ERR, "Failed to parse bus message: %s", strerror_safe(r));
return PAM_BUF_ERR;
va_start(ap, format);
pam_vsyslog(handle, LOG_ERR, format, ap);
va_end(ap);
return error == -ENOMEM ? PAM_BUF_ERR : PAM_SERVICE_ERR;
}
static void cleanup_system_bus(pam_handle_t *handle, void *data, int error_status) {
@ -50,10 +44,8 @@ int pam_acquire_bus_connection(pam_handle_t *handle, sd_bus **ret) {
}
r = sd_bus_open_system(&bus);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror_safe(r));
return PAM_SERVICE_ERR;
}
if (r < 0)
return pam_syslog_errno(handle, LOG_ERR, r, "Failed to connect to system bus: %m");
r = pam_set_data(handle, "systemd-system-bus", bus, cleanup_system_bus);
if (r != PAM_SUCCESS) {

19
src/shared/pam-util.h
View File

@ -5,9 +5,22 @@
#include "sd-bus.h"
int pam_log_oom(pam_handle_t *handle);
int pam_bus_log_create_error(pam_handle_t *handle, int r);
int pam_bus_log_parse_error(pam_handle_t *handle, int r);
int pam_syslog_errno(pam_handle_t *handle, int level, int error, const char *format, ...) _printf_(4,5);
static inline int pam_log_oom(pam_handle_t *handle) {
/* This is like log_oom(), but uses PAM logging */
return pam_syslog_errno(handle, LOG_ERR, ENOMEM, "Out of memory.");
}
static inline int pam_bus_log_create_error(pam_handle_t *handle, int r) {
/* This is like bus_log_create_error(), but uses PAM logging */
return pam_syslog_errno(handle, LOG_ERR, r, "Failed to create bus message: %m");
}
static inline int pam_bus_log_parse_error(pam_handle_t *handle, int r) {
/* This is like bus_log_parse_error(), but uses PAM logging */
return pam_syslog_errno(handle, LOG_ERR, r, "Failed to parse bus message: %m");
}
int pam_acquire_bus_connection(pam_handle_t *handle, sd_bus **ret);
int pam_release_bus_connection(pam_handle_t *handle);