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sysdeps: Improve error reporting for looking up a user

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Our implementation always assumed that both code paths set errno, but
according to their API documentation, getpwnam_r and getpwuid_r actually
don't: they *return* a code from the same pseudo-enum as errno. They
also return 0 (but with a NULL struct passwd) if the user is not found,
which these APIs don't count as an error (but we do).

Similarly, in the legacy getpwnam/getpwuid code path, it is unspecified
whether looking up a nonexistent user will set errno or not.

Having retrieved an errno-like error code, we might as well use it in
the human-readable message and not just the machine-readable code,
because the human-readable message is what ends up in the system log.

Helps: https://gitlab.freedesktop.org/dbus/dbus/-/issues/343
Signed-off-by: Simon McVittie <smcv@collabora.com>
This commit is contained in:
Simon McVittie 2023-06-29 17:28:40 +01:00
parent 12b367daaa
commit 8de818153b
1 changed files with 29 additions and 7 deletions
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36
dbus/dbus-sysdeps-unix.c
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@ -2730,8 +2730,8 @@ fill_user_info (DBusUserInfo *info,
{
struct passwd *p;
char *buf = NULL;
#ifdef HAVE_GETPWNAM_R
int result;
#ifdef HAVE_GETPWNAM_R
size_t buflen;
struct passwd p_str;
@ -2774,16 +2774,32 @@ fill_user_info (DBusUserInfo *info,
}
}
/* There are three possibilities:
* - an error: result is a nonzero error code, p should be NULL
* - name or uid not found: result is 0, p is NULL
* - success: result is 0, p should be &p_str
*
* Ensure that in all failure cases, p is set to NULL, matching the
* getpwuid/getpwnam interface. */
if (result != 0 || p != &p_str)
p = NULL;
#else /* ! HAVE_GETPWNAM_R */
/* I guess we're screwed on thread safety here */
#warning getpwnam_r() not available, please report this to the dbus maintainers with details of your OS
/* It is unspecified whether "failed to find" counts as an error,
* or whether it's reported as p == NULL without touching errno.
* Reset errno so we can distinguish. */
errno = 0;
if (uid != DBUS_UID_UNSET)
p = getpwuid (uid);
else
p = getpwnam (username_c);
/* Always initialized, but only meaningful if p is NULL */
result = errno;
#endif /* ! HAVE_GETPWNAM_R */
if (p != NULL)
@ -2798,15 +2814,21 @@ fill_user_info (DBusUserInfo *info,
else
{
DBusError local_error = DBUS_ERROR_INIT;
const char *error_str;
if (result == 0)
error_str = "not found";
else
error_str = _dbus_strerror (result);
if (uid != DBUS_UID_UNSET)
dbus_set_error (&local_error, _dbus_error_from_errno (errno),
"User ID " DBUS_UID_FORMAT " unknown or no memory to allocate password entry",
uid);
dbus_set_error (&local_error, _dbus_error_from_errno (result),
"Looking up user ID " DBUS_UID_FORMAT ": %s",
uid, error_str);
else
dbus_set_error (&local_error, _dbus_error_from_errno (errno),
"User \"%s\" unknown or no memory to allocate password entry\n",
username_c ? username_c : "???");
dbus_set_error (&local_error, _dbus_error_from_errno (result),
"Looking up user \"%s\": %s",
username_c ? username_c : "???", error_str);
_dbus_verbose ("%s", local_error.message);
dbus_move_error (&local_error, error);