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/*-------------------------------------------------------------------------
*
* thread.c
*
* Prototypes and macros around system calls, used to help make
* threaded libraries reentrant and safe to use from threaded applications.
*
* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
*
* src/port/thread.c
*
*-------------------------------------------------------------------------
*/
#include "c.h"
#include <pwd.h>
/*
* Threading sometimes requires specially-named versions of functions
* that return data in static buffers, like strerror_r() instead of
* strerror(). Other operating systems use pthread_setspecific()
* and pthread_getspecific() internally to allow standard library
* functions to return static data to threaded applications. And some
* operating systems have neither.
*
* Additional confusion exists because many operating systems that
* use pthread_setspecific/pthread_getspecific() also have *_r versions
* of standard library functions for compatibility with operating systems
* that require them. However, internally, these *_r functions merely
* call the thread-safe standard library functions.
*
* For example, BSD/OS 4.3 uses Bind 8.2.3 for getpwuid(). Internally,
* getpwuid() calls pthread_setspecific/pthread_getspecific() to return
* static data to the caller in a thread-safe manner. However, BSD/OS
* also has getpwuid_r(), which merely calls getpwuid() and shifts
* around the arguments to match the getpwuid_r() function declaration.
* Therefore, while BSD/OS has getpwuid_r(), it isn't required. It also
* doesn't have strerror_r(), so we can't fall back to only using *_r
* functions for threaded programs.
*
* The current setup is to try threading in this order:
*
* use *_r function names if they exit
* (*_THREADSAFE=yes)
* use non-*_r functions if they are thread-safe
*/
#ifndef WIN32
/*
* Wrapper around getpwuid() or getpwuid_r() to mimic POSIX getpwuid_r()
* behaviour, if that function is not available or required.
*
* Per POSIX, the possible cases are:
* success: returns zero, *result is non-NULL
* uid not found: returns zero, *result is NULL
* error during lookup: returns an errno code, *result is NULL
* (caller should *not* assume that the errno variable is set)
*/
static int
pqGetpwuid(uid_t uid, struct passwd *resultbuf, char *buffer,
size_t buflen, struct passwd **result)
{
#if defined(FRONTEND) && defined(ENABLE_THREAD_SAFETY) && defined(HAVE_GETPWUID_R)
return getpwuid_r(uid, resultbuf, buffer, buflen, result);
#else
/* no getpwuid_r() available, just use getpwuid() */
errno = 0;
*result = getpwuid(uid);
/* paranoia: ensure we return zero on success */
return (*result == NULL) ? errno : 0;
#endif
}
/*
* pg_get_user_name - get the name of the user with the given ID
*
* On success, the user name is returned into the buffer (of size buflen),
* and "true" is returned. On failure, a localized error message is
* returned into the buffer, and "false" is returned.
*/
bool
pg_get_user_name(uid_t user_id, char *buffer, size_t buflen)
{
char pwdbuf[BUFSIZ];
struct passwd pwdstr;
struct passwd *pw = NULL;
int pwerr;
pwerr = pqGetpwuid(user_id, &pwdstr, pwdbuf, sizeof(pwdbuf), &pw);
if (pw != NULL)
{
strlcpy(buffer, pw->pw_name, buflen);
return true;
}
if (pwerr != 0)
snprintf(buffer, buflen,
_("could not look up local user ID %d: %s"),
(int) user_id,
strerror_r(pwerr, pwdbuf, sizeof(pwdbuf)));
else
snprintf(buffer, buflen,
_("local user with ID %d does not exist"),
(int) user_id);
return false;
}
/*
* pg_get_user_home_dir - get the home directory of the user with the given ID
*
* On success, the directory path is returned into the buffer (of size buflen),
* and "true" is returned. On failure, a localized error message is
* returned into the buffer, and "false" is returned.
*
* Note that this does not incorporate the common behavior of checking
* $HOME first, since it's independent of which user_id is queried.
*/
bool
pg_get_user_home_dir(uid_t user_id, char *buffer, size_t buflen)
{
char pwdbuf[BUFSIZ];
struct passwd pwdstr;
struct passwd *pw = NULL;
int pwerr;
pwerr = pqGetpwuid(user_id, &pwdstr, pwdbuf, sizeof(pwdbuf), &pw);
if (pw != NULL)
{
strlcpy(buffer, pw->pw_dir, buflen);
return true;
}
if (pwerr != 0)
snprintf(buffer, buflen,
_("could not look up local user ID %d: %s"),
(int) user_id,
strerror_r(pwerr, pwdbuf, sizeof(pwdbuf)));
else
snprintf(buffer, buflen,
_("local user with ID %d does not exist"),
(int) user_id);
return false;
}
#endif /* !WIN32 */
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