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