getpeereid.c

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/*-------------------------------------------------------------------------
 *
 * getpeereid.c
 *      get peer userid for UNIX-domain socket connection
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/port/getpeereid.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "c.h"
 
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#ifdef HAVE_UCRED_H
#include <ucred.h>
#endif
#ifdef HAVE_SYS_UCRED_H
#include <sys/ucred.h>
#endif
 
 
/*
 * BSD-style getpeereid() for platforms that lack it.
 */
int
getpeereid(int sock, uid_t *uid, gid_t *gid)
{
#if defined(SO_PEERCRED)
    /* Linux: use getsockopt(SO_PEERCRED) */
    struct ucred peercred;
    socklen_t   so_len = sizeof(peercred);
 
    if (getsockopt(sock, SOL_SOCKET, SO_PEERCRED, &peercred, &so_len) != 0 ||
        so_len != sizeof(peercred))
        return -1;
    *uid = peercred.uid;
    *gid = peercred.gid;
    return 0;
#elif defined(LOCAL_PEERCRED)
    /* Debian with FreeBSD kernel: use getsockopt(LOCAL_PEERCRED) */
    struct xucred peercred;
    socklen_t   so_len = sizeof(peercred);
 
    if (getsockopt(sock, 0, LOCAL_PEERCRED, &peercred, &so_len) != 0 ||
        so_len != sizeof(peercred) ||
        peercred.cr_version != XUCRED_VERSION)
        return -1;
    *uid = peercred.cr_uid;
    *gid = peercred.cr_gid;
    return 0;
#elif defined(HAVE_GETPEERUCRED)
    /* Solaris: use getpeerucred() */
    ucred_t    *ucred;
 
    ucred = NULL;               /* must be initialized to NULL */
    if (getpeerucred(sock, &ucred) == -1)
        return -1;
 
    *uid = ucred_geteuid(ucred);
    *gid = ucred_getegid(ucred);
    ucred_free(ucred);
 
    if (*uid == (uid_t) (-1) || *gid == (gid_t) (-1))
        return -1;
    return 0;
#else
    /* No implementation available on this platform */
    errno = ENOSYS;
    return -1;
#endif
}