src/lib/safe-mkstemp.c

	safe-mkstemp.c revision 7b9f0c6aba07358e5520dc60c058126a4cae4056
/* Copyright (c) 2007-2008 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "str.h"
#include "hex-binary.h"
#include "randgen.h"
#include "hostpid.h"
#include "safe-mkstemp.h"

#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>

int safe_mkstemp(string_t *prefix, mode_t mode, uid_t uid, gid_t gid)
{
    size_t prefix_len;
    struct stat st;
    unsigned char randbuf[8];
    int fd;

    prefix_len = str_len(prefix);
    for (;;) {
        do {
            random_fill_weak(randbuf, sizeof(randbuf));
            str_truncate(prefix, prefix_len);
            str_append(prefix,
                   binary_to_hex(randbuf, sizeof(randbuf)));
        } while (lstat(str_c(prefix), &st) == 0);

        if (errno != ENOENT) {
            i_error("stat(%s) failed: %m", str_c(prefix));
            return -1;
        }

        fd = open(str_c(prefix), O_RDWR | O_EXCL | O_CREAT, mode);
        if (fd != -1)
            break;

        if (errno != EEXIST) {
            if (errno != ENOENT && errno != EACCES)
                i_error("open(%s) failed: %m", str_c(prefix));
            return -1;
        }
    }
    if (uid != (uid_t)-1 || gid != (gid_t)-1) {
        if (fchown(fd, uid, gid) < 0) {
            i_error("fchown(%s, %ld, %ld) failed: %m",
                str_c(prefix),
                uid == (uid_t)-1 ? -1L : (long)uid,
                gid == (gid_t)-1 ? -1L : (long)gid);
            (void)close(fd);
            (void)unlink(str_c(prefix));
            return -1;
        }
    }
    return fd;
}

int safe_mkstemp_hostpid(string_t *prefix, mode_t mode, uid_t uid, gid_t gid)
{
    str_printfa(prefix, "%s.%s.", my_hostname, my_pid);
    return safe_mkstemp(prefix, mode, uid, gid);
}