/*
 * touch2 v2.0
 *    Change last-inode-change times on files
 *
 * (c) 2002, 2005, 2006 by Ighighi (ighighi at gmail dot com)
 * Venezuela
 *
 * BSD License
 *
 * DISCLAIMER: USE AT YOUR OWN RISK. I'M NOT RESPONSIBLE FOR ANYTHING!
 *
 * OVERVIEW:
 *    You use touch(1) to change the last-access & last-modification times
 *    of the files (or directories) you read or modify. The problem is that
 *    doing this will change the last-inode-change time to the current time.
 *    Now you may use touch2 right after using touch(1) to erase all evidence.
 *    Stealth hacking is the motto!
 *    IT MUST BE RUN AS ROOT!
 *
 * DETAILS:
 *    Firstly, we set the system time to the desired ctime (you must be root).
 *    Then we call chmod(2) to force an update of the inode's ctime.
 *    Later, we restore the system time as if nothing happened.
 *
 * BUGS / LIMITATIONS:
 *    + Nanosecond resolution (if supported) it's impossible to get it right.
 *    + Newer *BSD restrict settimeofday(2) when running in secure mode.
 *
 * TO DO:
 *    + Low-level filesystem hacking to overcome limitations #1 & #2
 *    + lutimes() for symbolic links
 *
 * CHANGELOG v2.0:
 *    + Enhanced portability. Bug fixes. New options. Signal handling.
 *    + chmod() is a more cleaner way to touch the inode than utime/utimes
 */

#define _FILE_OFFSET_BITS 64

static char usage[] =
    "Usage: ./touch2 [-a|-m] [-r file|-t timestamp] files...\n"
    "  Options:\n"
    "  -h       Print this help and exit\n"
    "  -a       Use the file's last-access time\n"
    "  -m       Use the file's last-modification time\n"
    "  -r file  Use this file's time instead of current time\n"
    "  -t [[[YYYY:]MM:]DD:]hh:mm:ss[.uuuuuu]\n"
    "           Use this timestamp instead of current time\n";

#define ERROR_MUTUALLY_EXCLUSIVE1 \
    "ERROR: The -a, -m & -t options are mutually exclusive!\n"

#define ERROR_MUTUALLY_EXCLUSIVE2 \
    "ERROR: The -r & -t options are mutually exclusive!\n"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <time.h>

#ifndef timerisset
#define timerisset(tvp)        ((tvp)->tv_sec || (tvp)->tv_usec)
#endif

#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
#ifndef _POSIX_SOURCE
#define ST_ATIME_NSEC      st_atimespec.tv_nsec
#define ST_MTIME_NSEC      st_mtimespec.tv_nsec
#define ST_CTIME_NSEC      st_ctimespec.tv_nsec
#else
#define ST_ATIME_NSEC      st_atimensec
#define ST_MTIME_NSEC      st_mtimensec
#define ST_CTIME_NSEC      st_ctimensec
#endif
#elif defined(__linux__) && defined(_STATBUF_ST_NSEC)
#if defined(_BSD_SOURCE) || defined(_SVID_SOURCE)
#define ST_ATIME_NSEC      st_atim.tv_nsec
#define ST_MTIME_NSEC      st_mtim.tv_nsec
#define ST_CTIME_NSEC      st_ctim.tv_nsec
#else
#define ST_ATIME_NSEC      st_atimensec
#define ST_MTIME_NSEC      st_mtimensec
#define ST_CTIME_NSEC      st_ctimensec
#endif
#elif defined(sun) && (defined(__SVR4) || defined(__svr4__))
#if defined(_XOPEN_SOURCE) || defined(_POSIX_C_SOURCE)
#define ST_ATIME_NSEC      st_atim.__tv_nsec
#define ST_MTIME_NSEC      st_mtim.__tv_nsec
#define ST_CTIME_NSEC      st_ctim.__tv_nsec
#else
#define ST_ATIME_NSEC      st_atim.tv_nsec
#define ST_MTIME_NSEC      st_mtim.tv_nsec
#define ST_CTIME_NSEC      st_ctim.tv_nsec
#endif
#endif

/* Use the file's atime instead of ctime as reference */
static int use_atime = 0;
/* Use the file's mtime... */
static int use_mtime = 0;

/*
 * Returns 0 on success, -1 on (system call) error
 */
static int change_ctime(const char *file, struct timeval ctime)
{
#ifdef SIG_SETMASK
    sigset_t newsigmask, oldsigmask;
#endif
    struct timeval now;
    struct stat inode;
    int status = 0;

    if (file == NULL)
	return -1;

    /* Get file's inode information */
    while (stat(file, &inode) < 0) {
        if (errno != EINTR) {
            perror("stat()");
            return -1;
        }
    }

    if (!timerisset(&ctime)) {
        if (use_atime) {        /* Use the file's own atime */
            ctime.tv_sec = inode.st_atime;
#ifdef ST_ATIME_NSEC
            ctime.tv_usec = inode.ST_ATIME_NSEC / 1000;
#endif
        }
        else
        if (use_mtime) {        /* Use the file's own mtime */
            ctime.tv_sec = inode.st_mtime;
#ifdef ST_MTIME_NSEC
            ctime.tv_usec = inode.ST_MTIME_NSEC / 1000;
#endif
        }
    }

    /* Save current time */
    if (gettimeofday(&now, NULL) < 0) {
        perror("gettimeofday()");
        return -1;
    }

#ifdef SIG_SETMASK
    /* Block ALL signals */
    if (sigfillset(&newsigmask) < 0) {
        perror("sigfillset()");
        return -1;
    }
    if (sigprocmask(SIG_SETMASK, &newsigmask, &oldsigmask) < 0) {
        perror("sigprocmask()");
        return -1;
    }
#endif

/* ----- BEGIN CRITICAL SECTION ----- */

    /* If there's no time, it will be the current time */
    if (timerisset(&ctime)) {
        /* Set system time to ctime */
        if (settimeofday(&ctime, NULL) < 0) {
            perror("settimeofday(ctime)");
            status--;
            goto end;   /* Restore signal mask */
        }
    }

    /* Touch inode */
    while (chmod(file, inode.st_mode) < 0) {
        if (errno != EINTR) {
            perror("chmod()");
            status--;
        }
    }

    if (timerisset(&ctime)) {
        /* Restore system time */
        if (settimeofday(&now, NULL) < 0) {
            perror("settimeofday(now)");
            status--;
        }
    }

/* ----- END CRITICAL SECTION ----- */

end:

#ifdef SIG_SETMASK
    /* Unblock signals */
    if (sigprocmask(SIG_SETMASK, &oldsigmask, NULL) < 0) {
        perror("sigprocmask()");
        return -1;
    }
#endif

    return ((status != 0) ? -1 : 0);
}

static int nstrchr(const char *s, char c)
{
    int n = 0;

    if (!s) return 0;

    while (*s)
        if (*s++ == c) n++;

    return n;
}

/* converts from "[[[YYYY:]MM:]DD:]hh:mm:ss[.uuuuuu]" to struct timeval */
static void str2timeval(const char *s, struct timeval *tvp)
{
#define DELIM ':'
#define DOT '.'
    struct tm *tp;
    struct tm tm;
    time_t now;
    int n;

    if (s == NULL || tvp == NULL)
        return;

    now = time(NULL);
    tp = localtime(&now);

    memset(&tm, 0, sizeof(tm));
    /* Default is current date & time */
    memcpy(&tm, tp, sizeof(tm));

    tvp->tv_sec = tvp->tv_usec = 0;

    n = nstrchr(s, DELIM);

    if (n > 4) {
        tm.tm_year = atoi(s) - 1900;
        s = strchr(s, DELIM) + 1;
    }
    if (n > 3) {
        tm.tm_mon = atoi(s) - 1;
        s = strchr(s, DELIM) + 1;
    }
    if (n > 2) {
        tm.tm_mday = atoi(s);
        s = strchr(s, DELIM) + 1;
    }
    if (n > 1) {
        tm.tm_hour = atoi(s);
        s = strchr(s, DELIM) + 1;
    }
    if (n > 0) {
        tm.tm_min = atoi(s);
        s = strchr(s, DELIM) + 1;
    }
    tm.tm_sec = atoi(s);

    tvp->tv_sec = mktime(&tm);

    if ((s = strchr(s, DOT)) != NULL)
        if (*++s != '\0')
	    tvp->tv_usec = atol(s);

    return;
}

static void exit_usage(int status)
{
    FILE *fp;

    if (status) fp = stderr;
    else        fp = stdout;

    fprintf(fp, "touch2 by Ighighi\n");
    fprintf(fp, "%s\n", usage);

    exit(status);
}

int main(int argc, char *argv[])
{
    struct timeval new_ctime = { 0, 0 };
    char *rfile = NULL; /* Reference file */
    struct stat inode;
    int i;

    for (i = 1; i < argc; i++) {
        if (argv[i][0] == '-') {
            switch (argv[i][1]) {
            case 'a':   /* use atime */
                if (use_mtime || timerisset(&new_ctime)) {
                    fprintf(stderr, "%s: %s\n", argv[0], ERROR_MUTUALLY_EXCLUSIVE1);
                    exit_usage(1);
                }
                use_atime = 1;
                break;
            case 'm':   /* use mtime */
                if (use_atime || timerisset(&new_ctime)) {
                    fprintf(stderr, "%s: %s\n", argv[0], ERROR_MUTUALLY_EXCLUSIVE1);
                    exit_usage(1);
                }
                use_mtime = 1;
                break;
            case 'r':   /* use rfile's ctime */
                if (timerisset(&new_ctime)) {
                    fprintf(stderr, "%s: %s\n", argv[0], ERROR_MUTUALLY_EXCLUSIVE2);
                    exit_usage(1);
                }
                if ((rfile = argv[++i]) == NULL)
                    exit_usage(1);
                break;
            case 't':   /* use timestamp */
                if (use_atime || use_mtime) {
                    fprintf(stderr, "%s: %s\n", argv[0], ERROR_MUTUALLY_EXCLUSIVE1);
                    exit_usage(1);
                }
                if (rfile != NULL) {
                    fprintf(stderr, "%s: %s\n", argv[0], ERROR_MUTUALLY_EXCLUSIVE2);
                    exit_usage(1);
                }
                if (argv[++i] == NULL)
                    exit_usage(1);
                str2timeval(argv[i], &new_ctime);
                break;
            case 'h':   /* help */
                exit_usage(0);
            default:
                exit_usage(1);
            }
        }
        else {
            break;
        }
    }

    if (i >= argc) {
        exit_usage(1);
    }

    if (rfile != NULL) {
        while (stat(rfile, &inode) < 0) {
            if (errno != EINTR) {
                perror(rfile);
                exit(1);
            }
        }

        if (use_atime) {
            new_ctime.tv_sec = inode.st_atime;
#ifdef ST_ATIME_NSEC
            new_ctime.tv_usec = inode.ST_ATIME_NSEC / 1000;
#endif
        }
        else if (use_mtime) {
            new_ctime.tv_sec = inode.st_mtime;
#ifdef ST_MTIME_NSEC
            new_ctime.tv_usec = inode.ST_MTIME_NSEC / 1000;
#endif
        }
        else {
            new_ctime.tv_sec = inode.st_ctime;
#ifdef ST_CTIME_NSEC
            new_ctime.tv_usec = inode.ST_CTIME_NSEC / 1000;
#endif
        }

    }

    for (; i < argc; i++) {
        if (change_ctime(argv[i], new_ctime) < 0) {
            fprintf(stderr, "%s: There was an error processing \"%s\"\n",
                    argv[0], argv[i]);
        }
    }

    exit(0);
}