make_dirs.c

[詳解]

/*++
/* NAME
/*  make_dirs 3
/* SUMMARY
/*  create directory hierarchy
/* SYNOPSIS
/*  #include <make_dirs.h>
/*
/*  int make_dirs(path, perms)
/*  const char *path;
/*  int perms;
/* DESCRIPTION
/*  make_dirs() creates the directory specified in \fIpath\fR, and
/*  creates any missing intermediate directories as well. Directories
/*  are created with the permissions specified in \fIperms\fR, as
/*  modified by the process umask.
/* DIAGNOSTICS:
/*  Fatal: out of memory. make_dirs() returns 0 in case of success.
/*  In case of problems. make_dirs() returns -1 and \fIerrno\fR
/*  reflects the nature of the problem.
/* SEE ALSO
/*  mkdir(2)
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

/* System library. */

#include <sys_defs.h>
#include <sys/stat.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>

/* Utility library. */

#include "msg.h"
#include "mymalloc.h"
#include "stringops.h"
#include "make_dirs.h"
#include "warn_stat.h"

/* make_dirs - create directory hierarchy */

int     make_dirs(const char *path, int perms)
{
    const char *myname = "make_dirs";
    char   *saved_path;
    unsigned char *cp;
    int     saved_ch;
    struct stat st;
    int     ret;
    mode_t  saved_mode = 0;
    gid_t   egid = -1;

    /*
     * Initialize. Make a copy of the path that we can safely clobber.
     */
    cp = (unsigned char *) (saved_path = mystrdup(path));

    /*
     * I didn't like the 4.4BSD "mkdir -p" implementation, but coming up with
     * my own took a day, spread out over several days.
     */
#define SKIP_WHILE(cond, ptr) { while(*ptr && (cond)) ptr++; }

    SKIP_WHILE(*cp == '/', cp);

    for (;;) {
    SKIP_WHILE(*cp != '/', cp);
    if ((saved_ch = *cp) != 0)
        *cp = 0;
    if ((ret = stat(saved_path, &st)) >= 0) {
        if (!S_ISDIR(st.st_mode)) {
        errno = ENOTDIR;
        ret = -1;
        break;
        }
        saved_mode = st.st_mode;
    } else {
        if (errno != ENOENT)
        break;

        /*
         * mkdir(foo) fails with EEXIST if foo is a symlink.
         */
#if 0

        /*
         * Create a new directory. Unfortunately, mkdir(2) has no
         * equivalent of open(2)'s O_CREAT|O_EXCL safety net, so we must
         * require that the parent directory is not world writable.
         * Detecting a lost race condition after the fact is not
         * sufficient, as an attacker could repeat the attack and add one
         * directory level at a time.
         */
        if (saved_mode & S_IWOTH) {
        msg_warn("refusing to mkdir %s: parent directory is writable by everyone",
             saved_path);
        errno = EPERM;
        ret = -1;
        break;
        }
#endif
        if ((ret = mkdir(saved_path, perms)) < 0) {
        if (errno != EEXIST)
            break;
        /* Race condition? */
        if ((ret = stat(saved_path, &st)) < 0)
            break;
        if (!S_ISDIR(st.st_mode)) {
            errno = ENOTDIR;
            ret = -1;
            break;
        }
        }

        /*
         * Fix directory ownership when mkdir() ignores the effective
         * GID. Don't change the effective UID for doing this.
         */
        if ((ret = stat(saved_path, &st)) < 0) {
        msg_warn("%s: stat %s: %m", myname, saved_path);
        break;
        }
        if (egid == -1)
        egid = getegid();
        if (st.st_gid != egid && (ret = chown(saved_path, -1, egid)) < 0) {
        msg_warn("%s: chgrp %s: %m", myname, saved_path);
        break;
        }
    }
    if (saved_ch != 0)
        *cp = saved_ch;
    SKIP_WHILE(*cp == '/', cp);
    if (*cp == 0)
        break;
    }

    /*
     * Cleanup.
     */
    myfree(saved_path);
    return (ret);
}

#ifdef TEST

 /*
  * Test program. Usage: make_dirs path...
  */
#include <stdlib.h>
#include <msg_vstream.h>

int     main(int argc, char **argv)
{
    msg_vstream_init(argv[0], VSTREAM_ERR);
    if (argc < 2)
    msg_fatal("usage: %s path...", argv[0]);
    while (--argc > 0 && *++argv != 0)
    if (make_dirs(*argv, 0755))
        msg_fatal("%s: %m", *argv);
    exit(0);
}

#endif