/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include "lint.h"
#include "mtlib.h"
#include <sys/types.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdlib.h>
#include <limits.h>
#include <pthread.h>
#include <thread.h>
#include <string.h>
#include <dirent.h>
#include <stdio.h>
#include <dlfcn.h>
#include <atomic.h>
#include <md5.h>
#include "pos4obj.h"

#define HASHSTRLEN      32

static  char    *__pos4obj_name(const char *, const char *);
static  void    __pos4obj_md5toa(unsigned char *, unsigned char *);
static  void    __pos4obj_clean(char *);

static  char    objroot[] = "/tmp/";
static  long int        name_max = 0;

int
__open_nc(const char *path, int oflag, mode_t mode)
{
        int             cancel_state;
        int             val;
        struct stat64   statbuf;

        /*
         * Ensure path is not a symlink to somewhere else. This provides
         * a modest amount of protection against easy security attacks.
         */
        if (lstat64(path, &statbuf) == 0) {
                if (S_ISLNK(statbuf.st_mode)) {
                        errno = EINVAL;
                        return (-1);
                }
        }

        (void) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cancel_state);
        val = open64(path, oflag, mode);
        (void) pthread_setcancelstate(cancel_state, NULL);

        return (val);
}

int
__close_nc(int fildes)
{
        int     cancel_state;
        int     val;

        (void) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cancel_state);
        val = close(fildes);
        (void) pthread_setcancelstate(cancel_state, NULL);

        return (val);
}

/*
 * This is to avoid loading libmd.so.1 unless we absolutely have to.
 */
typedef void (*md5_calc_t)(unsigned char *, unsigned char *, unsigned int);
static md5_calc_t real_md5_calc = NULL;
static mutex_t md5_lock = DEFAULTMUTEX;

static void
load_md5_calc(void)
{
        void *md5_handle = dlopen("libmd.so.1", RTLD_LAZY);
        md5_calc_t md5_calc = (md5_handle == NULL)? NULL :
            (md5_calc_t)dlsym(md5_handle, "md5_calc");

        lmutex_lock(&md5_lock);
        if (real_md5_calc == NULL) {
                if (md5_calc == NULL)
                        real_md5_calc = (md5_calc_t)(-1);
                else {
                        real_md5_calc = md5_calc;
                        md5_handle = NULL;      /* don't dlclose it */
                }
                membar_producer();
        }
        lmutex_unlock(&md5_lock);

        if (md5_handle)
                (void) dlclose(md5_handle);
}

static char *
__pos4obj_name(const char *path, const char *type)
{
        int     shortpath = 1;
        int     olderrno;
        size_t  len;
        char    *dfile;
        unsigned char   hashbuf[HASHSTRLEN + 1];
        unsigned char   md5_digest[MD5_DIGEST_LENGTH];

        /*
         * If the path is path_max - strlen(type) characters or less,
         * the name of the file to use will be the path prefixed by
         * the type.
         *
         * In the special case where the path is longer than
         * path_max - strlen(type) characters, we create a string based on the
         * MD5 hash of the path. We prefix that string with a '.' to
         * make it obscure, and create a directory in objroot with
         * that name. In that directory, we create a directory named
         * after the type of object requested.  Inside the type
         * directory, the filename will be the path of the object. This
         * prevents collisions in all namespaces.
         *
         * Example:
         * Let objroot = "/tmp/", path = "/<longpath>", and type = ".MQD"
         * Let the MD5 hash of "<longpath>" = "<hash>"
         *
         * The desired file is /tmp/.<hash>/.MQD/<longpath>
         */

        /*
         * Do not include the leading '/' in the path length.
         * Assumes __pos4obj_check(path) has already been called.
         */
        if ((strlen(path) - 1) > (name_max - strlen(type)))
                shortpath = 0;

        if (shortpath) {
                /*
                 * strlen(path) includes leading slash as space for NUL.
                 */
                len = strlen(objroot) + strlen(type) + strlen(path);
        } else {
                /*
                 * Long path name. Add 3 for extra '/', '.' and '\0'
                 */
                len = strlen(objroot) + HASHSTRLEN + strlen(type) +
                    strlen(path) + 3;
        }

        if ((dfile = malloc(len)) == NULL)
                return (NULL);

        (void) memset(dfile, 0, len);
        (void) strcpy(dfile, objroot);

        if (shortpath) {
                (void) strcat(dfile, type);
                (void) strcat(dfile, path + 1);
                return (dfile);
        }

        /*
         * If we can successfully load it, call md5_calc().
         * Otherwise, (this "can't happen") return NULL.
         */
        if (real_md5_calc == NULL)
                load_md5_calc();
        if (real_md5_calc == (md5_calc_t)(-1)) {
                free(dfile);
                return (NULL);
        }

        real_md5_calc(md5_digest, (unsigned char *)path + 1, strlen(path + 1));
        __pos4obj_md5toa(hashbuf, md5_digest);
        (void) strcat(dfile, ".");
        (void) strcat(dfile, (const char *)hashbuf);

        /*
         * Errno must be preserved across the following calls to
         * mkdir.  This needs to be done to prevent incorrect error
         * reporting in certain cases. When we attempt to open a
         * non-existent object without the O_CREAT flag, it will
         * always create a lock file first.  The lock file is created
         * and then the open is attempted, but fails with ENOENT. The
         * lock file is then destroyed. In the following code path, we
         * are finding the absolute path to the lock file after
         * already having attempted the open (which set errno to
         * ENOENT). The following calls to mkdir will return -1 and
         * set errno to EEXIST, since the hash and type directories
         * were created when the lock file was created. The correct
         * errno is the ENOENT from the attempted open of the desired
         * object.
         */
        olderrno = errno;

        /*
         * Create hash directory. Use 777 permissions so everyone can use it.
         */
        if (mkdir(dfile, S_IRWXU|S_IRWXG|S_IRWXO) == 0) {
                if (chmod(dfile, S_IRWXU|S_IRWXG|S_IRWXO) == -1) {
                        free(dfile);
                        return (NULL);
                }
        } else {
                if (errno != EEXIST) {
                        free(dfile);
                        return (NULL);
                }
        }

        (void) strcat(dfile, "/");
        (void) strcat(dfile, type);

        /*
         * Create directory for requested type. Use 777 perms so everyone
         * can use it.
         */
        if (mkdir(dfile, S_IRWXU|S_IRWXG|S_IRWXO) == 0) {
                if (chmod(dfile, S_IRWXU|S_IRWXG|S_IRWXO) == -1) {
                        free(dfile);
                        return (NULL);
                }
        } else {
                if (errno != EEXIST) {
                        free(dfile);
                        return (NULL);
                }
        }

        errno = olderrno;
        (void) strcat(dfile, path);
        return (dfile);
}

/*
 * Takes a 128-bit MD5 digest and transforms to a sequence of 32 ASCII
 * characters. Output is the hexadecimal representation of the digest.
 *
 * The output buffer must be at least HASHSTRLEN + 1 characters
 * long.  HASHSTRLEN is the size of the MD5 digest (128 bits)
 * divided by the number of bits used per char of output (4). The
 * extra character at the end is for the NUL terminating character.
 */

static void
__pos4obj_md5toa(unsigned char *dest, unsigned char *src)
{
        int i;
        uint32_t *p;

        /* LINTED pointer cast may result in improper alignment */
        p = (uint32_t *)src;

        for (i = 0; i < (MD5_DIGEST_LENGTH / 4); i++)
                (void) snprintf((char *)dest + (i * 8), 9, "%.8x", *p++);

        dest[HASHSTRLEN] = '\0';
}

/*
 * This open function assume that there is no simultaneous
 * open/unlink operation is going on. The caller is supposed
 * to ensure that both open in O_CREAT mode happen atomically.
 * It returns the crflag as 1 if file is created else 0.
 */
int
__pos4obj_open(const char *name, char *type, int oflag,
                mode_t mode, int *crflag)
{
        int fd;
        char *dfile;

        errno = 0;
        *crflag = 0;

        if ((dfile = __pos4obj_name(name, type)) == NULL) {
                return (-1);
        }

        if (!(oflag & O_CREAT)) {
                if ((fd = __open_nc(dfile, oflag, mode)) == -1)
                        __pos4obj_clean(dfile);

                free(dfile);
                return (fd);
        }

        /*
         * We need to make sure that crflag is set iff we actually create
         * the file.  We do this by or'ing in O_EXCL, and attempting an
         * open.  If that fails with an EEXIST, and O_EXCL wasn't specified
         * by the caller, then the file seems to exist;  we'll try an
         * open with O_CREAT cleared.  If that succeeds, then the file
         * did indeed exist.  If that fails with an ENOENT, however, the
         * file was removed between the opens;  we need to take another
         * lap.
         */
        for (;;) {
                if ((fd = __open_nc(dfile, (oflag | O_EXCL), mode)) == -1) {
                        if (errno == EEXIST && !(oflag & O_EXCL)) {
                                fd = __open_nc(dfile, oflag & ~O_CREAT, mode);

                                if (fd == -1 && errno == ENOENT)
                                        continue;
                                break;
                        }
                } else {
                        *crflag = 1;
                }
                break;
        }

        free(dfile);
        return (fd);
}


int
__pos4obj_unlink(const char *name, const char *type)
{
        int     err;
        char    *dfile;

        if ((dfile = __pos4obj_name(name, type)) == NULL) {
                return (-1);
        }

        err = unlink(dfile);

        __pos4obj_clean(dfile);

        free(dfile);

        return (err);
}

/*
 * This function opens the lock file for each named object
 * the presence of this file in the file system is the lock
 */
int
__pos4obj_lock(const char *name, const char *ltype)
{
        char    *dfile;
        int     fd;
        int     limit = 64;

        if ((dfile = __pos4obj_name(name, ltype)) == NULL) {
                return (-1);
        }

        while (limit-- > 0) {
                if ((fd = __open_nc(dfile, O_RDWR | O_CREAT | O_EXCL, 0666))
                    < 0) {
                        if (errno != EEXIST)
                                break;
                        (void) sleep(1);
                        continue;
                }

                (void) __close_nc(fd);
                free(dfile);
                return (1);
        }

        free(dfile);
        return (-1);
}

/*
 * Unlocks the file by unlinking it from the filesystem
 */
int
__pos4obj_unlock(const char *path, const char *type)
{
        return (__pos4obj_unlink(path, type));
}

/*
 * Removes unused hash and type directories that may exist in specified path.
 */
static void
__pos4obj_clean(char *path)
{
        char    *p;
        int     olderrno;

        /*
         * path is either
         * 1) /<objroot>/<type><path>  or
         * 2) /<objroot>/.<hash>/<type>/<path>
         *
         * In case 1, there is nothing to clean.
         *
         * Detect case 2 by looking for a '/' after /objroot/ and
         * remove the two trailing directories, if empty.
         */
        if (strchr(path + strlen(objroot), '/') == NULL)
                return;

        /*
         * Preserve errno across calls to rmdir. See block comment in
         * __pos4obj_name() for explanation.
         */
        olderrno = errno;

        if ((p = strrchr(path, '/')) == NULL)
                return;
        *p = '\0';

        (void) rmdir(path);

        if ((p = strrchr(path, '/')) == NULL)
                return;
        *p = '\0';

        (void) rmdir(path);

        errno = olderrno;
}


/*
 * Check that path starts with a /, does not contain a / within it
 * and is not longer than PATH_MAX or NAME_MAX
 */
int
__pos4obj_check(const char *path)
{
        long int        i;

        /*
         * This assumes that __pos4obj_check() is called before
         * any of the other functions in this file
         */
        if (name_max == 0 || name_max == -1) {
                name_max = pathconf(objroot, _PC_NAME_MAX);
                if (name_max == -1)
                        return (-1);
        }

        if (*path++ != '/') {
                errno = EINVAL;
                return (-1);
        }

        for (i = 0; *path != '\0'; i++) {
                if (*path++ == '/') {
                        errno = EINVAL;
                        return (-1);
                }
        }

        if (i > PATH_MAX || i > name_max) {
                errno = ENAMETOOLONG;
                return (-1);
        }

        return (0);
}