smbd: Fix crossing automounter mount points

[Samba.git] / lib / util / util.c

/*
   Unix SMB/CIFS implementation.
   Samba utility functions
   Copyright (C) Andrew Tridgell 1992-1998
   Copyright (C) Jeremy Allison 2001-2002
   Copyright (C) Simo Sorce 2001-2011
   Copyright (C) Jim McDonough (jmcd@us.ibm.com)  2003.
   Copyright (C) James J Myers 2003
   Copyright (C) Volker Lendecke 2010
   Copyright (C) Swen Schillig 2019

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include <talloc.h>
#include <tevent.h>
#include "system/network.h"
#include "system/filesys.h"
#include "system/locale.h"
#include "system/shmem.h"
#include "system/passwd.h"
#include "system/time.h"
#include "system/wait.h"
#include "debug.h"
#include "samba_util.h"
#include "lib/util/select.h"
#include <libgen.h>
#include <gnutls/gnutls.h>

#ifdef HAVE_SYS_PRCTL_H
#include <sys/prctl.h>
#endif

#undef malloc
#undef strcasecmp
#undef strncasecmp
#undef strdup
#undef realloc
#undef calloc

/**
 * @file
 * @brief Misc utility functions
 */

/**
 Find a suitable temporary directory. The result should be copied immediately
 as it may be overwritten by a subsequent call.
**/
_PUBLIC_ const char *tmpdir(void)
{
        char *p;
        if ((p = getenv("TMPDIR")))
                return p;
        return "/tmp";
}


/**
 Create a tmp file, open it and immediately unlink it.
 If dir is NULL uses tmpdir()
 Returns the file descriptor or -1 on error.
**/
int create_unlink_tmp(const char *dir)
{
        size_t len = strlen(dir ? dir : (dir = tmpdir()));
        char fname[len+25];
        int fd;
        mode_t mask;

        len = snprintf(fname, sizeof(fname), "%s/listenerlock_XXXXXX", dir);
        if (len >= sizeof(fname)) {
                errno = ENOMEM;
                return -1;
        }
        mask = umask(S_IRWXO | S_IRWXG);
        fd = mkstemp(fname);
        umask(mask);
        if (fd == -1) {
                return -1;
        }
        if (unlink(fname) == -1) {
                int sys_errno = errno;
                close(fd);
                errno = sys_errno;
                return -1;
        }
        return fd;
}


/**
 Check if a file exists - call vfs_file_exist for samba files.
**/
_PUBLIC_ bool file_exist(const char *fname)
{
        struct stat st;

        if (stat(fname, &st) != 0) {
                return false;
        }

        return ((S_ISREG(st.st_mode)) || (S_ISFIFO(st.st_mode)));
}

/**
 * @brief Return a files modification time.
 *
 * @param fname  The name of the file.
 *
 * @param mt     A pointer to store the modification time.
 *
 * @return 0 on success, errno otherwise.
 */
_PUBLIC_ int file_modtime(const char *fname, struct timespec *mt)
{
        struct stat st = {0};

        if (stat(fname, &st) != 0) {
                return errno;
        }

        *mt = get_mtimespec(&st);
        return 0;
}

/**
 Check file permissions.
**/

_PUBLIC_ bool file_check_permissions(const char *fname,
                                     uid_t uid,
                                     mode_t file_perms,
                                     struct stat *pst)
{
        int ret;
        struct stat st;

        if (pst == NULL) {
                pst = &st;
        }

        ZERO_STRUCTP(pst);

        ret = stat(fname, pst);
        if (ret != 0) {
                DEBUG(0, ("stat failed on file '%s': %s\n",
                         fname, strerror(errno)));
                return false;
        }

        if (pst->st_uid != uid && !uid_wrapper_enabled()) {
                DEBUG(0, ("invalid ownership of file '%s': "
                         "owned by uid %u, should be %u\n",
                         fname, (unsigned int)pst->st_uid,
                         (unsigned int)uid));
                return false;
        }

        if ((pst->st_mode & 0777) != file_perms) {
                DEBUG(0, ("invalid permissions on file "
                         "'%s': has 0%o should be 0%o\n", fname,
                         (unsigned int)(pst->st_mode & 0777),
                         (unsigned int)file_perms));
                return false;
        }

        return true;
}

/**
 Check if a directory exists.
**/

_PUBLIC_ bool directory_exist(const char *dname)
{
        struct stat st;
        bool ret;

        if (stat(dname,&st) != 0) {
                return false;
        }

        ret = S_ISDIR(st.st_mode);
        if(!ret)
                errno = ENOTDIR;
        return ret;
}

/**
 * Try to create the specified directory if it didn't exist.
 * A symlink to a directory is also accepted as a valid existing directory.
 *
 * @retval true if the directory already existed
 * or was successfully created.
 */
_PUBLIC_ bool directory_create_or_exist(const char *dname,
                                        mode_t dir_perms)
{
        int ret;
        mode_t old_umask;

        /* Create directory */
        old_umask = umask(0);
        ret = mkdir(dname, dir_perms);
        if (ret == -1 && errno != EEXIST) {
                int dbg_level = geteuid() == 0 ? DBGLVL_ERR : DBGLVL_NOTICE;

                DBG_PREFIX(dbg_level,
                           ("mkdir failed on directory %s: %s\n",
                            dname,
                            strerror(errno)));
                umask(old_umask);
                return false;
        }
        umask(old_umask);

        if (ret != 0 && errno == EEXIST) {
                struct stat sbuf;

                ret = lstat(dname, &sbuf);
                if (ret != 0) {
                        return false;
                }

                if (S_ISDIR(sbuf.st_mode)) {
                        return true;
                }

                if (S_ISLNK(sbuf.st_mode)) {
                        ret = stat(dname, &sbuf);
                        if (ret != 0) {
                                return false;
                        }

                        if (S_ISDIR(sbuf.st_mode)) {
                                return true;
                        }
                }

                return false;
        }

        return true;
}

_PUBLIC_ bool directory_create_or_exists_recursive(
                const char *dname,
                mode_t dir_perms)
{
        bool ok;

        ok = directory_create_or_exist(dname, dir_perms);
        if (!ok) {
                if (!directory_exist(dname)) {
                        char tmp[PATH_MAX] = {0};
                        char *parent = NULL;
                        size_t n;

                        /* Use the null context */
                        n = strlcpy(tmp, dname, sizeof(tmp));
                        if (n < strlen(dname)) {
                                DBG_ERR("Path too long!\n");
                                return false;
                        }

                        parent = dirname(tmp);
                        if (parent == NULL) {
                                DBG_ERR("Failed to create dirname!\n");
                                return false;
                        }

                        ok = directory_create_or_exists_recursive(parent,
                                                                  dir_perms);
                        if (!ok) {
                                return false;
                        }

                        ok = directory_create_or_exist(dname, dir_perms);
                }
        }

        return ok;
}

/**
 * @brief Try to create a specified directory if it doesn't exist.
 *
 * The function creates a directory with the given uid and permissions if it
 * doesn't exist. If it exists it makes sure the uid and permissions are
 * correct and it will fail if they are different.
 *
 * @param[in]  dname  The directory to create.
 *
 * @param[in]  uid    The uid the directory needs to belong too.
 *
 * @param[in]  dir_perms  The expected permissions of the directory.
 *
 * @return True on success, false on error.
 */
_PUBLIC_ bool directory_create_or_exist_strict(const char *dname,
                                               uid_t uid,
                                               mode_t dir_perms)
{
        struct stat st;
        bool ok;
        int rc;

        ok = directory_create_or_exist(dname, dir_perms);
        if (!ok) {
                return false;
        }

        rc = lstat(dname, &st);
        if (rc == -1) {
                DEBUG(0, ("lstat failed on created directory %s: %s\n",
                          dname, strerror(errno)));
                return false;
        }

        /* Check ownership and permission on existing directory */
        if (!S_ISDIR(st.st_mode)) {
                DEBUG(0, ("directory %s isn't a directory\n",
                        dname));
                return false;
        }
        if (st.st_uid != uid && !uid_wrapper_enabled()) {
                DBG_NOTICE("invalid ownership on directory "
                          "%s\n", dname);
                return false;
        }
        if ((st.st_mode & 0777) != dir_perms) {
                DEBUG(0, ("invalid permissions on directory "
                          "'%s': has 0%o should be 0%o\n", dname,
                          (unsigned int)(st.st_mode & 0777), (unsigned int)dir_perms));
                return false;
        }

        return true;
}


/**
 Sleep for a specified number of milliseconds.
**/

_PUBLIC_ void smb_msleep(unsigned int t)
{
        sys_poll_intr(NULL, 0, t);
}

/**
 Get my own name, return in talloc'ed storage.
**/

_PUBLIC_ char *get_myname(TALLOC_CTX *ctx)
{
        char *p;
        char hostname[HOST_NAME_MAX];

        /* get my host name */
        if (gethostname(hostname, sizeof(hostname)) == -1) {
                DEBUG(0,("gethostname failed\n"));
                return NULL;
        }

        /* Ensure null termination. */
        hostname[sizeof(hostname)-1] = '\0';

        /* split off any parts after an initial . */
        p = strchr_m(hostname, '.');
        if (p) {
                *p = 0;
        }

        return talloc_strdup(ctx, hostname);
}

/**
 Check if a process exists. Does this work on all unixes?
**/

_PUBLIC_ bool process_exists_by_pid(pid_t pid)
{
        /* Doing kill with a non-positive pid causes messages to be
         * sent to places we don't want. */
        if (pid <= 0) {
                return false;
        }
        return(kill(pid,0) == 0 || errno != ESRCH);
}

/**
 Simple routine to do POSIX file locking. Cruft in NFS and 64->32 bit mapping
 is dealt with in posix.c
**/

_PUBLIC_ bool fcntl_lock(int fd, int op, off_t offset, off_t count, int type)
{
        struct flock lock;
        int ret;

        DEBUG(8,("fcntl_lock %d %d %.0f %.0f %d\n",fd,op,(double)offset,(double)count,type));

        lock.l_type = type;
        lock.l_whence = SEEK_SET;
        lock.l_start = offset;
        lock.l_len = count;
        lock.l_pid = 0;

        ret = fcntl(fd,op,&lock);

        if (ret == -1 && errno != 0)
                DEBUG(3,("fcntl_lock: fcntl lock gave errno %d (%s)\n",errno,strerror(errno)));

        /* a lock query */
        if (op == F_GETLK) {
                if ((ret != -1) &&
                                (lock.l_type != F_UNLCK) &&
                                (lock.l_pid != 0) &&
                                (lock.l_pid != tevent_cached_getpid())) {
                        DEBUG(3,("fcntl_lock: fd %d is locked by pid %d\n",fd,(int)lock.l_pid));
                        return true;
                }

                /* it must be not locked or locked by me */
                return false;
        }

        /* a lock set or unset */
        if (ret == -1) {
                DEBUG(3,("fcntl_lock: lock failed at offset %.0f count %.0f op %d type %d (%s)\n",
                        (double)offset,(double)count,op,type,strerror(errno)));
                return false;
        }

        /* everything went OK */
        DEBUG(8,("fcntl_lock: Lock call successful\n"));

        return true;
}

struct debug_channel_level {
        int channel;
        int level;
};

static void debugadd_channel_cb(const char *buf, void *private_data)
{
        struct debug_channel_level *dcl =
                (struct debug_channel_level *)private_data;

        DEBUGADDC(dcl->channel, dcl->level,("%s", buf));
}

static void debugadd_cb(const char *buf, void *private_data)
{
        int *plevel = (int *)private_data;
        DEBUGADD(*plevel, ("%s", buf));
}

void print_asc_cb(const uint8_t *buf, int len,
                  void (*cb)(const char *buf, void *private_data),
                  void *private_data)
{
        int i;
        char s[2];
        s[1] = 0;

        for (i=0; i<len; i++) {
                s[0] = isprint(buf[i]) ? buf[i] : '.';
                cb(s, private_data);
        }
}

void print_asc(int level, const uint8_t *buf,int len)
{
        print_asc_cb(buf, len, debugadd_cb, &level);
}

static void dump_data_block16(const char *prefix, size_t idx,
                              const uint8_t *buf, size_t len,
                              void (*cb)(const char *buf, void *private_data),
                              void *private_data)
{
        size_t prefix_len = strlen(prefix);
        /* 16 (=%04zX) + 2 (=[]) + 1 (='\0') => 19 */
        char tmp[prefix_len + 19];
        size_t i;

        SMB_ASSERT(len <= 16);

        snprintf(tmp, sizeof(tmp), "%s[%04zX]", prefix, idx);
        cb(tmp, private_data);

        for (i=0; i<16; i++) {
                if (i == 8) {
                        cb("  ", private_data);
                }
                if (i < len) {
                        snprintf(tmp, sizeof(tmp), " %02X", (int)buf[i]);
                } else {
                        snprintf(tmp, sizeof(tmp), "   ");
                }
                cb(tmp, private_data);
        }

        cb("   ", private_data);

        if (len == 0) {
                cb("EMPTY   BLOCK\n", private_data);
                return;
        }

        for (i=0; i<len; i++) {
                if (i == 8) {
                        cb(" ", private_data);
                }
                print_asc_cb(&buf[i], 1, cb, private_data);
        }

        cb("\n", private_data);
}

/**
 * Write dump of binary data to a callback
 */
void dump_data_cb(const uint8_t *buf, int len,
                  bool omit_zero_bytes,
                  void (*cb)(const char *buf, void *private_data),
                  void *private_data)
{
        int i=0;
        bool skipped = false;

        if (len<=0) return;

        for (i=0;i<len;i+=16) {
                size_t remaining_len = len - i;
                size_t this_len = MIN(remaining_len, 16);
                const uint8_t *this_buf = &buf[i];

                if ((omit_zero_bytes == true) &&
                    (i > 0) && (remaining_len > 16) &&
                    (this_len == 16) && all_zero(this_buf, 16))
                {
                        if (!skipped) {
                                cb("skipping zero buffer bytes\n",
                                   private_data);
                                skipped = true;
                        }
                        continue;
                }

                skipped = false;
                dump_data_block16("", i, this_buf, this_len,
                                  cb, private_data);
        }
}

/**
 * Write dump of binary data to the log file.
 *
 * The data is only written if the log level is at least level.
 */
_PUBLIC_ void dump_data(int level, const uint8_t *buf, int len)
{
        if (!DEBUGLVL(level)) {
                return;
        }
        dump_data_cb(buf, len, false, debugadd_cb, &level);
}

/**
 * Write dump of binary data to the log file.
 *
 * The data is only written if the log level is at least level for
 * debug class dbgc_class.
 */
_PUBLIC_ void dump_data_dbgc(int dbgc_class, int level, const uint8_t *buf, int len)
{
        struct debug_channel_level dcl = { dbgc_class, level };

        if (!DEBUGLVLC(dbgc_class, level)) {
                return;
        }
        dump_data_cb(buf, len, false, debugadd_channel_cb, &dcl);
}

/**
 * Write dump of binary data to the log file.
 *
 * The data is only written if the log level is at least level.
 * 16 zero bytes in a row are omitted
 */
_PUBLIC_ void dump_data_skip_zeros(int level, const uint8_t *buf, int len)
{
        if (!DEBUGLVL(level)) {
                return;
        }
        dump_data_cb(buf, len, true, debugadd_cb, &level);
}

static void fprintf_cb(const char *buf, void *private_data)
{
        FILE *f = (FILE *)private_data;
        fprintf(f, "%s", buf);
}

void dump_data_file(const uint8_t *buf, int len, bool omit_zero_bytes,
                    FILE *f)
{
        dump_data_cb(buf, len, omit_zero_bytes, fprintf_cb, f);
}

/**
 * Write dump of compared binary data to a callback
 */
void dump_data_diff_cb(const uint8_t *buf1, size_t len1,
                       const uint8_t *buf2, size_t len2,
                       bool omit_zero_bytes,
                       void (*cb)(const char *buf, void *private_data),
                       void *private_data)
{
        size_t len = MAX(len1, len2);
        size_t i;
        bool skipped = false;

        for (i=0; i<len; i+=16) {
                size_t remaining_len = len - i;
                size_t remaining_len1 = 0;
                size_t this_len1 = 0;
                const uint8_t *this_buf1 = NULL;
                size_t remaining_len2 = 0;
                size_t this_len2 = 0;
                const uint8_t *this_buf2 = NULL;

                if (i < len1) {
                        remaining_len1 = len1 - i;
                        this_len1 = MIN(remaining_len1, 16);
                        this_buf1 = &buf1[i];
                }
                if (i < len2) {
                        remaining_len2 = len2 - i;
                        this_len2 = MIN(remaining_len2, 16);
                        this_buf2 = &buf2[i];
                }

                if ((omit_zero_bytes == true) &&
                    (i > 0) && (remaining_len > 16) &&
                    (this_len1 == 16) && all_zero(this_buf1, 16) &&
                    (this_len2 == 16) && all_zero(this_buf2, 16))
                {
                        if (!skipped) {
                                cb("skipping zero buffer bytes\n",
                                   private_data);
                                skipped = true;
                        }
                        continue;
                }

                skipped = false;

                if ((this_len1 == this_len2) &&
                    (memcmp(this_buf1, this_buf2, this_len1) == 0))
                {
                        dump_data_block16(" ", i, this_buf1, this_len1,
                                          cb, private_data);
                        continue;
                }

                dump_data_block16("-", i, this_buf1, this_len1,
                                  cb, private_data);
                dump_data_block16("+", i, this_buf2, this_len2,
                                  cb, private_data);
        }
}

_PUBLIC_ void dump_data_diff(int dbgc_class, int level,
                             bool omit_zero_bytes,
                             const uint8_t *buf1, size_t len1,
                             const uint8_t *buf2, size_t len2)
{
        struct debug_channel_level dcl = { dbgc_class, level };

        if (!DEBUGLVLC(dbgc_class, level)) {
                return;
        }
        dump_data_diff_cb(buf1, len1, buf2, len2, true, debugadd_channel_cb, &dcl);
}

_PUBLIC_ void dump_data_file_diff(FILE *f,
                                  bool omit_zero_bytes,
                                  const uint8_t *buf1, size_t len1,
                                  const uint8_t *buf2, size_t len2)
{
        dump_data_diff_cb(buf1, len1, buf2, len2, omit_zero_bytes, fprintf_cb, f);
}

/**
 malloc that aborts with smb_panic on fail or zero size.
**/

_PUBLIC_ void *smb_xmalloc(size_t size)
{
        void *p;
        if (size == 0)
                smb_panic("smb_xmalloc: called with zero size.\n");
        if ((p = malloc(size)) == NULL)
                smb_panic("smb_xmalloc: malloc fail.\n");
        return p;
}

/**
 Memdup with smb_panic on fail.
**/

_PUBLIC_ void *smb_xmemdup(const void *p, size_t size)
{
        void *p2;
        p2 = smb_xmalloc(size);
        memcpy(p2, p, size);
        return p2;
}

/**
 strdup that aborts on malloc fail.
**/

char *smb_xstrdup(const char *s)
{
#if defined(PARANOID_MALLOC_CHECKER)
#ifdef strdup
#undef strdup
#endif
#endif

#ifndef HAVE_STRDUP
#define strdup rep_strdup
#endif

        char *s1 = strdup(s);
#if defined(PARANOID_MALLOC_CHECKER)
#ifdef strdup
#undef strdup
#endif
#define strdup(s) __ERROR_DONT_USE_STRDUP_DIRECTLY
#endif
        if (!s1) {
                smb_panic("smb_xstrdup: malloc failed");
        }
        return s1;

}

/**
 strndup that aborts on malloc fail.
**/

char *smb_xstrndup(const char *s, size_t n)
{
#if defined(PARANOID_MALLOC_CHECKER)
#ifdef strndup
#undef strndup
#endif
#endif

#if (defined(BROKEN_STRNDUP) || !defined(HAVE_STRNDUP))
#undef HAVE_STRNDUP
#define strndup rep_strndup
#endif

        char *s1 = strndup(s, n);
#if defined(PARANOID_MALLOC_CHECKER)
#ifdef strndup
#undef strndup
#endif
#define strndup(s,n) __ERROR_DONT_USE_STRNDUP_DIRECTLY
#endif
        if (!s1) {
                smb_panic("smb_xstrndup: malloc failed");
        }
        return s1;
}



/**
 Like strdup but for memory.
**/

_PUBLIC_ void *smb_memdup(const void *p, size_t size)
{
        void *p2;
        if (size == 0)
                return NULL;
        p2 = malloc(size);
        if (!p2)
                return NULL;
        memcpy(p2, p, size);
        return p2;
}

/**
 * Write a password to the log file.
 *
 * @note Only actually does something if DEBUG_PASSWORD was defined during
 * compile-time.
 */
_PUBLIC_ void dump_data_pw(const char *msg, const uint8_t * data, size_t len)
{
#ifdef DEBUG_PASSWORD
        DEBUG(11, ("%s", msg));
        if (data != NULL && len > 0)
        {
                dump_data(11, data, len);
        }
#endif
}

static void dump_data_addbuf_cb(const char *buf, void *private_data)
{
        char **str = private_data;
        talloc_asprintf_addbuf(str, "%s", buf);
}

_PUBLIC_ void dump_data_addbuf(const uint8_t *buf, size_t buflen, char **str)
{
        dump_data_cb(buf, buflen, false, dump_data_addbuf_cb, str);
}


/**
 * see if a range of memory is all zero. A NULL pointer is considered
 * to be all zero
 */
_PUBLIC_ bool all_zero(const uint8_t *ptr, size_t size)
{
        size_t i;
        if (!ptr) return true;
        for (i=0;i<size;i++) {
                if (ptr[i]) return false;
        }
        return true;
}

/**
  realloc an array, checking for integer overflow in the array size
*/
_PUBLIC_ void *realloc_array(void *ptr, size_t el_size, unsigned count, bool free_on_fail)
{
#define MAX_MALLOC_SIZE 0x7fffffff
        if (count == 0 ||
            count >= MAX_MALLOC_SIZE/el_size) {
                if (free_on_fail)
                        SAFE_FREE(ptr);
                return NULL;
        }
        if (!ptr) {
                return malloc(el_size * count);
        }
        return realloc(ptr, el_size * count);
}

/****************************************************************************
 Type-safe malloc.
****************************************************************************/

void *malloc_array(size_t el_size, unsigned int count)
{
        return realloc_array(NULL, el_size, count, false);
}

/****************************************************************************
 Type-safe memalign
****************************************************************************/

void *memalign_array(size_t el_size, size_t align, unsigned int count)
{
        if (el_size == 0 || count >= MAX_MALLOC_SIZE/el_size) {
                return NULL;
        }

        return memalign(align, el_size*count);
}

/****************************************************************************
 Type-safe calloc.
****************************************************************************/

void *calloc_array(size_t size, size_t nmemb)
{
        if (nmemb >= MAX_MALLOC_SIZE/size) {
                return NULL;
        }
        if (size == 0 || nmemb == 0) {
                return NULL;
        }
        return calloc(nmemb, size);
}

/**
 Trim the specified elements off the front and back of a string.
**/
_PUBLIC_ bool trim_string(char *s, const char *front, const char *back)
{
        bool ret = false;
        size_t front_len;
        size_t back_len;
        size_t len;

        /* Ignore null or empty strings. */
        if (!s || (s[0] == '\0')) {
                return false;
        }
        len = strlen(s);

        front_len       = front? strlen(front) : 0;
        back_len        = back? strlen(back) : 0;

        if (front_len) {
                size_t front_trim = 0;

                while (strncmp(s+front_trim, front, front_len)==0) {
                        front_trim += front_len;
                }
                if (front_trim > 0) {
                        /* Must use memmove here as src & dest can
                         * easily overlap. Found by valgrind. JRA. */
                        memmove(s, s+front_trim, (len-front_trim)+1);
                        len -= front_trim;
                        ret=true;
                }
        }

        if (back_len) {
                while ((len >= back_len) && strncmp(s+len-back_len,back,back_len)==0) {
                        s[len-back_len]='\0';
                        len -= back_len;
                        ret=true;
                }
        }
        return ret;
}

/**
 Find the number of 'c' chars in a string
**/
_PUBLIC_ _PURE_ size_t count_chars(const char *s, char c)
{
        size_t count = 0;

        while (*s) {
                if (*s == c) count++;
                s ++;
        }

        return count;
}

/**
 * Routine to get hex characters and turn them into a byte array.
 * the array can be variable length.
 * -  "0xnn" or "0Xnn" is specially catered for.
 * - The first non-hex-digit character (apart from possibly leading "0x"
 *   finishes the conversion and skips the rest of the input.
 * - A single hex-digit character at the end of the string is skipped.
 *
 * valid examples: "0A5D15"; "0x123456"
 */
_PUBLIC_ size_t strhex_to_str(char *p, size_t p_len, const char *strhex, size_t strhex_len)
{
        size_t i = 0;
        size_t num_chars = 0;

        /* skip leading 0x prefix */
        if (strncasecmp(strhex, "0x", 2) == 0) {
                i += 2; /* skip two chars */
        }

        while ((i < strhex_len) && (num_chars < p_len)) {
                bool ok = hex_byte(&strhex[i], (uint8_t *)&p[num_chars]);
                if (!ok) {
                        break;
                }
                i += 2;
                num_chars += 1;
        }

        return num_chars;
}

/**
 * Parse a hex string and return a data blob.
 */
_PUBLIC_ DATA_BLOB strhex_to_data_blob(TALLOC_CTX *mem_ctx, const char *strhex)
{
        DATA_BLOB ret_blob = data_blob_talloc(mem_ctx, NULL, strlen(strhex)/2+1);
        if (ret_blob.data == NULL) {
                /* ret_blob.length is already 0 */
                return ret_blob;
        }
        ret_blob.length = strhex_to_str((char *)ret_blob.data, ret_blob.length,
                                        strhex,
                                        strlen(strhex));

        return ret_blob;
}

/**
 * Parse a hex dump and return a data blob. Hex dump is structured as
 * is generated from dump_data_cb() elsewhere in this file
 *
 */
_PUBLIC_ DATA_BLOB hexdump_to_data_blob(TALLOC_CTX *mem_ctx, const char *hexdump, size_t hexdump_len)
{
        DATA_BLOB ret_blob = { 0 };
        size_t i = 0;
        size_t char_count = 0;
        /* hexdump line length is 77 chars long. We then use the ASCII representation of the bytes
         * at the end of the final line to calculate how many are in that line, minus the extra space
         * and newline. */
        size_t hexdump_byte_count = (16 * (hexdump_len / 77));
        if (hexdump_len % 77) {
                hexdump_byte_count += ((hexdump_len % 77) - 59 - 2);
        }

        ret_blob = data_blob_talloc(mem_ctx, NULL, hexdump_byte_count+1);
        for (; i+1 < hexdump_len && hexdump[i] != 0 && hexdump[i+1] != 0; i++) {
                if ((i%77) == 0)
                        i += 7; /* Skip the offset at the start of the line */
                if ((i%77) < 56) { /* position 56 is after both hex chunks */
                        if (hexdump[i] != ' ') {
                                char_count += strhex_to_str((char *)&ret_blob.data[char_count],
                                                            hexdump_byte_count - char_count,
                                                            &hexdump[i], 2);
                                i += 2;
                        } else {
                                i++;
                        }
                } else {
                        i++;
                }
        }
        ret_blob.length = char_count;

        return ret_blob;
}

/**
 * Print a buf in hex. Assumes dst is at least (srclen*2)+1 large.
 */
_PUBLIC_ void hex_encode_buf(char *dst, const uint8_t *src, size_t srclen)
{
        size_t i;
        for (i=0; i<srclen; i++) {
                snprintf(dst + i*2, 3, "%02X", src[i]);
        }
        /*
         * Ensure 0-termination for 0-length buffers
         */
        dst[srclen*2] = '\0';
}

/**
 * talloc version of hex_encode_buf()
 */
_PUBLIC_ char *hex_encode_talloc(TALLOC_CTX *mem_ctx, const unsigned char *buff_in, size_t len)
{
        char *hex_buffer;

        hex_buffer = talloc_array(mem_ctx, char, (len*2)+1);
        if (!hex_buffer) {
                return NULL;
        }
        hex_encode_buf(hex_buffer, buff_in, len);
        talloc_set_name_const(hex_buffer, hex_buffer);
        return hex_buffer;
}

/**
  variant of strcmp() that handles NULL ptrs
**/
_PUBLIC_ int strcmp_safe(const char *s1, const char *s2)
{
        if (s1 == s2) {
                return 0;
        }
        if (s1 == NULL || s2 == NULL) {
                return s1?-1:1;
        }
        return strcmp(s1, s2);
}


/**
return the number of bytes occupied by a buffer in ASCII format
the result includes the null termination
limited by 'n' bytes
**/
_PUBLIC_ size_t ascii_len_n(const char *src, size_t n)
{
        size_t len;

        len = strnlen(src, n);
        if (len+1 <= n) {
                len += 1;
        }

        return len;
}

_PUBLIC_ bool mem_equal_const_time(const void *s1, const void *s2, size_t n)
{
        /* Ensure we won't overflow the unsigned index used by gnutls. */
        SMB_ASSERT(n <= UINT_MAX);

        return gnutls_memcmp(s1, s2, n) == 0;
}

struct anonymous_shared_header {
        union {
                size_t length;
                uint8_t pad[16];
        } u;
};

/* Map a shared memory buffer of at least nelem counters. */
void *anonymous_shared_allocate(size_t orig_bufsz)
{
        void *ptr;
        void *buf;
        size_t pagesz = getpagesize();
        size_t pagecnt;
        size_t bufsz = orig_bufsz;
        struct anonymous_shared_header *hdr;

        bufsz += sizeof(*hdr);

        /* round up to full pages */
        pagecnt = bufsz / pagesz;
        if (bufsz % pagesz) {
                pagecnt += 1;
        }
        bufsz = pagesz * pagecnt;

        if (orig_bufsz >= bufsz) {
                /* integer wrap */
                errno = ENOMEM;
                return NULL;
        }

#ifdef MAP_ANON
        /* BSD */
        buf = mmap(NULL, bufsz, PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED,
                        -1 /* fd */, 0 /* offset */);
#else
{
        int saved_errno;
        int fd;

        fd = open("/dev/zero", O_RDWR);
        if (fd == -1) {
                return NULL;
        }

        buf = mmap(NULL, bufsz, PROT_READ|PROT_WRITE, MAP_FILE|MAP_SHARED,
                   fd, 0 /* offset */);
        saved_errno = errno;
        close(fd);
        errno = saved_errno;
}
#endif

        if (buf == MAP_FAILED) {
                return NULL;
        }

        hdr = (struct anonymous_shared_header *)buf;
        hdr->u.length = bufsz;

        ptr = (void *)(&hdr[1]);

        return ptr;
}

void *anonymous_shared_resize(void *ptr, size_t new_size, bool maymove)
{
#ifdef HAVE_MREMAP
        void *buf;
        size_t pagesz = getpagesize();
        size_t pagecnt;
        size_t bufsz;
        struct anonymous_shared_header *hdr;
        int flags = 0;

        if (ptr == NULL) {
                errno = EINVAL;
                return NULL;
        }

        hdr = (struct anonymous_shared_header *)ptr;
        hdr--;
        if (hdr->u.length > (new_size + sizeof(*hdr))) {
                errno = EINVAL;
                return NULL;
        }

        bufsz = new_size + sizeof(*hdr);

        /* round up to full pages */
        pagecnt = bufsz / pagesz;
        if (bufsz % pagesz) {
                pagecnt += 1;
        }
        bufsz = pagesz * pagecnt;

        if (new_size >= bufsz) {
                /* integer wrap */
                errno = ENOSPC;
                return NULL;
        }

        if (bufsz <= hdr->u.length) {
                return ptr;
        }

        if (maymove) {
                flags = MREMAP_MAYMOVE;
        }

        buf = mremap(hdr, hdr->u.length, bufsz, flags);

        if (buf == MAP_FAILED) {
                errno = ENOSPC;
                return NULL;
        }

        hdr = (struct anonymous_shared_header *)buf;
        hdr->u.length = bufsz;

        ptr = (void *)(&hdr[1]);

        return ptr;
#else
        errno = ENOSPC;
        return NULL;
#endif
}

void anonymous_shared_free(void *ptr)
{
        struct anonymous_shared_header *hdr;

        if (ptr == NULL) {
                return;
        }

        hdr = (struct anonymous_shared_header *)ptr;

        hdr--;

        munmap(hdr, hdr->u.length);
}

#ifdef DEVELOPER
/* used when you want a debugger started at a particular point in the
   code. Mostly useful in code that runs as a child process, where
   normal gdb attach is harder to organise.
*/
void samba_start_debugger(void)
{
        int ready_pipe[2];
        char c;
        int ret;
        pid_t pid;

        ret = pipe(ready_pipe);
        SMB_ASSERT(ret == 0);

        pid = fork();
        SMB_ASSERT(pid >= 0);

        if (pid) {
                c = 0;

                ret = close(ready_pipe[0]);
                SMB_ASSERT(ret == 0);
#if defined(HAVE_PRCTL) && defined(PR_SET_PTRACER)
                /*
                 * Make sure the child process can attach a debugger.
                 *
                 * We don't check the error code as the debugger
                 * will tell us if it can't attach.
                 */
                (void)prctl(PR_SET_PTRACER, pid, 0, 0, 0);
#endif
                ret = write(ready_pipe[1], &c, 1);
                SMB_ASSERT(ret == 1);

                ret = close(ready_pipe[1]);
                SMB_ASSERT(ret == 0);

                /* Wait for gdb to attach. */
                sleep(2);
        } else {
                char *cmd = NULL;

                ret = close(ready_pipe[1]);
                SMB_ASSERT(ret == 0);

                ret = read(ready_pipe[0], &c, 1);
                SMB_ASSERT(ret == 1);

                ret = close(ready_pipe[0]);
                SMB_ASSERT(ret == 0);

                ret = asprintf(&cmd, "gdb --pid %u", getppid());
                SMB_ASSERT(ret != -1);

                execlp("xterm", "xterm", "-e", cmd, (char *) NULL);
                smb_panic("execlp() failed");
        }
}
#endif