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|
/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 8 -*-
*
* (c) 2000 Eazel, Inc.
* (c) 2001,2002 George Lebl
* Copyright (C) 2007 William Jon McCann <mccann@jhu.edu>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include "config.h"
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <locale.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <setjmp.h>
#include <dirent.h>
#ifdef HAVE_CRT_EXTERNS_H
#include <crt_externs.h>
#endif
#include <glib.h>
#include <glib/gi18n.h>
#include "gdm-common.h"
#include "gdm-md5.h"
static int sigchld_blocked = 0;
static sigset_t sigchldblock_mask, sigchldblock_oldmask;
static int sigterm_blocked = 0;
static sigset_t sigtermblock_mask, sigtermblock_oldmask;
static int sigusr2_blocked = 0;
static sigset_t sigusr2block_mask, sigusr2block_oldmask;
void
gdm_sigchld_block_push (void)
{
sigchld_blocked++;
if (sigchld_blocked == 1) {
/* Set signal mask */
sigemptyset (&sigchldblock_mask);
sigaddset (&sigchldblock_mask, SIGCHLD);
sigprocmask (SIG_BLOCK, &sigchldblock_mask, &sigchldblock_oldmask);
}
}
void
gdm_sigchld_block_pop (void)
{
sigchld_blocked --;
if (sigchld_blocked == 0) {
/* Reset signal mask back */
sigprocmask (SIG_SETMASK, &sigchldblock_oldmask, NULL);
}
}
void
gdm_sigterm_block_push (void)
{
sigterm_blocked++;
if (sigterm_blocked == 1) {
/* Set signal mask */
sigemptyset (&sigtermblock_mask);
sigaddset (&sigtermblock_mask, SIGTERM);
sigaddset (&sigtermblock_mask, SIGINT);
sigaddset (&sigtermblock_mask, SIGHUP);
sigprocmask (SIG_BLOCK, &sigtermblock_mask, &sigtermblock_oldmask);
}
}
void
gdm_sigterm_block_pop (void)
{
sigterm_blocked --;
if (sigterm_blocked == 0) {
/* Reset signal mask back */
sigprocmask (SIG_SETMASK, &sigtermblock_oldmask, NULL);
}
}
void
gdm_sigusr2_block_push (void)
{
sigset_t oldmask;
if (sigusr2_blocked == 0) {
/* Set signal mask */
sigemptyset (&sigusr2block_mask);
sigaddset (&sigusr2block_mask, SIGUSR2);
sigprocmask (SIG_BLOCK, &sigusr2block_mask, &oldmask);
}
sigusr2_blocked++;
sigusr2block_oldmask = oldmask;
}
void
gdm_sigusr2_block_pop (void)
{
sigset_t oldmask;
oldmask = sigusr2block_oldmask;
sigusr2_blocked--;
if (sigusr2_blocked == 0) {
/* Reset signal mask back */
sigprocmask (SIG_SETMASK, &sigusr2block_oldmask, NULL);
}
}
/* Like fopen with "w" */
FILE *
gdm_safe_fopen_w (const char *file,
mode_t perm)
{
int fd;
FILE *ret;
VE_IGNORE_EINTR (g_unlink (file));
do {
int flags;
errno = 0;
flags = O_EXCL | O_CREAT | O_TRUNC | O_WRONLY;
#ifdef O_NOCTTY
flags |= O_NOCTTY;
#endif
#ifdef O_NOFOLLOW
flags |= O_NOFOLLOW;
#endif
fd = g_open (file, flags, perm);
} while (errno == EINTR);
if (fd < 0) {
return NULL;
}
ret = fdopen (fd, "w");
return ret;
}
/**
* ve_clearenv:
*
* Description: Clears out the environment completely.
* In case there is no native implementation of clearenv,
* this could cause leaks depending on the implementation
* of environment.
*
**/
void
ve_clearenv (void)
{
#ifdef HAVE_CLEARENV
clearenv ();
#else
#ifdef HAVE__NSGETENVIRON
#define environ (*_NSGetEnviron())
#else
extern char **environ;
#endif
if (environ != NULL)
environ[0] = NULL;
#endif
}
/* hex conversion adapted from D-Bus */
/**
* Appends a two-character hex digit to a string, where the hex digit
* has the value of the given byte.
*
* @param str the string
* @param byte the byte
*/
static void
_gdm_string_append_byte_as_hex (GString *str,
int byte)
{
const char hexdigits[16] = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'a', 'b', 'c', 'd', 'e', 'f'
};
str = g_string_append_c (str, hexdigits[(byte >> 4)]);
str = g_string_append_c (str, hexdigits[(byte & 0x0f)]);
}
/**
* Encodes a string in hex, the way MD5 and SHA-1 are usually
* encoded. (Each byte is two hex digits.)
*
* @param source the string to encode
* @param start byte index to start encoding
* @param dest string where encoded data should be placed
* @param insert_at where to place encoded data
* @returns #TRUE if encoding was successful, #FALSE if no memory etc.
*/
gboolean
gdm_string_hex_encode (const GString *source,
int start,
GString *dest,
int insert_at)
{
GString *result;
const unsigned char *p;
const unsigned char *end;
gboolean retval;
g_assert (start <= source->len);
result = g_string_new (NULL);
retval = FALSE;
p = (const unsigned char*) source->str;
end = p + source->len;
p += start;
while (p != end) {
_gdm_string_append_byte_as_hex (result, *p);
++p;
}
dest = g_string_insert (dest, insert_at, result->str);
retval = TRUE;
g_string_free (result, TRUE);
return retval;
}
/**
* Decodes a string from hex encoding.
*
* @param source the string to decode
* @param start byte index to start decode
* @param end_return return location of the end of the hex data, or #NULL
* @param dest string where decoded data should be placed
* @param insert_at where to place decoded data
* @returns #TRUE if decoding was successful, #FALSE if no memory.
*/
gboolean
gdm_string_hex_decode (const GString *source,
int start,
int *end_return,
GString *dest,
int insert_at)
{
GString *result;
const unsigned char *p;
const unsigned char *end;
gboolean retval;
gboolean high_bits;
g_assert (start <= source->len);
result = g_string_new (NULL);
retval = FALSE;
high_bits = TRUE;
p = (const unsigned char*) source->str;
end = p + source->len;
p += start;
while (p != end) {
unsigned int val;
switch (*p) {
case '0':
val = 0;
break;
case '1':
val = 1;
break;
case '2':
val = 2;
break;
case '3':
val = 3;
break;
case '4':
val = 4;
break;
case '5':
val = 5;
break;
case '6':
val = 6;
break;
case '7':
val = 7;
break;
case '8':
val = 8;
break;
case '9':
val = 9;
break;
case 'a':
case 'A':
val = 10;
break;
case 'b':
case 'B':
val = 11;
break;
case 'c':
case 'C':
val = 12;
break;
case 'd':
case 'D':
val = 13;
break;
case 'e':
case 'E':
val = 14;
break;
case 'f':
case 'F':
val = 15;
break;
default:
goto done;
}
if (high_bits) {
result = g_string_append_c (result, val << 4);
} else {
int len;
unsigned char b;
len = result->len;
b = result->str[len - 1];
b |= val;
result->str[len - 1] = b;
}
high_bits = !high_bits;
++p;
}
done:
dest = g_string_insert (dest, insert_at, result->str);
if (end_return) {
*end_return = p - (const unsigned char*) source->str;
}
retval = TRUE;
g_string_free (result, TRUE);
return retval;
}
static void
_gdm_generate_pseudorandom_bytes_buffer (char *buffer,
int n_bytes)
{
int i;
/* fall back to pseudorandom */
g_debug ("Falling back to pseudorandom for %d bytes\n",
n_bytes);
i = 0;
while (i < n_bytes) {
int b;
b = g_random_int_range (0, 255);
buffer[i] = b;
++i;
}
}
static gboolean
_gdm_generate_pseudorandom_bytes (GString *str,
int n_bytes)
{
int old_len;
char *p;
old_len = str->len;
str = g_string_set_size (str, old_len + n_bytes);
p = str->str + old_len;
_gdm_generate_pseudorandom_bytes_buffer (p, n_bytes);
return TRUE;
}
static int
_gdm_fdread (int fd,
GString *buffer,
int count)
{
int bytes_read;
int start;
char *data;
g_assert (count >= 0);
start = buffer->len;
buffer = g_string_set_size (buffer, start + count);
data = buffer->str + start;
again:
bytes_read = read (fd, data, count);
if (bytes_read < 0) {
if (errno == EINTR) {
goto again;
} else {
/* put length back (note that this doesn't actually realloc anything) */
buffer = g_string_set_size (buffer, start);
return -1;
}
} else {
/* put length back (doesn't actually realloc) */
buffer = g_string_set_size (buffer, start + bytes_read);
return bytes_read;
}
}
/**
* Closes a file descriptor.
*
* @param fd the file descriptor
* @param error error object
* @returns #FALSE if error set
*/
static gboolean
_gdm_fdclose (int fd)
{
again:
if (close (fd) < 0) {
if (errno == EINTR)
goto again;
g_warning ("Could not close fd %d: %s",
fd,
g_strerror (errno));
return FALSE;
}
return TRUE;
}
/**
* Generates the given number of random bytes,
* using the best mechanism we can come up with.
*
* @param str the string
* @param n_bytes the number of random bytes to append to string
*/
gboolean
gdm_generate_random_bytes (GString *str,
int n_bytes)
{
int old_len;
int fd;
/* FALSE return means "no memory", if it could
* mean something else then we'd need to return
* a DBusError. So we always fall back to pseudorandom
* if the I/O fails.
*/
old_len = str->len;
fd = -1;
/* note, urandom on linux will fall back to pseudorandom */
fd = g_open ("/dev/urandom", O_RDONLY, 0);
if (fd < 0) {
return _gdm_generate_pseudorandom_bytes (str, n_bytes);
}
if (_gdm_fdread (fd, str, n_bytes) != n_bytes) {
_gdm_fdclose (fd);
str = g_string_set_size (str, old_len);
return _gdm_generate_pseudorandom_bytes (str, n_bytes);
}
g_debug ("Read %d bytes from /dev/urandom\n", n_bytes);
_gdm_fdclose (fd);
return TRUE;
}
/**
* Computes the ASCII hex-encoded md5sum of the given data and
* appends it to the output string.
*
* @param data input data to be hashed
* @param ascii_output string to append ASCII md5sum to
* @returns #FALSE if not enough memory
*/
static gboolean
gdm_md5_compute (const GString *data,
GString *ascii_output)
{
GdmMD5Context context;
GString *digest;
gdm_md5_init (&context);
gdm_md5_update (&context, data);
digest = g_string_new (NULL);
if (digest == NULL)
return FALSE;
if (! gdm_md5_final (&context, digest))
goto error;
if (! gdm_string_hex_encode (digest,
0,
ascii_output,
ascii_output->len))
goto error;
g_string_free (digest, TRUE);
return TRUE;
error:
g_string_free (digest, TRUE);
return FALSE;
}
gboolean
gdm_generate_cookie (GString *result)
{
gboolean ret;
GString *data;
data = g_string_new (NULL);
gdm_generate_random_bytes (data, 16);
ret = gdm_md5_compute (data, result);
g_string_free (data, TRUE);
return ret;
}
|