/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* Copyright (C) 2010 Red Hat, Inc.
*
* This program is free software: you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation
*
* 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 .
*/
#include
#include
#include
#include
#include
#include
#include "utils.h"
#include "errors.h"
/* QCDM protocol frames are pseudo Async HDLC frames which end with a 3-byte
* trailer. This trailer consists of the 16-bit CRC of the frame plus an ending
* "async control character" whose value is 0x7E. The frame *and* the CRC are
* escaped before adding the trailing control character so that the control
* character (0x7E) and the escape marker (0x7D) are never seen in the frame.
*/
/* Table of CRCs for each possible byte, with a generator polynomial of 0x8408 */
const u_int16_t crc_table[256] = {
0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
};
/* Calculate the CRC for a buffer using a seed of 0xffff */
u_int16_t
crc16 (const char *buffer, size_t len)
{
u_int16_t crc = 0xffff;
while (len--)
crc = crc_table[(crc ^ *buffer++) & 0xff] ^ (crc >> 8);
return ~crc;
}
#define DIAG_ESC_CHAR 0x7D /* Escape sequence 1st character value */
#define DIAG_ESC_MASK 0x20 /* Escape sequence complement value */
/* Performs DM escaping on inbuf putting the result into outbuf, and returns
* the final length of the buffer.
*/
size_t
dm_escape (const char *inbuf,
size_t inbuf_len,
char *outbuf,
size_t outbuf_len)
{
const char *src = inbuf;
char *dst = outbuf;
size_t i = inbuf_len;
qcdm_return_val_if_fail (inbuf != NULL, 0);
qcdm_return_val_if_fail (inbuf_len > 0, 0);
qcdm_return_val_if_fail (outbuf != NULL, 0);
qcdm_return_val_if_fail (outbuf_len > inbuf_len, 0);
/* Since escaping potentially doubles the # of bytes, short-circuit the
* length check if destination buffer is clearly large enough. Note the
*
*/
if (outbuf_len <= inbuf_len << 1) {
size_t outbuf_required = inbuf_len + 1; /* +1 for the trailing control char */
/* Each escaped character takes up two bytes in the output buffer */
while (i--) {
if (*src == DIAG_CONTROL_CHAR || *src == DIAG_ESC_CHAR)
outbuf_required++;
src++;
}
if (outbuf_len < outbuf_required)
return 0;
}
/* Do the actual escaping. Replace both the control character and
* the escape character in the source buffer with the following sequence:
*
*
*/
src = inbuf;
i = inbuf_len;
while (i--) {
if (*src == DIAG_CONTROL_CHAR || *src == DIAG_ESC_CHAR) {
*dst++ = DIAG_ESC_CHAR;
*dst++ = *src ^ DIAG_ESC_MASK;
} else
*dst++ = *src;
src++;
}
return (dst - outbuf);
}
size_t
dm_unescape (const char *inbuf,
size_t inbuf_len,
char *outbuf,
size_t outbuf_len,
qcdmbool *escaping)
{
size_t i, outsize;
qcdm_return_val_if_fail (inbuf_len > 0, 0);
qcdm_return_val_if_fail (outbuf_len >= inbuf_len, 0);
qcdm_return_val_if_fail (escaping != NULL, 0);
for (i = 0, outsize = 0; i < inbuf_len; i++) {
if (*escaping) {
outbuf[outsize++] = inbuf[i] ^ DIAG_ESC_MASK;
*escaping = FALSE;
} else if (inbuf[i] == DIAG_ESC_CHAR)
*escaping = TRUE;
else
outbuf[outsize++] = inbuf[i];
/* About to overrun output buffer size */
if (outsize >= outbuf_len)
return 0;
}
return outsize;
}
/**
* dm_encapsulate_buffer:
* @inbuf: buffer in which a valid QCDM packet exists
* @cmd_len: size of the QCDM packet contained in @inbuf
* @inbuf_len: total size of @inbuf itself (not just the packet)
* @outbuf: buffer in which to put the encapsulated QCDM packet
* @outbuf_len: total size of @outbuf
*
* Escapes and CRCs a QCDM packet, and finally adds the trailing control
* character that denotes the end of the QCDM packet.
*
* Returns: size of the encapsulated QCDM command writted to @outbuf.
**/
size_t
dm_encapsulate_buffer (char *inbuf,
size_t cmd_len,
size_t inbuf_len,
char *outbuf,
size_t outbuf_len)
{
u_int16_t crc;
size_t escaped_len;
qcdm_return_val_if_fail (inbuf != NULL, 0);
qcdm_return_val_if_fail (cmd_len >= 1, 0);
qcdm_return_val_if_fail (inbuf_len >= cmd_len + 2, 0); /* space for CRC */
qcdm_return_val_if_fail (outbuf != NULL, 0);
/* Add the CRC */
crc = crc16 (inbuf, cmd_len);
inbuf[cmd_len++] = crc & 0xFF;
inbuf[cmd_len++] = (crc >> 8) & 0xFF;
escaped_len = dm_escape (inbuf, cmd_len, outbuf, outbuf_len);
qcdm_return_val_if_fail (outbuf_len > escaped_len, 0);
outbuf[escaped_len++] = DIAG_CONTROL_CHAR;
return escaped_len;
}
/**
* dm_decapsulate_buffer:
* @inbuf: buffer in which to look for a QCDM packet
* @inbuf_len: length of valid data in @inbuf
* @outbuf: buffer in which to put decapsulated QCDM packet
* @outbuf_len: max size of @outbuf
* @out_decap_len: on success, size of the decapsulated QCDM packet
* @out_used: on either success or failure, amount of data used; caller should
* discard this much data from @inbuf before the next call to this function
* @out_need_more: when TRUE, indicates that more data is required before
* and determination about a valid QCDM packet can be made; caller should add
* more data to @inbuf before calling this function again.
*
* Attempts to retrieve, unescape, and CRC-check a QCDM packet from the given
* buffer.
*
* Returns: FALSE on error (packet was invalid or malformed, or the CRC check
* failed, etc) and places number of bytes to discard from @inbuf in @out_used.
* When TRUE, either more data is required (in which case @out_need_more will
* be TRUE), or a QCDM packet was successfully retrieved from @inbuf and the
* decapsulated packet of length @out_decap_len was placed into @outbuf. In
* all cases the caller should advance the buffer by the number of bytes
* returned in @out_used before calling this function again.
**/
qcdmbool
dm_decapsulate_buffer (const char *inbuf,
size_t inbuf_len,
char *outbuf,
size_t outbuf_len,
size_t *out_decap_len,
size_t *out_used,
qcdmbool *out_need_more)
{
qcdmbool escaping = FALSE;
size_t i, pkt_len = 0, unesc_len;
u_int16_t crc, pkt_crc;
qcdm_return_val_if_fail (inbuf != NULL, FALSE);
qcdm_return_val_if_fail (outbuf != NULL, FALSE);
qcdm_return_val_if_fail (outbuf_len > 0, FALSE);
qcdm_return_val_if_fail (out_decap_len != NULL, FALSE);
qcdm_return_val_if_fail (out_used != NULL, FALSE);
qcdm_return_val_if_fail (out_need_more != NULL, FALSE);
*out_decap_len = 0;
*out_used = 0;
*out_need_more = FALSE;
if (inbuf_len < 4) {
*out_need_more = TRUE;
return TRUE;
}
/* Find the async control character */
for (i = 0; i < inbuf_len; i++) {
if (inbuf[i] == DIAG_CONTROL_CHAR) {
/* If the control character shows up in a position before a valid
* QCDM packet length (4), the packet is malformed.
*/
if (i < 3) {
/* Tell the caller to advance the buffer past the control char */
*out_used = i + 1;
return FALSE;
}
pkt_len = i;
break;
}
}
/* No control char yet, need more data */
if (!pkt_len) {
*out_need_more = TRUE;
return TRUE;
}
/* Unescape first; note that pkt_len */
unesc_len = dm_unescape (inbuf, pkt_len, outbuf, outbuf_len, &escaping);
if (!unesc_len) {
/* Tell the caller to advance the buffer past the control char */
*out_used = pkt_len + 1;
return FALSE;
}
if (escaping) {
*out_need_more = TRUE;
return TRUE;
}
/* Check the CRC of the packet's data */
crc = crc16 (outbuf, unesc_len - 2);
pkt_crc = outbuf[unesc_len - 2] & 0xFF;
pkt_crc |= (outbuf[unesc_len - 1] & 0xFF) << 8;
if (crc != pkt_crc) {
*out_used = pkt_len + 1; /* packet + CRC + 0x7E */
return FALSE;
}
*out_used = pkt_len + 1; /* packet + CRC + 0x7E */
*out_decap_len = unesc_len - 2; /* decap_len should not include the CRC */
return TRUE;
}