353 lines
8.7 KiB
C
353 lines
8.7 KiB
C
/*
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* Dropbear SSH
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*
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* Copyright (c) 2002,2003 Matt Johnston
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* All rights reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE. */
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/* Buffer handling routines, designed to avoid overflows/using invalid data */
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#include "includes.h"
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#include "dbutil.h"
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#include "buffer.h"
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/* Prevent integer overflows when incrementing buffer position/length.
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* Calling functions should check arguments first, but this provides a
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* backstop */
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#define BUF_MAX_INCR 1000000000
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#define BUF_MAX_SIZE 1000000000
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/* avoid excessively large numbers, > ~8192 bits */
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#define BUF_MAX_MPINT (8240 / 8)
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/* Create (malloc) a new buffer of size */
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buffer* buf_new(unsigned int size) {
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buffer* buf;
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if (size > BUF_MAX_SIZE) {
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dropbear_exit("buf->size too big");
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}
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buf = (buffer*)m_malloc(sizeof(buffer));
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if (size > 0) {
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buf->data = (unsigned char*)m_malloc(size);
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} else {
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buf->data = NULL;
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}
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buf->size = size;
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buf->pos = 0;
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buf->len = 0;
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return buf;
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}
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/* free the buffer's data and the buffer itself */
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void buf_free(buffer* buf) {
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m_free(buf->data)
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m_free(buf);
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}
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/* overwrite the contents of the buffer to clear it */
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void buf_burn(buffer* buf) {
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m_burn(buf->data, buf->size);
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}
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/* resize a buffer, pos and len will be repositioned if required when
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* downsizing */
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void buf_resize(buffer *buf, unsigned int newsize) {
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if (newsize > BUF_MAX_SIZE) {
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dropbear_exit("buf->size too big");
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}
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buf->data = m_realloc(buf->data, newsize);
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buf->size = newsize;
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buf->len = MIN(newsize, buf->len);
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buf->pos = MIN(newsize, buf->pos);
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}
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/* Create a copy of buf, allocating required memory etc. */
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/* The new buffer is sized the same as the length of the source buffer. */
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buffer* buf_newcopy(buffer* buf) {
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buffer* ret;
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ret = buf_new(buf->len);
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ret->len = buf->len;
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memcpy(ret->data, buf->data, buf->len);
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return ret;
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}
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/* Set the length of the buffer */
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void buf_setlen(buffer* buf, unsigned int len) {
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if (len > buf->size) {
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dropbear_exit("Bad buf_setlen");
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}
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buf->len = len;
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}
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/* Increment the length of the buffer */
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void buf_incrlen(buffer* buf, unsigned int incr) {
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if (incr > BUF_MAX_INCR || buf->len + incr > buf->size) {
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dropbear_exit("Bad buf_incrlen");
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}
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buf->len += incr;
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}
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/* Set the position of the buffer */
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void buf_setpos(buffer* buf, unsigned int pos) {
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if (pos > buf->len) {
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dropbear_exit("Bad buf_setpos");
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}
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buf->pos = pos;
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}
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/* increment the postion by incr, increasing the buffer length if required */
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void buf_incrwritepos(buffer* buf, unsigned int incr) {
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if (incr > BUF_MAX_INCR || buf->pos + incr > buf->size) {
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dropbear_exit("Bad buf_incrwritepos");
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}
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buf->pos += incr;
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if (buf->pos > buf->len) {
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buf->len = buf->pos;
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}
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}
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/* increment the position by incr, negative values are allowed, to
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* decrement the pos*/
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void buf_incrpos(buffer* buf, int incr) {
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if (incr > BUF_MAX_INCR ||
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(unsigned int)((int)buf->pos + incr) > buf->len
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|| ((int)buf->pos + incr) < 0) {
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dropbear_exit("Bad buf_incrpos");
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}
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buf->pos += incr;
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}
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/* Get a byte from the buffer and increment the pos */
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unsigned char buf_getbyte(buffer* buf) {
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/* This check is really just ==, but the >= allows us to check for the
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* bad case of pos > len, which should _never_ happen. */
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if (buf->pos >= buf->len) {
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dropbear_exit("Bad buf_getbyte");
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}
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return buf->data[buf->pos++];
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}
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/* Get a bool from the buffer and increment the pos */
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unsigned char buf_getbool(buffer* buf) {
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unsigned char b;
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b = buf_getbyte(buf);
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if (b != 0)
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b = 1;
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return b;
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}
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/* put a byte, incrementing the length if required */
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void buf_putbyte(buffer* buf, unsigned char val) {
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if (buf->pos >= buf->len) {
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buf_incrlen(buf, 1);
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}
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buf->data[buf->pos] = val;
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buf->pos++;
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}
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/* returns an in-place pointer to the buffer, checking that
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* the next len bytes from that position can be used */
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unsigned char* buf_getptr(buffer* buf, unsigned int len) {
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if (buf->pos + len > buf->len) {
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dropbear_exit("Bad buf_getptr");
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}
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return &buf->data[buf->pos];
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}
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/* like buf_getptr, but checks against total size, not used length.
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* This allows writing past the used length, but not past the size */
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unsigned char* buf_getwriteptr(buffer* buf, unsigned int len) {
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if (buf->pos + len > buf->size) {
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dropbear_exit("Bad buf_getwriteptr");
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}
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return &buf->data[buf->pos];
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}
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/* Return a null-terminated string, it is malloced, so must be free()ed
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* Note that the string isn't checked for null bytes, hence the retlen
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* may be longer than what is returned by strlen */
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unsigned char* buf_getstring(buffer* buf, unsigned int *retlen) {
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unsigned int len;
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unsigned char* ret;
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len = buf_getint(buf);
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if (len > MAX_STRING_LEN) {
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dropbear_exit("String too long");
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}
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if (retlen != NULL) {
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*retlen = len;
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}
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ret = m_malloc(len+1);
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memcpy(ret, buf_getptr(buf, len), len);
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buf_incrpos(buf, len);
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ret[len] = '\0';
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return ret;
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}
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/* Return a string as a newly allocated buffer */
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buffer * buf_getstringbuf(buffer *buf) {
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buffer *ret;
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unsigned char* str;
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unsigned int len;
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str = buf_getstring(buf, &len);
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ret = m_malloc(sizeof(*ret));
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ret->data = str;
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ret->len = len;
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ret->size = len;
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ret->pos = 0;
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return ret;
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}
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/* Just increment the buffer position the same as if we'd used buf_getstring,
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* but don't bother copying/malloc()ing for it */
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void buf_eatstring(buffer *buf) {
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buf_incrpos( buf, buf_getint(buf) );
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}
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/* Get an uint32 from the buffer and increment the pos */
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unsigned int buf_getint(buffer* buf) {
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unsigned int ret;
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LOAD32H(ret, buf_getptr(buf, 4));
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buf_incrpos(buf, 4);
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return ret;
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}
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/* put a 32bit uint into the buffer, incr bufferlen & pos if required */
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void buf_putint(buffer* buf, int unsigned val) {
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STORE32H(val, buf_getwriteptr(buf, 4));
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buf_incrwritepos(buf, 4);
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}
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/* put a SSH style string into the buffer, increasing buffer len if required */
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void buf_putstring(buffer* buf, const unsigned char* str, unsigned int len) {
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buf_putint(buf, len);
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buf_putbytes(buf, str, len);
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}
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/* put the set of len bytes into the buffer, incrementing the pos, increasing
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* len if required */
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void buf_putbytes(buffer *buf, const unsigned char *bytes, unsigned int len) {
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memcpy(buf_getwriteptr(buf, len), bytes, len);
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buf_incrwritepos(buf, len);
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}
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/* for our purposes we only need positive (or 0) numbers, so will
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* fail if we get negative numbers */
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void buf_putmpint(buffer* buf, mp_int * mp) {
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unsigned int len, pad = 0;
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TRACE(("enter buf_putmpint"))
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dropbear_assert(mp != NULL);
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if (SIGN(mp) == MP_NEG) {
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dropbear_exit("negative bignum");
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}
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/* zero check */
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if (USED(mp) == 1 && DIGIT(mp, 0) == 0) {
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len = 0;
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} else {
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/* SSH spec requires padding for mpints with the MSB set, this code
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* implements it */
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len = mp_count_bits(mp);
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/* if the top bit of MSB is set, we need to pad */
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pad = (len%8 == 0) ? 1 : 0;
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len = len / 8 + 1; /* don't worry about rounding, we need it for
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padding anyway when len%8 == 0 */
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}
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/* store the length */
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buf_putint(buf, len);
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/* store the actual value */
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if (len > 0) {
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if (pad) {
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buf_putbyte(buf, 0x00);
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}
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if (mp_to_unsigned_bin(mp, buf_getwriteptr(buf, len-pad)) != MP_OKAY) {
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dropbear_exit("mpint error");
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}
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buf_incrwritepos(buf, len-pad);
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}
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TRACE(("leave buf_putmpint"))
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}
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/* Retrieve an mp_int from the buffer.
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* Will fail for -ve since they shouldn't be required here.
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* Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
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int buf_getmpint(buffer* buf, mp_int* mp) {
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unsigned int len;
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len = buf_getint(buf);
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if (len == 0) {
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mp_zero(mp);
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return DROPBEAR_SUCCESS;
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}
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if (len > BUF_MAX_MPINT) {
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return DROPBEAR_FAILURE;
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}
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/* check for negative */
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if (*buf_getptr(buf, 1) & (1 << (CHAR_BIT-1))) {
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return DROPBEAR_FAILURE;
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}
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if (mp_read_unsigned_bin(mp, buf_getptr(buf, len), len) != MP_OKAY) {
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return DROPBEAR_FAILURE;
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}
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buf_incrpos(buf, len);
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return DROPBEAR_SUCCESS;
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}
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