Mercurial > dropbear
view buffer.c @ 76:95f4bc4bcd58
- It'll be called 0.44test1
- Debian stuff
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Sat, 14 Aug 2004 18:03:36 +0000 |
parents | b0316ce64e4b |
children | 10f4d3319780 |
line wrap: on
line source
/* * Dropbear - a SSH2 server * * Copyright (c) 2002,2003 Matt Johnston * All rights reserved. * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ /* Buffer handling routines, designed to avoid overflows/using invalid data */ #include "includes.h" #include "dbutil.h" #include "buffer.h" /* Prevent integer overflows when incrementing buffer position/length. * Calling functions should check arguments first, but this provides a * backstop */ #define BUF_MAX_INCR 1000000000 #define BUF_MAX_SIZE 1000000000 /* avoid excessively large numbers, > ~8192 bits */ #define BUF_MAX_MPINT (8240 / 8) /* Create (malloc) a new buffer of size */ buffer* buf_new(unsigned int size) { buffer* buf; if (size > BUF_MAX_SIZE) { dropbear_exit("buf->size too big"); } buf = (buffer*)m_malloc(sizeof(buffer)); if (size > 0) { buf->data = (unsigned char*)m_malloc(size); } else { buf->data = NULL; } buf->size = size; buf->pos = 0; buf->len = 0; return buf; } /* free the buffer's data and the buffer itself */ void buf_free(buffer* buf) { m_free(buf->data) m_free(buf); } /* overwrite the contents of the buffer to clear it */ void buf_burn(buffer* buf) { m_burn(buf->data, buf->size); } /* resize a buffer, pos and len will be repositioned if required when * downsizing */ void buf_resize(buffer *buf, unsigned int newsize) { if (newsize > BUF_MAX_SIZE) { dropbear_exit("buf->size too big"); } buf->data = m_realloc(buf->data, newsize); buf->size = newsize; buf->len = MIN(newsize, buf->len); buf->pos = MIN(newsize, buf->pos); } /* Create a copy of buf, allocating required memory etc. */ /* The new buffer is sized the same as the length of the source buffer. */ buffer* buf_newcopy(buffer* buf) { buffer* ret; ret = buf_new(buf->len); ret->len = buf->len; memcpy(ret->data, buf->data, buf->len); return ret; } /* Set the length of the buffer */ void buf_setlen(buffer* buf, unsigned int len) { if (len > buf->size) { dropbear_exit("bad buf_setlen"); } buf->len = len; } /* Increment the length of the buffer */ void buf_incrlen(buffer* buf, unsigned int incr) { if (incr > BUF_MAX_INCR || buf->len + incr > buf->size) { dropbear_exit("bad buf_incrlen"); } buf->len += incr; } /* Set the position of the buffer */ void buf_setpos(buffer* buf, unsigned int pos) { if (pos > buf->len) { dropbear_exit("bad buf_setpos"); } buf->pos = pos; } /* increment the postion by incr, increasing the buffer length if required */ void buf_incrwritepos(buffer* buf, unsigned int incr) { if (incr > BUF_MAX_INCR || buf->pos + incr > buf->size) { dropbear_exit("bad buf_incrwritepos"); } buf->pos += incr; if (buf->pos > buf->len) { buf->len = buf->pos; } } /* increment the position by incr, negative values are allowed, to * decrement the pos*/ void buf_incrpos(buffer* buf, int incr) { if (incr > BUF_MAX_INCR || (unsigned int)((int)buf->pos + incr) > buf->len || ((int)buf->pos + incr) < 0) { dropbear_exit("bad buf_incrpos"); } buf->pos += incr; } /* Get a byte from the buffer and increment the pos */ unsigned char buf_getbyte(buffer* buf) { /* This check is really just ==, but the >= allows us to check for the * assert()able case of pos > len, which should _never_ happen. */ if (buf->pos >= buf->len) { dropbear_exit("bad buf_getbyte"); } return buf->data[buf->pos++]; } /* put a byte, incrementing the length if required */ void buf_putbyte(buffer* buf, unsigned char val) { if (buf->pos >= buf->len) { buf_incrlen(buf, 1); } buf->data[buf->pos] = val; buf->pos++; } /* returns an in-place pointer to the buffer, checking that * the next len bytes from that position can be used */ unsigned char* buf_getptr(buffer* buf, unsigned int len) { if (buf->pos + len > buf->len) { dropbear_exit("bad buf_getptr"); } return &buf->data[buf->pos]; } /* like buf_getptr, but checks against total size, not used length. * This allows writing past the used length, but not past the size */ unsigned char* buf_getwriteptr(buffer* buf, unsigned int len) { if (buf->pos + len > buf->size) { dropbear_exit("bad buf_getwriteptr"); } return &buf->data[buf->pos]; } /* Return a null-terminated string, it is malloced, so must be free()ed * Note that the string isn't checked for null bytes, hence the retlen * may be longer than what is returned by strlen */ unsigned char* buf_getstring(buffer* buf, unsigned int *retlen) { unsigned int len; unsigned char* ret; len = buf_getint(buf); if (len > MAX_STRING_LEN) { dropbear_exit("string too long"); } if (retlen != NULL) { *retlen = len; } ret = m_malloc(len+1); memcpy(ret, buf_getptr(buf, len), len); buf_incrpos(buf, len); ret[len] = '\0'; return ret; } /* Just increment the buffer position the same as if we'd used buf_getstring, * but don't bother copying/malloc()ing for it */ void buf_eatstring(buffer *buf) { buf_incrpos( buf, buf_getint(buf) ); } /* Get an uint32 from the buffer and increment the pos */ unsigned int buf_getint(buffer* buf) { unsigned int ret; LOAD32H(ret, buf_getptr(buf, 4)); buf_incrpos(buf, 4); return ret; } /* put a 32bit uint into the buffer, incr bufferlen & pos if required */ void buf_putint(buffer* buf, int unsigned val) { STORE32H(val, buf_getwriteptr(buf, 4)); buf_incrwritepos(buf, 4); } /* put a SSH style string into the buffer, increasing buffer len if required */ void buf_putstring(buffer* buf, const unsigned char* str, unsigned int len) { buf_putint(buf, len); buf_putbytes(buf, str, len); } /* put the set of len bytes into the buffer, incrementing the pos, increasing * len if required */ void buf_putbytes(buffer *buf, const unsigned char *bytes, unsigned int len) { memcpy(buf_getwriteptr(buf, len), bytes, len); buf_incrwritepos(buf, len); } /* for our purposes we only need positive (or 0) numbers, so will * fail if we get negative numbers */ void buf_putmpint(buffer* buf, mp_int * mp) { unsigned int len, pad = 0; TRACE(("enter buf_putmpint")); assert(mp != NULL); if (SIGN(mp) == MP_NEG) { dropbear_exit("negative bignum"); } /* zero check */ if (USED(mp) == 1 && DIGIT(mp, 0) == 0) { len = 0; } else { /* SSH spec requires padding for mpints with the MSB set, this code * implements it */ len = mp_count_bits(mp); /* if the top bit of MSB is set, we need to pad */ pad = (len%8 == 0) ? 1 : 0; len = len / 8 + 1; /* don't worry about rounding, we need it for padding anyway when len%8 == 0 */ } /* store the length */ buf_putint(buf, len); /* store the actual value */ if (len > 0) { if (pad) { buf_putbyte(buf, 0x00); } if (mp_to_unsigned_bin(mp, buf_getwriteptr(buf, len-pad)) != MP_OKAY) { dropbear_exit("mpint error"); } buf_incrwritepos(buf, len-pad); } TRACE(("leave buf_putmpint")); } /* Retrieve an mp_int from the buffer. * Will fail for -ve since they shouldn't be required here. * Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */ int buf_getmpint(buffer* buf, mp_int* mp) { unsigned int len; len = buf_getint(buf); if (len == 0) { mp_zero(mp); return DROPBEAR_SUCCESS; } if (len > BUF_MAX_MPINT) { return DROPBEAR_FAILURE; } /* check for negative */ if (*buf_getptr(buf, 1) & (1 << (CHAR_BIT-1))) { return DROPBEAR_FAILURE; } if (mp_read_unsigned_bin(mp, buf_getptr(buf, len), len) != MP_OKAY) { return DROPBEAR_FAILURE; } buf_incrpos(buf, len); return DROPBEAR_SUCCESS; }