view buffer.c @ 1156:a8f4dade70e5

avoid getpass when not used some systems (like android's bionic) do not provide getpass. you can disable ENABLE_CLI_PASSWORD_AUTH & ENABLE_CLI_INTERACT_AUTH to avoid its use (and rely on pubkey auth), but the link still fails because the support file calls getpass. do not define this func if both of those auth methods are not used.
author Mike Frysinger <vapier@gentoo.org>
date Wed, 21 Oct 2015 22:39:55 +0800
parents aaf576b27a10
children 2bb4c662d1c2
line wrap: on
line source

/*
 * Dropbear SSH
 * 
 * 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)+size);

	if (size > 0) {
		buf->data = (unsigned char*)buf + sizeof(buffer);
	} else {
		buf->data = NULL;
	}

	buf->size = size;

	return buf;

}

/* free the buffer's data and the buffer itself */
void buf_free(buffer* buf) {

	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 */
buffer* buf_resize(buffer *buf, unsigned int newsize) {

	if (newsize > BUF_MAX_SIZE) {
		dropbear_exit("buf->size too big");
	}

	buf = m_realloc(buf, sizeof(buffer)+newsize);
	buf->data = (unsigned char*)buf + sizeof(buffer);
	buf->size = newsize;
	buf->len = MIN(newsize, buf->len);
	buf->pos = MIN(newsize, buf->pos);
	return buf;
}

/* 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;
	if (buf->len > 0) {
	    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 position 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
	 * bad case of pos > len, which should _never_ happen. */
	if (buf->pos >= buf->len) {
		dropbear_exit("Bad buf_getbyte");
	}
	return buf->data[buf->pos++];
}

/* Get a bool from the buffer and increment the pos */
unsigned char buf_getbool(buffer* buf) {

	unsigned char b;
	b = buf_getbyte(buf);
	if (b != 0)
		b = 1;
	return b;
}

/* 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 */
char* buf_getstring(buffer* buf, unsigned int *retlen) {

	unsigned int len;
	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;
}

/* Return a string as a newly allocated buffer */
buffer * buf_getstringbuf(buffer *buf) {
	buffer *ret = NULL;
	unsigned int len = buf_getint(buf);
	if (len > MAX_STRING_LEN) {
		dropbear_exit("String too long");
	}
	ret = buf_new(len);
	memcpy(buf_getwriteptr(ret, len), buf_getptr(buf, len), len);
	buf_incrpos(buf, len);
	buf_incrlen(ret, len);
	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 char* str, unsigned int len) {
	
	buf_putint(buf, len);
	buf_putbytes(buf, (const unsigned char*)str, len);

}

/* puts an entire buffer as a SSH string. ignore pos of buf_str. */
void buf_putbufstring(buffer *buf, const buffer* buf_str) {
	buf_putstring(buf, (const char*)buf_str->data, 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;
	TRACE2(("enter buf_putmpint"))

	dropbear_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);
	}

	TRACE2(("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;
}