bufaux.c

/* $OpenBSD: bufaux.c,v 1.57 2014/04/16 23:22:45 djm Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Auxiliary functions for storing and retrieving various data types to/from
 * Buffers.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 *
 * SSH2 packet format added by Markus Friedl
 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"

#include <sys/types.h>

#include <openssl/bn.h>

#include <string.h>
#include <stdarg.h>
#include <stdlib.h>

#include "xmalloc.h"
#include "buffer.h"
#include "log.h"
#include "misc.h"

/*
 * Returns integers from the buffer (msb first).
 */

int
buffer_get_short_ret(u_short *ret, Buffer *buffer)
{
	u_char buf[2];

	if (buffer_get_ret(buffer, (char *) buf, 2) == -1)
		return (-1);
	*ret = get_u16(buf);
	return (0);
}

u_short
buffer_get_short(Buffer *buffer)
{
	u_short ret;

	if (buffer_get_short_ret(&ret, buffer) == -1)
		fatal("buffer_get_short: buffer error");

	return (ret);
}

int
buffer_get_int_ret(u_int *ret, Buffer *buffer)
{
	u_char buf[4];

	if (buffer_get_ret(buffer, (char *) buf, 4) == -1)
		return (-1);
	if (ret != NULL)
		*ret = get_u32(buf);
	return (0);
}

u_int
buffer_get_int(Buffer *buffer)
{
	u_int ret;

	if (buffer_get_int_ret(&ret, buffer) == -1)
		fatal("buffer_get_int: buffer error");

	return (ret);
}

int
buffer_get_int64_ret(u_int64_t *ret, Buffer *buffer)
{
	u_char buf[8];

	if (buffer_get_ret(buffer, (char *) buf, 8) == -1)
		return (-1);
	if (ret != NULL)
		*ret = get_u64(buf);
	return (0);
}

u_int64_t
buffer_get_int64(Buffer *buffer)
{
	u_int64_t ret;

	if (buffer_get_int64_ret(&ret, buffer) == -1)
		fatal("buffer_get_int: buffer error");

	return (ret);
}

/*
 * Stores integers in the buffer, msb first.
 */
void
buffer_put_short(Buffer *buffer, u_short value)
{
	char buf[2];

	put_u16(buf, value);
	buffer_append(buffer, buf, 2);
}

void
buffer_put_int(Buffer *buffer, u_int value)
{
	char buf[4];

	put_u32(buf, value);
	buffer_append(buffer, buf, 4);
}

void
buffer_put_int64(Buffer *buffer, u_int64_t value)
{
	char buf[8];

	put_u64(buf, value);
	buffer_append(buffer, buf, 8);
}

/*
 * Returns an arbitrary binary string from the buffer.  The string cannot
 * be longer than 256k.  The returned value points to memory allocated
 * with xmalloc; it is the responsibility of the calling function to free
 * the data.  If length_ptr is non-NULL, the length of the returned data
 * will be stored there.  A null character will be automatically appended
 * to the returned string, and is not counted in length.
 */
void *
buffer_get_string_ret(Buffer *buffer, u_int *length_ptr)
{
	u_char *value;
	u_int len;

	/* Get the length. */
	if (buffer_get_int_ret(&len, buffer) != 0) {
		error("buffer_get_string_ret: cannot extract length");
		return (NULL);
	}
	if (len > 256 * 1024) {
		error("buffer_get_string_ret: bad string length %u", len);
		return (NULL);
	}
	/* Allocate space for the string.  Add one byte for a null character. */
	value = xmalloc(len + 1);
	/* Get the string. */
	if (buffer_get_ret(buffer, value, len) == -1) {
		error("buffer_get_string_ret: buffer_get failed");
		free(value);
		return (NULL);
	}
	/* Append a null character to make processing easier. */
	value[len] = '\0';
	/* Optionally return the length of the string. */
	if (length_ptr)
		*length_ptr = len;
	return (value);
}

void *
buffer_get_string(Buffer *buffer, u_int *length_ptr)
{
	void *ret;

	if ((ret = buffer_get_string_ret(buffer, length_ptr)) == NULL)
		fatal("buffer_get_string: buffer error");
	return (ret);
}

char *
buffer_get_cstring_ret(Buffer *buffer, u_int *length_ptr)
{
	u_int length;
	char *cp, *ret = buffer_get_string_ret(buffer, &length);

	if (ret == NULL)
		return NULL;
	if ((cp = memchr(ret, '\0', length)) != NULL) {
		/* XXX allow \0 at end-of-string for a while, remove later */
		if (cp == ret + length - 1)
			error("buffer_get_cstring_ret: string contains \\0");
		else {
			explicit_bzero(ret, length);
			free(ret);
			return NULL;
		}
	}
	if (length_ptr != NULL)
		*length_ptr = length;
	return ret;
}

char *
buffer_get_cstring(Buffer *buffer, u_int *length_ptr)
{
	char *ret;

	if ((ret = buffer_get_cstring_ret(buffer, length_ptr)) == NULL)
		fatal("buffer_get_cstring: buffer error");
	return ret;
}

void *
buffer_get_string_ptr_ret(Buffer *buffer, u_int *length_ptr)
{
	void *ptr;
	u_int len;

	if (buffer_get_int_ret(&len, buffer) != 0)
		return NULL;
	if (len > 256 * 1024) {
		error("buffer_get_string_ptr: bad string length %u", len);
		return NULL;
	}
	ptr = buffer_ptr(buffer);
	buffer_consume(buffer, len);
	if (length_ptr)
		*length_ptr = len;
	return (ptr);
}

void *
buffer_get_string_ptr(Buffer *buffer, u_int *length_ptr)
{
	void *ret;

	if ((ret = buffer_get_string_ptr_ret(buffer, length_ptr)) == NULL)
		fatal("buffer_get_string_ptr: buffer error");
	return (ret);
}

/*
 * Stores and arbitrary binary string in the buffer.
 */
void
buffer_put_string(Buffer *buffer, const void *buf, u_int len)
{
	buffer_put_int(buffer, len);
	buffer_append(buffer, buf, len);
}
void
buffer_put_cstring(Buffer *buffer, const char *s)
{
	if (s == NULL)
		fatal("buffer_put_cstring: s == NULL");
	buffer_put_string(buffer, s, strlen(s));
}

/*
 * Returns a character from the buffer (0 - 255).
 */
int
buffer_get_char_ret(u_char *ret, Buffer *buffer)
{
	if (buffer_get_ret(buffer, ret, 1) == -1) {
		error("buffer_get_char_ret: buffer_get_ret failed");
		return (-1);
	}
	return (0);
}

int
buffer_get_char(Buffer *buffer)
{
	u_char ch;

	if (buffer_get_char_ret(&ch, buffer) == -1)
		fatal("buffer_get_char: buffer error");
	return ch;
}

/*
 * Stores a character in the buffer.
 */
void
buffer_put_char(Buffer *buffer, int value)
{
	char ch = value;

	buffer_append(buffer, &ch, 1);
}

/* Pseudo bignum functions */

void *
buffer_get_bignum2_as_string_ret(Buffer *buffer, u_int *length_ptr)
{
	u_int len;
	u_char *bin, *p, *ret;

	if ((p = bin = buffer_get_string_ret(buffer, &len)) == NULL) {
		error("%s: invalid bignum", __func__);
		return NULL;
	}

	if (len > 0 && (bin[0] & 0x80)) {
		error("%s: negative numbers not supported", __func__);
		free(bin);
		return NULL;
	}
	if (len > 8 * 1024) {
		error("%s: cannot handle BN of size %d", __func__, len);
		free(bin);
		return NULL;
	}
	/* Skip zero prefix on numbers with the MSB set */
	if (len > 1 && bin[0] == 0x00 && (bin[1] & 0x80) != 0) {
		p++;
		len--;
	}
	ret = xmalloc(len);
	memcpy(ret, p, len);
	explicit_bzero(p, len);
	free(bin);
	return ret;
}

void *
buffer_get_bignum2_as_string(Buffer *buffer, u_int *l)
{
	void *ret = buffer_get_bignum2_as_string_ret(buffer, l);

	if (ret == NULL)
		fatal("%s: buffer error", __func__);
	return ret;
}

/*
 * Stores a string using the bignum encoding rules (\0 pad if MSB set).
 */
void
buffer_put_bignum2_from_string(Buffer *buffer, const u_char *s, u_int l)
{
	u_char *buf, *p;
	int pad = 0;

	if (l > 8 * 1024)
		fatal("%s: length %u too long", __func__, l);
	/* Skip leading zero bytes */
	for (; l > 0 && *s == 0; l--, s++)
		;
	p = buf = xmalloc(l + 1);
	/*
	 * If most significant bit is set then prepend a zero byte to
	 * avoid interpretation as a negative number.
	 */
	if (l > 0 && (s[0] & 0x80) != 0) {
		*p++ = '\0';
		pad = 1;
	}
	memcpy(p, s, l);
	buffer_put_string(buffer, buf, l + pad);
	explicit_bzero(buf, l + pad);
	free(buf);
}