IABSD.fr/src/lib/libssl/tls_buffer.c

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• Author : jsing
  Date : 2022-11-10 18:06:37
  Hash : b1a5c5c8
  Message : Use tls_buffer for alert and handshake fragments in the legacy stack. This avoids a bunch of pointer munging and a handrolled memmove. ok tb@

• lib/libssl/tls_buffer.c

• /* $OpenBSD: tls_buffer.c,v 1.4 2022/11/10 18:06:37 jsing Exp $ */
  /*
   * Copyright (c) 2018, 2019, 2022 Joel Sing <jsing@openbsd.org>
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <stdlib.h>
  #include <string.h>
  
  #include "bytestring.h"
  #include "tls_internal.h"
  
  #define TLS_BUFFER_CAPACITY_LIMIT	(1024 * 1024)
  
  struct tls_buffer {
  	size_t capacity;
  	size_t capacity_limit;
  	uint8_t *data;
  	size_t len;
  	size_t offset;
  };
  
  static int tls_buffer_resize(struct tls_buffer *buf, size_t capacity);
  
  struct tls_buffer *
  tls_buffer_new(size_t init_size)
  {
  	struct tls_buffer *buf = NULL;
  
  	if ((buf = calloc(1, sizeof(struct tls_buffer))) == NULL)
  		goto err;
  
  	buf->capacity_limit = TLS_BUFFER_CAPACITY_LIMIT;
  
  	if (!tls_buffer_resize(buf, init_size))
  		goto err;
  
  	return buf;
  
   err:
  	tls_buffer_free(buf);
  
  	return NULL;
  }
  
  void
  tls_buffer_clear(struct tls_buffer *buf)
  {
  	freezero(buf->data, buf->capacity);
  
  	buf->data = NULL;
  	buf->capacity = 0;
  	buf->len = 0;
  	buf->offset = 0;
  }
  
  void
  tls_buffer_free(struct tls_buffer *buf)
  {
  	if (buf == NULL)
  		return;
  
  	tls_buffer_clear(buf);
  
  	freezero(buf, sizeof(struct tls_buffer));
  }
  
  static int
  tls_buffer_grow(struct tls_buffer *buf, size_t capacity)
  {
  	if (buf->capacity >= capacity)
  		return 1;
  
  	return tls_buffer_resize(buf, capacity);
  }
  
  static int
  tls_buffer_resize(struct tls_buffer *buf, size_t capacity)
  {
  	uint8_t *data;
  
  	/*
  	 * XXX - Consider maintaining a minimum size and growing more
  	 * intelligently (rather than exactly).
  	 */
  	if (buf->capacity == capacity)
  		return 1;
  
  	if (capacity > buf->capacity_limit)
  		return 0;
  
  	if ((data = recallocarray(buf->data, buf->capacity, capacity, 1)) == NULL)
  		return 0;
  
  	buf->data = data;
  	buf->capacity = capacity;
  
  	/* Ensure that len and offset are valid if capacity decreased. */
  	if (buf->len > buf->capacity)
  		buf->len = buf->capacity;
  	if (buf->offset > buf->len)
  		buf->offset = buf->len;
  
  	return 1;
  }
  
  void
  tls_buffer_set_capacity_limit(struct tls_buffer *buf, size_t limit)
  {
  	/*
  	 * XXX - do we want to force a resize if this limit is less than current
  	 * capacity... and what do we do with existing data? Force a clear?
  	 */
  	buf->capacity_limit = limit;
  }
  
  ssize_t
  tls_buffer_extend(struct tls_buffer *buf, size_t len,
      tls_read_cb read_cb, void *cb_arg)
  {
  	ssize_t ret;
  
  	if (len == buf->len)
  		return buf->len;
  
  	if (len < buf->len)
  		return TLS_IO_FAILURE;
  
  	if (!tls_buffer_resize(buf, len))
  		return TLS_IO_FAILURE;
  
  	for (;;) {
  		if ((ret = read_cb(&buf->data[buf->len],
  		    buf->capacity - buf->len, cb_arg)) <= 0)
  			return ret;
  
  		if (ret > buf->capacity - buf->len)
  			return TLS_IO_FAILURE;
  
  		buf->len += ret;
  
  		if (buf->len == buf->capacity)
  			return buf->len;
  	}
  }
  
  size_t
  tls_buffer_remaining(struct tls_buffer *buf)
  {
  	if (buf->offset > buf->len)
  		return 0;
  
  	return buf->len - buf->offset;
  }
  
  ssize_t
  tls_buffer_read(struct tls_buffer *buf, uint8_t *rbuf, size_t n)
  {
  	if (buf->offset > buf->len)
  		return TLS_IO_FAILURE;
  
  	if (buf->offset == buf->len)
  		return TLS_IO_WANT_POLLIN;
  
  	if (n > buf->len - buf->offset)
  		n = buf->len - buf->offset;
  
  	memcpy(rbuf, &buf->data[buf->offset], n);
  
  	buf->offset += n;
  
  	return n;
  }
  
  ssize_t
  tls_buffer_write(struct tls_buffer *buf, const uint8_t *wbuf, size_t n)
  {
  	if (buf->offset > buf->len)
  		return TLS_IO_FAILURE;
  
  	/*
  	 * To avoid continually growing the buffer, pull data up to the
  	 * start of the buffer. If all data has been read then we can simply
  	 * reset, otherwise wait until we're going to save at least 4KB of
  	 * memory to reduce overhead.
  	 */
  	if (buf->offset == buf->len) {
  		buf->len = 0;
  		buf->offset = 0;
  	}
  	if (buf->offset >= 4096) {
  		memmove(buf->data, &buf->data[buf->offset],
  		    buf->len - buf->offset);
  		buf->len -= buf->offset;
  		buf->offset = 0;
  	}
  
  	if (buf->len > SIZE_MAX - n)
  		return TLS_IO_FAILURE;
  	if (!tls_buffer_grow(buf, buf->len + n))
  		return TLS_IO_FAILURE;
  
  	memcpy(&buf->data[buf->len], wbuf, n);
  
  	buf->len += n;
  
  	return n;
  }
  
  int
  tls_buffer_append(struct tls_buffer *buf, const uint8_t *wbuf, size_t n)
  {
  	return tls_buffer_write(buf, wbuf, n) == n;
  }
  
  int
  tls_buffer_data(struct tls_buffer *buf, CBS *out_cbs)
  {
  	CBS cbs;
  
  	CBS_init(&cbs, buf->data, buf->len);
  
  	if (!CBS_skip(&cbs, buf->offset))
  		return 0;
  
  	CBS_dup(&cbs, out_cbs);
  
  	return 1;
  }
  
  int
  tls_buffer_finish(struct tls_buffer *buf, uint8_t **out, size_t *out_len)
  {
  	if (out == NULL || out_len == NULL)
  		return 0;
  
  	*out = buf->data;
  	*out_len = buf->len;
  
  	buf->data = NULL;
  	buf->capacity = 0;
  	buf->len = 0;
  	buf->offset = 0;
  
  	return 1;
  }