libssh/src/buffer.c

/*
 * buffer.c - buffer functions
 *
 * This file is part of the SSH Library
 *
 * Copyright (c) 2003-2009 by Aris Adamantiadis
 *
 * The SSH Library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 *
 * The SSH Library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with the SSH Library; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

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

#ifndef _WIN32
#include <arpa/inet.h>
#endif

#include "libssh/priv.h"
#include "libssh/buffer.h"

/**
 * @defgroup libssh_buffer The SSH buffer functions.
 * @ingroup libssh
 *
 * Functions to handle SSH buffers.
 *
 * @{
 */


#ifdef DEBUG_BUFFER
/**
 * @internal
 *
 * @brief Check that preconditions and postconditions are valid.
 *
 * @param[in]  buf      The buffer to check.
 */
static void buffer_verify(ssh_buffer buf){
  int doabort=0;
  if(buf->data == NULL)
    return;
  if(buf->used > buf->allocated){
    fprintf(stderr,"Buffer error : allocated %u, used %u\n",buf->allocated, buf->used);
    doabort=1;
  }
  if(buf->pos > buf->used){
    fprintf(stderr,"Buffer error : position %u, used %u\n",buf->pos, buf->used);
    doabort=1;
  }
  if(buf->pos > buf->allocated){
      fprintf(stderr,"Buffer error : position %u, allocated %u\n",buf->pos, buf->allocated);
      doabort=1;
  }
  if(doabort)
    abort();
}

#else
#define buffer_verify(x)
#endif

/**
 * @brief Create a new SSH buffer.
 *
 * @return A newly initialized SSH buffer, NULL on error.
 */
struct ssh_buffer_struct *ssh_buffer_new(void) {
  struct ssh_buffer_struct *buf = malloc(sizeof(struct ssh_buffer_struct));

  if (buf == NULL) {
    return NULL;
  }
  memset(buf, 0, sizeof(struct ssh_buffer_struct));
  buffer_verify(buf);
  return buf;
}

/**
 * @brief Deallocate a SSH buffer.
 *
 * \param[in]  buffer   The buffer to free.
 */
void ssh_buffer_free(struct ssh_buffer_struct *buffer) {
  if (buffer == NULL) {
    return;
  }
  buffer_verify(buffer);

  if (buffer->data) {
    /* burn the data */
    memset(buffer->data, 0, buffer->allocated);
    SAFE_FREE(buffer->data);
  }
  memset(buffer, 'X', sizeof(*buffer));
  SAFE_FREE(buffer);
}

static int realloc_buffer(struct ssh_buffer_struct *buffer, int needed) {
  int smallest = 1;
  char *new = NULL;
  buffer_verify(buffer);
  /* Find the smallest power of two which is greater or equal to needed */
  while(smallest <= needed) {
    smallest <<= 1;
  }
  needed = smallest;
  new = realloc(buffer->data, needed);
  if (new == NULL) {
    return -1;
  }
  buffer->data = new;
  buffer->allocated = needed;
  buffer_verify(buffer);
  return 0;
}

/** @internal
 * @brief shifts a buffer to remove unused data in the beginning
 * @param buffer SSH buffer
 */
static void buffer_shift(ssh_buffer buffer){
  buffer_verify(buffer);
  if(buffer->pos==0)
    return;
  memmove(buffer->data, buffer->data + buffer->pos, buffer->used - buffer->pos);
  buffer->used -= buffer->pos;
  buffer->pos=0;
  buffer_verify(buffer);
}

/**
 * @internal
 *
 * @brief Reinitialize a SSH buffer.
 *
 * @param[in]  buffer   The buffer to reinitialize.
 *
 * @return              0 on success, < 0 on error.
 */
int buffer_reinit(struct ssh_buffer_struct *buffer) {
  buffer_verify(buffer);
  memset(buffer->data, 0, buffer->used);
  buffer->used = 0;
  buffer->pos = 0;
  if(buffer->allocated > 127) {
    if (realloc_buffer(buffer, 127) < 0) {
      return -1;
    }
  }
  buffer_verify(buffer);
  return 0;
}

/**
 * @internal
 *
 * @brief Add data at the tail of a buffer.
 *
 * @param[in]  buffer   The buffer to add the data.
 *
 * @param[in]  data     A pointer to the data to add.
 *
 * @param[in]  len      The length of the data to add.
 *
 * @return              0 on success, < 0 on error.
 */
int buffer_add_data(struct ssh_buffer_struct *buffer, const void *data, uint32_t len) {
  buffer_verify(buffer);
  if (buffer->allocated < (buffer->used + len)) {
    if(buffer->pos > 0)
      buffer_shift(buffer);
    if (realloc_buffer(buffer, buffer->used + len) < 0) {
      return -1;
    }
  }

  memcpy(buffer->data+buffer->used, data, len);
  buffer->used+=len;
  buffer_verify(buffer);
  return 0;
}

/**
 * @internal
 *
 * @brief Add a SSH string to the tail of a buffer.
 *
 * @param[in]  buffer   The buffer to add the string.
 *
 * @param[in]  string   The SSH String to add.
 *
 * @return              0 on success, < 0 on error.
 */
int buffer_add_ssh_string(struct ssh_buffer_struct *buffer,
    struct ssh_string_struct *string) {
  uint32_t len = 0;

  len = ssh_string_len(string);
  if (buffer_add_data(buffer, string, len + sizeof(uint32_t)) < 0) {
    return -1;
  }

  return 0;
}

/**
 * @internal
 *
 * @brief Add a 32 bits unsigned integer to the tail of a buffer.
 *
 * @param[in]  buffer   The buffer to add the integer.
 *
 * @param[in]  data     The 32 bits integer to add.
 *
 * @return              0 on success, -1 on error.
 */
int buffer_add_u32(struct ssh_buffer_struct *buffer,uint32_t data){
  if (buffer_add_data(buffer, &data, sizeof(data)) < 0) {
    return -1;
  }

  return 0;
}

/**
 * @internal
 *
 * @brief Add a 16 bits unsigned integer to the tail of a buffer.
 *
 * @param[in]  buffer   The buffer to add the integer.
 *
 * @param[in]  data     The 16 bits integer to add.
 *
 * @return              0 on success, -1 on error.
 */
int buffer_add_u16(struct ssh_buffer_struct *buffer,uint16_t data){
  if (buffer_add_data(buffer, &data, sizeof(data)) < 0) {
    return -1;
  }

  return 0;
}

/**
 * @internal
 *
 * @brief Add a 64 bits unsigned integer to the tail of a buffer.
 *
 * @param[in]  buffer   The buffer to add the integer.
 *
 * @param[in]  data     The 64 bits integer to add.
 *
 * @return              0 on success, -1 on error.
 */
int buffer_add_u64(struct ssh_buffer_struct *buffer, uint64_t data){
  if (buffer_add_data(buffer, &data, sizeof(data)) < 0) {
    return -1;
  }

  return 0;
}

/**
 * @internal
 *
 * @brief Add a 8 bits unsigned integer to the tail of a buffer.
 *
 * @param[in]  buffer   The buffer to add the integer.
 *
 * @param[in]  data     The 8 bits integer to add.
 *
 * @return              0 on success, -1 on error.
 */
int buffer_add_u8(struct ssh_buffer_struct *buffer,uint8_t data){
  if (buffer_add_data(buffer, &data, sizeof(uint8_t)) < 0) {
    return -1;
  }

  return 0;
}

/**
 * @internal
 *
 * @brief Add data at the head of a buffer.
 *
 * @param[in]  buffer   The buffer to add the data.
 *
 * @param[in]  data     The data to prepend.
 *
 * @param[in]  len      The length of data to prepend.
 *
 * @return              0 on success, -1 on error.
 */
int buffer_prepend_data(struct ssh_buffer_struct *buffer, const void *data,
    uint32_t len) {
  buffer_verify(buffer);

  if(len <= buffer->pos){
    /* It's possible to insert data between begin and pos */
    memcpy(buffer->data + (buffer->pos - len), data, len);
    buffer->pos -= len;
    buffer_verify(buffer);
    return 0;
  }
  /* pos isn't high enough */
  if (buffer->allocated < (buffer->used - buffer->pos + len)) {
    if (realloc_buffer(buffer, buffer->used - buffer->pos + len) < 0) {
      return -1;
    }
  }
  memmove(buffer->data + len, buffer->data + buffer->pos, buffer->used - buffer->pos);
  memcpy(buffer->data, data, len);
  buffer->used += len - buffer->pos;
  buffer->pos = 0;
  buffer_verify(buffer);
  return 0;
}

/**
 * @internal
 *
 * @brief Append data from a buffer to the tail of another buffer.
 *
 * @param[in]  buffer   The destination buffer.
 *
 * @param[in]  source   The source buffer to append. It doesn't take the
 *                      position of the buffer into account.
 *
 * @return              0 on success, -1 on error.
 */
int buffer_add_buffer(struct ssh_buffer_struct *buffer,
    struct ssh_buffer_struct *source) {
  if (buffer_add_data(buffer, buffer_get_rest(source), buffer_get_rest_len(source)) < 0) {
    return -1;
  }

  return 0;
}

/**
 * @brief Get a pointer on the head of a buffer.
 *
 * @param[in]  buffer   The buffer to get the head pointer.
 *
 * @return              A data pointer on the head. It doesn't take the position
 *                      into account.
 *
 * @warning Don't expect data to be nul-terminated.
 *
 * @see buffer_get_rest()
 * @see buffer_get_len()
 */
void *ssh_buffer_get_begin(struct ssh_buffer_struct *buffer){
  return buffer->data;
}

/**
 * @internal
 *
 * @brief Get a pointer to the head of a buffer at the current position.
 *
 * @param[in]  buffer   The buffer to get the head pointer.
 *
 * @return              A pointer to the data from current position.
 *
 * @see buffer_get_rest_len()
 * @see buffer_get()
 */
void *buffer_get_rest(struct ssh_buffer_struct *buffer){
    return buffer->data + buffer->pos;
}

/**
 * @brief Get the length of the buffer, not counting position.
 *
 * @param[in]  buffer   The buffer to get the length from.
 *
 * @return              The length of the buffer.
 *
 * @see buffer_get()
 */
uint32_t ssh_buffer_get_len(struct ssh_buffer_struct *buffer){
    return buffer->used;
}

/**
 * @internal
 *
 * @brief Get the length of the buffer from the current position.
 *
 * @param[in]  buffer   The buffer to get the length from.
 *
 * @return              The length of the buffer.
 *
 * @see buffer_get_rest()
 */
uint32_t buffer_get_rest_len(struct ssh_buffer_struct *buffer){
  buffer_verify(buffer);
  return buffer->used - buffer->pos;
}

/**
 * @internal
 *
 * @brief Advance the position in the buffer.
 *
 * This has effect to "eat" bytes at head of the buffer.
 *
 * @param[in]  buffer   The buffer to advance the position.
 *
 * @param[in]  len      The number of bytes to eat.
 *
 * @return              The new size of the buffer.
 */
uint32_t buffer_pass_bytes(struct ssh_buffer_struct *buffer, uint32_t len){
    buffer_verify(buffer);
    if(buffer->used < buffer->pos+len)
        return 0;
    buffer->pos+=len;
    /* if the buffer is empty after having passed the whole bytes into it, we can clean it */
    if(buffer->pos==buffer->used){
        buffer->pos=0;
        buffer->used=0;
    }
    buffer_verify(buffer);
    return len;
}

/**
 * @internal
 *
 * @brief Cut the end of the buffer.
 *
 * @param[in]  buffer   The buffer to cut.
 *
 * @param[in]  len      The number of bytes to remove from the tail.
 *
 * @return              The new size of the buffer.
 */
uint32_t buffer_pass_bytes_end(struct ssh_buffer_struct *buffer, uint32_t len){
  buffer_verify(buffer);
  if(buffer->used < buffer->pos + len)
    return 0;
  buffer->used-=len;
  buffer_verify(buffer);
  return len;
}

/**
 * @internal
 *
 * @brief Get the remaining data out of the buffer and adjust the read pointer.
 *
 * @param[in]  buffer   The buffer to read.
 *
 * @param[in]  data     The data buffer where to store the data.
 *
 * @param[in]  len      The length to read from the buffer.
 *
 * @returns             0 if there is not enough data in buffer, len otherwise.
 */
uint32_t buffer_get_data(struct ssh_buffer_struct *buffer, void *data, uint32_t len){
    /*
     * Check for a integer overflow first, then check if not enough data is in
     * the buffer.
     */
    if (buffer->pos + len < len || buffer->pos + len > buffer->used) {
      return 0;
    }
    memcpy(data,buffer->data+buffer->pos,len);
    buffer->pos+=len;
    return len;   /* no yet support for partial reads (is it really needed ?? ) */
}

/**
 * @internal
 *
 * @brief Get a 8 bits unsigned int out of the buffer and adjusts the read
 * pointer.
 *
 * @param[in]  buffer   The buffer to read.
 *
 * @param[in]   data    A pointer to a uint8_t where to store the data.
 *
 * @returns             0 if there is not enough data in buffer, 1 otherwise.
 */
int buffer_get_u8(struct ssh_buffer_struct *buffer, uint8_t *data){
    return buffer_get_data(buffer,data,sizeof(uint8_t));
}

/** \internal
 * \brief gets a 32 bits unsigned int out of the buffer. Adjusts the read pointer.
 * \param buffer Buffer to read
 * \param data pointer to a uint32_t where to store the data
 * \returns 0 if there is not enough data in buffer
 * \returns 4 otherwise.
 */
int buffer_get_u32(struct ssh_buffer_struct *buffer, uint32_t *data){
    return buffer_get_data(buffer,data,sizeof(uint32_t));
}
/**
 * @internal
 *
 * @brief Get a 64 bits unsigned int out of the buffer and adjusts the read
 * pointer.
 *
 * @param[in]  buffer   The buffer to read.
 *
 * @param[in]  data     A pointer to a uint64_t where to store the data.
 *
 * @returns             0 if there is not enough data in buffer, 8 otherwise.
 */
int buffer_get_u64(struct ssh_buffer_struct *buffer, uint64_t *data){
    return buffer_get_data(buffer,data,sizeof(uint64_t));
}

/**
 * @internal
 *
 * @brief Get a SSH String out of the buffer and adjusts the read pointer.
 *
 * @param[in]  buffer   The buffer to read.
 *
 * @returns             The SSH String, NULL on error.
 */
struct ssh_string_struct *buffer_get_ssh_string(struct ssh_buffer_struct *buffer) {
  uint32_t stringlen;
  uint32_t hostlen;
  struct ssh_string_struct *str = NULL;

  if (buffer_get_u32(buffer, &stringlen) == 0) {
    return NULL;
  }
  hostlen = ntohl(stringlen);
  /* verify if there is enough space in buffer to get it */
  if ((buffer->pos + hostlen) > buffer->used) {
    return NULL; /* it is indeed */
  }
  str = ssh_string_new(hostlen);
  if (str == NULL) {
    return NULL;
  }
  if (buffer_get_data(buffer, ssh_string_data(str), hostlen) != hostlen) {
    /* should never happen */
    SAFE_FREE(str);
    return NULL;
  }

  return str;
}

/**
 * @internal
 *
 * @brief Get a mpint out of the buffer and adjusts the read pointer.
 *
 * @note This function is SSH-1 only.
 *
 * @param[in]  buffer   The buffer to read.
 *
 * @returns             The SSH String containing the mpint, NULL on error.
 */
struct ssh_string_struct *buffer_get_mpint(struct ssh_buffer_struct *buffer) {
  uint16_t bits;
  uint32_t len;
  struct ssh_string_struct *str = NULL;

  if (buffer_get_data(buffer, &bits, sizeof(uint16_t)) != sizeof(uint16_t)) {
    return NULL;
  }
  bits = ntohs(bits);
  len = (bits + 7) / 8;
  if ((buffer->pos + len) > buffer->used) {
    return NULL;
  }
  str = ssh_string_new(len);
  if (str == NULL) {
    return NULL;
  }
  if (buffer_get_data(buffer, ssh_string_data(str), len) != len) {
    SAFE_FREE(str);
    return NULL;
  }
  return str;
}

/** @} */

/* vim: set ts=4 sw=4 et cindent: */