Buf.cc

/***************************************************************************
 * Buf.cc -- The Buf class is reponsible for I/O buffer manipulation       *
 * and is based on the buffer code used in OpenSSH.                        *
 *                                                                         *
 ***********************IMPORTANT NMAP LICENSE TERMS************************
 *                                                                         *
 * The Nmap Security Scanner is (C) 1996-2021 Insecure.Com LLC ("The Nmap  *
 * Project"). Nmap is also a registered trademark of the Nmap Project.     *
 * This program is free software; you may redistribute and/or modify it    *
 * under the terms of the GNU General Public License as published by the   *
 * Free Software Foundation; Version 2 ("GPL"), BUT ONLY WITH ALL OF THE   *
 * CLARIFICATIONS AND EXCEPTIONS DESCRIBED HEREIN.  This guarantees your   *
 * right to use, modify, and redistribute this software under certain      *
 * conditions.  If you wish to embed Nmap technology into proprietary      *
 * software, we sell alternative licenses (contact sales@nmap.com).        *
 * Dozens of software vendors already license Nmap technology such as      *
 * host discovery, port scanning, OS detection, version detection, and     *
 * the Nmap Scripting Engine.                                              *
 *                                                                         *
 * Note that the GPL places important restrictions on "derivative works",  *
 * yet it does not provide a detailed definition of that term.  To avoid   *
 * misunderstandings, we interpret that term as broadly as copyright law   *
 * allows.  For example, we consider an application to constitute a        *
 * derivative work for the purpose of this license if it does any of the   *
 * following with any software or content covered by this license          *
 * ("Covered Software"):                                                   *
 *                                                                         *
 * o Integrates source code from Covered Software.                         *
 *                                                                         *
 * o Reads or includes copyrighted data files, such as Nmap's nmap-os-db   *
 * or nmap-service-probes.                                                 *
 *                                                                         *
 * o Is designed specifically to execute Covered Software and parse the    *
 * results (as opposed to typical shell or execution-menu apps, which will *
 * execute anything you tell them to).                                     *
 *                                                                         *
 * o Includes Covered Software in a proprietary executable installer.  The *
 * installers produced by InstallShield are an example of this.  Including *
 * Nmap with other software in compressed or archival form does not        *
 * trigger this provision, provided appropriate open source decompression  *
 * or de-archiving software is widely available for no charge.  For the    *
 * purposes of this license, an installer is considered to include Covered *
 * Software even if it actually retrieves a copy of Covered Software from  *
 * another source during runtime (such as by downloading it from the       *
 * Internet).                                                              *
 *                                                                         *
 * o Links (statically or dynamically) to a library which does any of the  *
 * above.                                                                  *
 *                                                                         *
 * o Executes a helper program, module, or script to do any of the above.  *
 *                                                                         *
 * This list is not exclusive, but is meant to clarify our interpretation  *
 * of derived works with some common examples.  Other people may interpret *
 * the plain GPL differently, so we consider this a special exception to   *
 * the GPL that we apply to Covered Software.  Works which meet any of     *
 * these conditions must conform to all of the terms of this license,      *
 * particularly including the GPL Section 3 requirements of providing      *
 * source code and allowing free redistribution of the work as a whole.    *
 *                                                                         *
 * As another special exception to the GPL terms, the Nmap Project grants  *
 * permission to link the code of this program with any version of the     *
 * OpenSSL library which is distributed under a license identical to that  *
 * listed in the included docs/licenses/OpenSSL.txt file, and distribute   *
 * linked combinations including the two.                                  *
 *                                                                         *
 * The Nmap Project has permission to redistribute Npcap, a packet         *
 * capturing driver and library for the Microsoft Windows platform.        *
 * Npcap is a separate work with it's own license rather than this Nmap    *
 * license.  Since the Npcap license does not permit redistribution        *
 * without special permission, our Nmap Windows binary packages which      *
 * contain Npcap may not be redistributed without special permission.      *
 *                                                                         *
 * Any redistribution of Covered Software, including any derived works,    *
 * must obey and carry forward all of the terms of this license, including *
 * obeying all GPL rules and restrictions.  For example, source code of    *
 * the whole work must be provided and free redistribution must be         *
 * allowed.  All GPL references to "this License", are to be treated as    *
 * including the terms and conditions of this license text as well.        *
 *                                                                         *
 * Because this license imposes special exceptions to the GPL, Covered     *
 * Work may not be combined (even as part of a larger work) with plain GPL *
 * software.  The terms, conditions, and exceptions of this license must   *
 * be included as well.  This license is incompatible with some other open *
 * source licenses as well.  In some cases we can relicense portions of    *
 * Nmap or grant special permissions to use it in other open source        *
 * software.  Please contact fyodor@nmap.org with any such requests.       *
 * Similarly, we don't incorporate incompatible open source software into  *
 * Covered Software without special permission from the copyright holders. *
 *                                                                         *
 * If you have any questions about the licensing restrictions on using     *
 * Nmap in other works, we are happy to help.  As mentioned above, we also *
 * offer an alternative license to integrate Nmap into proprietary         *
 * applications and appliances.  These contracts have been sold to dozens  *
 * of software vendors, and generally include a perpetual license as well  *
 * as providing support and updates.  They also fund the continued         *
 * development of Nmap.  Please email sales@nmap.com for further           *
 * information.                                                            *
 *                                                                         *
 * If you have received a written license agreement or contract for        *
 * Covered Software stating terms other than these, you may choose to use  *
 * and redistribute Covered Software under those terms instead of these.   *
 *                                                                         *
 * Source is provided to this software because we believe users have a     *
 * right to know exactly what a program is going to do before they run it. *
 * This also allows you to audit the software for security holes.          *
 *                                                                         *
 * Source code also allows you to port Nmap to new platforms, fix bugs,    *
 * and add new features.  You are highly encouraged to send your changes   *
 * to the dev@nmap.org mailing list for possible incorporation into the    *
 * main distribution.  By sending these changes to Fyodor or one of the    *
 * Insecure.Org development mailing lists, or checking them into the Nmap  *
 * source code repository, it is understood (unless you specify            *
 * otherwise) that you are offering the Nmap Project the unlimited,        *
 * non-exclusive right to reuse, modify, and relicense the code.  Nmap     *
 * will always be available Open Source, but this is important because     *
 * the inability to relicense code has caused devastating problems for     *
 * other Free Software projects (such as KDE and NASM).  We also           *
 * occasionally relicense the code to third parties as discussed above.    *
 * If you wish to specify special license conditions of your               *
 * contributions, just say so when you send them.                          *
 *                                                                         *
 * This program 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 Nmap      *
 * license file for more details (it's in a COPYING file included with     *
 * Nmap, and also available from https://svn.nmap.org/nmap/COPYING)        *
 *                                                                         *
 ***************************************************************************/

#include "Buf.h"
#include "NcrackOps.h"

extern NcrackOps o;

Buf::Buf()
{
	const u_int len = DEFAULT_BUF_SIZE;

	alloc = 0;
	buf = (u_char *)safe_malloc(len);
	alloc = len;
	offset = 0;
	end = 0;
}


/* Frees any memory used for the buffer. */
Buf::~Buf()
{
	if (alloc > 0) {
    free(buf);
    buf = NULL;
	}
}


/*
 * Clears any data from the buffer, making it empty.  This does not actually
 * zero the memory.
 */
void
Buf::clear(void)
{
	offset = 0;
	end = 0;
}


/* 
 * Similar to way snprintf works, but data get saved inside the buffer.
 * Warning: data won't get null terminated
 * the len argument is the real length of the _actual_ data
 */
void
Buf::snprintf(u_int len, const void *fmt, ...)
{

  void *p;
  va_list ap;

  /* Since vsnprintf always null terminates the data, we
   * allocate one extra byte for the trailing '\0' and then
   * drop it by decreasing 'end' by 1
   */
  p = append_space(len + 1);

  va_start(ap, fmt);
  vsnprintf((char *)p, len + 1, (char *)fmt, ap);
  va_end(ap);
  end--;

  //memcpy(p, data, len);

}



/* Appends data to the buffer, expanding it if necessary. */
void
Buf::append(const void *data, u_int len)
{
	void *p;
	p = append_space(len);
	memcpy(p, data, len);
}



/*
 * Appends space to the buffer, expanding the buffer if necessary. This does
 * not actually copy the data into the buffer, but instead returns a pointer
 * to the allocated region.
 */
void *
Buf::append_space(u_int len)
{
	u_int newlen;
	void *p;

	if (len > BUFFER_MAX_CHUNK)
		fatal("%s: len %u not supported", __func__, len);

	/* If the buffer is empty, start using it from the beginning. */
	if (offset == end) {
		offset = 0;
		end = 0;
	}
restart:
	/* If there is enough space to store all data, store it now. */
	if (end + len < alloc) {
		p = buf + end;
		end += len;
		return p;
	}

	/* Compact data back to the start of the buffer if necessary */
	if (compact())
		goto restart;

	/* Increase the size of the buffer and retry. */
	newlen = roundup(alloc + len, BUFFER_ALLOCSZ);
	if (newlen > BUFFER_MAX_LEN)
		fatal("%s: alloc %u not supported", __func__, newlen);
	buf = (u_char *)safe_realloc(buf, newlen);
	alloc = newlen;
	goto restart;
	/* NOTREACHED */
}


/*
 * Check whether an allocation of 'len' will fit in the buffer
 * This must follow the same math as buffer_append_space
 */
int
Buf::check_alloc(u_int len)
{
	if (offset == end) {
		offset = 0;
		end = 0;
	}
 restart:
	if (end + len < alloc)
		return (1);
	if (compact())
		goto restart;
	if (roundup(alloc + len, BUFFER_ALLOCSZ) <= BUFFER_MAX_LEN)
		return (1);
	return (0);
}


/* Returns the number of bytes of data in the buffer. */
u_int
Buf::get_len(void)
{
	return end - offset;
}


/* Gets data from the beginning of the buffer. */
int
Buf::get_data(void *dst, u_int len)
{
	if (len > end - offset) {
    if (o.debugging > 9) {
  		error("%s: trying to get more bytes %d than in buffer %d",
		    __func__, len, end - offset);
    }
		return (-1);
	}
  
  /* If dst is NULL then don't copy anything */
  if (dst) {
  	memcpy(dst, buf + offset, len);
  }

	offset += len;
	return (0);
}


int
Buf::compact(void)
{
	/*
	 * If the buffer is quite empty, but all data is at the end, move the
	 * data to the beginning.
	 */
	if (offset > MIN(alloc, BUFFER_MAX_CHUNK)) {
		memmove(buf, buf + offset, end - offset);
		end -= offset;
		offset = 0;
		return (1);
	}
	return (0);
}


/* Returns a pointer to the first used byte in the buffer. */
void *
Buf::get_dataptr(void)
{
	return buf + offset;
}


/* Dumps the contents of the buffer to stderr. */
void
Buf::data_dump(void)
{
	u_int i;
	u_char *ucp = buf;

	for (i = offset; i < end; i++) {
		fprintf(stderr, "%02x", ucp[i]);
		if ((i-offset)%16==15)
			fprintf(stderr, "\r\n");
		else if ((i-offset)%2==1)
			fprintf(stderr, " ");
	}
	fprintf(stderr, "\r\n");
}



/* Consumes the given number of bytes from the beginning of the buffer. */

#if 0
int
buffer_consume_ret(Buffer *buffer, u_int bytes)
{
	if (bytes > buffer->end - buffer->offset) {
		error("buffer_consume_ret: trying to get more bytes than in buffer");
		return (-1);
	}
	buffer->offset += bytes;
	return (0);
}

void
buffer_consume(Buffer *buffer, u_int bytes)
{
	if (buffer_consume_ret(buffer, bytes) == -1)
		fatal("buffer_consume: buffer error");
}

/* Consumes the given number of bytes from the end of the buffer. */

int
buffer_consume_end_ret(Buffer *buffer, u_int bytes)
{
	if (bytes > buffer->end - buffer->offset)
		return (-1);
	buffer->end -= bytes;
	return (0);
}

void
buffer_consume_end(Buffer *buffer, u_int bytes)
{
	if (buffer_consume_end_ret(buffer, bytes) == -1)
		fatal("buffer_consume_end: trying to get more bytes than in buffer");
}

#endif