IABSD.fr/src/usr.bin/rsync/hash.c

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• Author : claudio
  Date : 2024-02-27 11:28:30
  Hash : dcad62ec
  Message : Split hash_file into three steps, setup, add buf and final. Setup inits the context and adds the seed. The buf function simply adds a block from the file to the hash. The final function calls MD4_Final() to close the context and generate the hash. This will help to remove the mmap in the sender and should result in a more atomic view of the file since hash_file() is now called together with the other hash_functions. OK deraadt@ tb@

• usr.bin/rsync/hash.c

• /*	$OpenBSD: hash.c,v 1.5 2024/02/27 11:28:30 claudio Exp $ */
  /*
   * Copyright (c) 2019 Kristaps Dzonsons <kristaps@bsd.lv>
   *
   * 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 <sys/types.h>
  
  #include <assert.h>
  #include <endian.h>
  #include <stdint.h>
  #include <stdlib.h>
  
  #include <openssl/md4.h>
  
  #include "extern.h"
  
  /*
   * A fast 32-bit hash.
   * Described in Tridgell's "Efficient Algorithms for Sorting and
   * Synchronization" thesis and the "Rolling checksum" document.
   */
  uint32_t
  hash_fast(const void *buf, size_t len)
  {
  	size_t			 i = 0;
  	uint32_t		 a = 0, /* part of a(k, l) */
  				 b = 0; /* b(k, l) */
  	const signed char	*dat = buf;
  
  	if (len > 4)
  		for ( ; i < len - 4; i += 4) {
  			b += 4 * (a + dat[i]) +
  			    3 * dat[i + 1] +
  			    2 * dat[i + 2] +
  			    dat[i + 3];
  			a += dat[i + 0] +
  			    dat[i + 1] +
  			    dat[i + 2] +
  			    dat[i + 3];
  		}
  
  	for ( ; i < len; i++) {
  		a += dat[i];
  		b += a;
  	}
  
  	/* s(k, l) = (eps % M) + 2^16 b(k, l) % M */
  
  	return (a & 0xffff) + (b << 16);
  }
  
  /*
   * Slow MD4-based hash with trailing seed.
   */
  void
  hash_slow(const void *buf, size_t len,
  	unsigned char *md, const struct sess *sess)
  {
  	MD4_CTX		 ctx;
  	int32_t		 seed = htole32(sess->seed);
  
  	MD4_Init(&ctx);
  	MD4_Update(&ctx, buf, len);
  	MD4_Update(&ctx, (unsigned char *)&seed, sizeof(int32_t));
  	MD4_Final(md, &ctx);
  }
  
  /*
   * Hash an entire file.
   * This is similar to hash_slow() except the seed is hashed at the end
   * of the sequence, not the beginning.
   */
  void
  hash_file_start(MD4_CTX *ctx, const struct sess *sess)
  {
  	int32_t		 seed = htole32(sess->seed);
  
  	MD4_Init(ctx);
  	MD4_Update(ctx, (unsigned char *)&seed, sizeof(int32_t));
  }
  
  void
  hash_file_buf(MD4_CTX *ctx, const void *buf, size_t len)
  {
  	MD4_Update(ctx, buf, len);
  }
  void
  hash_file_final(MD4_CTX *ctx, unsigned char *md)
  {
  	MD4_Final(md, ctx);
  }