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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 2001-2002
* Sleepycat Software. All rights reserved.
*
* Some parts of this code originally written by Adam Stubblefield,
* astubble@rice.edu.
*/
#include "db_config.h"
#ifndef lint
static const char revid[] = "$Id: hmac.c,v 1.1.1.1 2003/11/20 22:13:32 toshok Exp $";
#endif /* not lint */
#ifndef NO_SYSTEM_INCLUDES
#include <string.h>
#endif
#include "db_int.h"
#include "dbinc/crypto.h"
#include "dbinc/db_page.h" /* for hash.h only */
#include "dbinc/hash.h"
#include "dbinc/hmac.h"
#define HMAC_OUTPUT_SIZE 20
#define HMAC_BLOCK_SIZE 64
static void __db_hmac __P((u_int8_t *, u_int8_t *, size_t, u_int8_t *));
/*
* !!!
* All of these functions use a ctx structure on the stack. The __db_SHA1Init
* call does not initialize the 64-byte buffer portion of it. The
* underlying SHA1 functions will properly pad the buffer if the data length
* is less than 64-bytes, so there isn't a chance of reading uninitialized
* memory. Although it would be cleaner to do a memset(ctx.buffer, 0, 64)
* we do not want to incur that penalty if we don't have to for performance.
*/
/*
* __db_hmac --
* Do a hashed MAC.
*/
static void
__db_hmac(k, data, data_len, mac)
u_int8_t *k, *data, *mac;
size_t data_len;
{
SHA1_CTX ctx;
u_int8_t key[HMAC_BLOCK_SIZE];
u_int8_t ipad[HMAC_BLOCK_SIZE];
u_int8_t opad[HMAC_BLOCK_SIZE];
u_int8_t tmp[HMAC_OUTPUT_SIZE];
int i;
memset(key, 0x00, HMAC_BLOCK_SIZE);
memset(ipad, 0x36, HMAC_BLOCK_SIZE);
memset(opad, 0x5C, HMAC_BLOCK_SIZE);
memcpy(key, k, HMAC_OUTPUT_SIZE);
for (i = 0; i < HMAC_BLOCK_SIZE; i++) {
ipad[i] ^= key[i];
opad[i] ^= key[i];
}
__db_SHA1Init(&ctx);
__db_SHA1Update(&ctx, ipad, HMAC_BLOCK_SIZE);
__db_SHA1Update(&ctx, data, data_len);
__db_SHA1Final(tmp, &ctx);
__db_SHA1Init(&ctx);
__db_SHA1Update(&ctx, opad, HMAC_BLOCK_SIZE);
__db_SHA1Update(&ctx, tmp, HMAC_OUTPUT_SIZE);
__db_SHA1Final(mac, &ctx);
return;
}
/*
* __db_chksum --
* Create a MAC/SHA1 checksum.
*
* PUBLIC: void __db_chksum __P((u_int8_t *, size_t, u_int8_t *, u_int8_t *));
*/
void
__db_chksum(data, data_len, mac_key, store)
u_int8_t *data;
size_t data_len;
u_int8_t *mac_key;
u_int8_t *store;
{
int sumlen;
u_int32_t hash4;
u_int8_t tmp[DB_MAC_KEY];
/*
* Since the checksum might be on a page of data we are checksumming
* we might be overwriting after checksumming, we zero-out the
* checksum value so that we can have a known value there when
* we verify the checksum.
*/
if (mac_key == NULL)
sumlen = sizeof(u_int32_t);
else
sumlen = DB_MAC_KEY;
memset(store, 0, sumlen);
if (mac_key == NULL) {
/* Just a hash, no MAC */
hash4 = __ham_func4(NULL, data, (u_int32_t)data_len);
memcpy(store, &hash4, sumlen);
} else {
memset(tmp, 0, DB_MAC_KEY);
__db_hmac(mac_key, data, data_len, tmp);
memcpy(store, tmp, sumlen);
}
return;
}
/*
* __db_derive_mac --
* Create a MAC/SHA1 key.
*
* PUBLIC: void __db_derive_mac __P((u_int8_t *, size_t, u_int8_t *));
*/
void
__db_derive_mac(passwd, plen, mac_key)
u_int8_t *passwd;
size_t plen;
u_int8_t *mac_key;
{
SHA1_CTX ctx;
/* Compute the MAC key. mac_key must be 20 bytes. */
__db_SHA1Init(&ctx);
__db_SHA1Update(&ctx, passwd, plen);
__db_SHA1Update(&ctx, (u_int8_t *)DB_MAC_MAGIC, strlen(DB_MAC_MAGIC));
__db_SHA1Update(&ctx, passwd, plen);
__db_SHA1Final(mac_key, &ctx);
return;
}
/*
* __db_check_chksum --
* Verify a checksum.
*
* Return 0 on success, >0 (errno) on error, -1 on checksum mismatch.
*
* PUBLIC: int __db_check_chksum __P((DB_ENV *,
* PUBLIC: DB_CIPHER *, u_int8_t *, void *, size_t, int));
*/
int
__db_check_chksum(dbenv, db_cipher, chksum, data, data_len, is_hmac)
DB_ENV *dbenv;
DB_CIPHER *db_cipher;
u_int8_t *chksum;
void *data;
size_t data_len;
int is_hmac;
{
int ret;
size_t sum_len;
u_int32_t hash4;
u_int8_t *mac_key, old[DB_MAC_KEY], new[DB_MAC_KEY];
/*
* If we are just doing checksumming and not encryption, then checksum
* is 4 bytes. Otherwise, it is DB_MAC_KEY size. Check for illegal
* combinations of crypto/non-crypto checksums.
*/
if (is_hmac == 0) {
if (db_cipher != NULL) {
__db_err(dbenv,
"Unencrypted checksum with a supplied encryption key");
return (EINVAL);
}
sum_len = sizeof(u_int32_t);
mac_key = NULL;
} else {
if (db_cipher == NULL) {
__db_err(dbenv,
"Encrypted checksum: no encryption key specified");
return (EINVAL);
}
sum_len = DB_MAC_KEY;
mac_key = db_cipher->mac_key;
}
/*
* !!!
* Since the checksum might be on the page, we need to have known data
* there so that we can generate the same original checksum. We zero
* it out, just like we do in __db_chksum above.
*/
memcpy(old, chksum, sum_len);
memset(chksum, 0, sum_len);
if (mac_key == NULL) {
/* Just a hash, no MAC */
hash4 = __ham_func4(NULL, data, (u_int32_t)data_len);
ret = memcmp((u_int32_t *)old, &hash4, sum_len) ? -1 : 0;
} else {
__db_hmac(mac_key, data, data_len, new);
ret = memcmp(old, new, sum_len) ? -1 : 0;
}
return (ret);
}
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