1 // SPDX-License-Identifier: BSD-2-Clause
2 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
3 *
4 * LibTomCrypt is a library that provides various cryptographic
5 * algorithms in a highly modular and flexible manner.
6 *
7 * The library is free for all purposes without any express
8 * guarantee it works.
9 */
10
11 /**
12 @file ocb_decrypt_verify_memory.c
13 OCB implementation, helper to decrypt block of memory, by Tom St Denis
14 */
15 #include "tomcrypt_private.h"
16
17 #ifdef LTC_OCB_MODE
18
19 /**
20 Decrypt and compare the tag with OCB.
21 @param cipher The index of the cipher desired
22 @param key The secret key
23 @param keylen The length of the secret key (octets)
24 @param nonce The session nonce (length of the block size of the block cipher)
25 @param ct The ciphertext
26 @param ctlen The length of the ciphertext (octets)
27 @param pt [out] The plaintext
28 @param tag The tag to compare against
29 @param taglen The length of the tag (octets)
30 @param stat [out] The result of the tag comparison (1==valid, 0==invalid)
31 @return CRYPT_OK if successful regardless of the tag comparison
32 */
ocb_decrypt_verify_memory(int cipher,const unsigned char * key,unsigned long keylen,const unsigned char * nonce,const unsigned char * ct,unsigned long ctlen,unsigned char * pt,const unsigned char * tag,unsigned long taglen,int * stat)33 int ocb_decrypt_verify_memory(int cipher,
34 const unsigned char *key, unsigned long keylen,
35 const unsigned char *nonce,
36 const unsigned char *ct, unsigned long ctlen,
37 unsigned char *pt,
38 const unsigned char *tag, unsigned long taglen,
39 int *stat)
40 {
41 int err;
42 ocb_state *ocb;
43
44 LTC_ARGCHK(key != NULL);
45 LTC_ARGCHK(nonce != NULL);
46 LTC_ARGCHK(pt != NULL);
47 LTC_ARGCHK(ct != NULL);
48 LTC_ARGCHK(tag != NULL);
49 LTC_ARGCHK(stat != NULL);
50
51 /* allocate memory */
52 ocb = XMALLOC(sizeof(ocb_state));
53 if (ocb == NULL) {
54 return CRYPT_MEM;
55 }
56
57 if ((err = ocb_init(ocb, cipher, key, keylen, nonce)) != CRYPT_OK) {
58 goto LBL_ERR;
59 }
60
61 while (ctlen > (unsigned long)ocb->block_len) {
62 if ((err = ocb_decrypt(ocb, ct, pt)) != CRYPT_OK) {
63 goto LBL_ERR;
64 }
65 ctlen -= ocb->block_len;
66 pt += ocb->block_len;
67 ct += ocb->block_len;
68 }
69
70 err = ocb_done_decrypt(ocb, ct, ctlen, pt, tag, taglen, stat);
71 LBL_ERR:
72 #ifdef LTC_CLEAN_STACK
73 zeromem(ocb, sizeof(ocb_state));
74 #endif
75
76 XFREE(ocb);
77
78 return err;
79 }
80
81 #endif
82
83 /* ref: $Format:%D$ */
84 /* git commit: $Format:%H$ */
85 /* commit time: $Format:%ai$ */
86