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Implement CTS in terms of CBC

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This commit is contained in:
Love Hornquist Astrand
2009-08-25 20:26:01 -07:00
parent 31871b4990
commit 6ead770ad1
1 changed files with 100 additions and 4 deletions
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104
lib/krb5/crypto.c
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@@ -853,7 +853,7 @@ static struct key_type keytype_aes128 = {
AES_salt,
NULL,
evp_cleanup,
EVP_hcrypto_aes_128_cts
EVP_aes_128_cbc
};
static struct key_type keytype_aes256 = {
@@ -867,7 +867,7 @@ static struct key_type keytype_aes256 = {
AES_salt,
NULL,
evp_cleanup,
EVP_hcrypto_aes_256_cts
EVP_aes_256_cbc
};
static struct key_type keytype_arcfour = {
@@ -2068,6 +2068,102 @@ evp_encrypt(krb5_context context,
return 0;
}
static const char zero_ivec[EVP_MAX_BLOCK_LENGTH] = { 0 };
static krb5_error_code
evp_encrypt_cts(krb5_context context,
struct key_data *key,
void *data,
size_t len,
krb5_boolean encryptp,
int usage,
void *ivec)
{
size_t i, blocksize;
struct evp_schedule *ctx = key->schedule->data;
char tmp[EVP_MAX_BLOCK_LENGTH], ivec2[EVP_MAX_BLOCK_LENGTH];
EVP_CIPHER_CTX *c;
unsigned char *p;
c = encryptp ? &ctx->ectx : &ctx->dctx;
blocksize = EVP_CIPHER_CTX_block_size(c);
if (len < blocksize) {
krb5_set_error_message(context, EINVAL,
"message block too short");
return EINVAL;
} else if (len == blocksize) {
EVP_CipherInit_ex(c, NULL, NULL, NULL, zero_ivec, -1);
EVP_Cipher(c, data, data, len);
return 0;
}
if (ivec)
EVP_CipherInit_ex(c, NULL, NULL, NULL, ivec, -1);
else
EVP_CipherInit_ex(c, NULL, NULL, NULL, zero_ivec, -1);
if (encryptp) {
p = data;
i = ((len - 1) / blocksize) * blocksize;
EVP_Cipher(c, p, p, i);
p += i - blocksize;
len -= i;
memcpy(ivec2, p, blocksize);
for (i = 0; i < len; i++)
tmp[i] = p[i + blocksize] ^ ivec2[i];
for (; i < blocksize; i++)
tmp[i] = 0 ^ ivec2[i];
EVP_CipherInit_ex(c, NULL, NULL, NULL, zero_ivec, -1);
EVP_Cipher(c, p, tmp, blocksize);
memcpy(p + blocksize, ivec2, len);
if (ivec)
memcpy(ivec, p, blocksize);
} else {
char tmp2[EVP_MAX_BLOCK_LENGTH], tmp3[EVP_MAX_BLOCK_LENGTH];
p = data;
if (len > blocksize * 2) {
/* remove last two blocks and round up, decrypt this with cbc, then do cts dance */
i = ((((len - blocksize * 2) + blocksize - 1) / blocksize) * blocksize);
memcpy(ivec2, p + i - blocksize, blocksize);
EVP_Cipher(c, p, p, i);
p += i;
len -= i + blocksize;
} else {
if (ivec)
memcpy(ivec2, ivec, blocksize);
else
memcpy(ivec2, zero_ivec, blocksize);
len -= blocksize;
}
memcpy(tmp, p, blocksize);
EVP_CipherInit_ex(c, NULL, NULL, NULL, zero_ivec, -1);
EVP_Cipher(c, tmp2, p, blocksize);
memcpy(tmp3, p + blocksize, len);
memcpy(tmp3 + len, tmp2 + len, blocksize - len); /* xor 0 */
for (i = 0; i < len; i++)
p[i + blocksize] = tmp2[i] ^ tmp3[i];
EVP_CipherInit_ex(c, NULL, NULL, NULL, zero_ivec, -1);
EVP_Cipher(c, p, tmp3, blocksize);
for (i = 0; i < blocksize; i++)
p[i] ^= ivec2[i];
if (ivec)
memcpy(ivec, tmp, blocksize);
}
return 0;
}
#ifdef HEIM_WEAK_CRYPTO
static krb5_error_code
evp_des_encrypt_null_ivec(krb5_context context,
@@ -2485,7 +2581,7 @@ static struct encryption_type enctype_aes128_cts_hmac_sha1 = {
&checksum_sha1,
&checksum_hmac_sha1_aes128,
F_DERIVED,
evp_encrypt,
evp_encrypt_cts,
16,
AES_PRF
};
@@ -2499,7 +2595,7 @@ static struct encryption_type enctype_aes256_cts_hmac_sha1 = {
&checksum_sha1,
&checksum_hmac_sha1_aes256,
F_DERIVED,
evp_encrypt,
evp_encrypt_cts,
16,
AES_PRF
};