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SIV properly handle zero AD components #777

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56 changes: 45 additions & 11 deletions src/encauth/siv/siv.c
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Original file line number Diff line number Diff line change
Expand Up @@ -191,15 +191,16 @@ static int s_siv_S2V(int cipher,
return err;
}

do {
/* With zero AD components the loop runs zero times. */
while (n < adnum) {
if (n >= s_siv_max_aad_components) {
return CRYPT_INPUT_TOO_LONG;
}
if ((err = s_siv_S2V_dbl_xor_cmac(&ctx, ad ? ad[n] : NULL, adlen ? adlen[n] : 0, &D)) != CRYPT_OK) {
return err;
}
n++;
} while(n < adnum);
}

return s_siv_S2V_T(&ctx, in, inlen, &D, V);
}
Expand Down Expand Up @@ -470,23 +471,19 @@ int siv_memory( int cipher, int direction,
goto err_out;
}
va_start(args, adnum);
do {
if (adnum) {
aad = va_arg(args, const unsigned char*);
aadlen = va_arg(args, unsigned long);
} else {
aad = NULL;
aadlen = 0;
}
/* With zero AD components the loop runs zero times. */
while (n < adnum) {
if (n >= s_siv_max_aad_components) {
err = CRYPT_INPUT_TOO_LONG;
goto err_out2;
}
aad = va_arg(args, const unsigned char*);
aadlen = va_arg(args, unsigned long);
if ((err = s_siv_S2V_dbl_xor_cmac(&ctx, aad, aadlen, &D)) != CRYPT_OK) {
goto err_out2;
}
n++;
} while (n < adnum);
}

if ((err = s_siv_S2V_T(&ctx, in_work, in_work_len, &D, &siv.V)) != CRYPT_OK) {
goto err_out2;
Expand Down Expand Up @@ -549,6 +546,13 @@ int siv_test(void)
unsigned long adlen_A1[] =
{ sizeof(AD_A1), 0 };

/* Key_A1/Plaintext_A1 with zero AD components */
const unsigned char output_A1_noad[] =
{ 0xf1, 0xc5, 0xfd, 0xea, 0xc1, 0xf1, 0x5a, 0x26,
0x77, 0x9c, 0x15, 0x01, 0xf9, 0xfb, 0x75, 0x88,
0x27, 0xe9, 0x46, 0xc6, 0x69, 0x08, 0x8a, 0xb0,
0x6d, 0xa5, 0x8c, 0x5c, 0x83, 0x1c };

const unsigned char Key_A2[] =
{ 0x7f, 0x7e, 0x7d, 0x7c, 0x7b, 0x7a, 0x79, 0x78,
0x77, 0x76, 0x75, 0x74, 0x73, 0x72, 0x71, 0x70,
Expand Down Expand Up @@ -736,6 +740,36 @@ int siv_test(void)
return CRYPT_FAIL_TESTVECTOR;
}

/* Zero AD components */
buflen = sizeof(buf);
if ((err = siv_encrypt_memory(cipher, Key_A1, sizeof(Key_A1), 0, NULL, NULL, Plaintext_A1, sizeof(Plaintext_A1), buf, &buflen)) != CRYPT_OK) {
return err;
}
if (ltc_compare_testvector(buf, buflen, output_A1_noad, sizeof(output_A1_noad), "SIV encrypt no AD", 0x5000) != 0) {
return CRYPT_FAIL_TESTVECTOR;
}
buflen = sizeof(buf);
if ((err = siv_decrypt_memory(cipher, Key_A1, sizeof(Key_A1), 0, NULL, NULL, output_A1_noad, sizeof(output_A1_noad), buf, &buflen)) != CRYPT_OK) {
return err;
}
if (ltc_compare_testvector(buf, buflen, Plaintext_A1, sizeof(Plaintext_A1), "SIV decrypt no AD", 0x5001) != 0) {
return CRYPT_FAIL_TESTVECTOR;
}
buflen = sizeof(buf);
if ((err = siv_memory(cipher, LTC_ENCRYPT, Key_A1, sizeof(Key_A1), Plaintext_A1, sizeof(Plaintext_A1), buf, &buflen, 0, NULL)) != CRYPT_OK) {
return err;
}
if (ltc_compare_testvector(buf, buflen, output_A1_noad, sizeof(output_A1_noad), "siv_memory encrypt no AD", 0x5002) != 0) {
return CRYPT_FAIL_TESTVECTOR;
}
buflen = sizeof(buf);
if ((err = siv_memory(cipher, LTC_DECRYPT, Key_A1, sizeof(Key_A1), output_A1_noad, sizeof(output_A1_noad), buf, &buflen, 0, NULL)) != CRYPT_OK) {
return err;
}
if (ltc_compare_testvector(buf, buflen, Plaintext_A1, sizeof(Plaintext_A1), "siv_memory decrypt no AD", 0x5003) != 0) {
return CRYPT_FAIL_TESTVECTOR;
}

for (n = 0; n < LTC_ARRAY_SIZE(tmp); ++n) {
tmp[n] = XCALLOC(1, tmpmax);
if (tmp[n] == NULL) {
Expand Down
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