// verify the signature in sig. The original (hash of the message) message is in digest
int ccrsa_verify_pss(ccrsa_pub_ctx_t key,
const struct ccdigest_info* di, const struct ccdigest_info* MgfDi,
size_t digestSize, const uint8_t *digest,
size_t sigSize, const uint8_t *sig,
size_t saltSize, bool *valid)
{
const cc_size modBits =ccn_bitlen(ccrsa_ctx_n(key), ccrsa_ctx_m(key));
const cc_size modBytes = cc_ceiling(modBits, 8);
const cc_size emBits = modBits-1; //as defined in §8.1.1
const cc_size emSize = cc_ceiling(emBits, 8);
*valid = false;
int rc=0;
//1.
if(modBytes!= sigSize) return CCRSA_INVALID_INPUT;
if(digestSize != di->output_size) return CCRSA_INVALID_INPUT;
//2.
const cc_size modWords=ccrsa_ctx_n(key);
cc_unit EM[modWords]; //EM islarge enough to fit sig variable
//2.a read sig to tmp array and make sure it fits
cc_require_action(ccn_read_uint(modWords, EM, sigSize, sig)==0,errOut,rc=CCRSA_INVALID_INPUT);
//2.b
cc_require((rc=ccrsa_pub_crypt(key, EM, EM))==0,errOut);
//2.c
ccn_swap(modWords, EM);
//3
const size_t ofs = modWords*sizeof(cc_unit)-emSize;
cc_assert(ofs<=sizeof(cc_unit)); //make sure sizes are consistent and we don't overrun buffers.
rc|= ccrsa_emsa_pss_decode(di, MgfDi, saltSize, digestSize, digest, emBits, (uint8_t *) EM+ofs);
*valid = (rc==0)?true:false;
errOut:
return rc;
}
int ccrsa_eme_pkcs1v15_encode(struct ccrng_state *rng,
size_t r_size, cc_unit *r,
size_t s_size, const uint8_t *s)
{
cc_size n = ccrsa_n_from_size(r_size);
uint8_t *out = ccrsa_block_start(r_size, r, 1);
uint8_t *pad;
size_t padlen;
size_t i;
for(uint8_t *p = (uint8_t *) r; p < out; p++) *p = 0;
pad = out + 2;
if ((r_size < 3) || ((r_size - 3) < s_size)) {
return CCRSA_INVALID_INPUT;
}
padlen = r_size - s_size - 3;
int result = ccrng_generate(rng, padlen, pad);
if (result) {
return result;
}
for(i=0; i<padlen; i++) { // pad can't have zero bytes
while(pad[i] == 0)
if((result = ccrng_generate(rng, 1, &pad[i])) != 0) return result;
}
out[0] = 0x00;
out[1] = 0x02;
out[2+padlen] = 0x00;
CC_MEMCPY(out+3+padlen, s, s_size);
ccn_swap(n, r);
return 0;
}
static OSStatus SecRSAPrivateKeyRawDecrypt(SecKeyRef key, SecPadding padding,
const uint8_t *cipherText, size_t cipherTextLen,
uint8_t *plainText, size_t *plainTextLen) {
OSStatus result = errSSLCrypto;
ccrsa_full_ctx_t fullkey;
fullkey.full = key->key;
size_t m_size = ccn_write_uint_size(ccrsa_ctx_n(fullkey), ccrsa_ctx_m(fullkey));
cc_unit s[ccrsa_ctx_n(fullkey)];
uint8_t recoveredData[ccn_sizeof_n(ccrsa_ctx_n(fullkey))];
ccn_read_uint(ccrsa_ctx_n(fullkey), s, cipherTextLen, cipherText);
ccrsa_priv_crypt(ccrsa_ctx_private(fullkey), s, s);
const uint8_t* sBytes = (uint8_t*) s;
const uint8_t* sEnd = (uint8_t*) (s + ccrsa_ctx_n(fullkey));
require(plainTextLen, errOut);
switch (padding) {
case kSecPaddingNone:
ccn_swap(ccrsa_ctx_n(fullkey), s);
// Skip Zeros since our contract is to do so.
while (sBytes < sEnd && *sBytes == 0x00)
++sBytes;
break;
case kSecPaddingPKCS1:
{
ccn_swap(ccrsa_ctx_n(fullkey), s);
// Verify and skip PKCS1 padding:
//
// 0x00, 0x01 (RSA_PKCS1_PAD_ENCRYPT), 0xFF .. 0x00, signedData
//
size_t prefix_zeros = ccn_sizeof_n(ccrsa_ctx_n(fullkey)) - m_size;
while (prefix_zeros--)
require_quiet(*sBytes++ == 0x00, errOut);
require_quiet(*sBytes++ == 0x00, errOut);
require_quiet(*sBytes++ == RSA_PKCS1_PAD_ENCRYPT, errOut);
while (*sBytes != 0x00) {
require_quiet(++sBytes < sEnd, errOut);
}
// Required to have at least 8 non-zeros
require_quiet((sBytes - (uint8_t*)s) - 2 >= 8, errOut);
require_quiet(*sBytes == 0x00, errOut);
require_quiet(++sBytes < sEnd, errOut);
break;
}
case kSecPaddingOAEP:
{
size_t length = sizeof(recoveredData);
require_noerr_quiet(ccrsa_oaep_decode(ccsha1_di(),
ccn_write_uint_size(ccrsa_ctx_n(fullkey),ccrsa_ctx_m(fullkey)), s,
&length, recoveredData), errOut);
sBytes = recoveredData;
sEnd = recoveredData + length;
break;
}
default:
goto errOut;
}
require((sEnd - sBytes) <= (ptrdiff_t)*plainTextLen, errOut);
*plainTextLen = sEnd - sBytes;
memcpy(plainText, sBytes, *plainTextLen);
result = errSecSuccess;
errOut:
bzero(recoveredData, sizeof(recoveredData));
ccn_zero(ccrsa_ctx_n(fullkey), s);
return result;
}
static OSStatus SecRSAPrivateKeyRawSign(SecKeyRef key, SecPadding padding,
const uint8_t *dataToSign, size_t dataToSignLen,
uint8_t *sig, size_t *sigLen) {
OSStatus result = errSecParam;
ccrsa_full_ctx_t fullkey;
fullkey.full = key->key;
size_t m_size = ccn_write_uint_size(ccrsa_ctx_n(fullkey), ccrsa_ctx_m(fullkey));
cc_unit s[ccrsa_ctx_n(fullkey)];
uint8_t* sBytes = (uint8_t*) s;
require(sigLen, errOut);
require(*sigLen >= m_size, errOut);
switch (padding) {
case kSecPaddingNone:
require_noerr_quiet(ccn_read_uint(ccrsa_ctx_n(fullkey), s, dataToSignLen, dataToSign), errOut);
require_quiet(ccn_cmp(ccrsa_ctx_n(fullkey), s, ccrsa_ctx_m(fullkey)) < 0, errOut);
break;
case kSecPaddingPKCS1:
{
// Create PKCS1 padding:
//
// 0x00, 0x01 (RSA_PKCS1_PAD_SIGN), 0xFF .. 0x00, signedData
//
const int kMinimumPadding = 1 + 1 + 8 + 1;
require(dataToSignLen < m_size - kMinimumPadding, errOut);
size_t prefix_zeros = ccn_sizeof_n(ccrsa_ctx_n(fullkey)) - m_size;
while (prefix_zeros--)
*sBytes++ = 0x00;
size_t pad_size = m_size - dataToSignLen;
*sBytes++ = 0x00;
*sBytes++ = RSA_PKCS1_PAD_SIGN;
size_t ff_size;
for(ff_size = pad_size - 3; ff_size > 0; --ff_size)
*sBytes++ = 0xFF;
*sBytes++ = 0x00;
// Get the user data into s looking like a ccn.
memcpy(sBytes, dataToSign, dataToSignLen);
ccn_swap(ccrsa_ctx_n(fullkey), s);
break;
}
case kSecPaddingOAEP:
result = errSecParam;
default:
goto errOut;
}
ccrsa_priv_crypt(ccrsa_ctx_private(fullkey), s, s);
// Pad with leading zeros to fit in modulus size
ccn_write_uint_padded(ccrsa_ctx_n(fullkey), s, m_size, sig);
*sigLen = m_size;
result = errSecSuccess;
errOut:
ccn_zero(ccrsa_ctx_n(fullkey), s);
return result;
}
static OSStatus SecRSAPublicKeyRawDecrypt(SecKeyRef key, SecPadding padding,
const uint8_t *cipherText, size_t cipherTextLen, uint8_t *plainText, size_t *plainTextLen) {
OSStatus result = errSSLCrypto;
ccrsa_pub_ctx_t pubkey;
pubkey.pub = key->key;
cc_unit s[ccrsa_ctx_n(pubkey)];
require_action_quiet(cipherText != NULL, errOut, result = errSecParam);
require_action_quiet(plainText != NULL, errOut, result = errSecParam);
require_action_quiet(plainTextLen != NULL, errOut, result = errSecParam);
ccn_read_uint(ccrsa_ctx_n(pubkey), s, cipherTextLen, cipherText);
ccrsa_pub_crypt(pubkey, s, s);
ccn_swap(ccrsa_ctx_n(pubkey), s);
const uint8_t* sBytes = (uint8_t*) s;
const uint8_t* sEnd = (uint8_t*) (s + ccrsa_ctx_n(pubkey));
switch (padding) {
case kSecPaddingNone:
// Skip leading zeros
// We return the bytes for a number and
// trim leading zeroes
while (sBytes < sEnd && *sBytes == 0x00)
++sBytes;
break;
case kSecPaddingPKCS1:
{
// Verify and skip PKCS1 padding:
//
// 0x00, 0x01 (RSA_PKCS1_PAD_ENCRYPT), 0xFF .. 0x00, signedData
//
size_t m_size = ccn_write_uint_size(ccrsa_ctx_n(pubkey), ccrsa_ctx_m(pubkey));
size_t prefix_zeros = ccn_sizeof_n(ccrsa_ctx_n(pubkey)) - m_size;
while (prefix_zeros--)
require_quiet(*sBytes++ == 0x00, errOut);
require_quiet(*sBytes++ == 0x00, errOut);
require_quiet(*sBytes++ == RSA_PKCS1_PAD_ENCRYPT, errOut);
while (*sBytes != 0x00) {
require_quiet(++sBytes < sEnd, errOut);
}
// Required to have at least 8 0xFFs
require_quiet((sBytes - (uint8_t*)s) - 2 >= 8, errOut);
require_quiet(*sBytes == 0x00, errOut);
require_quiet(++sBytes < sEnd, errOut);
break;
}
case kSecPaddingOAEP:
result = errSecParam;
default:
goto errOut;
}
// Return the rest.
require_action((sEnd - sBytes) <= (ptrdiff_t)*plainTextLen, errOut, result = errSecParam);
*plainTextLen = sEnd - sBytes;
memcpy(plainText, sBytes, *plainTextLen);
result = errSecSuccess;
errOut:
ccn_zero(ccrsa_ctx_n(pubkey), s);
return result;
}
static OSStatus SecRSAPublicKeyRawEncrypt(SecKeyRef key, SecPadding padding,
const uint8_t *plainText, size_t plainTextLen,
uint8_t *cipherText, size_t *cipherTextLen) {
OSStatus result = errSecParam;
ccrsa_pub_ctx_t pubkey;
pubkey.pub = key->key;
cc_unit s[ccrsa_ctx_n(pubkey)];
const size_t m_size = ccn_write_uint_size(ccrsa_ctx_n(pubkey), ccrsa_ctx_m(pubkey));
require(cipherTextLen, errOut);
require(*cipherTextLen >= m_size, errOut);
uint8_t* sBytes = (uint8_t*) s;
switch (padding) {
case kSecPaddingNone:
require_noerr_quiet(ccn_read_uint(ccrsa_ctx_n(pubkey), s, plainTextLen, plainText), errOut);
require_quiet(ccn_cmp(ccrsa_ctx_n(pubkey), s, ccrsa_ctx_m(pubkey)) < 0, errOut);
break;
case kSecPaddingPKCS1:
{
// Create PKCS1 padding:
//
// 0x00, 0x01 (RSA_PKCS1_PAD_ENCRYPT), 0xFF .. 0x00, signedData
//
const int kMinimumPadding = 1 + 1 + 8 + 1;
require_quiet(plainTextLen < m_size - kMinimumPadding, errOut);
size_t prefix_zeros = ccn_sizeof_n(ccrsa_ctx_n(pubkey)) - m_size;
while (prefix_zeros--)
*sBytes++ = 0x00;
size_t pad_size = m_size - plainTextLen;
*sBytes++ = 0x00;
*sBytes++ = RSA_PKCS1_PAD_ENCRYPT;
ccrng_generate(ccrng_seckey, pad_size - 3, sBytes);
// Remove zeroes from the random pad
const uint8_t* sEndOfPad = sBytes + (pad_size - 3);
while (sBytes < sEndOfPad)
{
if (*sBytes == 0x00)
*sBytes = 0xFF; // Michael said 0xFF was good enough.
++sBytes;
}
*sBytes++ = 0x00;
memcpy(sBytes, plainText, plainTextLen);
ccn_swap(ccrsa_ctx_n(pubkey), s);
break;
}
case kSecPaddingOAEP:
{
const struct ccdigest_info* di = ccsha1_di();
const size_t encodingOverhead = 2 + 2 * di->output_size;
require_action(m_size > encodingOverhead, errOut, result = errSecParam);
require_action_quiet(plainTextLen < m_size - encodingOverhead, errOut, result = errSSLCrypto);
require_noerr_action(ccrsa_oaep_encode(di,
ccrng_seckey,
m_size, s,
plainTextLen, plainText), errOut, result = errSecInternal);
break;
}
default:
goto errOut;
}
ccrsa_pub_crypt(pubkey, s, s);
ccn_write_uint_padded(ccrsa_ctx_n(pubkey), s, m_size, cipherText);
*cipherTextLen = m_size;
result = errSecSuccess;
errOut:
ccn_zero(ccrsa_ctx_n(pubkey), s);
return result;
}
static OSStatus SecRSAPublicKeyRawVerify(SecKeyRef key, SecPadding padding,
const uint8_t *signedData, size_t signedDataLen,
const uint8_t *sig, size_t sigLen) {
OSStatus result = errSSLCrypto;
ccrsa_pub_ctx_t pubkey;
pubkey.pub = key->key;
cc_unit s[ccrsa_ctx_n(pubkey)];
ccn_read_uint(ccrsa_ctx_n(pubkey), s, sigLen, sig);
ccrsa_pub_crypt(pubkey, s, s);
ccn_swap(ccrsa_ctx_n(pubkey), s);
const uint8_t* sBytes = (uint8_t*) s;
const uint8_t* sEnd = (uint8_t*) (s + ccrsa_ctx_n(pubkey));
switch (padding) {
case kSecPaddingNone:
// Skip leading zeros as long as s is bigger than signedData.
while (((ptrdiff_t)signedDataLen < (sEnd - sBytes)) && (*sBytes == 0))
++sBytes;
break;
case kSecPaddingPKCS1:
{
// Verify and skip PKCS1 padding:
//
// 0x00, 0x01 (RSA_PKCS1_PAD_SIGN), 0xFF .. 0x00, signedData
//
size_t m_size = ccn_write_uint_size(ccrsa_ctx_n(pubkey), ccrsa_ctx_m(pubkey));
size_t prefix_zeros = ccn_sizeof_n(ccrsa_ctx_n(pubkey)) - m_size;
while (prefix_zeros--)
require_quiet(*sBytes++ == 0x00, errOut);
require_quiet(*sBytes++ == 0x00, errOut);
require_quiet(*sBytes++ == RSA_PKCS1_PAD_SIGN, errOut);
while (*sBytes == 0xFF) {
require_quiet(++sBytes < sEnd, errOut);
}
// Required to have at least 8 0xFFs
require_quiet((sBytes - (uint8_t*)s) - 2 >= 8, errOut);
require_quiet(*sBytes == 0x00, errOut);
require_quiet(++sBytes < sEnd, errOut);
break;
}
case kSecPaddingOAEP:
result = errSecParam;
goto errOut;
default:
result = errSecUnimplemented;
goto errOut;
}
// Compare the rest.
require_quiet((sEnd - sBytes) == (ptrdiff_t)signedDataLen, errOut);
require_quiet(memcmp(sBytes, signedData, signedDataLen) == 0, errOut);
result = errSecSuccess;
errOut:
cc_zero(ccrsa_ctx_n(pubkey), s);
return result;
}
