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Verification procedure cleanup

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This commit is contained in:
Andrew 2023-06-05 00:27:50 +03:00
parent 983acba760
commit d20cb1fa49
2 changed files with 27 additions and 38 deletions
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1
src/header.h
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@ -41,6 +41,7 @@
#define FIELD_BYTES_2003 64
#define SHA_MSG_LENGTH_XP (4 + 2 * FIELD_BYTES)
#define SHA_MSG_LENGTH_2003 (3 + 2 * FIELD_BYTES_2003)
#define NEXTSNBITS(field, n, offset) (((QWORD)field >> offset) & ((1ULL << (n)) - 1))
#define FIRSTNBITS(field, n) NEXTSNBITS(field, n, 0)

64
src/server.cpp
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@ -60,11 +60,7 @@ bool verifyServerKey(EC_GROUP *eCurve, EC_POINT *generator, EC_POINT *publicKey,
BYTE t[FIELD_BYTES_2003]{}, md[SHA_DIGEST_LENGTH]{};
DWORD checkHash, newHash[2]{};
SHA_CTX hContext;
// H = SHA-1(5D || OS Family || Hash || Prefix || 00 00)
SHA1_Init(&hContext);
t[0] = 0x5D;
t[1] = (osFamily & 0xff);
t[2] = (osFamily & 0xff00) >> 8;
@ -77,8 +73,7 @@ bool verifyServerKey(EC_GROUP *eCurve, EC_POINT *generator, EC_POINT *publicKey,
t[9] = 0x00;
t[10] = 0x00;
SHA1_Update(&hContext, t, 11);
SHA1_Final(md, &hContext);
SHA1(t, 11, md);
// First word.
newHash[0] = md[0] | (md[1] << 8) | (md[2] << 16) | (md[3] << 24);
@ -114,39 +109,32 @@ bool verifyServerKey(EC_GROUP *eCurve, EC_POINT *generator, EC_POINT *publicKey,
// EC_POINT_get_affine_coordinates() sets x and y, either of which may be nullptr, to the corresponding coordinates of p.
// x = v.x; y = v.y;
EC_POINT_get_affine_coordinates_GFp(eCurve, v, x, y, context);
EC_POINT_get_affine_coordinates(eCurve, v, x, y, context);
BYTE msgDigest[SHA_DIGEST_LENGTH]{},
msgBuffer[SHA_MSG_LENGTH_2003]{},
xBin[FIELD_BYTES_2003]{},
yBin[FIELD_BYTES_2003]{};
// Convert resulting point coordinates to bytes.
BN_bn2lebin(x, xBin, FIELD_BYTES_2003);
BN_bn2lebin(y, yBin, FIELD_BYTES_2003);
// Assemble the SHA message.
msgBuffer[0] = 0x79;
msgBuffer[1] = (osFamily & 0xff);
msgBuffer[2] = (osFamily & 0xff00) >> 8;
memcpy((void *)&msgBuffer[3], (void *)xBin, FIELD_BYTES_2003);
memcpy((void *)&msgBuffer[3 + FIELD_BYTES_2003], (void *)yBin, FIELD_BYTES_2003);
// Retrieve the message digest.
SHA1(msgBuffer, SHA_MSG_LENGTH_2003, msgDigest);
// Translate the byte digest into a 32-bit integer - this is our computed hash.
// Truncate the hash to 28 bits.
// Hash = First31(SHA-1(79 || OS Family || v.x || v.y))
SHA1_Init(&hContext);
t[0] = 0x79;
t[1] = (osFamily & 0xff);
t[2] = (osFamily & 0xff00) >> 8;
// Hash chunk of data.
SHA1_Update(&hContext, t, 3);
// Empty buffer, place v.y in little-endian.
memset(t, 0, FIELD_BYTES_2003);
BN_bn2bin(x, t);
endian(t, FIELD_BYTES_2003);
// Hash chunk of data.
SHA1_Update(&hContext, t, FIELD_BYTES_2003);
// Empty buffer, place v.y in little-endian.
memset(t, 0, FIELD_BYTES_2003);
BN_bn2bin(y, t);
endian(t, FIELD_BYTES_2003);
// Hash chunk of data.
SHA1_Update(&hContext, t, FIELD_BYTES_2003);
// Store the final message from hContext in md.
SHA1_Final(md, &hContext);
// Hash = First31(SHA-1(79 || OS Family || v.x || v.y))
checkHash = (md[0] | (md[1] << 8) | (md[2] << 16) | (md[3] << 24)) & 0x7fffffff;
DWORD compHash = BYDWORD(msgDigest) & BITMASK(31);
BN_free(s);
BN_free(e);
@ -159,7 +147,7 @@ bool verifyServerKey(EC_GROUP *eCurve, EC_POINT *generator, EC_POINT *publicKey,
EC_POINT_free(u);
// If we managed to generate a key with the same hash, the key is correct.
return checkHash == hash;
return compHash == hash;
}
void generateServerKey(char *pKey, EC_GROUP *eCurve, EC_POINT *generator, BIGNUM *order, BIGNUM *privateKey, DWORD *osFamily, DWORD *prefix) {