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Harden pegin address generation

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instagibbs 2016-08-30 10:45:40 -04:00 • committed by Gregory Sanders
parent bedb684e47
commit af4c071607
1 changed files with 22 additions and 5 deletions
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27
src/wallet/rpcwallet.cpp
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@ -3123,7 +3123,7 @@ static secp256k1_context *secp256k1_ctx;
class CSecp256k1Init {
public:
CSecp256k1Init() {
secp256k1_ctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
secp256k1_ctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY | SECP256K1_CONTEXT_SIGN);
}
~CSecp256k1Init() {
secp256k1_context_destroy(secp256k1_ctx);
@ -3170,12 +3170,29 @@ CScriptID calculate_contract(const CScript& federationRedeemScript, const CBitco
size_t pub_len = 33;
unsigned char *pub_start = &(*(sdpc - pub_len));
CHMAC_SHA256(pub_start, pub_len).Write(fullcontract, 40).Finalize(tweak);
secp256k1_pubkey pubkey;
assert(secp256k1_ec_pubkey_parse(secp256k1_ctx, &pubkey, pub_start, pub_len) == 1);
secp256k1_pubkey watchman;
secp256k1_pubkey tweaked;
assert(secp256k1_ec_pubkey_parse(secp256k1_ctx, &watchman, pub_start, pub_len) == 1);
assert(secp256k1_ec_pubkey_parse(secp256k1_ctx, &tweaked, pub_start, pub_len) == 1);
// If someone creates a tweak that makes this fail, they broke SHA256
assert(secp256k1_ec_pubkey_tweak_add(secp256k1_ctx, &pubkey, tweak) == 1);
assert(secp256k1_ec_pubkey_serialize(secp256k1_ctx, pub_start, &pub_len, &pubkey, SECP256K1_EC_COMPRESSED) == 1);
assert(secp256k1_ec_pubkey_tweak_add(secp256k1_ctx, &tweaked, tweak) == 1);
assert(secp256k1_ec_pubkey_serialize(secp256k1_ctx, pub_start, &pub_len, &tweaked, SECP256K1_EC_COMPRESSED) == 1);
assert(pub_len == 33);
// Sanity checks to reduce pegin risk. If the tweaked
// value flips a bit, we may lose pegin funds irretrievably.
// We take the tweak, derive its pubkey and check that
// `tweaked - watchman = tweak` to check the computation
// two different ways
secp256k1_pubkey tweaked2;
assert(secp256k1_ec_pubkey_create(secp256k1_ctx, &tweaked2, tweak));
assert(secp256k1_ec_pubkey_negate(secp256k1_ctx, &watchman));
secp256k1_pubkey* pubkey_combined[2];
pubkey_combined[0] = &watchman;
pubkey_combined[1] = &tweaked;
secp256k1_pubkey maybe_tweaked2;
assert(secp256k1_ec_pubkey_combine(secp256k1_ctx, &maybe_tweaked2, pubkey_combined, 2));
assert(!memcmp(&maybe_tweaked2, &tweaked2, 64));
}
}
}