Sign.cpp

#include <xrpl/protocol/AccountID.h>
#include <xrpl/protocol/HashPrefix.h>
#include <xrpl/protocol/KeyType.h>
#include <xrpl/protocol/PublicKey.h>
#include <xrpl/protocol/SField.h>
#include <xrpl/protocol/STExchange.h>
#include <xrpl/protocol/STObject.h>
#include <xrpl/protocol/SecretKey.h>
#include <xrpl/protocol/Serializer.h>
#include <xrpl/protocol/Sign.h>
 
namespace xrpl {
 
void
sign(STObject& st, HashPrefix const& prefix, KeyType type, SecretKey const& sk, SF_VL const& sigField)
{
    Serializer ss;
    ss.add32(prefix);
    st.addWithoutSigningFields(ss);
    set(st, sigField, sign(type, sk, ss.slice()));
}
 
bool
verify(STObject const& st, HashPrefix const& prefix, PublicKey const& pk, SF_VL const& sigField)
{
    auto const sig = get(st, sigField);
    if (!sig)
        return false;
    Serializer ss;
    ss.add32(prefix);
    st.addWithoutSigningFields(ss);
    return verify(pk, Slice(ss.data(), ss.size()), Slice(sig->data(), sig->size()));
}
 
// Questions regarding buildMultiSigningData:
//
// Why do we include the Signer.Account in the blob to be signed?
//
// Unless you include the Account which is signing in the signing blob,
// you could swap out any Signer.Account for any other, which may also
// be on the SignerList and have a RegularKey matching the
// Signer.SigningPubKey.
//
// That RegularKey may be set to allow some 3rd party to sign transactions
// on the account's behalf, and that RegularKey could be common amongst all
// users of the 3rd party. That's just one example of sharing the same
// RegularKey amongst various accounts and just one vulnerability.
//
//   "When you have something that's easy to do that makes entire classes of
//    attacks clearly and obviously impossible, you need a damn good reason
//    not to do it."  --  David Schwartz
//
// Why would we include the signingFor account in the blob to be signed?
//
// In the current signing scheme, the account that a signer is `signing
// for/on behalf of` is the tx_json.Account.
//
// Later we might support more levels of signing.  Suppose Bob is a signer
// for Alice, and Carol is a signer for Bob, so Carol can sign for Bob who
// signs for Alice.  But suppose Alice has two signers: Bob and Dave.  If
// Carol is a signer for both Bob and Dave, then the signature needs to
// distinguish between Carol signing for Bob and Carol signing for Dave.
//
// So, if we support multiple levels of signing, then we'll need to
// incorporate the "signing for" accounts into the signing data as well.
Serializer
buildMultiSigningData(STObject const& obj, AccountID const& signingID)
{
    Serializer s{startMultiSigningData(obj)};
    finishMultiSigningData(signingID, s);
    return s;
}
 
Serializer
startMultiSigningData(STObject const& obj)
{
    Serializer s;
    s.add32(HashPrefix::txMultiSign);
    obj.addWithoutSigningFields(s);
    return s;
}
 
}  // namespace xrpl