Merge #17275: pubkey: Assert CPubKey's ECCVerifyHandle precondition

d8daa8f371 pubkey: Assert CPubKey's ECCVerifyHandle precondition (practicalswift)

Pull request description:

  Assert `CPubKey`'s `ECCVerifyHandle` precondition.

  This makes it more clear for fuzzing harness writers and others that `ECCVerifyHandle` is expected to be held when interacting with `CPubKey`.

  Related PR #17274.

ACKs for top commit:
  sipa:
    ACK d8daa8f371

Tree-SHA512: 9e74086599799dc9b5c3fb8357445b662e5bf896d826af63d6d6b6ddb616612966f3bb5de3bd3ae0e692c47de85672f64b8ab6d3a1c45899dc25ba46990b5ec7

src/pubkey.cpp

@@ -171,6 +171,7 @@ bool CPubKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchS
         return false;
     secp256k1_pubkey pubkey;
     secp256k1_ecdsa_signature sig;
+    assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
     if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, vch, size())) {
         return false;
     }
@@ -190,6 +191,7 @@ bool CPubKey::RecoverCompact(const uint256 &hash, const std::vector<unsigned cha
     bool fComp = ((vchSig[0] - 27) & 4) != 0;
     secp256k1_pubkey pubkey;
     secp256k1_ecdsa_recoverable_signature sig;
+    assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
     if (!secp256k1_ecdsa_recoverable_signature_parse_compact(secp256k1_context_verify, &sig, &vchSig[1], recid)) {
         return false;
     }
@@ -207,6 +209,7 @@ bool CPubKey::IsFullyValid() const {
     if (!IsValid())
         return false;
     secp256k1_pubkey pubkey;
+    assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
     return secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, vch, size());
 }
 
@@ -214,6 +217,7 @@ bool CPubKey::Decompress() {
     if (!IsValid())
         return false;
     secp256k1_pubkey pubkey;
+    assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
     if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, vch, size())) {
         return false;
     }
@@ -232,6 +236,7 @@ bool CPubKey::Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChi
     BIP32Hash(cc, nChild, *begin(), begin()+1, out);
     memcpy(ccChild.begin(), out+32, 32);
     secp256k1_pubkey pubkey;
+    assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
     if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, vch, size())) {
         return false;
     }
@@ -273,6 +278,7 @@ bool CExtPubKey::Derive(CExtPubKey &out, unsigned int _nChild) const {
 
 /* static */ bool CPubKey::CheckLowS(const std::vector<unsigned char>& vchSig) {
     secp256k1_ecdsa_signature sig;
+    assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
     if (!ecdsa_signature_parse_der_lax(secp256k1_context_verify, &sig, vchSig.data(), vchSig.size())) {
         return false;
     }