Merge #7193: fix: reject identity elements in deserialization and key generation

42b707b fix: reject identity elements in deserialization and key generation (UdjinM6)

Pull request description:

  ## Issue being fixed or feature implemented
  Identity elements are mathematically valid curve points but have no legitimate use in the protocol.

  ## What was done?
  Reject BLS identity elements (point at infinity for G1/G2) at the deserialization boundary in SetBytes(). Also reject zero private keys in MakeNewKey(). Identity elements would not pass further validation anyway, reject them early.

  ## How Has This Been Tested?
  Run tests

  ## Breaking Changes
  n/a

  ## Checklist:
  - [ ] I have performed a self-review of my own code
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have added or updated relevant unit/integration/functional/e2e tests
  - [ ] I have made corresponding changes to the documentation
  - [ ] I have assigned this pull request to a milestone

ACKs for top commit:
  PastaPastaPasta:
    utACK 42b707b

Tree-SHA512: 047b098fd56b5da07099fde9b03ada7dd4b42698f47cdc84d3c855c11b0122d46a74765fcaaad5d73465abd0d19605445c9e4b6ab6182cf2b318bfe695d2ef0a

Author: PastaPastaPasta

src/bls/bls.cpp

@@ -66,6 +66,9 @@ void CBLSSecretKey::MakeNewKey()
         GetStrongRandBytes({buf, sizeof(buf)});
         try {
             impl = bls::PrivateKey::FromBytes(bls::Bytes(reinterpret_cast<const uint8_t*>(buf), SerSize));
+            if (impl == bls::PrivateKey()) {
+                continue;
+            }
             break;
         } catch (...) {
         }

src/bls/bls.h

@@ -111,6 +111,11 @@ class CBLSWrapper
         } else {
             try {
                 impl = ImplType::FromBytes(bls::Bytes(vecBytes.data(), vecBytes.size()), specificLegacyScheme);
+                if (impl == ImplType()) {
+                    Reset();
+                    cachedHash.SetNull();
+                    return;
+                }
                 fValid = true;
             } catch (...) {
                 Reset();