Introduce signature version flags

Author: ComputerCraftr

src/pubkey.cpp

@@ -53,7 +53,7 @@ int ecdsa_signature_parse_der_lax(secp256k1_ecdsa_signature* sig, const unsigned
     secp256k1_ecdsa_signature_parse_compact(secp256k1_context_static, sig, tmpsig);
 
     /* Sequence tag byte */
-    if (pos == inputlen || input[pos] != 0x30) {
+    if (pos == inputlen || input[pos] != CPubKey::SigFlag::VERSION_SIG_DER) {
         return 0;
     }
     pos++;

src/pubkey.h

@@ -48,6 +48,41 @@ class CPubKey
         SIZE >= COMPRESSED_SIZE,
         "COMPRESSED_SIZE is larger than SIZE");
 
+    enum SigType {
+        SIG_COMPACT = 0,
+        SIG_DER = 1,
+        SIG_COUNT
+    };
+
+    enum SigFlag {
+        VERSION_SIG_COMPACT = 1<<3, // must be greater than zero to avoid being interpreted as an uncompressed public key
+        VERSION_SIG_DER = 6<<3,
+        VERSION_SIG_MASK = 31<<3
+    };
+
+    static int GetSigType(unsigned char flag)
+    {
+        switch (flag & VERSION_SIG_MASK) {
+        case VERSION_SIG_COMPACT:
+            return SIG_COMPACT;
+        case VERSION_SIG_DER:
+            return SIG_DER;
+        default:
+            return -1;
+        }
+    }
+
+    static unsigned char GetSigFlag(int type)
+    {
+        switch (type) {
+        case SIG_COMPACT:
+            return VERSION_SIG_COMPACT;
+        case SIG_DER:
+        default:
+            return VERSION_SIG_DER;
+        }
+    }
+
 private:
 
     /**

src/script/interpreter.cpp

@@ -122,7 +122,7 @@ bool static IsValidSignatureEncoding(const std::vector<unsigned char> &sig) {
     if (sig.size() > 73) return false;
 
     // A signature is of type 0x30 (compound).
-    if (sig[0] != 0x30) return false;
+    if (sig[0] != CPubKey::SigFlag::VERSION_SIG_DER) return false;
 
     // Make sure the length covers the entire signature.
     if (sig[1] != sig.size() - 3) return false;

src/script/sign.cpp

@@ -721,7 +721,7 @@ class DummySignatureCreator final : public BaseSignatureCreator {
     {
         // Create a dummy signature that is a valid DER-encoding
         vchSig.assign(m_r_len + m_s_len + 7, '\000');
-        vchSig[0] = 0x30;
+        vchSig[0] = CPubKey::SigFlag::VERSION_SIG_DER;
         vchSig[1] = m_r_len + m_s_len + 4;
         vchSig[2] = 0x02;
         vchSig[3] = m_r_len;