Require compressed keys in segwit as policy and disable signing with uncompressed keys for segwit scripts

Github-Pull: #8499
Rebased-From: 4c0c25a604cec39675187507df423cff5d707ab5

1 files changed, 22 insertions, 6 deletions

diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index 41756ea711..836cf9ee35 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -79,8 +79,20 @@ bool static IsCompressedOrUncompressedPubKey(const valtype &vchPubKey) {
             return false;
         }
     } else {
-          //  Non-canonical public key: neither compressed nor uncompressed
-          return false;
+        //  Non-canonical public key: neither compressed nor uncompressed
+        return false;
+    }
+    return true;
+}
+
+bool static IsCompressedPubKey(const valtype &vchPubKey) {
+    if (vchPubKey.size() != 33) {
+        //  Non-canonical public key: invalid length for compressed key
+        return false;
+    }
+    if (vchPubKey[0] != 0x02 && vchPubKey[0] != 0x03) {
+        //  Non-canonical public key: invalid prefix for compressed key
+        return false;
     }
     return true;
 }
@@ -199,10 +211,14 @@ bool CheckSignatureEncoding(const vector<unsigned char> &vchSig, unsigned int fl
     return true;
 }
 
-bool static CheckPubKeyEncoding(const valtype &vchSig, unsigned int flags, ScriptError* serror) {
-    if ((flags & SCRIPT_VERIFY_STRICTENC) != 0 && !IsCompressedOrUncompressedPubKey(vchSig)) {
+bool static CheckPubKeyEncoding(const valtype &vchPubKey, unsigned int flags, const SigVersion &sigversion, ScriptError* serror) {
+    if ((flags & SCRIPT_VERIFY_STRICTENC) != 0 && !IsCompressedOrUncompressedPubKey(vchPubKey)) {
         return set_error(serror, SCRIPT_ERR_PUBKEYTYPE);
     }
+    // Only compressed keys are accepted in segwit
+    if ((flags & SCRIPT_VERIFY_WITNESS_PUBKEYTYPE) != 0 && sigversion == SIGVERSION_WITNESS_V0 && !IsCompressedPubKey(vchPubKey)) {
+        return set_error(serror, SCRIPT_ERR_WITNESS_PUBKEYTYPE);
+    }
     return true;
 }
 
@@ -879,7 +895,7 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
                         scriptCode.FindAndDelete(CScript(vchSig));
                     }
 
-                    if (!CheckSignatureEncoding(vchSig, flags, serror) || !CheckPubKeyEncoding(vchPubKey, flags, serror)) {
+                    if (!CheckSignatureEncoding(vchSig, flags, serror) || !CheckPubKeyEncoding(vchPubKey, flags, sigversion, serror)) {
                         //serror is set
                         return false;
                     }
@@ -953,7 +969,7 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
                         // Note how this makes the exact order of pubkey/signature evaluation
                         // distinguishable by CHECKMULTISIG NOT if the STRICTENC flag is set.
                         // See the script_(in)valid tests for details.
-                        if (!CheckSignatureEncoding(vchSig, flags, serror) || !CheckPubKeyEncoding(vchPubKey, flags, serror)) {
+                        if (!CheckSignatureEncoding(vchSig, flags, serror) || !CheckPubKeyEncoding(vchPubKey, flags, sigversion, serror)) {
                             // serror is set
                             return false;
                         }