Merge pull request #5264

af3208b Resolve issue 3166. These changes decode valid SIGHASH types on signatures in assembly (asm) representations of scriptSig scripts. This squashed commit incorporates substantial helpful feedback from jtimon, laanwj, and sipa. (mruddy)

1 files changed, 64 insertions, 2 deletions

diff --git a/src/core_write.cpp b/src/core_write.cpp
index c3babec2fc..2ad42baddf 100644
--- a/src/core_write.cpp
+++ b/src/core_write.cpp
@@ -15,6 +15,7 @@
 #include "utilmoneystr.h"
 #include "utilstrencodings.h"
 
+#include <boost/assign/list_of.hpp>
 #include <boost/foreach.hpp>
 
 using namespace std;
@@ -54,6 +55,67 @@ string FormatScript(const CScript& script)
     return ret.substr(0, ret.size() - 1);
 }
 
+const map<unsigned char, string> mapSigHashTypes =
+    boost::assign::map_list_of
+    (static_cast<unsigned char>(SIGHASH_ALL), string("ALL"))
+    (static_cast<unsigned char>(SIGHASH_ALL|SIGHASH_ANYONECANPAY), string("ALL|ANYONECANPAY"))
+    (static_cast<unsigned char>(SIGHASH_NONE), string("NONE"))
+    (static_cast<unsigned char>(SIGHASH_NONE|SIGHASH_ANYONECANPAY), string("NONE|ANYONECANPAY"))
+    (static_cast<unsigned char>(SIGHASH_SINGLE), string("SINGLE"))
+    (static_cast<unsigned char>(SIGHASH_SINGLE|SIGHASH_ANYONECANPAY), string("SINGLE|ANYONECANPAY"))
+    ;
+
+/**
+ * Create the assembly string representation of a CScript object.
+ * @param[in] script    CScript object to convert into the asm string representation.
+ * @param[in] fAttemptSighashDecode    Whether to attempt to decode sighash types on data within the script that matches the format
+ *                                     of a signature. Only pass true for scripts you believe could contain signatures. For example,
+ *                                     pass false, or omit the this argument (defaults to false), for scriptPubKeys.
+ */
+string ScriptToAsmStr(const CScript& script, const bool fAttemptSighashDecode)
+{
+    string str;
+    opcodetype opcode;
+    vector<unsigned char> vch;
+    CScript::const_iterator pc = script.begin();
+    while (pc < script.end()) {
+        if (!str.empty()) {
+            str += " ";
+        }
+        if (!script.GetOp(pc, opcode, vch)) {
+            str += "[error]";
+            return str;
+        }
+        if (0 <= opcode && opcode <= OP_PUSHDATA4) {
+            if (vch.size() <= static_cast<vector<unsigned char>::size_type>(4)) {
+                str += strprintf("%d", CScriptNum(vch, false).getint());
+            } else {
+                // the IsUnspendable check makes sure not to try to decode OP_RETURN data that may match the format of a signature
+                if (fAttemptSighashDecode && !script.IsUnspendable()) {
+                    string strSigHashDecode;
+                    // goal: only attempt to decode a defined sighash type from data that looks like a signature within a scriptSig.
+                    // this won't decode correctly formatted public keys in Pubkey or Multisig scripts due to
+                    // the restrictions on the pubkey formats (see IsCompressedOrUncompressedPubKey) being incongruous with the
+                    // checks in CheckSignatureEncoding.
+                    if (CheckSignatureEncoding(vch, SCRIPT_VERIFY_STRICTENC, NULL)) {
+                        const unsigned char chSigHashType = vch.back();
+                        if (mapSigHashTypes.count(chSigHashType)) {
+                            strSigHashDecode = "[" + mapSigHashTypes.find(chSigHashType)->second + "]";
+                            vch.pop_back(); // remove the sighash type byte. it will be replaced by the decode.
+                        }
+                    }
+                    str += HexStr(vch) + strSigHashDecode;
+                } else {
+                    str += HexStr(vch);
+                }
+            }
+        } else {
+            str += GetOpName(opcode);
+        }
+    }
+    return str;
+}
+
 string EncodeHexTx(const CTransaction& tx)
 {
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
@@ -68,7 +130,7 @@ void ScriptPubKeyToUniv(const CScript& scriptPubKey,
     vector<CTxDestination> addresses;
     int nRequired;
 
-    out.pushKV("asm", scriptPubKey.ToString());
+    out.pushKV("asm", ScriptToAsmStr(scriptPubKey));
     if (fIncludeHex)
         out.pushKV("hex", HexStr(scriptPubKey.begin(), scriptPubKey.end()));
 
@@ -101,7 +163,7 @@ void TxToUniv(const CTransaction& tx, const uint256& hashBlock, UniValue& entry)
             in.pushKV("txid", txin.prevout.hash.GetHex());
             in.pushKV("vout", (int64_t)txin.prevout.n);
             UniValue o(UniValue::VOBJ);
-            o.pushKV("asm", txin.scriptSig.ToString());
+            o.pushKV("asm", ScriptToAsmStr(txin.scriptSig, true));
             o.pushKV("hex", HexStr(txin.scriptSig.begin(), txin.scriptSig.end()));
             in.pushKV("scriptSig", o);
         }