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.

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);
         }