bitcoin-tx: Stricter check for valid integers

Just calling atoi to convert strings to integers does not check for
valid integers very thoroughly; in particular, it just ignores
everything starting from the first non-numeral character.  Even a string
like "foo" is fine and silently returns 0.

This meant that bitcoin-tx would not fail if such a string was passed in
various places where an integer is expected (like the locktime or an
input/output index); this means that it would, for instance, silently
accept a typo and interpret it in an unexpected way.

In this change, we use ParseInt64 for parsing strings to integers,
which actually verifies that the full string is valid as number.
New tests in the bitcoin-util-test cover the new error paths.

1 files changed, 20 insertions, 22 deletions

diff --git a/src/bitcoin-tx.cpp b/src/bitcoin-tx.cpp
index ab0efde05c..181e2bb1bc 100644
--- a/src/bitcoin-tx.cpp
+++ b/src/bitcoin-tx.cpp
@@ -1,4 +1,4 @@
-// Copyright (c) 2009-2017 The Bitcoin Core developers
+// Copyright (c) 2009-2018 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -193,18 +193,18 @@ static CAmount ExtractAndValidateValue(const std::string& strValue)
 
 static void MutateTxVersion(CMutableTransaction& tx, const std::string& cmdVal)
 {
-    int64_t newVersion = atoi64(cmdVal);
-    if (newVersion < 1 || newVersion > CTransaction::MAX_STANDARD_VERSION)
-        throw std::runtime_error("Invalid TX version requested");
+    int64_t newVersion;
+    if (!ParseInt64(cmdVal, &newVersion) || newVersion < 1 || newVersion > CTransaction::MAX_STANDARD_VERSION)
+        throw std::runtime_error("Invalid TX version requested: '" + cmdVal + "'");
 
     tx.nVersion = (int) newVersion;
 }
 
 static void MutateTxLocktime(CMutableTransaction& tx, const std::string& cmdVal)
 {
-    int64_t newLocktime = atoi64(cmdVal);
-    if (newLocktime < 0LL || newLocktime > 0xffffffffLL)
-        throw std::runtime_error("Invalid TX locktime requested");
+    int64_t newLocktime;
+    if (!ParseInt64(cmdVal, &newLocktime) || newLocktime < 0LL || newLocktime > 0xffffffffLL)
+        throw std::runtime_error("Invalid TX locktime requested: '" + cmdVal + "'");
 
     tx.nLockTime = (unsigned int) newLocktime;
 }
@@ -212,8 +212,8 @@ static void MutateTxLocktime(CMutableTransaction& tx, const std::string& cmdVal)
 static void MutateTxRBFOptIn(CMutableTransaction& tx, const std::string& strInIdx)
 {
     // parse requested index
-    int inIdx = atoi(strInIdx);
-    if (inIdx < 0 || inIdx >= (int)tx.vin.size()) {
+    int64_t inIdx;
+    if (!ParseInt64(strInIdx, &inIdx) || inIdx < 0 || inIdx >= static_cast<int64_t>(tx.vin.size())) {
         throw std::runtime_error("Invalid TX input index '" + strInIdx + "'");
     }
 
@@ -248,10 +248,10 @@ static void MutateTxAddInput(CMutableTransaction& tx, const std::string& strInpu
     static const unsigned int maxVout = MAX_BLOCK_WEIGHT / (WITNESS_SCALE_FACTOR * minTxOutSz);
 
     // extract and validate vout
-    std::string strVout = vStrInputParts[1];
-    int vout = atoi(strVout);
-    if ((vout < 0) || (vout > (int)maxVout))
-        throw std::runtime_error("invalid TX input vout");
+    const std::string& strVout = vStrInputParts[1];
+    int64_t vout;
+    if (!ParseInt64(strVout, &vout) || vout < 0 || vout > static_cast<int64_t>(maxVout))
+        throw std::runtime_error("invalid TX input vout '" + strVout + "'");
 
     // extract the optional sequence number
     uint32_t nSequenceIn=std::numeric_limits<unsigned int>::max();
@@ -481,10 +481,9 @@ static void MutateTxAddOutScript(CMutableTransaction& tx, const std::string& str
 static void MutateTxDelInput(CMutableTransaction& tx, const std::string& strInIdx)
 {
     // parse requested deletion index
-    int inIdx = atoi(strInIdx);
-    if (inIdx < 0 || inIdx >= (int)tx.vin.size()) {
-        std::string strErr = "Invalid TX input index '" + strInIdx + "'";
-        throw std::runtime_error(strErr.c_str());
+    int64_t inIdx;
+    if (!ParseInt64(strInIdx, &inIdx) || inIdx < 0 || inIdx >= static_cast<int64_t>(tx.vin.size())) {
+        throw std::runtime_error("Invalid TX input index '" + strInIdx + "'");
     }
 
     // delete input from transaction
@@ -494,10 +493,9 @@ static void MutateTxDelInput(CMutableTransaction& tx, const std::string& strInId
 static void MutateTxDelOutput(CMutableTransaction& tx, const std::string& strOutIdx)
 {
     // parse requested deletion index
-    int outIdx = atoi(strOutIdx);
-    if (outIdx < 0 || outIdx >= (int)tx.vout.size()) {
-        std::string strErr = "Invalid TX output index '" + strOutIdx + "'";
-        throw std::runtime_error(strErr.c_str());
+    int64_t outIdx;
+    if (!ParseInt64(strOutIdx, &outIdx) || outIdx < 0 || outIdx >= static_cast<int64_t>(tx.vout.size())) {
+        throw std::runtime_error("Invalid TX output index '" + strOutIdx + "'");
     }
 
     // delete output from transaction
@@ -593,7 +591,7 @@ static void MutateTxSign(CMutableTransaction& tx, const std::string& flagStr)
 
             uint256 txid = ParseHashStr(prevOut["txid"].get_str(), "txid");
 
-            int nOut = atoi(prevOut["vout"].getValStr());
+            const int nOut = prevOut["vout"].get_int();
             if (nOut < 0)
                 throw std::runtime_error("vout must be positive");