Do not allow negative fees.

src/cpp/ripple/TransactionErr.cpp

@@ -39,6 +39,7 @@ bool transResultInfo(TER terCode, std::string& strToken, std::string& strHuman)
 		{	temMALFORMED,			"temMALFORMED",				"Malformed transaction."								},
 		{	temBAD_AMOUNT,			"temBAD_AMOUNT",			"Can only send positive amounts."						},
 		{	temBAD_AUTH_MASTER,		"temBAD_AUTH_MASTER",		"Auth for unclaimed account needs correct master key."	},
+		{	temBAD_FEE,				"temBAD_FEE",				"Negative fee."											},
 		{	temBAD_EXPIRATION,		"temBAD_EXPIRATION",		"Malformed."											},
 		{	temBAD_ISSUER,			"temBAD_ISSUER",			"Malformed."											},
 		{	temBAD_LIMIT,			"temBAD_LIMIT",				"Limits must be non-negative."							},
@@ -51,7 +52,6 @@ bool transResultInfo(TER terCode, std::string& strToken, std::string& strHuman)
 		{	temBAD_SEQUENCE,		"temBAD_SEQUENCE",			"Malformed: Sequence in not in the past."				},
 		{	temDST_IS_SRC,			"temDST_IS_SRC",			"Destination may not be source."						},
 		{	temDST_NEEDED,			"temDST_NEEDED",			"Destination not specified."							},
-		{	temINSUF_FEE_P,			"temINSUF_FEE_P",			"Fee not allowed."										},
 		{	temINVALID,				"temINVALID",				"The transaction is ill-formed."						},
 		{	temINVALID_FLAG,		"temINVALID_FLAG",			"The transaction has an invalid flag."					},
 		{	temREDUNDANT,			"temREDUNDANT",				"Sends same currency to self."							},

src/cpp/ripple/TransactionErr.h

@@ -27,6 +27,7 @@ enum TER	// aka TransactionEngineResult
 	temMALFORMED	= -299,
 	temBAD_AMOUNT,
 	temBAD_AUTH_MASTER,
+	temBAD_FEE,
 	temBAD_EXPIRATION,
 	temBAD_ISSUER,
 	temBAD_LIMIT,
@@ -39,7 +40,6 @@ enum TER	// aka TransactionEngineResult
 	temBAD_SET_ID,
 	temDST_IS_SRC,
 	temDST_NEEDED,
-	temINSUF_FEE_P,
 	temINVALID,
 	temINVALID_FLAG,
 	temREDUNDANT,

src/cpp/ripple/Transactor.cpp

@@ -57,6 +57,9 @@ TER Transactor::payFee()
 		return telINSUF_FEE_P;
 	}
 
+	if (saPaid.isNegative())
+		return temBAD_AMOUNT;
+
 	if (!saPaid) return tesSUCCESS;
 
 	// Deduct the fee, so it's not available during the transaction.