fix: ABI decoder - crashing during the attempt to use data slices

Sources/Web3Core/Contract/ContractProtocol.swift

@@ -210,8 +210,8 @@ extension ContractProtocol {
 
     func decodeInputData(_ data: Data) -> [String: Any]? {
         guard data.count >= 4 else { return nil }
-        let methodId = data[0..<4].toHexString()
-        let data = data[4...]
+        let methodId = data[data.startIndex ..< data.startIndex + 4].toHexString()
+        let data = data[(data.startIndex + 4)...]
         return decodeInputData(methodId, data: data)
     }
 }
@@ -333,14 +333,14 @@ extension DefaultContractProtocol {
 
     public func decodeInputData(_ data: Data) -> [String: Any]? {
         guard data.count % 32 == 4 else { return nil }
-        let methodSignature = data[0..<4].toHexString().addHexPrefix().lowercased()
+        let methodSignature = data[data.startIndex ..< data.startIndex + 4].toHexString().addHexPrefix().lowercased()
 
         guard let function = methods[methodSignature]?.first else { return nil }
-        return function.decodeInputData(Data(data[4 ..< data.count]))
+        return function.decodeInputData(Data(data[data.startIndex + 4 ..< data.startIndex + data.count]))
     }
 
     public func getFunctionCalled(_ data: Data) -> ABI.Element.Function? {
         guard data.count >= 4 else { return nil }
-        return methods[data[0..<4].toHexString().addHexPrefix()]?.first
+        return methods[data[data.startIndex ..< data.startIndex + 4].toHexString().addHexPrefix()]?.first
     }
 }

Sources/Web3Core/EthereumABI/ABIDecoding.swift

@@ -34,27 +34,28 @@ extension ABIDecoder {
         guard let elementItself = elData, let nextElementPointer = nextPtr else {
             return (nil, nil)
         }
+        let startIndex = UInt64(elementItself.startIndex)
         switch type {
         case .uint(let bits):
             guard elementItself.count >= 32 else {break}
             let mod = BigUInt(1) << bits
-            let dataSlice = elementItself[0 ..< 32]
+            let dataSlice = elementItself[startIndex ..< startIndex + 32]
             let v = BigUInt(dataSlice) % mod
             return (v, type.memoryUsage)
         case .int(let bits):
             guard elementItself.count >= 32 else {break}
             let mod = BigInt(1) << bits
-            let dataSlice = elementItself[0 ..< 32]
+            let dataSlice = elementItself[startIndex ..< startIndex + 32]
             let v = BigInt.fromTwosComplement(data: dataSlice) % mod
             return (v, type.memoryUsage)
         case .address:
             guard elementItself.count >= 32 else {break}
-            let dataSlice = elementItself[12 ..< 32]
+            let dataSlice = elementItself[startIndex + 12 ..< startIndex + 32]
             let address = EthereumAddress(dataSlice)
             return (address, type.memoryUsage)
         case .bool:
             guard elementItself.count >= 32 else {break}
-            let dataSlice = elementItself[0 ..< 32]
+            let dataSlice = elementItself[startIndex ..< startIndex + 32]
             let v = BigUInt(dataSlice)
             if v == BigUInt(36) ||
                 v == BigUInt(32) ||
@@ -69,33 +70,33 @@ extension ABIDecoder {
             }
         case .bytes(let length):
             guard elementItself.count >= 32 else {break}
-            let dataSlice = elementItself[0 ..< length]
-            return (dataSlice, type.memoryUsage)
+            let dataSlice = elementItself[startIndex ..< startIndex + length]
+            return (Data(dataSlice), type.memoryUsage)
         case .string:
             guard elementItself.count >= 32 else {break}
-            var dataSlice = elementItself[0 ..< 32]
+            var dataSlice = elementItself[startIndex ..< startIndex + 32]
             let length = UInt64(BigUInt(dataSlice))
-            guard elementItself.count >= 32+length else {break}
+            guard elementItself.count >= 32 + length else {break}
             dataSlice = elementItself[32 ..< 32 + length]
             guard let string = String(data: dataSlice, encoding: .utf8) else {break}
             return (string, type.memoryUsage)
         case .dynamicBytes:
             guard elementItself.count >= 32 else {break}
-            var dataSlice = elementItself[0 ..< 32]
+            var dataSlice = elementItself[startIndex ..< startIndex + 32]
             let length = UInt64(BigUInt(dataSlice))
-            guard elementItself.count >= 32+length else {break}
-            dataSlice = elementItself[32 ..< 32 + length]
-            return (dataSlice, nextElementPointer)
+            guard elementItself.count >= 32 + length else {break}
+            dataSlice = elementItself[startIndex + 32 ..< startIndex + 32 + length]
+            return (Data(dataSlice), nextElementPointer)
         case .array(type: let subType, length: let length):
             switch type.arraySize {
             case .dynamicSize:
                 if subType.isStatic {
                     // uint[] like, expect length and elements
                     guard elementItself.count >= 32 else {break}
-                    var dataSlice = elementItself[0 ..< 32]
+                    var dataSlice = elementItself[startIndex ..< startIndex + 32]
                     let length = UInt64(BigUInt(dataSlice))
                     guard elementItself.count >= 32 + subType.memoryUsage*length else {break}
-                    dataSlice = elementItself[32 ..< 32 + subType.memoryUsage*length]
+                    dataSlice = elementItself[startIndex + 32 ..< startIndex + 32 + subType.memoryUsage*length]
                     var subpointer: UInt64 = 32
                     var toReturn = [Any]()
                     for _ in 0 ..< length {
@@ -108,10 +109,10 @@ extension ABIDecoder {
                 } else {
                     // in principle is true for tuple[], so will work for string[] too
                     guard elementItself.count >= 32 else {break}
-                    var dataSlice = elementItself[0 ..< 32]
+                    var dataSlice = elementItself[startIndex ..< startIndex + 32]
                     let length = UInt64(BigUInt(dataSlice))
                     guard elementItself.count >= 32 else {break}
-                    dataSlice = Data(elementItself[32 ..< elementItself.count])
+                    dataSlice = Data(elementItself[startIndex + 32 ..< UInt64(elementItself.count)])
                     var subpointer: UInt64 = 0
                     var toReturn = [Any]()
                     for _ in 0 ..< length {
@@ -179,21 +180,21 @@ extension ABIDecoder {
             }
         case .function:
             guard elementItself.count >= 32 else {break}
-            let dataSlice = elementItself[8 ..< 32]
-            return (dataSlice, type.memoryUsage)
+            let dataSlice = elementItself[startIndex + 8 ..< startIndex + 32]
+            return (Data(dataSlice), type.memoryUsage)
         }
         return (nil, nil)
     }
 
     fileprivate static func followTheData(type: ABI.Element.ParameterType, data: Data, pointer: UInt64 = 0) -> (elementEncoding: Data?, nextElementPointer: UInt64?) {
         if type.isStatic {
             guard data.count >= pointer + type.memoryUsage else {return (nil, nil)}
-            let elementItself = data[pointer ..< pointer + type.memoryUsage]
+            let elementItself = data[data.startIndex + Int(pointer) ..< data.startIndex + Int(pointer + type.memoryUsage)]
             let nextElement = pointer + type.memoryUsage
             return (Data(elementItself), nextElement)
         } else {
             guard data.count >= pointer + type.memoryUsage else {return (nil, nil)}
-            let dataSlice = data[pointer ..< pointer + type.memoryUsage]
+            let dataSlice = data[data.startIndex + Int(pointer) ..< data.startIndex + Int(pointer + type.memoryUsage)]
             let bn = BigUInt(dataSlice)
             if bn > UInt64.max || bn >= data.count {
                 // there are ERC20 contracts that use bytes32 instead of string. Let's be optimistic and return some data
@@ -209,7 +210,8 @@ extension ABIDecoder {
                 return (nil, nil)
             }
             let elementPointer = UInt64(bn)
-            let elementItself = data[elementPointer ..< UInt64(data.count)]
+            let startIndex = UInt64(data.startIndex)
+            let elementItself = data[startIndex + elementPointer ..< startIndex + UInt64(data.count)]
             let nextElement = pointer + type.memoryUsage
             return (Data(elementItself), nextElement)
         }

Sources/Web3Core/EthereumABI/ABIElements.swift

@@ -397,9 +397,9 @@ extension ABI.Element.Function {
         /// 4) `messageLength` is used to determine where message bytes end to decode string correctly.
         /// 5) The rest of the `data` must be 0 bytes or empty.
         if data.bytes.count >= 100,
-           Data(data[0..<4]) == Data.fromHex("08C379A0"),
-           BigInt(data[4..<36]) == 32,
-           let messageLength = Int(Data(data[36..<68]).toHexString(), radix: 16),
+           Data(data[data.startIndex ..< data.startIndex + 4]) == Data.fromHex("08C379A0"),
+           BigInt(data[data.startIndex + 4 ..< data.startIndex + 36]) == 32,
+           let messageLength = Int(Data(data[data.startIndex + 36 ..< data.startIndex + 68]).toHexString(), radix: 16),
            let message = String(bytes: data.bytes[68..<(68+messageLength)], encoding: .utf8),
            (68+messageLength == data.count || data.bytes[68+messageLength..<data.count].reduce(0) { $0 + $1 } == 0) {
             return ["_success": false,
@@ -410,11 +410,11 @@ extension ABI.Element.Function {
 
         if data.count >= 4,
            let errors = errors,
-           let customError = errors[data[0..<4].toHexString().stripHexPrefix()] {
+           let customError = errors[data[data.startIndex ..< data.startIndex + 4].toHexString().stripHexPrefix()] {
             var errorResponse: [String: Any] = ["_success": false, "_abortedByRevertOrRequire": true, "_error": customError.errorDeclaration]
 
             if (data.count > 32 && !customError.inputs.isEmpty),
-               let decodedInputs = ABIDecoder.decode(types: customError.inputs, data: Data(data[4..<data.count])) {
+               let decodedInputs = ABIDecoder.decode(types: customError.inputs, data: Data(data[data.startIndex + 4 ..< data.startIndex + data.count])) {
                 for idx in decodedInputs.indices {
                     errorResponse["\(idx)"] = decodedInputs[idx]
                     if !customError.inputs[idx].name.isEmpty {