SwiftHook

A Swift Library for hooking swift methods and functions.

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How works

• Function / Struct Method
  Hook by facebook/fishhook.

• Objective-C Class Method
  Simply, Objective-C runtime is used.

• Swift Class Method
  Hook by rewriting Vtable.

Usage

[!NOTE]
To hook a function that exists in your own image, you must specify the following linker flag.
"-Xlinker -interposable"

Reference: johnno1962/SwiftTrace

Hook

Function / Struct Method

The targetFunction implementation is replaced by the replacementFunction implementation.
The original implementation is moved to originalFunction.

It is possible to call an originalFunction within a replacementFunction.

swiftCopy
try SwiftHook.hookFunction(
    "SwiftHookTests.targetFunction() -> Swift.String",
    "SwiftHookTests.replacementFunction() -> Swift.String",
    "SwiftHookTests.originalFunction() -> Swift.String",
    isMangled: false
)

/* using mangled symbol names */
try SwiftHook.hookFunction(
    "$s14SwiftHookTests14targetFunctionSSyF",
    "$s14SwiftHookTests19replacementFunctionSSyF",
    "$s14SwiftHookTests16originalFunctionSSyF",
    isMangled: true
)

Exchange Implementation

Function / Struct Method

swiftCopy
SwiftHook.exchangeFuncImplementation(
    "SwiftHookTests.StructItem.printA() -> Swift.String",
    "SwiftHookTests.StructItem.printB() -> Swift.String",
    isMangled: false
)

/* using mangled symbol names */
SwiftHook.exchangeFuncImplementation(
    "$s14SwiftHookTests21hook_assertionFailure__4file4line5flagss5NeverOs12StaticStringV_SSAISus6UInt32VtF",
    "$s14SwiftHookTests25XXXXhook_assertionFailure__4file4line5flagss5NeverOs12StaticStringV_A2ISus6UInt32VtF",
    isMangled: true
)

Class Method

swiftCopy
/// Swift Class
try SwiftHook.exchangeMethodImplementation(
    "SwiftHookTests.SwiftClassItem.mul2(Swift.Int) -> Swift.Int",
    "SwiftHookTests.SwiftClassItem.add2(Swift.Int) -> Swift.Int",
    for: SwiftClassItem.self
)

// Objective-C Class
try SwiftHook.exchangeMethodImplementation(
    "mul2:",
    "add2:",
    for: ObjCClassItem.self
)

License

swift-hook is released under the MIT License. See LICENSE