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本页为社区译文；如有疑义，请以英文原文为准。 英文原文

如果你迫不及待想开始，下面就是使用 Frida 进行函数跟踪的方法：

~ $ pip install frida-tools
~ $ frida-trace -i "recv*" -i "read*" twitter
recv: Auto-generated handler: …/recv.js
# (snip)
recvfrom: Auto-generated handler: …/recvfrom.js
Started tracing 21 functions. Press Ctrl+C to stop.
    39 ms	recv()
   112 ms	recvfrom()
   128 ms	recvfrom()
   129 ms	recvfrom()

如你所见，Frida 将自身注入 Twitter，枚举已加载的共享库，并挂钩所有名称以 recv 或 read 开头的函数。它还生成了一些样板脚本，用于在函数调用发生时对其进行检查。这些脚本只是供你按需编辑的示例；文件系统中的脚本一旦发生变化，就会自动重新加载。默认情况下，它们只会打印函数名称，就像上面的输出所示。

现在来看一下生成的 recvfrom.js：

/*
 * Auto-generated by Frida. Please modify to match the
 * signature of recvfrom.
 *
 * This stub is somewhat dumb. Future verions of Frida
 * could auto-generate based on OS API references, manpages,
 * etc. (Pull-requests appreciated!)
 *
 * For full API reference, see:
 * https://frida.re/docs/javascript-api/
 */

{
    /**
     * Called synchronously when about to call recvfrom.
     *
     * @this {object} - Object allowing you to store state for
     * use in onLeave.
     * @param {function} log - Call this function with a string
     * to be presented to the user.
     * @param {array} args - Function arguments represented as
     * an array of NativePointer objects.
     * For example use args[0].readUtf8String() if the first
     * argument is a pointer to a C string encoded as UTF-8.
     * It is also possible to modify arguments by assigning a
     * NativePointer object to an element of this array.
     * @param {object} state - Object allowing you to keep
     * state across function calls.
     * Only one JavaScript function will execute at a time, so
     * do not worry about race-conditions. However, do not use
     * this to store function arguments across onEnter/onLeave,
     * but instead use "this" which is an object for keeping
     * state local to an invocation.
     */
    onEnter(log, args, state) {
        log("recvfrom()");
    },

    /**
     * Called synchronously when about to return from recvfrom.
     *
     * See onEnter for details.
     *
     * @this {object} - Object allowing you to access state
     * stored in onEnter.
     * @param {function} log - Call this function with a string
     * to be presented to the user.
     * @param {NativePointer} retval - Return value represented
     * as a NativePointer object.
     * @param {object} state - Object allowing you to keep
     * state across function calls.
     */
    onLeave(log, retval, state) {
    }
}

现在，将 log() 那一行替换成以下内容：

log("recvfrom(socket=" + args[0].toInt32()
    + ", buffer=" + args[1]
    + ", length=" + args[2].toInt32()
    + ", flags=" + args[3]
    + ", address=" + args[4]
    + ", address_len=" + args[5].readPointer().toInt32()
    + ")");

保存文件（它会自动重新加载），然后在 Twitter 应用中执行某项操作，以触发一些网络活动。此时你应该会看到类似下面的内容：

  8098 ms	recvfrom(socket=70,
                         buffer=0x32cc018, length=65536,
                         flags=0x0,
                         address=0xb0420bd8, address_len=16)

不过，这还不算什么。真正的魔法始于你使用 frida-trace 所基于的 Python API 构建自己的工具。

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