在上一篇文章中，我们通过一个徽章挑战，为读者详细介绍了如何转储Atmel芯片的固件，在本文中，我们将继续为读者演示如何转储更复杂的一个电路板：Belkin N300路由器。

　　接下来我们要转储的板子是Belkin N300路由器。当前，Belkin是更受欢迎的消费类路由器品牌之一，这意味着与之前的CTF徽章不同，这次的挑战提供了更多的真实场景。因此，在该设备中发现漏洞的话，则可能会影响到全球的家庭。

　　首先我们要做的就是再去尝试定位一个闪存芯片。这次我们确定的是一款MX25L1606E芯片（图11），相关的参数见

　　

　　图11 mx25l1606e芯片

　　接下来，我们将使用Attify Badge（图12）来转储我们的固件，因为Bus Pirate已经“ *** ”了。

　　

　　图12 Attify Badge

　　引脚输出如下所示：

　　

　　图13 mx25l1606e示意图

　　MX25L1606E

　　Attify Badge

　　CS

　　CS

　　SO

　　MOSI

　　GND

　　GND

　　VCC

　　3.3V

　　SCLK

　　SCK

　　SI

　　MOSI

　　完成上述操作后，它应该是这样的：

　　

　　图14 mx25l1606E（已经连接Attify Badge）

　　由于闪存芯片周围有金属框，所以这块板子上使用SOIC夹的空间有限，因此，这次我们采用了鳄鱼夹。

　　现在，准备工作已经就绪了，下面我们继续转储这个固件。但是，这次我们将使用名为“flashrom”的实用程序，而不是avrdude，因为我们要处理的是闪存 SPI芯片，而不是Atmel芯片。

　　首先，我们可以使用下面的命令来确定flashrom是否可以转储我们的芯片：“flashrom -p ft2232_spi:type=232H”。

　　该命令将尝试自动识别我们的芯片。如果你使用的是Bus Pirate，可以用下面的参数代替传递给-p的参数：“flashrom -p buspirate_spi:dev=/dev/ttyUSB0”。

　　其中，/dev/ttyUSB0是Bus Pirate连接的串口，读者可以根据需要进行修改。运行该命令后，成功返回如下内容：

　　flashrom v0.9.9-r1954 on Linux 4.15.0-88-generic (x86_64)

　　flashrom is free software, get the source code at

　　Calibrating delay loop... delay loop is unreliable, trying to continue OK.

　　Found Macronix flash chip "MX25L1605A/MX25L1606E/MX25L1608E" (2048 kB, SPI) on ft2232_spi.

　　如果芯片识别失败也不要担心，可以用“flashrom -L”在列表中手动找到您的芯片，然后运行下面的命令，看看是否还能读取芯片：“flashrom -p ft2232_spi:type=232H -c MX25L1605A/MX25L1606E/MX25L1608E -r dump.bin”。

　　其中，-p选项表明我们要使用ft2232编程器（如果使用Bus Pirate，则用上面的-p参数进行相应的替换），-c选项表明我们要转储哪种闪存芯片（本例中是MX25L1606E），-r dump.bin告诉它将内容读入文件dump.bin。如果一切顺利的话，我们应该得到一个有效的固件文件。如果失败的话，则会报错，或者创建一个充满空字节的文件。

　　当然，这个过程可能需要一段时间，特别是对于较大的芯片；另外，我们可以从数据表中识别尺寸大小。由于MX25L1606E以地址1FFFFF结束，所以，其长度为2097151字节或2MB（图15）。

　　

　　图15 mx25l1606e的存储器组织结构

　　这块2MB的芯片用了大约2分钟才完全转储过来。最后，我们很幸运，之一次就成功转储了固件。

　　iot@attifyos ~> flashrom -p ft2232_spi:type=232H -c MX25L1605A/MX25L1606E/MX25L1608E -r dump.bin

　　flashrom v0.9.9-r1954 on Linux 4.15.0-88-generic (x86_64)

　　flashrom is free software, get the source code at

　　Calibrating delay loop... delay loop is unreliable, trying to continue OK.

　　Found Macronix flash chip "MX25L1605A/MX25L1606E/MX25L1608E" (2048 kB, SPI) on ft2232_spi.

　　Reading flash... done.

　　这时，该binwalk上场了：

　　iot@attifyos ~> binwalk dump.bin

　　DECIMAL HEXADECIMAL DESCRIPTION

　　--------------------------------------------------------------------------------

　　5440 0x1540 LZMA compressed data, properties: 0x5D, dictionary size: 8388608 bytes, uncompressed size: 85344 bytes

　　28570 0x6F9A Sercomm firmware signature, version control: 256, download control: 0, hardware ID: "AAZ", hardware version: 0x3200, firmware version: 0x6, starting code segment: 0x0, code size: 0x7310

　　142352 0x22C10 LZMA compressed data, properties: 0x5D, dictionary size: 8388608 bytes, uncompressed size: 2764800 bytes

　　881324 0xD72AC LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 3450 bytes

　　882534 0xD7766 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 10162 bytes

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　　1371229 0x14EC5D LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 114 bytes

　　1371363 0x14ECE3 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 290 bytes

　　1371584 0x14EDC0 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 929 bytes

　　从“Sercomm Firmware Signature”这一行，我们可以看到一个硬件的ID为“AAZ”，它与电路板上的硬件ID完全匹配（图16）。现在，我们就可以继续分析这个固件的漏洞了。请记住，如果我们可以转储固件，我们也可以将自定义固件和后门写入闪存芯片。

　　

　　图16 硬件标识

　　如果期间出错的话，最可能的两个原因是引脚没有正确连接，或者（如果引脚已经正确连接）它们正在给SPI芯片供电，使得芯片无法进行转储。第二种情况可能很常见，一般来说，更好的解决 *** 是用热*对芯片进行脱焊，然后用芯片自行转储固件。如前所述，更好检查一下电缆的长度，以确保故障不是由于电缆太长造成的。

　　虽然转储这些设备可能需要不少时间，但这可以帮助我们加深对这些设备的工作原理的了解。例如，通过转储Belkin设备的固件，我们可以直接分析源web文件，从而使我们可以更容易识别设备内的远程漏洞并加以利用。

　　通过利用这些类型的设备的安全漏洞，攻击者可以在受害者的路由器内创建一个后门，并重新路由所有 *** 流量，窃取受害者的银行和电子商务账户等账户的凭证。了解这些漏洞存在的地方，让我们有机会在它们造成任何重大损害之前修复它们。

　　在本系列的下一部分，我们将讨论JTAG和UART串行接口，如何访问它们，以及我们可以从中得到什么。

　　我们可以借助一些工具来成功地转储这些固件，例如：

　　SOIC Clip:

　　A device for dumping firmware (Bus Pirate):

　　Cables and clips:

　　Additional useful wires:

　　Bus Pirate用于与SPI串行协议进行交互，以便为我们转储固件。其他可行的替代方案包括Shikra（和Attify Badge（当然，每个工具都有自己的优缺点。但是，Bus Pirate以及被广泛使用，并且有很好的文档，在我看来，它是最容易使用的。但是，Shikra被认为比Bus Pirate更稳定，速度更快，但没有那么多的支持。相比之下，Attify Badge则更易于设置，但同样支持有限。此外，Bus Pirate还提供了一个很好的串行接口，如果你愿意的话，可以很轻松与设备进行手动通信。读者可以根据自己的喜好和条件进行选择。

　　此外，由于电缆和夹子相当便宜，并且容易买到，因此，我特别推荐这些，因为它们已经为我提供了我迄今为止所需的一切，并且可以很好地夹在针脚上。