Category: Technology

What’s the deal with Cisco devices in `file` output, anyway?

If you work on PowerPC systems of some kind – or maybe you work on car MCUs that use the NEC V800 CPU – you may have run across some strange output when you run the file command on any binary:

/usr/bin/file: ELF 32-bit MSB pie executable, PowerPC or cisco 4500, version 1 (SYSV), dynamically linked, interpreter /lib/ld-musl-powerpc.so.1, stripped

Of course it’s a PowerPC binary, but why the mention of “cisco 4500” (or Cisco 7500s for 64-bit PowerPC binaries, or Cisco 12000s for NEC V800s)? The reason behind this is a fascinating insight into the world of proprietary computing architectures and the somewhat inventive way Cisco tried to lock down some of their older systems.

A brief primer on ELF

ELF, which stands for Extensible Linking Format or Executable and Linkable Format and is not a Will Ferrell character, is a file format for executable files and shared libraries (among others).

In layman’s terms, ELF specifies things like what processor the executable runs on, the ABI that it uses, the endianness and word size (32-bit or 64-bit, for example) that it uses, and so on.

One of the fields in an ELF file is the e_machine field, which specifies the type of machine the file is designed to run on. 0x02 is SPARC, 0x03 is the Intel x86, 0x14 is 32-bit PowerPC, 0x15 is 64-bit PowerPC, and so on.

This is the identifier that allows your OS to tell you “Exec format error” (or similar) when you run an executable for a CPU other than the one you are currently using. As a side note, it is also this field that allows qemu-user binfmt to work, if you are curious.

Cisco’s use of e_machine

The boot loader for Cisco IOS machines, also known as ROMMON, will refuse to load firmware for a different router model than the system. For example, on a Cisco 2911, you may see:

loadprog: error - Invalid image for platform
e_machine = 30, cpu_type = 194

ROMMON uses e_machine as a sort of “model number”. The Cisco 4500 uses cpu_type 20 or 0x14, which happens to also be the ELF e_machine for PowerPC.

The “magic” library that the file command uses to determine the machine type of ELF binaries only knows a few models of Cisco. I haven’t been able to determine their criteria for inclusion, or why some are present and some aren’t.

References

The ROMMON error was gleaned from an OpenWrt forum post; I don’t have hardware to show this error myself.

More information about how older Cisco devices use ELF can be found on the LinuxMIPS wiki.

This question was originally asked by some curious people on the #talos-workstation IRC channel on Libera.Chat. I knew the basics of Cisco’s ELF-scapades, but they were the ones who inspired me to make this write-up and learn a bit more.

Compiling XIBs with CMake without Xcode

I’ve been enjoying using the JetBrains IDE CLion to do some refactoring and improvements to the Auctions code base. However, when I tried to build the Mac app bundle with it, the app failed to launch:

2022-07-30 19:54:15.117 Auctions[80371:16543044] Unable to load nib file: Auctions, exiting

The XIB files were definitely part of the CMake project. I later learned that CMake does not automatically add XIB compilation targets to a project. It relies on the Xcode generator to do that.

I found a long-archived documentation page from CMake on the Kitware GitLab that described a method to build NIB files from XIBs, and have modified it to make it simpler for Auctions.

You can see the change in the commit diff, but I’ll include the snippet here for posterity.

First, you define an array with the XIB file names with no suffix. For instance, I’ve done set(COCOA_UI_XIBS AXAccountsWindow AXSignInWindow Auctions) for the three XIB files presently in the codebase.

Then we have the loop to build them:

find_program(IBTOOL ibtool REQUIRED)
foreach(XIBFILE ${COCOA_UI_XIBS})
    add_custom_command(TARGET Auctions POST_BUILD
            COMMAND ${IBTOOL} --compile ${CMAKE_CURRENT_BINARY_DIR}/Auctions.app/Contents/Resources/${XIBFILE}.nib ${CMAKE_CURRENT_SOURCE_DIR}/${XIBFILE}.xib
            COMMENT "Compiling NIB file ${XIBFILE}.nib")
endforeach()

Now it starts correctly and works properly when built from within CLion. This was surprisingly difficult to debug and fix, so I hope this post can help others avoid the hours of dead ends that I endured.

Until next time, Happy Hacking!

Expanding the Retro Lab, and Putting It to Work

Over the past month, I have been blessed with being in the right place at the right time to acquire a significant amount of really cool computers (and other technology) for the Retro Lab.

Between the collection I already had and these new “hauls”, I now have a lot of computers. I was, ahem, encouraged to stop using the closets in my flat to store them and finally obtained a storage locker for the computers I’m not using. It’s close to home, so I can swap between what I want to work on virtually at will.

Now I am thinking about ways to track all of the machines I have. One idea I’ve had is to use FileMaker Pro for the Power Macintosh to track the Macs, and FoxPro to track the PCs. One of my best friends, Horst, suggested I could even use ODBC to potentially connect the two.

This led me to all sorts of ideas regarding ways to safely and securely run some server services on older systems and software. One of my acquisitions was a Tyan 440LX-based server board with dual Pentium II processors. I’m thinking this would be a fun computer to use for NT. I have a legitimate boxed copy of BackOffice Server 2.5 that would be perfect for it, even!

Connecting this system to the Internet, though, would present a challenge if I want to have any modicum of security – so I’ve thought it out. And this is my plan for an eventual “Retro Cloud”.

Being a cybersecurity professional, my first thought was to completely isolate it on the network. I can set up a VLAN on my primary router, and connect that VLAN to a dedicated secondary router. That secondary router would have total isolation from my present network, so the “Retro Cloud” would have its own subnet and no way to touch any other system. This makes it safer to have an outbound connection. I’ll be able to explore Gopherspace, download updates via FTP, and all that good stuff.

Next, I’m thinking that it would make a lot of sense to have updated, secure software to proxy inbound connections. Apache and Postfix can hand sanitised requests to IIS and Exchange without exposing their old, potentially vulnerable protocol handlers directly to the Internet.

And finally, as long as everything on the NT system is public knowledge anyway – don’t (re)use any important passwords on it, don’t have private data stored on it – the risk is minimal even if an attacker were able to gain access despite these protections.

I’m still in the planning stages with this project, so I would love to hear further comments. Has anyone else set up a retro server build and had success securing it? Are there other cool projects that I may not have even thought of yet? Share your comments with me below!

Wherefore art thou, USB-C hubs?

I’ve been looking for weeks at various stores around Tulsa, and online, for USB-C hubs. I already have a USB-C hub that has ports like Ethernet, HDMI, and USB-A. What I am looking for is a hub that has many USB-C ports.

As my Lightning cables age out, and I replace more equipment with devices that have only USB-C, more of my devices are connected this way.

My M1 MacBook Pro has two USB-C ports, but I have:

  • A USB-C SSD with my photo library.
  • My iPhone 12 with a Lightning to USB-C cable (all of my Lightning to USB-As are finally worn out).
  • My iPad mini which is USB-C to USB-C.
  • The aforementioned hub for connecting an external display.
  • Sometimes an optical drive, which yes, also uses USB-C.
  • The charging cable, because all of these devices pull a lot of power.

So, as a ballpark estimate, I need about six USB-C ports here. I really do not want to have to use a bunch of C-to-A adaptors, especially since some of my devices seem to slow down when using them. Has anyone seen anything like that out there? I drastically prefer to shop local, but at this point I would even consider buying from Amazon.

Or to put it in the words of one of my favourite bloggers: Dear lazyweb, where can I buy USB-C hubs?