Fun times with gcc, musl and Alpine linux v3.8

This article is a quick start guide on how to debug issues with Virgil crypto library, Alpine linux v3.8 and Open JDK 1.8.

Recently, I was testing crypto libraries to see which one might be the best fit for my pet project. One of these libraries was Virgil. After a couple of hours of work, I had something that can be tested out. Everything worked fine on macOS and windows dev machines, but things started breaking once I've deployed code to Amazon.

Initial clue was the following exception (i.e. there was some problem loading libraries compiled by Virgil):

org.springframework.web.util.NestedServletException: Handler dispatch failed; 
nested exception is java.lang.NoClassDefFoundError:
Could not initialize class com.virgilsecurity.crypto.virgilcryptojavaJNI

Further analysis showed that Virgil copies precompiled .SO to tmp directory: /tmp/virgil_crypto_java3134786209685506331.so.

Logical step was to list shared libraries virgl_crypto_java by executing the following command: ldd /tmp/virgil_crypto_java3134786209685506331.so

Output of the ldd command:

ldd (0x7f47776a8000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x7f4776fbc000)
libm.so.6 => ldd (0x7f47776a8000)
libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x7f4776daa000)
libc.so.6 => ldd (0x7f47776a8000)
Error loading shared library ld-linux-x86-64.so.2: No such file or directory (needed by /tmp/virgil_crypto_java3134786209685506331.so)

Let's look at the following error message: Error loading shared library ld-linux-x86-64.so.2.

We need to figure out where ld-linux-x86-64.so.2 file resides. That can be checked the following website. We can see that libc6-compat needs to be installed and we will do that by executing the following command: apk add libc6-compat or by adding the following command to the docker file: RUN apk add --update --no-cache libc6-compat. By default libc6-compat is not installed because Alpine Linux comes with musl compiler by default.

So everything should work now? Right? Well, yes, it worked until Alpine Linux released patch that broke the code. I've decided to check the Alpine linux git repository and stumbled upon the following commit - click here.

The problem with this commit is that previosly /lib64 was just a symlink to lib directory. With this commit this is no longer true.

ld-linux-x86-64.so.2 is copied to /lib64 and not to lib thus breaking the code. Quick and dirty solution was to copy ld-linux-x86-64.so.2 to lib (e.g. cp /lib64/ld-linux-x86-64.so.2 /lib/).

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Date: 06 Jan 2019