elfdeps: look for 64 bit library matches first if binary is 64 bit

[nevun]

If you had 32 bits libraries in /lib, landrun --ldd would pick those before the 64 bit library in /lib64.

This MR just changes the lookup order if the binary we are running is 64 bit.

before:

$ ./landrun --log-level debug  --ldd --add-exec /bin/nc
[landrun:debug] 2025/12/03 11:33:45 Added executable path: /bin/nc
[landrun:debug] 2025/12/03 11:33:45 Added library paths: [/etc/ld.so.cache /lib64/ld-linux-x86-64.so.2 /lib64/libssl.so.3 /lib64/libpcap.so.1 /lib64/libibverbs.so.1 /lib64/libnl-3.so.200 /lib/libm.so.6 /lib/libc.so.6 /lib64/libcrypto.so.3 /lib/ld-linux.so.2 /lib/libz.so.1 /lib64/libnl-route-3.so.200 /lib/libgcc_s.so.1]
[landrun] 2025/12/03 11:33:45 Sandbox config: {ReadOnlyPaths:[] ReadWritePaths:[] ReadOnlyExecutablePaths:[/bin/nc /etc/ld.so.cache /lib64/ld-linux-x86-64.so.2 /lib64/libssl.so.3 /lib64/libpcap.so.1 /lib64/libibverbs.so.1 /lib64/libnl-3.so.200 /lib/libm.so.6 /lib/libc.so.6 /lib64/libcrypto.so.3 /lib/ld-linux.so.2 /lib/libz.so.1 /lib64/libnl-route-3.so.200 /lib/libgcc_s.so.1] ReadWriteExecutablePaths:[] BindTCPPorts:[] ConnectTCPPorts:[] BestEffort:false UnrestrictedFilesystem:false UnrestrictedNetwork:false}
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /bin/nc
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /etc/ld.so.cache
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/ld-linux-x86-64.so.2
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libssl.so.3
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libpcap.so.1
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libibverbs.so.1
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libnl-3.so.200
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib/libm.so.6
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib/libc.so.6
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libcrypto.so.3
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib/ld-linux.so.2
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib/libz.so.1
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libnl-route-3.so.200
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib/libgcc_s.so.1
[landrun:debug] 2025/12/03 11:33:45 Applying Landlock restrictions
[landrun] 2025/12/03 11:33:45 Landlock restrictions applied successfully
[landrun] 2025/12/03 11:33:45 Executing: [/bin/nc]
/bin/nc: error while loading shared libraries: libm.so.6: cannot open shared object file: Permission denied

Notice it resolves four deps to their 32 bit version in /lib

After this MR:

$ ./landrun --log-level debug  --ldd --add-exec /bin/nc
[landrun:debug] 2025/12/03 12:04:28 Added executable path: /bin/nc
[landrun:debug] 2025/12/03 12:04:28 Added library paths: [/etc/ld.so.cache /lib64/libm.so.6 /lib64/libc.so.6 /lib64/libcrypto.so.3 /lib64/libpcap.so.1 /lib64/libibverbs.so.1 /lib64/ld-linux-x86-64.so.2 /lib64/libssl.so.3 /lib64/libz.so.1 /lib64/libnl-route-3.so.200 /lib64/libnl-3.so.200 /lib64/libgcc_s.so.1]
[landrun] 2025/12/03 12:04:28 Sandbox config: {ReadOnlyPaths:[] ReadWritePaths:[] ReadOnlyExecutablePaths:[/bin/nc /etc/ld.so.cache /lib64/libm.so.6 /lib64/libc.so.6 /lib64/libcrypto.so.3 /lib64/libpcap.so.1 /lib64/libibverbs.so.1 /lib64/ld-linux-x86-64.so.2 /lib64/libssl.so.3 /lib64/libz.so.1 /lib64/libnl-route-3.so.200 /lib64/libnl-3.so.200 /lib64/libgcc_s.so.1] ReadWriteExecutablePaths:[] BindTCPPorts:[] ConnectTCPPorts:[] BestEffort:false UnrestrictedFilesystem:false UnrestrictedNetwork:false}
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /bin/nc
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /etc/ld.so.cache
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libm.so.6
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libc.so.6
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libcrypto.so.3
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libpcap.so.1
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libibverbs.so.1
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/ld-linux-x86-64.so.2
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libssl.so.3
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libz.so.1
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libnl-route-3.so.200
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libnl-3.so.200
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libgcc_s.so.1
[landrun:debug] 2025/12/03 12:04:28 Applying Landlock restrictions
[landrun] 2025/12/03 12:04:28 Landlock restrictions applied successfully
[landrun] 2025/12/03 12:04:28 Executing: [/bin/nc]
Ncat: You must specify a host to connect to. QUITTING.

Now it works

[abitrolly]

With hello process there is no conflict with 32-bit libs, so something else is going on.

$ landrun --log-level=debug --add-exec --ldd /usr/bin/echo "hello"                       
[landrun:debug] 2026/03/02 19:43:40 Added executable path: /usr/bin/echo
[landrun:debug] 2026/03/02 19:43:40 Added library paths: [/lib64/libc.so.6]
[landrun] 2026/03/02 19:43:40 Sandbox config: {ReadOnlyPaths:[] ReadWritePaths:[] ReadOnlyExecutablePaths:[/usr/bin/echo /lib64/libc.so.6] ReadWriteExecutablePaths:[] BindTCPPorts:[] ConnectTCPPorts:[] BestEffort:false UnrestrictedFilesystem:false UnrestrictedNetwork:false}
[landrun:debug] 2026/03/02 19:43:40 Adding read-only executable path: /usr/bin/echo
[landrun:debug] 2026/03/02 19:43:40 Adding read-only executable path: /lib64/libc.so.6
[landrun:debug] 2026/03/02 19:43:40 Applying Landlock restrictions
[landrun] 2026/03/02 19:43:40 Landlock restrictions applied successfully
[landrun] 2026/03/02 19:43:40 Executing: [/usr/bin/echo hello]
[landrun:error] 2026/03/02 19:43:40 permission denied

[joelanderson000]

I also ran into this on Fedora 43. This fix worked for me.

@abitrolly could your error be some other permissions issue? The error message doesn't report failing to load a shared object.

[abitrolly]

I need to build it to test.

[abitrolly]

Interesting. I compiled the landrun from source and my error is gone. #52 (comment)

So the problem in my case is on Homebrew side somewhere.

git clone https://github.com/Zouuup/landrun
cd landrun
go build -v cmd/landrun/main.go

./main --log-level=debug --add-exec --ldd /usr/bin/echo "hello"