Projects containing read-only files cannot be built

[acaloiaro]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When projects being built by nixpacks contain read-only files, nipacks build ... results in a permission error due to Rust's fs::copy retaining file permissions, and nixpacks rewriting all CRLF line endings with LF:

nixpacks/src/nixpacks/files.rs

Line 35 in 2ec70b7

fs::write(&to, data.replace("\r\n", "\n"))?;

To reproduce

In any project to be built by nixpacks, on a Linux system

touch test
chmod 444 test
nixpacks build .

╔══════ Nixpacks v1.20.0 ══════╗
║ setup      │ go_1_19         ║
║──────────────────────────────║
║ install    │ go mod download ║
║──────────────────────────────║
║ build      │ go build -o out ║
║──────────────────────────────║
║ start      │ ./out           ║
╚══════════════════════════════╝

Error: Writing app

Caused by:
    Permission denied (os error 13)

Here from the strace output, we can see that the permission error occurs opening test as writable

openat(AT_FDCWD, "/run/user/1000/nixpacks.k4jRGy09qM0S/test", O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 EACCES (Permission denied)

And stat shows us that that file retained its original read-only permissions, preventing the writable file handle

stat -c "%a %n" /run/user/1000/nixpacks.k4jRGy09qM0S/test
444 /run/user/1000/nixpacks.k4jRGy09qM0S/test

Expected behavior

• Nixpacks builds successfully as long as it can read files from project directories
• That nixpacks does not replace all CRLF with LF in project files.

Environment

OS: NixOS Unstable
Kernel: Linux version 6.6.17 (nixbld@localhost) (gcc (GCC) 13.2.0, GNU ld (GNU Binutils) 2.40) #1-NixOS SMP PREEMPT_DYNAMIC Fri Feb 16 18:10:57 UTC 2024
Nixpacks version: 1.20.0 / any

[acaloiaro]

This may be related to some instances of #700