bug: Dead validation code: local ignition config files never validated

[yasminvalim]

Created originally in Butane by @deepak0x: coreos/butane#724

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---

name: release checklist
about: release checklist template
title: Dead validation code: local ignition config files never validated
labels: jira,kind/bug
warning: |
⚠️ Template generated by https://github.com/coreos/repo-templates; do not edit downstream

Bug Report

File: base/v0_8_exp/translate.go, line 157 (same pattern at base/v0_7/translate.go:153)

Summary:

translateResource contains dead validation code. The strings.HasPrefix guard at line 157 is always false, so ValidateIgnitionConfig is never called for local files — even when those files are used in ignition.config.merge or ignition.config.replace contexts. Invalid or corrupt ignition config data in a local field passes through translation silently with no warning or error.

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Buggy code

https://github.com/coreos/butane/blob/cb34e120e5267bfd5bdfa83fa8c2e44e06dedda2/base/v0_8_exp/translate.go#L157

if from.Local != nil {
    c := path.New("yaml", "local")
    contents, err := baseutil.ReadLocalFile(*from.Local, options.FilesDir)
    if err != nil {
        r.AddOnError(c, err)
        return
    }
    // Validating the contents of the local file from here since there is no way to
    // get both the filename and filedirectory in the Validate context
    if strings.HasPrefix(c.String(), "$.ignition.config") {   // ← always false
        rp, err := ValidateIgnitionConfig(c, contents)
        r.Merge(rp)
        if err != nil {
            return
        }
    }
    ...
}

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Root cause

c is constructed as path.New("yaml", "local"). The first argument is the tag; the second is a path element.

path.ContextPath.String() (defined in vendor/github.com/coreos/vcontext/path/path.go:36) builds its output by joining path elements with dots, prefixed with $. The tag is not included in the string representation.

Therefore:

path.New("yaml", "local").String()  →  "$.local"
strings.HasPrefix("$.local", "$.ignition.config")  →  false

The condition can never be true regardless of where translateResource is called from. ValidateIgnitionConfig is dead code for all local field inputs.

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Impact

Local files referenced via the local field inside ignition.config.merge or ignition.config.replace blocks are never validated as Ignition configs at translation time. Malformed or invalid ignition config JSON/YAML in those files is silently accepted and encoded into the output without any diagnostic.

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Reproduction

Confirmed by evaluating the vendored vcontext library directly:

import "github.com/coreos/vcontext/path"
import "strings"

c := path.New("yaml", "local")
fmt.Println(c.String())                                         // "$.local"
fmt.Println(strings.HasPrefix(c.String(), "$.ignition.config")) // false

path.New("yaml", "local").String() returns "$.local", which does not satisfy strings.HasPrefix(..., "$.ignition.config").

The same dead-code pattern exists independently at base/v0_7/translate.go:153.

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Tagging:

• Confirm path.ContextPath.String() does not include the tag in any vcontext version vendored by this repo
• Confirm ValidateIgnitionConfig is unreachable for local field inputs in both base/v0_7 and base/v0_8_exp
• Confirm no test currently exercises the ValidateIgnitionConfig branch via a local field

Fedora packaging:

• No response

GitHub release:

• No response

Quay release:

• No response