-
Notifications
You must be signed in to change notification settings - Fork 368
Split template injection validator by responsibility #26580
New issue
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.
Already on GitHub? Sign in to your account
Merged
+166
−160
Merged
Changes from all commits
Commits
Show all changes
4 commits
Select commit
Hold shift + click to select a range
1ea79ea
Initial plan
Copilot 43c272b
chore: outline plan for template injection validator split
Copilot e590a3a
Revert "chore: outline plan for template injection validator split"
Copilot ba18392
Split template injection validator by responsibility
Copilot File filter
Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
There are no files selected for viewing
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,166 @@ | ||
| package workflow | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "regexp" | ||
| "strings" | ||
| ) | ||
|
|
||
| // extractRunBlocks walks the YAML tree and extracts all run: field values | ||
| func extractRunBlocks(data any) []string { | ||
| var runBlocks []string | ||
|
|
||
| switch v := data.(type) { | ||
| case map[string]any: | ||
| // Check if this map has a "run" key | ||
| if runValue, ok := v["run"]; ok { | ||
| if runStr, ok := runValue.(string); ok { | ||
| runBlocks = append(runBlocks, runStr) | ||
| } | ||
| } | ||
| // Recursively process all values in the map | ||
| for _, value := range v { | ||
| runBlocks = append(runBlocks, extractRunBlocks(value)...) | ||
| } | ||
| case []any: | ||
| // Recursively process all items in the slice | ||
| for _, item := range v { | ||
| runBlocks = append(runBlocks, extractRunBlocks(item)...) | ||
| } | ||
| } | ||
|
|
||
| return runBlocks | ||
| } | ||
|
|
||
| // heredocPattern holds pre-compiled regexp patterns for a single heredoc delimiter suffix. | ||
| type heredocPattern struct { | ||
| quoted *regexp.Regexp | ||
| unquoted *regexp.Regexp | ||
| } | ||
|
|
||
| // heredocPatterns are compiled once at program start for performance. | ||
| // Each entry covers one of the common delimiter suffixes used by heredocs in shell scripts. | ||
| // Since Go regex doesn't support backreferences, we match common heredoc delimiter suffixes explicitly. | ||
| // Matches both exact delimiters (EOF) and prefixed delimiters (GH_AW_SAFE_OUTPUTS_CONFIG_EOF). | ||
| var heredocPatterns = func() []heredocPattern { | ||
| suffixes := []string{"EOF", "EOL", "END", "HEREDOC", "JSON", "YAML", "SQL"} | ||
| patterns := make([]heredocPattern, len(suffixes)) | ||
| for i, suffix := range suffixes { | ||
| // Pattern for quoted delimiter ending with suffix: << 'PREFIX_SUFFIX' or << "PREFIX_SUFFIX" | ||
| // \w* matches zero or more word characters (allowing both exact match and prefixes) | ||
| // (?ms) enables multiline and dotall modes, .*? is non-greedy | ||
| // \s*\w*%s\s*$ allows for leading/trailing whitespace on the closing delimiter | ||
| patterns[i] = heredocPattern{ | ||
| quoted: regexp.MustCompile(fmt.Sprintf(`(?ms)<<\s*['"]\w*%s['"].*?\n\s*\w*%s\s*$`, suffix, suffix)), | ||
| unquoted: regexp.MustCompile(fmt.Sprintf(`(?ms)<<\s*\w*%s.*?\n\s*\w*%s\s*$`, suffix, suffix)), | ||
| } | ||
| } | ||
| return patterns | ||
| }() | ||
|
|
||
| // removeHeredocContent removes heredoc sections from shell commands. | ||
| // Heredocs (e.g., cat > file << 'EOF' ... EOF) are safe for template expressions | ||
| // because the content is written to files, not executed in the shell. | ||
| func removeHeredocContent(content string) string { | ||
| result := content | ||
| for _, p := range heredocPatterns { | ||
| result = p.quoted.ReplaceAllString(result, "# heredoc removed") | ||
| result = p.unquoted.ReplaceAllString(result, "# heredoc removed") | ||
| } | ||
| return result | ||
| } | ||
|
|
||
| // TemplateInjectionViolation represents a detected template injection risk | ||
| type TemplateInjectionViolation struct { | ||
| Expression string // The unsafe expression (e.g., "${{ github.event.issue.title }}") | ||
| Snippet string // Code snippet showing the violation context | ||
| Context string // Expression context (e.g., "github.event", "steps.*.outputs") | ||
| } | ||
|
|
||
| // extractRunSnippet extracts a relevant snippet from the run block containing the expression | ||
| func extractRunSnippet(runContent string, expression string) string { | ||
| lines := strings.SplitSeq(runContent, "\n") | ||
|
|
||
| for line := range lines { | ||
| if strings.Contains(line, expression) { | ||
| // Return the trimmed line containing the expression | ||
| trimmed := strings.TrimSpace(line) | ||
| // Limit snippet length to avoid overwhelming error messages | ||
| if len(trimmed) > 100 { | ||
| return trimmed[:97] + "..." | ||
| } | ||
| return trimmed | ||
| } | ||
| } | ||
|
|
||
| // Fallback: return the expression itself | ||
| return expression | ||
| } | ||
|
|
||
| // detectExpressionContext identifies what type of expression this is | ||
| func detectExpressionContext(expression string) string { | ||
| templateInjectionValidationLog.Printf("Detecting expression context for: %s", expression) | ||
| if strings.Contains(expression, "github.event.") { | ||
| return "github.event" | ||
| } | ||
| if strings.Contains(expression, "steps.") && strings.Contains(expression, ".outputs.") { | ||
| return "steps.*.outputs" | ||
| } | ||
| if strings.Contains(expression, "inputs.") { | ||
| return "workflow inputs" | ||
| } | ||
| return "unknown context" | ||
| } | ||
|
|
||
| // formatTemplateInjectionError formats a user-friendly error message for template injection violations | ||
| func formatTemplateInjectionError(violations []TemplateInjectionViolation) error { | ||
| var builder strings.Builder | ||
|
|
||
| builder.WriteString("template injection vulnerabilities detected in compiled workflow\n\n") | ||
| builder.WriteString("The following expressions are used directly in shell commands, which enables template injection attacks:\n\n") | ||
|
|
||
| // Group violations by context for clearer reporting | ||
| contextGroups := make(map[string][]TemplateInjectionViolation) | ||
| for _, v := range violations { | ||
| contextGroups[v.Context] = append(contextGroups[v.Context], v) | ||
| } | ||
|
|
||
| // Report violations grouped by context | ||
| for context, contextViolations := range contextGroups { | ||
| fmt.Fprintf(&builder, " %s context (%d occurrence(s)):\n", context, len(contextViolations)) | ||
|
|
||
| // Show up to 3 examples per context to keep error message manageable | ||
| maxExamples := 3 | ||
| for i, v := range contextViolations { | ||
| if i >= maxExamples { | ||
| fmt.Fprintf(&builder, " ... and %d more\n", len(contextViolations)-maxExamples) | ||
| break | ||
| } | ||
| fmt.Fprintf(&builder, " - %s\n", v.Expression) | ||
| fmt.Fprintf(&builder, " in: %s\n", v.Snippet) | ||
| } | ||
| builder.WriteString("\n") | ||
| } | ||
|
Comment on lines
+122
to
+143
|
||
|
|
||
| builder.WriteString("Security Risk:\n") | ||
| builder.WriteString(" When expressions are used directly in shell commands, an attacker can inject\n") | ||
| builder.WriteString(" malicious code through user-controlled inputs (issue titles, PR descriptions,\n") | ||
| builder.WriteString(" comments, etc.) to execute arbitrary commands, steal secrets, or modify the repository.\n\n") | ||
|
|
||
| builder.WriteString("Safe Pattern - Use environment variables instead:\n") | ||
| builder.WriteString(" env:\n") | ||
| builder.WriteString(" MY_VALUE: ${{ github.event.issue.title }}\n") | ||
| builder.WriteString(" run: |\n") | ||
| builder.WriteString(" echo \"Title: $MY_VALUE\"\n\n") | ||
|
|
||
| builder.WriteString("Unsafe Pattern - Do NOT use expressions directly:\n") | ||
| builder.WriteString(" run: |\n") | ||
| builder.WriteString(" echo \"Title: ${{ github.event.issue.title }}\" # UNSAFE!\n\n") | ||
|
|
||
| builder.WriteString("References:\n") | ||
| builder.WriteString(" - https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions\n") | ||
| builder.WriteString(" - https://docs.zizmor.sh/audits/#template-injection\n") | ||
| builder.WriteString(" - scratchpad/template-injection-prevention.md\n") | ||
|
|
||
| return fmt.Errorf("%s", builder.String()) | ||
| } | ||
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Oops, something went wrong.
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
TemplateInjectionViolationis exported (capitalized) but appears to be used only internally within theworkflowpackage. If it is not intended to be part of the package’s public API, consider unexporting it (e.g.,templateInjectionViolation) to reduce exposed surface area.