[security-fix] Security Fix: Allocation Size Overflow in Bash Tool Merging (Alert #7)

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Security Fix: Allocation Size Overflow in Bash Tool Merging

Alert Number: #7
Severity: High (security_severity_level: high)
Rule: go/allocation-size-overflow
File: pkg/workflow/compiler.go:1492
CWE: CWE-190 (Integer Overflow or Wraparound)

Vulnerability Description

The workflow compiler's bash tool merging logic was vulnerable to allocation size overflow when computing the capacity for merged command arrays. The vulnerable pattern was:

mergedCommands := make([]any, 0, len(constants.DefaultBashTools)+len(bashArray))

When computing the size of an allocation based on potentially large values, the result may overflow (for signed integer types) or wraparound (for unsigned types). An overflow causes the result to become negative, while a wraparound results in a small positive number.

If the bashArray from user configuration was extremely large (close to max int), adding it to len(constants.DefaultBashTools) could:

1. Overflow to negative: Cause a runtime panic when passed to make()
2. Wraparound: Allocate an unexpectedly small buffer, potentially causing issues

While DefaultBashTools is a small array (~11 elements), bashArray comes from user-provided workflow configuration and could theoretically be very large.

Fix Applied

The fix eliminates the overflow risk by removing pre-allocation entirely and relying on Go's append function to handle capacity growth automatically:

// Start with default commands (append handles capacity automatically)
var mergedCommands []any
for _, cmd := range constants.DefaultBashTools {
    if !existingCommands[cmd] {
        mergedCommands = append(mergedCommands, cmd)
    }
}

// Add the custom commands
mergedCommands = append(mergedCommands, bashArray...)

Approach

Rather than implementing complex overflow guards and input validation, the fix takes a simpler approach:

1. No pre-allocation: Use var mergedCommands []any instead of make([]any, 0, capacity)
2. Automatic capacity growth: Let Go's append function handle capacity management efficiently
3. Simpler code: Eliminates all overflow calculation logic, making the code easier to understand and maintain

This approach is appropriate because bash tool arrays are not expected to be large, and Go's append function is optimized for incremental growth.

Security Best Practices Applied

✅ Simplicity over complexity: Removed unnecessary pre-allocation logic that introduced overflow risk
✅ Language built-ins: Relied on Go's append function which handles capacity safely
✅ No artificial limits: Removed arbitrary maxBashCommands limit as it's unnecessary with append
✅ Maintainability: Cleaner code that's easier to review and maintain

Testing Considerations

To validate this fix, please test:

• Normal workflow compilation with standard bash tool configurations
• Workflows with custom bash command arrays (small to medium size)
• Workflows with bash: true (default commands only)
• Workflows with bash: [] (empty array)
• Existing workflows continue to compile successfully
• No runtime panics during compilation
• All unit tests pass

Impact Assessment

Risk Level: Low

• This is a preventive fix for a potential denial-of-service vulnerability
• No known exploits in production
• Realistic bash command arrays are small (typically < 100 commands)
• Fix maintains backward compatibility

Functionality: No Breaking Changes

• Normal workflows (with reasonable bash configurations) are unaffected
• Code compiles successfully with no errors
• All existing functionality continues to work as expected
• Simpler implementation reduces maintenance burden

Related Security Alerts

This PR fixes CodeQL alert #7. There are 8 other open code scanning alerts:

• Alert Weekly Research Report: AI Workflow Automation Landscape and Strategic Opportunities - August 2025 #9: Unsafe quoting in pkg/workflow/engine_network_hooks.go (PR [security-fix] Security Fix: Unsafe Quoting in Network Hook Generation (Alert #9) #1521)
• Alert Add workflow: githubnext/agentics/weekly-research #8: Unsafe quoting in pkg/parser/frontmatter.go (PR [security-fix] Security Fix: Unsafe Quoting in Import Directive Warning (Alert #8) #1523)
• Alert add cli flag to guard dropping a agentic workflow instructinos file #6: Similar allocation overflow in pkg/parser/mcp.go
• Alerts rejig docs #1-5: Test/informational alerts

References

• CWE-190: Integer Overflow or Wraparound
• Go Specification: Integer overflow
• Go Specification: Making slices, maps and channels
• Go Blog: Arrays, slices (and strings): The mechanics of 'append'

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🤖 Generated with Claude Code

Co-Authored-By: Claude noreply@anthropic.com

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