🛡️ Sentinel: [HIGH] Fix predictable temp file names#51
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Co-authored-by: himattm <6266621+himattm@users.noreply.github.com>
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Code Review
This pull request addresses a security vulnerability by replacing predictable temporary file names with os.CreateTemp in internal/burnrate/burnrate.go and internal/sparkline/sparkline.go. Feedback was provided to improve the robustness of these changes by checking for errors during f.Close() to ensure data integrity before renaming and utilizing defer os.Remove() for more reliable cleanup of temporary files.
| tmpPath := f.Name() | ||
| if _, err := f.Write(data); err != nil { | ||
| f.Close() | ||
| os.Remove(tmpPath) | ||
| return nil, false, err | ||
| } | ||
| f.Close() | ||
| os.Chmod(tmpPath, 0644) | ||
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| if err := os.Rename(tmpPath, path); err != nil { | ||
| os.Remove(tmpPath) | ||
| return nil, false, err |
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The errors from f.Close() and os.Chmod() are currently ignored. Checking the error from f.Close() is critical because it can reveal issues like disk full or I/O errors that occurred during the final flush. If Close fails, the file on disk might be incomplete, and proceeding to os.Rename would replace the target file with corrupted data. Additionally, using defer os.Remove(tmpPath) simplifies the logic by ensuring the temporary file is cleaned up on any failure path.
tmpPath := f.Name()
defer os.Remove(tmpPath)
if _, err := f.Write(data); err != nil {
f.Close()
return nil, false, err
}
if err := f.Chmod(0644); err != nil {
f.Close()
return nil, false, err
}
if err := f.Close(); err != nil {
return nil, false, err
}
if err := os.Rename(tmpPath, path); err != nil {
return nil, false, err
}| tmp := f.Name() | ||
| if _, err := f.Write(data); err != nil { | ||
| f.Close() | ||
| os.Remove(tmp) | ||
| return | ||
| } | ||
| os.Rename(tmp, path) | ||
| f.Close() | ||
| os.Chmod(tmp, 0644) | ||
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| if err := os.Rename(tmp, path); err != nil { | ||
| os.Remove(tmp) | ||
| } |
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Similar to the changes in burnrate.go, the error from f.Close() should be checked to ensure data integrity before renaming the file. Even though this function does not return an error, checking f.Close() ensures that we don't overwrite the existing cache with potentially corrupted data if the write/flush failed. Using defer os.Remove(tmp) also provides a cleaner way to handle temporary file cleanup across all error paths.
tmp := f.Name()
defer os.Remove(tmp)
if _, err := f.Write(data); err != nil {
f.Close()
return
}
f.Chmod(0644)
if err := f.Close(); err != nil {
return
}
if err := os.Rename(tmp, path); err != nil {
return
}
Understood. Acknowledging that this work is now superseded and stopping work on this task. |
1 participant
🚨 Severity: HIGH
💡 Vulnerability: Predictable temporary file names were used (
path + ".tmp") withos.WriteFilein shared temporary directories. Sinceos.WriteFilefollows existing symlinks, this creates a vulnerability where an attacker could pre-create a symlink at the predicted path to overwrite arbitrary files that the user running the application has write access to.🎯 Impact: Local attacker with access to the shared temp directory could conduct a symlink attack to overwrite sensitive files.
🔧 Fix: Replaced predictable
.tmpfile paths withos.CreateTempto generate random, unpredictable temporary file names. Ensured temporary files are closed before renaming to avoid cross-platform locking issues, and restored correct file permissions (0644).✅ Verification: Review the changes in
internal/burnrate/burnrate.goandinternal/sparkline/sparkline.goto confirmos.CreateTempis utilized. Rungo test ./...to ensure all functionality remains correct.PR created automatically by Jules for task 9138451665521596298 started by @himattm