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…es in atomic saves Co-authored-by: himattm <6266621+himattm@users.noreply.github.com>
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Code Review
This pull request addresses a symlink vulnerability by replacing predictable temporary file names with random ones using os.CreateTemp during atomic save operations in internal/burnrate and internal/sparkline. The feedback recommends enhancing these operations by adding f.Sync() for data durability and delaying the f.Chmod call until after writing to ensure the file remains private (0600) during the write process.
| if err := f.Chmod(0644); err != nil { | ||
| f.Close() | ||
| os.Remove(tmpPath) | ||
| return nil, false, err | ||
| } | ||
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||
| if _, err := f.Write(data); err != nil { | ||
| f.Close() | ||
| os.Remove(tmpPath) | ||
| return nil, false, err | ||
| } |
There was a problem hiding this comment.
To ensure the 'atomic save' is also durable, it is recommended to call f.Sync() before closing the file. This ensures that the data is physically written to disk before the rename operation occurs. Additionally, moving f.Chmod after the write operation keeps the file private (0600) while data is being written, which is a better security practice for temporary files in shared directories like /tmp.
| if err := f.Chmod(0644); err != nil { | |
| f.Close() | |
| os.Remove(tmpPath) | |
| return nil, false, err | |
| } | |
| if _, err := f.Write(data); err != nil { | |
| f.Close() | |
| os.Remove(tmpPath) | |
| return nil, false, err | |
| } | |
| if _, err := f.Write(data); err != nil { | |
| f.Close() | |
| os.Remove(tmpPath) | |
| return nil, false, err | |
| } | |
| if err := f.Sync(); err != nil { | |
| f.Close() | |
| os.Remove(tmpPath) | |
| return nil, false, err | |
| } | |
| if err := f.Chmod(0644); err != nil { | |
| f.Close() | |
| os.Remove(tmpPath) | |
| return nil, false, err | |
| } |
| if err := f.Chmod(0644); err != nil { | ||
| f.Close() | ||
| os.Remove(tmp) | ||
| return | ||
| } | ||
|
|
||
| if _, err := f.Write(data); err != nil { | ||
| f.Close() | ||
| os.Remove(tmp) | ||
| return | ||
| } |
There was a problem hiding this comment.
To ensure the 'atomic save' is also durable, it is recommended to call f.Sync() before closing the file. This ensures that the data is physically written to disk before the rename operation occurs. Additionally, moving f.Chmod after the write operation keeps the file private (0600) while data is being written, which is a better security practice for temporary files in shared directories like /tmp.
| if err := f.Chmod(0644); err != nil { | |
| f.Close() | |
| os.Remove(tmp) | |
| return | |
| } | |
| if _, err := f.Write(data); err != nil { | |
| f.Close() | |
| os.Remove(tmp) | |
| return | |
| } | |
| if _, err := f.Write(data); err != nil { | |
| f.Close() | |
| os.Remove(tmp) | |
| return | |
| } | |
| if err := f.Sync(); err != nil { | |
| f.Close() | |
| os.Remove(tmp) | |
| return | |
| } | |
| if err := f.Chmod(0644); err != nil { | |
| f.Close() | |
| os.Remove(tmp) | |
| return | |
| } |
himattm
deleted the
sentinel/fix-atomic-write-symlink-vuln-6231110558570238571
branch
Understood. Acknowledging that this work is now obsolete and stopping work on this task. |
1 participant
🚨 Severity: HIGH
💡 Vulnerability: Predictable temporary file names were being used (
path + ".tmp") during atomic file saves ininternal/burnrate/burnrate.goandinternal/sparkline/sparkline.go. This makes the application susceptible to symlink attacks, enabling malicious actors to perform unintended file overwrites if the application works with caching paths under globally writable directories (like/tmp).🎯 Impact: A local attacker could exploit the predictability of
.tmpto establish symlinks pointing to sensitive files on the system, which the application would then overwrite while completing its write operations.🔧 Fix: Replaced the custom appending logic with Go's
os.CreateTemptargeting the directory of the original file path. This ensures randomly generated, collision-free temporary filenames, mitigating symlink vulnerabilities while preserving atomic rename semantics. Proper file permissions (0644) were set matching the original requirements.✅ Verification:
go build ./...go test ./...internal/burnrate/burnrate.goandinternal/sparkline/sparkline.gochanges for safety validations.PR created automatically by Jules for task 6231110558570238571 started by @himattm