🛡️ Sentinel: [CRITICAL] Fix symlink attack vulnerability in atomic file writes#85
🛡️ Sentinel: [CRITICAL] Fix symlink attack vulnerability in atomic file writes#85
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…le writes Co-authored-by: himattm <6266621+himattm@users.noreply.github.com>
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Code Review
This pull request improves the security of atomic file writes in the burnrate and sparkline packages by replacing predictable temporary file names with os.CreateTemp, mitigating potential symlink attacks. The review feedback suggests further enhancing security by removing the explicit Chmod calls to maintain the default secure permissions (0600) and adding Sync() calls to ensure data durability before renaming the temporary files.
| if err := tmpFile.Chmod(0644); err != nil { | ||
| tmpFile.Close() | ||
| os.Remove(tmpPath) | ||
| return nil, false, err | ||
| } |
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The temporary file is created in the system's temporary directory (/tmp). Using 0644 permissions allows any local user to read the snapshot data, which contains session-specific information. Since os.CreateTemp already creates the file with secure 0600 permissions (owner read/write only), it is recommended to remove this Chmod call unless world-readability is explicitly required for other processes.
| if _, err := tmpFile.Write(data); err != nil { | ||
| tmpFile.Close() | ||
| os.Remove(tmpPath) | ||
| return nil, false, err | ||
| } |
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To ensure the atomic write is durable, tmpFile.Sync() should be called before closing the file. This guarantees that the data is flushed to stable storage before the rename operation occurs, preventing data loss or corruption in the event of a system crash.
| if _, err := tmpFile.Write(data); err != nil { | |
| tmpFile.Close() | |
| os.Remove(tmpPath) | |
| return nil, false, err | |
| } | |
| if _, err := tmpFile.Write(data); err != nil { | |
| tmpFile.Close() | |
| os.Remove(tmpPath) | |
| return nil, false, err | |
| } | |
| if err := tmpFile.Sync(); err != nil { | |
| tmpFile.Close() | |
| os.Remove(tmpPath) | |
| return nil, false, err | |
| } |
| if err := tmpFile.Chmod(0644); err != nil { | ||
| tmpFile.Close() | ||
| os.Remove(tmpPath) | ||
| return | ||
| } |
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The temporary file is created in the system's temporary directory. Using 0644 permissions allows any local user to read the sparkline data. Since os.CreateTemp already creates the file with secure 0600 permissions, it is recommended to remove this Chmod call unless world-readability is explicitly required.
| if _, err := tmpFile.Write(data); err != nil { | ||
| tmpFile.Close() | ||
| os.Remove(tmpPath) | ||
| return | ||
| } |
There was a problem hiding this comment.
To ensure the atomic write is durable, tmpFile.Sync() should be called before closing the file. This guarantees that the data is flushed to stable storage before the rename operation occurs, preventing data loss or corruption in the event of a system crash.
| if _, err := tmpFile.Write(data); err != nil { | |
| tmpFile.Close() | |
| os.Remove(tmpPath) | |
| return | |
| } | |
| if _, err := tmpFile.Write(data); err != nil { | |
| tmpFile.Close() | |
| os.Remove(tmpPath) | |
| return | |
| } | |
| if err := tmpFile.Sync(); err != nil { | |
| tmpFile.Close() | |
| os.Remove(tmpPath) | |
| return | |
| } |
Understood. Acknowledging that this work is superseded and stopping work on this task. |
1 participant
🚨 Severity: CRITICAL
💡 Vulnerability: The use of predictable temporary file names (appending
.tmpto the original path) during atomic writes opens a window for a symlink attack. An attacker with write access to the temporary directory could pre-create a symlink with the predictable name, causing arbitrary files to be overwritten when the temporary file is created.🎯 Impact: Local privilege escalation or arbitrary file overwrite.
🔧 Fix: Replaced predictable temporary file creation with
os.CreateTemp, ensuring unpredictable names. Permissions are explicitly set and the file descriptor is closed before the atomic rename to ensure cross-platform compatibility.✅ Verification: Tested atomic write patterns via standard library tools. Confirmed successful test runs
go test ./....PR created automatically by Jules for task 17060932732088299257 started by @himattm