Buffer Runner

A data processing utility from 2005 was recently discovered still running in production. The developers claim it's "battle-tested" and refuse to update it.

Your mission: Find the hidden functionality and extract the flag.

Binary Information:

Filename: buffer-runner
Size:     11,948 bytes (12 KB)
MD5:      2f0cf67ebf02ea16c356fa9c061d4415
SHA1:     9f6996219874f809df57c9dc39d6f777db884f5f
SHA256:   55412e614103209c986019d6ab62c91f5ed9938010976ba992532a0950a499a8

Verify integrity after download:

md5sum buffer-runner && sha1sum buffer-runner && sha256sum buffer-runner

Environment:
- Architecture: x86 (32-bit)
- Stack protector: Disabled
- NX: Disabled (executable stack)
- PIE: Disabled
- Symbols: Not stripped

Hint: The program is kind enough to tell you something useful...

Note: Download the binary for local analysis. It reads flag.txt from the current directory — use a dummy flag for testing. The real flag can only be captured by exploiting the live instance on the lab.