Add Linux Gather Environment Variable Secrets module

[bcoles]

Metasploit post module implementation of envex.

Extracts environment variables from all accessible processes via
/proc/<pid>/environ on Linux and flags potential secrets using a
three-layer detection engine: name heuristics, value pattern matching,
and Shannon entropy analysis.

Environment variables are a primary vector for secret exposure in modern
infrastructure. Processes receive sensitive values such as API keys,
database credentials, and tokens through their environment. These persist
in /proc/<pid>/environ for the lifetime of the process and are readable
by any process with the same UID (or by root).

In practice, many hardened environments that block memory inspection
still permit reading /proc/<pid>/environ for same-user processes.

Verification Steps

1. Start msfconsole
2. Get a session on a Linux target
3. Do: use post/linux/gather/enum_env_secrets
4. Do: set SESSION <session_id>
5. Do: run
6. You should see environment variables analyzed and any detected secrets reported

[Copilot]

Pull request overview

Adds a new Metasploit post module to enumerate /proc/<pid>/environ on Linux, analyze environment variables for potential secrets, and save both raw environment data and a flagged-secrets report as loot.

Changes:

• Introduces post/linux/gather/enum_env_secrets, implementing name heuristics, provider token regex matching, and entropy-based detection.
• Stores two loot artifacts: full environment variables and a filtered secrets report with confidence levels.
• Adds user-facing module documentation including options and example output.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
modules/post/linux/gather/enum_env_secrets.rb	New post module that enumerates /proc environments and flags likely secrets via 3-layer detection.
documentation/modules/post/linux/gather/enum_env_secrets.md	Documentation for usage, options, and sample output for the new module.

[bcoles]

Broken tests are not my fault.