V8.00.000.2025.06.17

Signed-off-by: Marc S. Weidner <msw@coresecret.dev>

docs/man/ERROR_HANDLING.md

@@ -29,21 +29,54 @@ and governs how the shell reacts to unexpected states, variable misuses, and sub
 
 The following Bash options are set to enforce secure and fail-fast behavior:
 
-- `errexit` (`set -e`): Immediately aborts execution on non-zero exit status.
-- `errtrace` (`set -E`): Ensures that `ERR` traps are inherited in functions and subshells.
-- `functrace` (`set -T`): Allows `DEBUG` and `RETURN` traps to be inherited as well.
-- `ignoreeof`: Prevents accidental termination via Ctrl-D on interactive shells.
-- `nounset` (`set -u`): Fails on use of undeclared variables.
-- `pipefail`: Propagates the first failing command's exit code in pipelines.
-- `noclobber` (`set -C`): Disallows overwriting of existing files via output redirection.
+#### 2.2.2.1. `set` Options
 
-### 2.2.3. Paradigm
+| Option             | Purpose                                                                                                      |
+|--------------------|--------------------------------------------------------------------------------------------------------------|
+| `errexit` (`-e`)   | Immediately exits the script if any command returns a non-zero status. Prevents silent failure continuation. |
+| `errtrace` (`-E`)  | Ensures that `ERR` traps are inherited by functions and subshells, maintaining error-handling consistency.   |
+| `functrace` (`-T`) | Ensures that `DEBUG` and `RETURN` traps are inherited, enabling full-stack debug tracing.                    |
+| `ignoreeof`        | Prevents accidental shell termination from a stray `EOF` (Ctrl-D) in interactive sessions.                   |
+| `noclobber` (`-C`) | Prohibits overwriting existing files via output redirection, mitigating destructive accidents.               |
+| `nounset` (`-u`)   | Treats use of undefined variables as fatal errors, preventing unpredictable logic paths.                     |
+| `pipefail`         | Returns the exit status of the first failed command in a pipeline, avoiding false-positive success states.   |
+
+#### 2.2.2.2. `shopt` Options
+
+| Option            | State | Purpose                                                                                                                    |
+|-------------------|-------|----------------------------------------------------------------------------------------------------------------------------|
+| `failglob`        | `on`  | Causes filename expansion to fail if no matches are found, avoiding unintended literal pattern usage.                      |
+| `inherit_errexit` | `on`  | Preserves `errexit` behaviour inside command substitutions, ensuring subshells do not mask failures.                       |
+| `lastpipe`        | `on`  | Runs the last command in a pipeline in the current shell (non-job-control mode), preserving variables set in that command. |
+| `expand_aliases`  | `off` | Disables alias expansion in non-interactive mode to maintain predictable parsing and avoid hidden behaviours.              |
+| `dotglob`         | `off` | Prevents inclusion of dotfiles in filename expansion unless explicitly requested, avoiding unintentional file processing.  |
+| `extglob`         | `off` | Disables extended pattern matching by default, reducing syntactic ambiguity unless explicitly enabled.                     |
+| `nullglob`        | `off` | Prevents non-matching globs from expanding to empty strings, preserving error signalling.                                  |
+
+#### 2.2.2.3. Environment Variables
+
+* **`PATH`** Explicitly set to a minimal, trusted search path: ``/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin``
+  This minimizes the risk of executing binaries from untrusted directories.
+* **`IFS`** Reset to the canonical safe value for whitespace splitting. This mitigates word-splitting injection vulnerabilities.
+* **`umask 0022`** Ensures newly created files are world-readable but only writable by their owner. This is a conservative 
+  default that prevents accidental creation of files with overly permissive access rights.
+
+### 2.2.3 Security Considerations
+
+- **Fail-fast principle**: By combining `set -Ceuo pipefail` with strict `shopt` rules, unexpected runtime states result in 
+  immediate termination and diagnostic reporting.
+- **Predictability**: Disabled features (such as `extglob`, `expand_aliases`) prevent accidental reliance on non-portable or 
+  side-effect-prone shell behavior.
+- **Isolation**: A fixed `PATH` ensures that only known system binaries are invoked, neutralizing the risk of executing 
+  malicious binaries from user-writable directories.
+- **Consistency across contexts**: `inherit_errexit` ensures subshell and function calls do not silently bypass global error policy.
+
+### 2.2.4. Paradigm
 
 All scripts and modules in the **CISS.debian.installer** framework operate under the principle of deterministic failure and 
 exhaustive state introspection. The defined options anticipate and actively prevent common scripting failures due to overlooked 
 conditions or shell misbehavior.
 
-
 ## 2.3. [0060_trap_err.sh](../../lib/cdi_0060_traps/0060_trap_err.sh)
 
 ### 2.3.1. Purpose