Preserve heredoc bodies for shell interpreters in deny checks#5
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jim80net merged 1 commit intofix/strip-heredocs-before-matchingfrom Mar 7, 2026
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StripHeredocs now preserves heredoc bodies when the heredoc is fed as stdin to a shell interpreter (bash, sh, python, ruby, perl, node, etc.). Previously, all heredoc bodies were stripped before deny rule matching, which allowed bypassing deny rules via e.g. `bash <<'EOF'\nrm -rf /\nEOF`. Non-interpreter heredocs (cat, git commit messages, PR descriptions) are still stripped as before to avoid false positives on data content. https://claude.ai/code/session_017iMvRYni3dU8UACw1Jok9c
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Mar 8, 2026
Preserve heredoc bodies for shell interpreters in deny checks
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Summary
Modified the
StripHeredocsfunction to preserve heredoc bodies when they are fed as stdin to shell interpreters (bash, sh, python, etc.), while continuing to strip heredoc bodies for other commands likecat. This ensures that deny rules can properly inspect executable code passed to interpreters.Key Changes
shellHeredocReregex pattern to detect when heredocs are piped to shell interpreters (bash, sh, dash, zsh, ksh, fish, python, ruby, perl, node, php)StripHeredocsto conditionally preserve heredoc bodies based on whether they're being fed to a shell interpreterkeepBodyflag to track whether the current heredoc body should be preserved or strippedcatcommand are still strippedImplementation Details
The solution distinguishes between two types of heredocs:
cat <<EOF) - bodies are stripped since they contain data, not executable codebash <<EOF) - bodies are preserved since they contain executable code that deny rules must inspectThe
shellHeredocRepattern matches heredoc syntax immediately following shell interpreter commands, accounting for command chaining with;,&, and|operators.https://claude.ai/code/session_017iMvRYni3dU8UACw1Jok9c