[template-graph] Add User-Side Data Encryption From Workflow Template Graph

[csegarragonz]

Closes #40

[gemini-code-assist]

Summary of Changes

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This pull request introduces a new template-graph Rust crate that enables user-side data encryption for workflow template graphs. It integrates a Ciphertext-Policy Attribute-Based Encryption (CP-ABE) scheme to secure data bundles associated with workflow nodes. The changes include defining the structure of workflow graphs, implementing policy compilation logic that considers workflow, node, and ancestral dependencies, and enhancing the underlying ABE library with necessary FFI wrappers and public modules. This allows for fine-grained access control over workflow data based on user attributes and workflow structure.

Highlights

• New template-graph Crate: A new Rust crate named template-graph has been introduced to define, parse, and manage workflow template graphs, which are YAML files specifying serverless workflow structures, security policies, and data dependencies.
• User-Side Data Encryption: The pull request implements user-side data encryption for workflow template graphs, leveraging the Ciphertext-Policy Attribute-Based Encryption (CP-ABE) scheme from the accless-abe4 library to secure data bundles associated with workflow nodes.
• Policy Compilation Logic: New logic has been added to compile comprehensive access control policies for each workflow node. These policies dynamically incorporate workflow identifiers, node-specific identifiers, and ancestral dependencies within the graph, ensuring robust access control.
• accless-abe4 Library Enhancements: The accless-abe4 library has been updated to expose its policy and scheme modules publicly, and FFI (Foreign Function Interface) wrappers for encrypt_abe4 and decrypt_abe4 now include detailed documentation for external use.
• Dependency Updates: The project's dependencies have been updated in Cargo.toml and Cargo.lock to include blake3 for hashing, and arrayref, arrayvec, and constant_time_eq to support the new cryptographic and data structure functionalities.
• Policy Validation: The TemplateGraph parsing now includes validation checks to ensure that policy attributes do not contain dashes and that all referenced authorities in policies are correctly defined within the workflow configuration, preventing malformed policies.

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Code Review

This pull request introduces a new template-graph crate for parsing and processing workflow templates, enabling user-side data encryption. The implementation is well-structured, with clear data models for the workflow graph and a policy compiler to generate ABE policies. I've identified a couple of high-severity issues related to potential panics and a bug in graph traversal that should be addressed. I've also suggested an improvement to the validation logic to make it more robust.