expose get oidc token optioin for github sia

[havetisyan]

Description

Contribution Checklist:

• The pull request does not introduce any breaking changes
• I have read the contribution guidelines.
• Create an issue and link to the pull request.

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[gemini-code-assist]

Summary of Changes

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This pull request enhances the GitHub SIA daemon to support the retrieval of OpenID Connect (OIDC) tokens from Athenz ZTS. This enhancement allows GitHub Actions workflows to obtain and utilize OIDC tokens for authentication, improving integration with services that rely on OIDC for identity verification by exposing the token via the GITHUB_ENV.

Highlights

• OIDC Token Retrieval Flags: New command-line flags --get-oidc-token and --oidc-token-audience were introduced to enable and configure OIDC token fetching from Athenz ZTS.
• ZTS Request Enhancement: The ZTS instance registration request was updated to conditionally include OIDC token parameters (requesting a token and specifying its audience) based on the new command-line flags.
• GitHub Environment Integration: Logic was added to extract the retrieved OIDC token from the ZTS response and write it to the GITHUB_ENV file, making it accessible as an environment variable within GitHub Actions workflows.

Changelog

• provider/github/sia-actions/cmd/siad/main.go
  • Added fmt package import for string formatting.
  • Declared new variables oidcTokenAudience and getOIDCToken to manage OIDC token options.
  • Registered new command-line flags --get-oidc-token and --oidc-token-audience for user configuration.
  • Updated the PostInstanceRegisterInformation request to conditionally include OIDC token parameters when getOIDCToken is true.
  • Implemented logic to check for and write the ServiceToken (OIDC token) to the GITHUB_ENV file if getOIDCToken is enabled, ensuring it's available for subsequent workflow steps.

Activity

• No specific activity (comments, reviews, or progress updates) was provided in the context for this pull request.

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Code Review

This pull request introduces a new feature to fetch an OIDC token from ZTS along with the X.509 certificate for GitHub SIA, exporting it to the GITHUB_ENV file for GitHub Actions workflows. However, it contains a high-severity environment variable injection vulnerability and a medium-severity secret leakage issue due to improper handling of the GITHUB_ENV file and lack of secret masking.

[psasidhar]

minor comment: if "GITHUB_ENV" is not set, the information is indirectly shown to the user when OpenFile fails, and program exits.

may be, better to do a "" check and return a more direct message?