feat: support pre-hashed RSA signing for HSM-backed PKCS#11 signers

[carlosmonastyrski]

Description 📣

Type ✨

• Bug fix
• New feature
• Improvement
• Breaking change
• Documentation

Tests 🛠️

# Here's some code block to paste some code snippets

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[linear]

PKI-319

[infisical-review-police]

💬 Discussion in Slack: #pr-review-cli-320-feat-support-pre-hashed-rsa-signing-for-hsm-backed-pkcs-11-sig

Posted by Review Police — reviews, comments, new commits, and CI failures will stream into this channel.

[greptile-apps]

Greptile Summary

This PR adds CKM_RSA_PKCS as a new supported mechanism in resolveMechanism, enabling HSM-backed PKCS#11 signers to perform raw RSA PKCS#1 v1.5 signing on externally pre-hashed (DigestInfo-wrapped) data.

• A two-line case "CKM_RSA_PKCS" branch is added to the resolveMechanism switch; it always returns the raw pkcs11.CKM_RSA_PKCS constant without consulting the isDigest parameter.
• Unlike the existing CKM_ECDSA_SHA256/CKM_ECDSA_SHA384 cases — where isDigest=true redirects to the raw CKM_ECDSA mechanism — RSA PKCS mechanisms already use distinct PKCS#11 constants for hash-then-sign vs. raw, so no redirect logic is needed; however, there is also no guard preventing callers from reaching CKM_RSA_PKCS with isDigest=false.

Confidence Score: 3/5

The change is small and scoped to a single switch case, but it introduces a raw cryptographic signing path with no input-contract enforcement; a caller that omits isDigest could silently sign unhashed data.

The new CKM_RSA_PKCS case ignores isDigest, so a caller that sends the mechanism name without explicitly setting isDigest=true (the JSON zero value is false) will still reach CKM_RSA_PKCS. Many HSMs accept small raw payloads under this mechanism and will produce a PKCS#1 v1.5 signature over unhashed data — a cryptographically weak output that is structurally indistinguishable from a valid signature to a naive verifier. The ECDSA raw path (CKM_ECDSA) has the same gap but predates this PR; this PR widens the surface by adding the RSA equivalent.

packages/gateway-v2/pkcs11_enabled.go — specifically the new CKM_RSA_PKCS branch in resolveMechanism and any callers that construct signParams with this mechanism.

Important Files Changed

Filename	Overview
packages/gateway-v2/pkcs11_enabled.go	Adds CKM_RSA_PKCS raw-RSA mechanism for pre-hashed signing; isDigest is ignored for this case, unlike the ECDSA counterparts, which may allow unsigned (unhashed) data to be signed if callers omit the flag.

_{Reviews (1): Last reviewed commit: "Support pre-hashed RSA signing for HSM-b..." | Re-trigger Greptile}

[veria-ai]

PR overview

All previously flagged issues have been addressed. No open security concerns remain on this pull request.

Security review

No open security issues remain on this pull request.

Fixed/addressed: 1 · PR risk: 0/10