fix(encryption): specify authTagLength on all AES-GCM cipher/decipher calls

[waleedlatif1]

Summary

• Adds explicit authTagLength: 16 to all createCipheriv calls, complementing fix: specify authTagLength in AES-GCM createDecipheriv calls #3881 which added it for createDecipheriv
• Ensures both encrypt and decrypt sides explicitly specify the GCM authentication tag length for full consistency and defense-in-depth

Affected Files

• apps/sim/lib/api-key/crypto.ts
• apps/sim/lib/core/security/encryption.ts
• packages/db/scripts/migrate-block-api-keys-to-byok.ts

Test plan

• Verify encryption/decryption round-trips still work (tag length matches on both sides)
• Confirm no changes to stored ciphertext format

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Project	Deployment	Actions	Updated (UTC)
docs	Ready	Preview, Comment	Apr 1, 2026 5:35pm

[cursor]

PR Summary

Medium Risk
Touches core encryption/decryption paths; while intended to be behavior-preserving, any mismatch could break decrypting previously stored secrets or migration output.

Overview
Ensures all AES-256-GCM operations explicitly use authTagLength: 16 on both createCipheriv and createDecipheriv for API key encryption, general secret encryption, and the BYOK migration script.

Also simplifies API-key ciphertext handling by requiring exactly three :-separated components (iv:encrypted:authTag) and reuses a cached ivHex, plus slightly hardens decryption error logging to handle non-Error exceptions.

^{Written by Cursor Bugbot for commit 276c281. Configure here.}

[greptile-apps]

Greptile Summary

This PR adds explicit authTagLength: 16 to all createCipheriv calls across three files, complementing PR #3881 which added it to createDecipheriv calls. The change is a defense-in-depth improvement — Node.js AES-256-GCM already defaults to a 16-byte auth tag, so there is no behavioral change to ciphertext format or stored data.

Key changes:

• apps/sim/lib/api-key/crypto.ts: Adds authTagLength: 16 to createCipheriv; refactors decryptApiKey to split the encrypted string once (avoiding a redundant .split(':') call), simplifies parse index access to direct parts[2]/parts[1], and narrows the catch error type from any to unknown.
• apps/sim/lib/core/security/encryption.ts: Adds authTagLength: 16 to both createCipheriv and createDecipheriv; improves catch (error: any) to catch (error: unknown) with proper instanceof Error narrowing.
• packages/db/scripts/migrate-block-api-keys-to-byok.ts: Adds authTagLength: 16 to both cipher and decipher calls in the standalone migration script, keeping it consistent with the app-level helpers.

All round-trips are unaffected. No migration or format change is required.

Confidence Score: 5/5

• Safe to merge — changes are additive/explicit defaults with no behavioral or format impact.
• All three files receive only the authTagLength: 16 option which matches Node.js's existing default for AES-GCM, so no encrypted data on disk is affected. The additional refactors (single split, direct index access, unknown error type) are demonstrably correct. The sole P2 comment flags a minor style inconsistency between decryptSecret and decryptApiKey parse patterns.
• No files require special attention.

Important Files Changed

Filename	Overview
apps/sim/lib/api-key/crypto.ts	Adds authTagLength: 16 to createCipheriv; refactors decryptApiKey to split once, use direct index access, and narrows error type to unknown — all correct and safe.
apps/sim/lib/core/security/encryption.ts	Adds authTagLength: 16 to createCipheriv and createDecipheriv; improves catch (error: any) → catch (error: unknown) with proper type narrowing. decryptSecret parsing style not updated to match crypto.ts, but functionally identical.
packages/db/scripts/migrate-block-api-keys-to-byok.ts	Adds authTagLength: 16 to both createCipheriv and createDecipheriv in the self-contained migration script, keeping it in sync with the app-level encryption helpers.

Sequence Diagram

sequenceDiagram
    participant Caller
    participant encryptFn as encryptSecret / encryptApiKey
    participant Node as Node.js crypto
    participant decryptFn as decryptSecret / decryptApiKey

    Caller->>encryptFn: plaintext
    encryptFn->>Node: createCipheriv('aes-256-gcm', key, iv, {authTagLength: 16})
    Node-->>encryptFn: cipher
    encryptFn->>Node: cipher.update() + cipher.final()
    Node-->>encryptFn: ciphertext (hex)
    encryptFn->>Node: cipher.getAuthTag()
    Node-->>encryptFn: authTag (16 bytes)
    encryptFn-->>Caller: "ivHex:cipherHex:authTagHex"

    Caller->>decryptFn: "ivHex:cipherHex:authTagHex"
    decryptFn->>Node: createDecipheriv('aes-256-gcm', key, iv, {authTagLength: 16})
    Node-->>decryptFn: decipher
    decryptFn->>Node: decipher.setAuthTag(authTag)
    decryptFn->>Node: decipher.update() + decipher.final()
    Node-->>decryptFn: plaintext (GCM tag verified)
    decryptFn-->>Caller: plaintext

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_{Reviews (2): Last reviewed commit: "refactor: clean up crypto modules" | Re-trigger Greptile}

[waleedlatif1]

@greptile

[waleedlatif1]

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