aes_gcm_decrypt_final(9)

💅 aes_gcm_decrypt_final(9) — like, the finale of your AES-GCM decrypt arc

Okay bestie, welcome to aes_gcm_decrypt_final, straight out of the Kernel API Manual (section 9, kernel API, iykyk). This is the last little step when you're decrypting a message with AES-GCM and you need to check the vibe — er, the authentication tag — before you trust anything you just decrypted. ✨

---

✨ SYNOPSIS ✨

int aes_gcm_decrypt_final (struct aes_gcm_ctx *ctx , const u8 *authtag
);

That's the whole signature, no cap. Returns an int, takes your context and the tag. Simple. Iconic. 🎀

---

🌸 ARGUMENTS 🌸

• ctx — An AES-GCM context. Like, the whole state of your operation lives in here, and spoiler alert: it's about to get zeroized (more on that in a sec 👀).
• authtag — The stored authentication tag. And its length? It's the authtag_len that was passed to aes_gcm_preparekey. So whatever length you told aes_gcm_preparekey about back at the start, that's the length here. Matching energy only, fr fr. 💖

---

🦋 DESCRIPTION 🦋

This is the "wrap it up" call — you finish decrypting and it checks your authentication tag.

And here's the cute little bonus: this also zeroizes ctx, so the caller doesn't need to do it. The function cleans up after itself. Main character energy, honestly. 🧹✨

---

🌈 CONTEXT 🌈

Any context. Literally any. No restrictions, go off. 🫶

---

⭐ RETURN ⭐

• 0 on success. And listen — this is the only case where any decrypted or associated data can be used. Like, periodt. If you didn't get 0, that data stays in the group chat unsent. 💀
• -EBADMSG if the message is inauthentic. Not authentic, not usable, do not pass go. 🙈

Bestie please internalize this: if the return value isn't 0, the decrypted data is not trustworthy. That's the whole point of the authentication tag. Don't be out here using unverified plaintext. 😭

---

👑 SEE ALSO 👑

All the siblings in the AES-GCM family, plus the header they live in:

• Kernel file ./include/crypto/aes-gcm.h
• struct aes_gcm_key(9)
• struct aes_gcm_ctx(9)
• aes_gcm_preparekey(9)
• aes_gcm_encrypt(9)
• aes_gcm_decrypt(9)
• aes_gcm_init(9)
• aes_gcm_auth_update(9)
• aes_gcm_encrypt_update(9)
• aes_gcm_decrypt_update(9)
• aes_gcm_encrypt_final(9)

---

💜 Okay that's the whole page, bestie — go forth and verify your tags. This lil' cutie came from ./include/crypto, dated October 2026, and it's filed under aes_gcm_decrypt_final(9). Slay, stay safe, and always check your return value. 🎀✨🔥