RE: [PATCH v2 08/17] crypto/cipher: Add setaad/gettag for AEAD modes

> -----Original Message-----
> From: Jamin Lin <[email protected]>
> Sent: Wednesday, July 15, 2026 11:33 AM
> To: Daniel P. Berrangé <[email protected]>; Cédric Le Goater
> <[email protected]>; Peter Maydell <[email protected]>; Steven Lee
> <[email protected]>; Troy Lee <[email protected]>; Kane Chen
> <[email protected]>; Andrew Jeffery
> <[email protected]>; Joel Stanley <[email protected]>; Eric Blake
> <[email protected]>; Markus Armbruster <[email protected]>; Fabiano
> Rosas <[email protected]>; Laurent Vivier <[email protected]>; Paolo Bonzini
> <[email protected]>; open list:All patches CC here
> <[email protected]>; open list:ASPEED BMCs
> <[email protected]>
> Cc: Jamin Lin <[email protected]>; Troy Lee
> <[email protected]>
> Subject: [PATCH v2 08/17] crypto/cipher: Add setaad/gettag for AEAD modes
> 
> AEAD modes such as GCM authenticate optional associated data (AAD) and
> produce an authentication tag, which the block-cipher encrypt/decrypt
> interface cannot express. Add qcrypto_cipher_setaad() and
> qcrypto_cipher_gettag() plus the matching backend driver hooks. The generic
> front-end reports an error when the selected mode's driver does not
> implement them, so calling them on a non-AEAD mode fails cleanly.
> 
> Signed-off-by: Jamin Lin <[email protected]>
> Reviewed-by: Daniel P. Berrangé <[email protected]>
> ---
>  crypto/cipherpriv.h     |  8 ++++++++
>  include/crypto/cipher.h | 36 ++++++++++++++++++++++++++++++++++++
>  crypto/cipher.c         | 31 +++++++++++++++++++++++++++++++
>  3 files changed, 75 insertions(+)
> 
> diff --git a/crypto/cipherpriv.h b/crypto/cipherpriv.h index
> 64737ce961..c4f995f369 100644
> --- a/crypto/cipherpriv.h
> +++ b/crypto/cipherpriv.h
> @@ -34,6 +34,14 @@ struct QCryptoCipherDriver {
>                          const uint8_t *iv, size_t niv,
>                          Error **errp);
> 
> +    int (*cipher_setaad)(QCryptoCipher *cipher,
> +                         const uint8_t *aad, size_t len,
> +                         Error **errp);
> +
> +    int (*cipher_gettag)(QCryptoCipher *cipher,
> +                         uint8_t *tag, size_t len,
> +                         Error **errp);
> +
>      void (*cipher_free)(QCryptoCipher *cipher);  };
> 
> diff --git a/include/crypto/cipher.h b/include/crypto/cipher.h index
> 92939310ef..2e361411b9 100644
> --- a/include/crypto/cipher.h
> +++ b/include/crypto/cipher.h
> @@ -235,4 +235,40 @@ int qcrypto_cipher_setiv(QCryptoCipher *cipher,
>                           const uint8_t *iv, size_t niv,
>                           Error **errp);
> 
> +/**
> + * qcrypto_cipher_setaad:
> + * @cipher: the cipher object
> + * @aad: the associated data to authenticate
> + * @len: the length of @aad
> + * @errp: pointer to a NULL-initialized error object
> + *
> + * For AEAD modes such as GCM, feed the associated data (AAD) that is
> + * authenticated but not encrypted. It must be called after
> + * qcrypto_cipher_setiv() and before the first encrypt/decrypt call. It
> +is
> + * an error to call this on a mode that is not an AEAD mode.
> + *
> + * Returns: 0 on success, -1 on error
> + */
> +int qcrypto_cipher_setaad(QCryptoCipher *cipher,
> +                          const uint8_t *aad, size_t len,
> +                          Error **errp);
> +
> +/**
> + * qcrypto_cipher_gettag:
> + * @cipher: the cipher object
> + * @tag: buffer to receive the authentication tag
> + * @len: the length of @tag
> + * @errp: pointer to a NULL-initialized error object
> + *
> + * For AEAD modes such as GCM, read back the authentication tag
> +computed
> + * over the associated data and the message. It must be called after
> +the
> + * encrypt/decrypt operation. It is an error to call this on a mode
> +that is
> + * not an AEAD mode.
> + *
> + * Returns: 0 on success, -1 on error
> + */
> +int qcrypto_cipher_gettag(QCryptoCipher *cipher,
> +                          uint8_t *tag, size_t len,
> +                          Error **errp);
> +
>  #endif /* QCRYPTO_CIPHER_H */
> diff --git a/crypto/cipher.c b/crypto/cipher.c index 52d071a90c..67014aad6f
> 100644
> --- a/crypto/cipher.c
> +++ b/crypto/cipher.c
> @@ -205,6 +205,37 @@ int qcrypto_cipher_setiv(QCryptoCipher *cipher,  }
> 
> 
> +int qcrypto_cipher_setaad(QCryptoCipher *cipher,
> +                          const uint8_t *aad, size_t len,
> +                          Error **errp) {
> +    const QCryptoCipherDriver *drv = cipher->driver;
> +
> +    if (!drv->cipher_setaad) {
> +        error_setg(errp, "The cipher mode does not support associated
> data");
> +        return -1;
> +    }
> +
> +    return drv->cipher_setaad(cipher, aad, len, errp); }
> +
> +
> +int qcrypto_cipher_gettag(QCryptoCipher *cipher,
> +                          uint8_t *tag, size_t len,
> +                          Error **errp) {
> +    const QCryptoCipherDriver *drv = cipher->driver;
> +
> +    if (!drv->cipher_gettag) {
> +        error_setg(errp,
> +                   "The cipher mode does not produce an authentication
> tag");
> +        return -1;
> +    }
> +
> +    return drv->cipher_gettag(cipher, tag, len, errp); }
> +
> +
>  void qcrypto_cipher_free(QCryptoCipher *cipher)  {
>      if (cipher) {
> --
> 2.43.0

Reviewed-by: Kane Chen <[email protected]>