[gnutls-devel] GnuTLS | WIP: Add Linux kernel AF_ALG backend (!1404)

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Stephan Mueller commented on a discussion on lib/accelerated/afalg.c: https://gitlab.com/gnutls/gnutls/-/merge_requests/1404#note_531265170

> +	}
> +
> +	return 0;
> +}
> +
> +static int afalg_aead_decrypt(void *_ctx,
> +			      const void *nonce, size_t nonce_size,
> +			      const void *auth, size_t auth_size,
> +			      size_t tag_size,
> +			      const void *encr, size_t encr_size,
> +			      void *plain, size_t plain_size)
> +{
> +	struct kcapi_aead_ctx *ctx = _ctx;
> +	struct iovec iov[3];
> +	uint32_t iovlen = 2;
> +	uint8_t authtmp[auth_size];

Or a combo of stack and heap?

For example, we could use something like the following that I used in a kernel patch:

```
        u8 tmpbuf[LRNG_DRNG_BLOCKSIZE] __aligned(LRNG_KCAPI_ALIGN);
        u8 *tmp_large = NULL, *tmp = tmpbuf;
        u32 tmplen = sizeof(tmpbuf);

        /*
         * Satisfy large read requests -- as the common case are smaller
         * request sizes, such as 16 or 32 bytes, avoid a kmalloc overhead for
         * those by using the stack variable of tmpbuf.
         */
        if (!CONFIG_BASE_SMALL && (nbytes > sizeof(tmpbuf))) {
                tmplen = min_t(u32, nbytes, LRNG_DRNG_MAX_REQSIZE);
                tmp_large = kmalloc(tmplen + LRNG_KCAPI_ALIGN, GFP_KERNEL);
                if (!tmp_large)
                        tmplen = sizeof(tmpbuf);
                else
                        tmp = PTR_ALIGN(tmp_large, LRNG_KCAPI_ALIGN);
        }
...
        /* Wipe data just returned from memory */
        if (tmp_large)
                kfree_sensitive(tmp_large);
        else
                memzero_explicit(tmpbuf, sizeof(tmpbuf));
```

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