On Tue, Jan 26, 2016 at 07:20:59AM +0100, Stephan Mueller wrote:

+/*
+ * Implementation of the KDF in counter mode according to SP800-108 section 5.1.
+ *
+ * The caller must provide Label || 0x00 || Context in src. This src pointer
+ * may also be NULL if the caller wishes not to provide anything.
+ */
+static int crypto_kdf_ctr_random(struct crypto_rng *rng,
+				 const u8 *src, unsigned int slen,
+				 u8 *dst, unsigned int dlen)
+{
+	struct crypto_kdf_ctx *ctx = crypto_tfm_ctx(crypto_rng_tfm(rng));
+	struct shash_desc *desc = &ctx->shash;
+	unsigned int h = crypto_shash_digestsize(desc->tfm);
+	int err = 0;
+	u8 *dst_orig = dst;
+	u32 i = 1;
+	u8 iteration[sizeof(u32)];
+
+	/* enforce the note from above */
+	if (dlen != h && src == dst)
+		return -EINVAL;

Why is this an RNG? It always produces exactly h bytes so it looks
like a hash function to me, no?

Cheers,
-- 
Email: Herbert Xu [off-list ref]
Home Page: http://gondor.apana.org.au/~herbert/
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