crypto: poly1305 - expose init/update/final library interface

Expose the existing generic Poly1305 code via a init/update/final
library interface so that callers are not required to go through
the crypto API's shash abstraction to access it. At the same time,
make some preparations so that the library implementation can be
superseded by an accelerated arch-specific version in the future.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

2 files changed, 100 insertions, 0 deletions

diff --git a/lib/crypto/Kconfig b/lib/crypto/Kconfig
index c4882d29879e..a731ea36bd5c 100644
--- a/lib/crypto/Kconfig
+++ b/lib/crypto/Kconfig
@@ -37,8 +37,34 @@ config CRYPTO_LIB_CHACHA
 config CRYPTO_LIB_DES
 	tristate
 
+config CRYPTO_LIB_POLY1305_RSIZE
+	int
+	default 1
+
+config CRYPTO_ARCH_HAVE_LIB_POLY1305
+	tristate
+	help
+	  Declares whether the architecture provides an arch-specific
+	  accelerated implementation of the Poly1305 library interface,
+	  either builtin or as a module.
+
 config CRYPTO_LIB_POLY1305_GENERIC
 	tristate
+	help
+	  This symbol can be depended upon by arch implementations of the
+	  Poly1305 library interface that require the generic code as a
+	  fallback, e.g., for SIMD implementations. If no arch specific
+	  implementation is enabled, this implementation serves the users
+	  of CRYPTO_LIB_POLY1305.
+
+config CRYPTO_LIB_POLY1305
+	tristate "Poly1305 library interface"
+	depends on CRYPTO_ARCH_HAVE_LIB_POLY1305 || !CRYPTO_ARCH_HAVE_LIB_POLY1305
+	select CRYPTO_LIB_POLY1305_GENERIC if CRYPTO_ARCH_HAVE_LIB_POLY1305=n
+	help
+	  Enable the Poly1305 library interface. This interface may be fulfilled
+	  by either the generic implementation or an arch-specific one, if one
+	  is available and enabled.
 
 config CRYPTO_LIB_SHA256
 	tristate
diff --git a/lib/crypto/poly1305.c b/lib/crypto/poly1305.c
index f019a57dbc1b..32ec293c65ae 100644
--- a/lib/crypto/poly1305.c
+++ b/lib/crypto/poly1305.c
@@ -154,5 +154,79 @@ void poly1305_core_emit(const struct poly1305_state *state, void *dst)
 }
 EXPORT_SYMBOL_GPL(poly1305_core_emit);
 
+void poly1305_init_generic(struct poly1305_desc_ctx *desc, const u8 *key)
+{
+	poly1305_core_setkey(desc->r, key);
+	desc->s[0] = get_unaligned_le32(key + 16);
+	desc->s[1] = get_unaligned_le32(key + 20);
+	desc->s[2] = get_unaligned_le32(key + 24);
+	desc->s[3] = get_unaligned_le32(key + 28);
+	poly1305_core_init(&desc->h);
+	desc->buflen = 0;
+	desc->sset = true;
+	desc->rset = 1;
+}
+EXPORT_SYMBOL_GPL(poly1305_init_generic);
+
+void poly1305_update_generic(struct poly1305_desc_ctx *desc, const u8 *src,
+			     unsigned int nbytes)
+{
+	unsigned int bytes;
+
+	if (unlikely(desc->buflen)) {
+		bytes = min(nbytes, POLY1305_BLOCK_SIZE - desc->buflen);
+		memcpy(desc->buf + desc->buflen, src, bytes);
+		src += bytes;
+		nbytes -= bytes;
+		desc->buflen += bytes;
+
+		if (desc->buflen == POLY1305_BLOCK_SIZE) {
+			poly1305_core_blocks(&desc->h, desc->r, desc->buf, 1, 1);
+			desc->buflen = 0;
+		}
+	}
+
+	if (likely(nbytes >= POLY1305_BLOCK_SIZE)) {
+		poly1305_core_blocks(&desc->h, desc->r, src,
+				     nbytes / POLY1305_BLOCK_SIZE, 1);
+		src += nbytes - (nbytes % POLY1305_BLOCK_SIZE);
+		nbytes %= POLY1305_BLOCK_SIZE;
+	}
+
+	if (unlikely(nbytes)) {
+		desc->buflen = nbytes;
+		memcpy(desc->buf, src, nbytes);
+	}
+}
+EXPORT_SYMBOL_GPL(poly1305_update_generic);
+
+void poly1305_final_generic(struct poly1305_desc_ctx *desc, u8 *dst)
+{
+	__le32 digest[4];
+	u64 f = 0;
+
+	if (unlikely(desc->buflen)) {
+		desc->buf[desc->buflen++] = 1;
+		memset(desc->buf + desc->buflen, 0,
+		       POLY1305_BLOCK_SIZE - desc->buflen);
+		poly1305_core_blocks(&desc->h, desc->r, desc->buf, 1, 0);
+	}
+
+	poly1305_core_emit(&desc->h, digest);
+
+	/* mac = (h + s) % (2^128) */
+	f = (f >> 32) + le32_to_cpu(digest[0]) + desc->s[0];
+	put_unaligned_le32(f, dst + 0);
+	f = (f >> 32) + le32_to_cpu(digest[1]) + desc->s[1];
+	put_unaligned_le32(f, dst + 4);
+	f = (f >> 32) + le32_to_cpu(digest[2]) + desc->s[2];
+	put_unaligned_le32(f, dst + 8);
+	f = (f >> 32) + le32_to_cpu(digest[3]) + desc->s[3];
+	put_unaligned_le32(f, dst + 12);
+
+	*desc = (struct poly1305_desc_ctx){};
+}
+EXPORT_SYMBOL_GPL(poly1305_final_generic);
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");