Add reference ChaCha20 and Poly1305 implementations.

Reviewed-by: Emilia Käsper <emilia@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Kurt Roeckx <kurt@openssl.org>

7 files changed, 1319 insertions, 2 deletions

diff --git a/Makefile.org b/Makefile.org
index 8f64a987bc..cadcaadca0 100644
--- a/Makefile.org
+++ b/Makefile.org
@@ -138,8 +138,8 @@ INSTALL_SUBS= engines apps tools
 # dirs in crypto to build
 SDIRS=  \
 	objects \
-	md2 md4 md5 sha mdc2 hmac ripemd whrlpool \
-	des aes rc2 rc4 rc5 idea bf cast camellia seed modes \
+	md2 md4 md5 sha mdc2 hmac ripemd whrlpool poly1305 \
+	des aes rc2 rc4 rc5 idea bf cast camellia seed chacha modes \
 	bn ec rsa dsa dh dso engine \
 	buffer bio stack lhash rand err \
 	evp asn1 pem x509 x509v3 conf txt_db pkcs7 pkcs12 comp ocsp ui \
diff --git a/crypto/chacha/Makefile b/crypto/chacha/Makefile
new file mode 100644
index 0000000000..cd249b1adf
--- /dev/null
+++ b/crypto/chacha/Makefile
@@ -0,0 +1,67 @@
+#
+# OpenSSL/crypto/chacha/Makefile
+#
+
+DIR=	chacha
+TOP=	../..
+CC=	cc
+CPP=    $(CC) -E
+INCLUDES=
+CFLAG=-g
+AR=		ar r
+
+CHACHA_ENC=chacha_enc.o
+
+CFLAGS= $(INCLUDES) $(CFLAG)
+ASFLAGS= $(INCLUDES) $(ASFLAG)
+AFLAGS= $(ASFLAGS)
+
+GENERAL=Makefile
+TEST=chachatest.c
+APPS=
+
+LIB=$(TOP)/libcrypto.a
+LIBSRC=chacha_enc.c
+LIBOBJ=$(CHACHA_ENC)
+
+SRC= $(LIBSRC)
+
+ALL=    $(GENERAL) $(SRC) $(HEADER)
+
+top:
+	(cd ../..; $(MAKE) DIRS=crypto SDIRS=$(DIR) sub_all)
+
+all:	lib
+
+lib:	$(LIBOBJ)
+	$(AR) $(LIB) $(LIBOBJ)
+	$(RANLIB) $(LIB) || echo Never mind.
+	@touch lib
+
+files:
+	$(PERL) $(TOP)/util/files.pl Makefile >> $(TOP)/MINFO
+
+tags:
+	ctags $(SRC)
+
+tests:
+
+lint:
+	lint -DLINT $(INCLUDES) $(SRC)>fluff
+
+update:	depend
+
+depend:
+	@[ -n "$(MAKEDEPEND)" ] # should be set by upper Makefile...
+	$(MAKEDEPEND) -- $(CFLAG) $(INCLUDES) $(DEPFLAG) -- $(PROGS) $(LIBSRC)
+
+dclean:
+	$(PERL) -pe 'if (/^# DO NOT DELETE THIS LINE/) {print; exit(0);}' $(MAKEFILE) >Makefile.new
+	mv -f Makefile.new $(MAKEFILE)
+
+clean:
+	rm -f *.s *.o *.obj lib tags core .pure .nfs* *.old *.bak fluff
+
+# DO NOT DELETE THIS LINE -- make depend depends on it.
+
+chacha_enc.o: ../include/internal/chacha.h chacha_enc.c
diff --git a/crypto/chacha/chacha_enc.c b/crypto/chacha/chacha_enc.c
new file mode 100644
index 0000000000..281a9be8a8
--- /dev/null
+++ b/crypto/chacha/chacha_enc.c
@@ -0,0 +1,157 @@
+/* ====================================================================
+ * Copyright (c) 2011-2013 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    licensing@OpenSSL.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ */
+
+/* Adapted from the public domain code by D. Bernstein from SUPERCOP. */
+
+#include <string.h>
+
+#include "internal/chacha.h"
+
+typedef unsigned int u32;
+typedef unsigned char u8;
+typedef union {
+    u32 u[16];
+    u8 c[64];
+} chacha_buf;
+
+# define ROTATE(v, n) (((v) << (n)) | ((v) >> (32 - (n))))
+
+# define U32TO8_LITTLE(p, v) do { \
+                                (p)[0] = (u8)(v >>  0); \
+                                (p)[1] = (u8)(v >>  8); \
+                                (p)[2] = (u8)(v >> 16); \
+                                (p)[3] = (u8)(v >> 24); \
+                                } while(0)
+
+/* QUARTERROUND updates a, b, c, d with a ChaCha "quarter" round. */
+# define QUARTERROUND(a,b,c,d) ( \
+                x[a] += x[b], x[d] = ROTATE((x[d] ^ x[a]),16), \
+                x[c] += x[d], x[b] = ROTATE((x[b] ^ x[c]),12), \
+                x[a] += x[b], x[d] = ROTATE((x[d] ^ x[a]), 8), \
+                x[c] += x[d], x[b] = ROTATE((x[b] ^ x[c]), 7)  )
+
+/* chacha_core performs 20 rounds of ChaCha on the input words in
+ * |input| and writes the 64 output bytes to |output|. */
+static void chacha20_core(chacha_buf *output, const u32 input[16])
+{
+    u32 x[16];
+    int i;
+    const union {
+        long one;
+        char little;
+    } is_endian = { 1 };
+
+    memcpy(x, input, sizeof(x));
+
+    for (i = 20; i > 0; i -= 2) {
+        QUARTERROUND(0, 4, 8, 12);
+        QUARTERROUND(1, 5, 9, 13);
+        QUARTERROUND(2, 6, 10, 14);
+        QUARTERROUND(3, 7, 11, 15);
+        QUARTERROUND(0, 5, 10, 15);
+        QUARTERROUND(1, 6, 11, 12);
+        QUARTERROUND(2, 7, 8, 13);
+        QUARTERROUND(3, 4, 9, 14);
+    }
+
+    if (is_endian.little) {
+        for (i = 0; i < 16; ++i)
+            output->u[i] = x[i] + input[i];
+    } else {
+        for (i = 0; i < 16; ++i)
+            U32TO8_LITTLE(output->c + 4 * i, (x[i] + input[i]));
+    }
+}
+
+void ChaCha20_ctr32(unsigned char *out, const unsigned char *inp,
+                    size_t len, const unsigned int key[8],
+                    const unsigned int counter[4])
+{
+    u32 input[16];
+    chacha_buf buf;
+    size_t todo, i;
+
+    /* sigma constant "expand 32-byte k" in little-endian encoding */
+    input[0] = ((u32)'e') | ((u32)'x'<<8) | ((u32)'p'<<16) | ((u32)'a'<<24);
+    input[1] = ((u32)'n') | ((u32)'d'<<8) | ((u32)' '<<16) | ((u32)'3'<<24);
+    input[2] = ((u32)'2') | ((u32)'-'<<8) | ((u32)'b'<<16) | ((u32)'y'<<24);
+    input[3] = ((u32)'t') | ((u32)'e'<<8) | ((u32)' '<<16) | ((u32)'k'<<24);
+
+    input[4] = key[0];
+    input[5] = key[1];
+    input[6] = key[2];
+    input[7] = key[3];
+    input[8] = key[4];
+    input[9] = key[5];
+    input[10] = key[6];
+    input[11] = key[7];
+
+    input[12] = counter[0];
+    input[13] = counter[1];
+    input[14] = counter[2];
+    input[15] = counter[3];
+
+    while (len > 0) {
+        todo = sizeof(buf);
+        if (len < todo)
+            todo = len;
+
+        chacha20_core(&buf, input);
+
+        for (i = 0; i < todo; i++)
+            out[i] = inp[i] ^ buf.c[i];
+        out += todo;
+        inp += todo;
+        len -= todo;
+
+        /* advance counter */
+        if (++input[12] == 0)
+            input[13]++;
+    }
+}
diff --git a/crypto/include/internal/chacha.h b/crypto/include/internal/chacha.h
new file mode 100644
index 0000000000..dacbdf59dc
--- /dev/null
+++ b/crypto/include/internal/chacha.h
@@ -0,0 +1,90 @@
+/* ====================================================================
+ * Copyright (c) 2014 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    openssl-core@openssl.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ *
+ */
+
+#ifndef HEADER_CHACHA_H
+#define HEADER_CHACHA_H
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * ChaCha20_ctr32 encrypts |len| bytes from |inp| with the given key and
+ * nonce and writes the result to |out|, which may be equal to |inp|.
+ * The |key| is not 32 bytes of verbatim key material though, but the
+ * said material collected into 8 32-bit elements array in host byte
+ * order. Same approach applies to nonce: the |counter| argument is
+ * pointer to concatenated nonce and counter values collected into 4
+ * 32-bit elements. This, passing crypto material collected into 32-bit
+ * elements as opposite to passing verbatim byte vectors, is chosen for
+ * efficiency in multi-call scenarios.
+ */
+void ChaCha20_ctr32(unsigned char *out, const unsigned char *inp,
+                    size_t len, const unsigned int key[8],
+                    const unsigned int counter[4]);
+/*
+ * You can notice that there is no key setup procedure. Because it's
+ * as trivial as collecting bytes into 32-bit elements, it's reckoned
+ * that below macro is sufficient.
+ */
+#define CHACHA_U8TOU32(p)  ( \
+                ((unsigned int)(p)[0])     | ((unsigned int)(p)[1]<<8) | \
+                ((unsigned int)(p)[2]<<16) | ((unsigned int)(p)[3]<<24)  )
+
+#define CHACHA_KEY_SIZE		32
+#define CHACHA_CTR_SIZE		16
+#define CHACHA_BLK_SIZE		64
+
+#ifdef __cplusplus
+}
+#endif
+#endif
diff --git a/crypto/include/internal/poly1305.h b/crypto/include/internal/poly1305.h
new file mode 100644
index 0000000000..8e2cac5215
--- /dev/null
+++ b/crypto/include/internal/poly1305.h
@@ -0,0 +1,59 @@
+/* ====================================================================
+ * Copyright (c) 2014 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    openssl-core@openssl.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ *
+ */
+#include <stddef.h>
+
+#define POLY1305_BLOCK_SIZE 16
+
+typedef struct poly1305_context POLY1305;
+
+size_t Poly1305_ctx_size(void);
+void Poly1305_Init(POLY1305 *ctx, const unsigned char key[32]);
+void Poly1305_Update(POLY1305 *ctx, const unsigned char *inp, size_t len);
+void Poly1305_Final(POLY1305 *ctx, unsigned char mac[16]);
diff --git a/crypto/poly1305/Makefile b/crypto/poly1305/Makefile
new file mode 100644
index 0000000000..366cd110f4
--- /dev/null
+++ b/crypto/poly1305/Makefile
@@ -0,0 +1,65 @@
+#
+# OpenSSL/crypto/poly1305/Makefile
+#
+
+DIR=	poly1305
+TOP=	../..
+CC=	cc
+CPP=    $(CC) -E
+INCLUDES=
+CFLAG=-g
+AR=		ar r
+
+CFLAGS= $(INCLUDES) $(CFLAG)
+ASFLAGS= $(INCLUDES) $(ASFLAG)
+AFLAGS= $(ASFLAGS)
+
+GENERAL=Makefile
+TEST=
+APPS=
+
+LIB=$(TOP)/libcrypto.a
+LIBSRC=poly1305.c
+LIBOBJ=poly1305.o
+
+SRC= $(LIBSRC)
+
+ALL=    $(GENERAL) $(SRC) $(HEADER)
+
+top:
+	(cd ../..; $(MAKE) DIRS=crypto SDIRS=$(DIR) sub_all)
+
+all:	lib
+
+lib:	$(LIBOBJ)
+	$(AR) $(LIB) $(LIBOBJ)
+	$(RANLIB) $(LIB) || echo Never mind.
+	@touch lib
+
+files:
+	$(PERL) $(TOP)/util/files.pl Makefile >> $(TOP)/MINFO
+
+tags:
+	ctags $(SRC)
+
+tests:
+
+lint:
+	lint -DLINT $(INCLUDES) $(SRC)>fluff
+
+update:	depend
+
+depend:
+	@[ -n "$(MAKEDEPEND)" ] # should be set by upper Makefile...
+	$(MAKEDEPEND) -- $(CFLAG) $(INCLUDES) $(DEPFLAG) -- $(PROGS) $(LIBSRC)
+
+dclean:
+	$(PERL) -pe 'if (/^# DO NOT DELETE THIS LINE/) {print; exit(0);}' $(MAKEFILE) >Makefile.new
+	mv -f Makefile.new $(MAKEFILE)
+
+clean:
+	rm -f *.s *.o *.obj lib tags core .pure .nfs* *.old *.bak fluff
+
+# DO NOT DELETE THIS LINE -- make depend depends on it.
+
+poly1305.o: ../include/internal/poly1305.h poly1305.c
diff --git a/crypto/poly1305/poly1305.c b/crypto/poly1305/poly1305.c
new file mode 100644
index 0000000000..9a44f27f04
--- /dev/null
+++ b/crypto/poly1305/poly1305.c
@@ -0,0 +1,879 @@
+/* ====================================================================
+ * Copyright (c) 2015 The OpenSSL Project. All rights reserved.
+ *
+ * Rights for redistribution and usage in source and binary
+ * forms are granted according to the OpenSSL license.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "internal/poly1305.h"
+
+typedef void (*poly1305_blocks_f) (void *ctx, const unsigned char *inp,
+                                   size_t len, unsigned int padbit);
+typedef void (*poly1305_emit_f) (void *ctx, unsigned char mac[16],
+                                 const unsigned int nonce[4]);
+
+struct poly1305_context {
+    double opaque[24];  /* large enough to hold internal state, declared
+                         * 'double' to ensure at least 64-bit invariant
+                         * alignment across all platforms and
+                         * configurations */
+    unsigned int nonce[4];
+    unsigned char data[POLY1305_BLOCK_SIZE];
+    size_t num;
+    struct {
+        poly1305_blocks_f blocks;
+        poly1305_emit_f emit;
+    } func;
+};
+
+size_t Poly1305_ctx_size ()
+{
+    return sizeof(struct poly1305_context);
+}
+
+/* pick 32-bit unsigned integer in little endian order */
+static unsigned int U8TOU32(const unsigned char *p)
+{
+    return (((unsigned int)(p[0] & 0xff)) |
+            ((unsigned int)(p[1] & 0xff) << 8) |
+            ((unsigned int)(p[2] & 0xff) << 16) |
+            ((unsigned int)(p[3] & 0xff) << 24));
+}
+
+/*
+ * Implementations can be classified by amount of significant bits in
+ * words making up the multi-precision value, or in other words radix
+ * or base of numerical representation, e.g. base 2^64, base 2^32,
+ * base 2^26. Complementary characteristic is how wide is the result of
+ * multiplication of pair of digits, e.g. it would take 128 bits to
+ * accommodate multiplication result in base 2^64 case. These are used
+ * interchangeably. To describe implementation that is. But interface
+ * is designed to isolate this so that low-level primitives implemented
+ * in assembly can be self-contained/self-coherent.
+ */
+#ifndef POLY1305_ASM
+/*
+ * Even though there is __int128 reference implementation targeting
+ * 64-bit platforms provided below, it's not obvious that it's optimal
+ * choice for every one of them. Depending on instruction set overall
+ * amount of instructions can be comparable to one in __int64
+ * implementation. Amount of multiplication instructions would be lower,
+ * but not necessarily overall. And in out-of-order execution context,
+ * it is the latter that can be crucial...
+ *
+ * On related note. Poly1305 author, D. J. Bernstein, discusses and
+ * provides floating-point implementations of the algorithm in question.
+ * It made a lot of sense by the time of introduction, because most
+ * then-modern processors didn't have pipelined integer multiplier.
+ * [Not to mention that some had non-constant timing for integer
+ * multiplications.] Floating-point instructions on the other hand could
+ * be issued every cycle, which allowed to achieve better performance.
+ * Nowadays, with SIMD and/or out-or-order execution, shared or
+ * even emulated FPU, it's more complicated, and floating-point
+ * implementation is not necessarily optimal choice in every situation,
+ * rather contrary...
+ *
+ *                                              <appro@openssl.org>
+ */
+
+typedef unsigned int u32;
+
+/*
+ * poly1305_blocks processes a multiple of POLY1305_BLOCK_SIZE blocks
+ * of |inp| no longer than |len|. Behaviour for |len| not divisible by
+ * block size is unspecified in general case, even though in reference
+ * implementation the trailing chunk is simply ignored. Per algorithm
+ * specification, every input block, complete or last partial, is to be
+ * padded with a bit past most significant byte. The latter kind is then
+ * padded with zeros till block size. This last partial block padding
+ * is caller(*)'s responsibility, and because of this the last partial
+ * block is always processed with separate call with |len| set to
+ * POLY1305_BLOCK_SIZE and |padbit| to 0. In all other cases |padbit|
+ * should be set to 1 to perform implicit padding with 128th bit.
+ * poly1305_blocks does not actually check for this constraint though,
+ * it's caller(*)'s resposibility to comply.
+ *
+ * (*)  In the context "caller" is not application code, but higher
+ *      level Poly1305_* from this very module, so that quirks are
+ *      handled locally.
+ */
+static void
+poly1305_blocks(void *ctx, const unsigned char *inp, size_t len, u32 padbit);
+
+/*
+ * Type-agnostic "rip-off" from constant_time_locl.h
+ */
+# define CONSTANT_TIME_CARRY(a,b) ( \
+         (a ^ ((a ^ b) | ((a - b) ^ b))) >> (sizeof(a) * 8 - 1) \
+         )
+
+# if !defined(PEDANTIC) && \
+     (defined(__SIZEOF_INT128__) && __SIZEOF_INT128__==16) && \
+     (defined(__SIZEOF_LONG__) && __SIZEOF_LONG__==8)
+
+typedef unsigned long u64;
+typedef unsigned __int128 u128;
+
+typedef struct {
+    u64 h[3];
+    u64 r[2];
+} poly1305_internal;
+
+/* pick 32-bit unsigned integer in little endian order */
+static u64 U8TOU64(const unsigned char *p)
+{
+    return (((u64)(p[0] & 0xff)) |
+            ((u64)(p[1] & 0xff) << 8) |
+            ((u64)(p[2] & 0xff) << 16) |
+            ((u64)(p[3] & 0xff) << 24) |
+            ((u64)(p[4] & 0xff) << 32) |
+            ((u64)(p[5] & 0xff) << 40) |
+            ((u64)(p[6] & 0xff) << 48) |
+            ((u64)(p[7] & 0xff) << 56));
+}
+
+/* store a 32-bit unsigned integer in little endian */
+static void U64TO8(unsigned char *p, u64 v)
+{
+    p[0] = (unsigned char)((v) & 0xff);
+    p[1] = (unsigned char)((v >> 8) & 0xff);
+    p[2] = (unsigned char)((v >> 16) & 0xff);
+    p[3] = (unsigned char)((v >> 24) & 0xff);
+    p[4] = (unsigned char)((v >> 32) & 0xff);
+    p[5] = (unsigned char)((v >> 40) & 0xff);
+    p[6] = (unsigned char)((v >> 48) & 0xff);
+    p[7] = (unsigned char)((v >> 56) & 0xff);
+}
+
+static void poly1305_init(void *ctx, const unsigned char key[16])
+{
+    poly1305_internal *st = (poly1305_internal *) ctx;
+
+    /* h = 0 */
+    st->h[0] = 0;
+    st->h[1] = 0;
+    st->h[2] = 0;
+
+    /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
+    st->r[0] = U8TOU64(&key[0]) & 0x0ffffffc0fffffff;
+    st->r[1] = U8TOU64(&key[8]) & 0x0ffffffc0ffffffc;
+}
+
+static void
+poly1305_blocks(void *ctx, const unsigned char *inp, size_t len, u32 padbit)
+{
+    poly1305_internal *st = (poly1305_internal *)ctx;
+    u64 r0, r1;
+    u64 s1;
+    u64 h0, h1, h2, c;
+    u128 d0, d1;
+
+    r0 = st->r[0];
+    r1 = st->r[1];
+
+    s1 = r1 + (r1 >> 2);
+
+    h0 = st->h[0];
+    h1 = st->h[1];
+    h2 = st->h[2];
+
+    while (len >= POLY1305_BLOCK_SIZE) {
+        /* h += m[i] */
+        h0 = (u64)(d0 = (u128)h0 + U8TOU64(inp + 0));
+        h1 = (u64)(d1 = (u128)h1 + (d0 >> 64) + U8TOU64(inp + 8));
+        /*
+	 * padbit can be zero only when original len was
+	 * POLY1306_BLOCK_SIZE, but we don't check
+	 */
+        h2 += (u64)(d1 >> 64) + padbit;
+
+        /* h *= r "%" p, where "%" stands for "partial remainder" */
+        d0 = ((u128)h0 * r0) +
+             ((u128)h1 * s1);
+        d1 = ((u128)h0 * r1) +
+             ((u128)h1 * r0) +
+	     (h2 * s1);
+        h2 = (h2 * r0);
+
+        /* last reduction step: */
+        /* a) h2:h0 = h2<<128 + d1<<64 + d0 */
+        h0 = (u64)d0;
+        h1 = (u64)(d1 += d0 >> 64);
+        h2 += (u64)(d1 >> 64);
+        /* b) (h2:h0 += (h2:h0>>130) * 5) %= 2^130 */
+        c = (h2 >> 2) + (h2 & ~3UL);
+        h2 &= 3;
+        h0 += c;
+        h1 += (c = CONSTANT_TIME_CARRY(h0,c));   /* doesn't overflow */
+
+        inp += POLY1305_BLOCK_SIZE;
+        len -= POLY1305_BLOCK_SIZE;
+    }
+
+    st->h[0] = h0;
+    st->h[1] = h1;
+    st->h[2] = h2;
+}
+
+static void poly1305_emit(void *ctx, unsigned char mac[16],
+                          const u32 nonce[4])
+{
+    poly1305_internal *st = (poly1305_internal *) ctx;
+    u64 h0, h1, h2;
+    u64 g0, g1, g2;
+    u128 t;
+    u64 mask;
+
+    h0 = st->h[0];
+    h1 = st->h[1];
+    h2 = st->h[2];
+
+    /* compute h + -p */
+    g0 = (u64)(t = (u128)h0 + 5);
+    g1 = (u64)(t = (u128)h1 + (t >> 64));
+    g2 = h2 + (u64)(t >> 64);
+
+    /* if there was carry into 130th bit, h1:h0 = g1:g0 */
+    mask = 0 - (g2 >> 2);
+    g0 &= mask;
+    g1 &= mask;
+    mask = ~mask;
+    h0 = (h0 & mask) | g0;
+    h1 = (h1 & mask) | g1;
+
+    /* mac = (h + nonce) % (2^128) */
+    h0 = (u64)(t = (u128)h0 + nonce[0] + ((u64)nonce[1]<<32));
+    h1 = (u64)(t = (u128)h1 + nonce[2] + ((u64)nonce[3]<<32) + (t >> 64));
+
+    U64TO8(mac + 0, h0);
+    U64TO8(mac + 8, h1);
+}
+
+# else
+
+#  if defined(_WIN32) && !defined(__MINGW32__)
+typedef unsigned __int64 u64;
+#  elif defined(__arch64__)
+typedef unsigned long u64;
+#  else
+typedef unsigned long long u64;
+#  endif
+
+typedef struct {
+    u32 h[5];
+    u32 r[4];
+} poly1305_internal;
+
+/* store a 32-bit unsigned integer in little endian */
+static void U32TO8(unsigned char *p, unsigned int v)
+{
+    p[0] = (unsigned char)((v) & 0xff);
+    p[1] = (unsigned char)((v >> 8) & 0xff);
+    p[2] = (unsigned char)((v >> 16) & 0xff);
+    p[3] = (unsigned char)((v >> 24) & 0xff);
+}
+
+static void poly1305_init(void *ctx, const unsigned char key[16])
+{
+    poly1305_internal *st = (poly1305_internal *) ctx;
+
+    /* h = 0 */
+    st->h[0] = 0;
+    st->h[1] = 0;
+    st->h[2] = 0;
+    st->h[3] = 0;
+    st->h[4] = 0;
+
+    /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
+    st->r[0] = U8TOU32(&key[0]) & 0x0fffffff;
+    st->r[1] = U8TOU32(&key[4]) & 0x0ffffffc;
+    st->r[2] = U8TOU32(&key[8]) & 0x0ffffffc;
+    st->r[3] = U8TOU32(&key[12]) & 0x0ffffffc;
+}
+
+static void
+poly1305_blocks(void *ctx, const unsigned char *inp, size_t len, u32 padbit)
+{
+    poly1305_internal *st = (poly1305_internal *)ctx;
+    u32 r0, r1, r2, r3;
+    u32 s1, s2, s3;
+    u32 h0, h1, h2, h3, h4, c;
+    u64 d0, d1, d2, d3;
+
+    r0 = st->r[0];
+    r1 = st->r[1];
+    r2 = st->r[2];
+    r3 = st->r[3];
+
+    s1 = r1 + (r1 >> 2);
+    s2 = r2 + (r2 >> 2);
+    s3 = r3 + (r3 >> 2);
+
+    h0 = st->h[0];
+    h1 = st->h[1];
+    h2 = st->h[2];
+    h3 = st->h[3];
+    h4 = st->h[4];
+
+    while (len >= POLY1305_BLOCK_SIZE) {
+        /* h += m[i] */
+        h0 = (u32)(d0 = (u64)h0 + U8TOU32(inp + 0));
+        h1 = (u32)(d1 = (u64)h1 + (d0 >> 32) + U8TOU32(inp + 4));
+        h2 = (u32)(d2 = (u64)h2 + (d1 >> 32) + U8TOU32(inp + 8));
+        h3 = (u32)(d3 = (u64)h3 + (d2 >> 32) + U8TOU32(inp + 12));
+        h4 += (u32)(d3 >> 32) + padbit;
+
+        /* h *= r "%" p, where "%" stands for "partial remainder" */
+        d0 = ((u64)h0 * r0) +
+             ((u64)h1 * s3) +
+             ((u64)h2 * s2) +
+             ((u64)h3 * s1);
+        d1 = ((u64)h0 * r1) +
+             ((u64)h1 * r0) +
+             ((u64)h2 * s3) +
+             ((u64)h3 * s2) +
+             (h4 * s1);
+        d2 = ((u64)h0 * r2) +
+             ((u64)h1 * r1) +
+             ((u64)h2 * r0) +
+             ((u64)h3 * s3) +
+             (h4 * s2);
+        d3 = ((u64)h0 * r3) +
+             ((u64)h1 * r2) +
+             ((u64)h2 * r1) +
+             ((u64)h3 * r0) +
+             (h4 * s3);
+        h4 = (h4 * r0);
+
+        /* last reduction step: */
+        /* a) h4:h0 = h4<<128 + d3<<96 + d2<<64 + d1<<32 + d0 */
+        h0 = (u32)d0;
+        h1 = (u32)(d1 += d0 >> 32);
+        h2 = (u32)(d2 += d1 >> 32);
+        h3 = (u32)(d3 += d2 >> 32);
+        h4 += (u32)(d3 >> 32);
+        /* b) (h4:h0 += (h4:h0>>130) * 5) %= 2^130 */
+        c = (h4 >> 2) + (h4 & ~3U);
+        h4 &= 3;
+        h0 += c;
+        h1 += (c = CONSTANT_TIME_CARRY(h0,c));
+        h2 += (c = CONSTANT_TIME_CARRY(h1,c));
+        h3 += (c = CONSTANT_TIME_CARRY(h2,c));   /* doesn't overflow */
+
+        inp += POLY1305_BLOCK_SIZE;
+        len -= POLY1305_BLOCK_SIZE;
+    }
+
+    st->h[0] = h0;
+    st->h[1] = h1;
+    st->h[2] = h2;
+    st->h[3] = h3;
+    st->h[4] = h4;
+}
+
+static void poly1305_emit(void *ctx, unsigned char mac[16],
+                          const u32 nonce[4])
+{
+    poly1305_internal *st = (poly1305_internal *) ctx;
+    u32 h0, h1, h2, h3, h4;
+    u32 g0, g1, g2, g3, g4;
+    u64 t;
+    u32 mask;
+
+    h0 = st->h[0];
+    h1 = st->h[1];
+    h2 = st->h[2];
+    h3 = st->h[3];
+    h4 = st->h[4];
+
+    /* compute h + -p */
+    g0 = (u32)(t = (u64)h0 + 5);
+    g1 = (u32)(t = (u64)h1 + (t >> 32));
+    g2 = (u32)(t = (u64)h2 + (t >> 32));
+    g3 = (u32)(t = (u64)h3 + (t >> 32));
+    g4 = h4 + (u32)(t >> 32);
+
+    /* if there was carry into 130th bit, h3:h0 = g3:g0 */
+    mask = 0 - (g4 >> 2);
+    g0 &= mask;
+    g1 &= mask;
+    g2 &= mask;
+    g3 &= mask;
+    mask = ~mask;
+    h0 = (h0 & mask) | g0;
+    h1 = (h1 & mask) | g1;
+    h2 = (h2 & mask) | g2;
+    h3 = (h3 & mask) | g3;
+
+    /* mac = (h + nonce) % (2^128) */
+    h0 = (u32)(t = (u64)h0 + nonce[0]);
+    h1 = (u32)(t = (u64)h1 + (t >> 32) + nonce[1]);
+    h2 = (u32)(t = (u64)h2 + (t >> 32) + nonce[2]);
+    h3 = (u32)(t = (u64)h3 + (t >> 32) + nonce[3]);
+
+    U32TO8(mac + 0, h0);
+    U32TO8(mac + 4, h1);
+    U32TO8(mac + 8, h2);
+    U32TO8(mac + 12, h3);
+}
+# endif
+#else
+int poly1305_init(void *ctx, const unsigned char key[16], void *func);
+void poly1305_blocks(void *ctx, const unsigned char *inp, size_t len,
+                     unsigned int padbit);
+void poly1305_emit(void *ctx, unsigned char mac[16],
+                   const unsigned int nonce[4]);
+#endif
+
+void Poly1305_Init(POLY1305 *ctx, const unsigned char key[32])
+{
+    ctx->nonce[0] = U8TOU32(&key[16]);
+    ctx->nonce[1] = U8TOU32(&key[20]);
+    ctx->nonce[2] = U8TOU32(&key[24]);
+    ctx->nonce[3] = U8TOU32(&key[28]);
+
+#ifndef POLY1305_ASM
+    poly1305_init(ctx->opaque, key);
+#else
+    /*
+     * Unlike reference poly1305_init assembly counterpart is expected
+     * to return a value: non-zero if it initializes ctx->func, and zero
+     * otherwise. Latter is to simplify assembly in cases when there no
+     * multiple code paths to switch between.
+     */
+    if (!poly1305_init(ctx->opaque, key, &ctx->func)) {
+        ctx->func.blocks = poly1305_blocks;
+        ctx->func.emit = poly1305_emit;
+    }
+#endif
+
+    ctx->num = 0;
+
+}
+
+void Poly1305_Update(POLY1305 *ctx, const unsigned char *inp, size_t len)
+{
+#ifdef POLY1305_ASM
+    /*
+     * As documented, poly1305_blocks is never called with input
+     * longer than single block and padbit argument set to 0. This
+     * property is fluently used in assembly modules to optimize
+     * padbit handling on loop boundary.
+     */
+    poly1305_blocks_f poly1305_blocks = ctx->func.blocks;
+#endif
+    size_t rem, num;
+
+    if ((num = ctx->num)) {
+        rem = POLY1305_BLOCK_SIZE - num;
+        if (len >= rem) {
+            memcpy(ctx->data + num, inp, rem);
+            poly1305_blocks(ctx->opaque, ctx->data, POLY1305_BLOCK_SIZE, 1);
+            inp += rem;
+            len -= rem;
+        } else {
+            /* Still not enough data to process a block. */
+            memcpy(ctx->data + num, inp, len);
+            ctx->num = num + len;
+            return;
+        }
+    }
+
+    rem = len % POLY1305_BLOCK_SIZE;