--- /dev/null
+/*
+ * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+#if BR_INT128 || BR_UMUL128
+
+#if BR_INT128
+
+#define MUL128(hi, lo, x, y) do { \
+ unsigned __int128 mul128tmp; \
+ mul128tmp = (unsigned __int128)(x) * (unsigned __int128)(y); \
+ (hi) = (uint64_t)(mul128tmp >> 64); \
+ (lo) = (uint64_t)mul128tmp; \
+ } while (0)
+
+#elif BR_UMUL128
+
+#include <intrin.h>
+
+#define MUL128(hi, lo, x, y) do { \
+ (lo) = _umul128((x), (y), &(hi)); \
+ } while (0)
+
+#endif
+
+#define MASK42 ((uint64_t)0x000003FFFFFFFFFF)
+#define MASK44 ((uint64_t)0x00000FFFFFFFFFFF)
+
+/*
+ * The "accumulator" word is nominally a 130-bit value. We split it into
+ * words of 44 bits, each held in a 64-bit variable.
+ *
+ * If the current accumulator is a = a0 + a1*W + a2*W^2 (where W = 2^44)
+ * and r = r0 + r1*W + r2*W^2, then:
+ *
+ * a*r = (a0*r0)
+ * + (a0*r1 + a1*r0) * W
+ * + (a0*r2 + a1*r1 + a2*r0) * W^2
+ * + (a1*r2 + a2*r1) * W^3
+ * + (a2*r2) * W^4
+ *
+ * We want to reduce that value modulo p = 2^130-5, so W^3 = 20 mod p,
+ * and W^4 = 20*W mod p. Thus, if we define u1 = 20*r1 and u2 = 20*r2,
+ * then the equations above become:
+ *
+ * b0 = a0*r0 + a1*u2 + a2*u1
+ * b1 = a0*r1 + a1*r0 + a2*u2
+ * b2 = a0*r2 + a1*r1 + a2*r0
+ *
+ * In order to make u1 fit in 44 bits, we can change these equations
+ * into:
+ *
+ * b0 = a0*r0 + a1*u2 + a2*t1
+ * b1 = a0*r1 + a1*r0 + a2*t2
+ * b2 = a0*r2 + a1*r1 + a2*r0
+ *
+ * Where t1 is u1 truncated to 44 bits, and t2 is u2 added to the extra
+ * bits of u1. Note that since r is clamped down to a 124-bit value, the
+ * values u2 and t2 fit on 44 bits too.
+ *
+ * The bx values are larger than 44 bits, so we may split them into a
+ * lower half (cx, 44 bits) and an upper half (dx). The new values for
+ * the accumulator are then:
+ *
+ * e0 = c0 + 20*d2
+ * e1 = c1 + d0
+ * e2 = c2 + d1
+ *
+ * The equations allow for some room, i.e. the ax values may be larger
+ * than 44 bits. Similarly, the ex values will usually be larger than
+ * the ax. Thus, some sort of carry propagation must be done regularly,
+ * though not necessarily at each iteration. In particular, we do not
+ * need to compute the additions (for the bx values) over 128-bit
+ * quantities; we can stick to 64-bit computations.
+ *
+ *
+ * Since the 128-bit result of a 64x64 multiplication is actually
+ * represented over two 64-bit registers, it is cheaper to arrange for
+ * any split that happens between the "high" and "low" halves to be on
+ * that 64-bit boundary. This is done by left shifting the rx, ux and tx
+ * by 20 bits (since they all fit on 44 bits each, this shift is
+ * always possible).
+ */
+
+static void
+poly1305_inner_big(uint64_t *acc, uint64_t *r, const void *data, size_t len)
+{
+
+#define MX(hi, lo, m0, m1, m2) do { \
+ uint64_t mxhi, mxlo; \
+ MUL128(mxhi, mxlo, a0, m0); \
+ (hi) = mxhi; \
+ (lo) = mxlo >> 20; \
+ MUL128(mxhi, mxlo, a1, m1); \
+ (hi) += mxhi; \
+ (lo) += mxlo >> 20; \
+ MUL128(mxhi, mxlo, a2, m2); \
+ (hi) += mxhi; \
+ (lo) += mxlo >> 20; \
+ } while (0)
+
+ const unsigned char *buf;
+ uint64_t a0, a1, a2;
+ uint64_t r0, r1, r2, t1, t2, u2;
+
+ r0 = r[0];
+ r1 = r[1];
+ r2 = r[2];
+ t1 = r[3];
+ t2 = r[4];
+ u2 = r[5];
+ a0 = acc[0];
+ a1 = acc[1];
+ a2 = acc[2];
+ buf = data;
+
+ while (len > 0) {
+ uint64_t v0, v1, v2;
+ uint64_t c0, c1, c2, d0, d1, d2;
+
+ v0 = br_dec64le(buf + 0);
+ v1 = br_dec64le(buf + 8);
+ v2 = v1 >> 24;
+ v1 = ((v0 >> 44) | (v1 << 20)) & MASK44;
+ v0 &= MASK44;
+ a0 += v0;
+ a1 += v1;
+ a2 += v2 + ((uint64_t)1 << 40);
+ MX(d0, c0, r0, u2, t1);
+ MX(d1, c1, r1, r0, t2);
+ MX(d2, c2, r2, r1, r0);
+ a0 = c0 + 20 * d2;
+ a1 = c1 + d0;
+ a2 = c2 + d1;
+
+ v0 = br_dec64le(buf + 16);
+ v1 = br_dec64le(buf + 24);
+ v2 = v1 >> 24;
+ v1 = ((v0 >> 44) | (v1 << 20)) & MASK44;
+ v0 &= MASK44;
+ a0 += v0;
+ a1 += v1;
+ a2 += v2 + ((uint64_t)1 << 40);
+ MX(d0, c0, r0, u2, t1);
+ MX(d1, c1, r1, r0, t2);
+ MX(d2, c2, r2, r1, r0);
+ a0 = c0 + 20 * d2;
+ a1 = c1 + d0;
+ a2 = c2 + d1;
+
+ v0 = br_dec64le(buf + 32);
+ v1 = br_dec64le(buf + 40);
+ v2 = v1 >> 24;
+ v1 = ((v0 >> 44) | (v1 << 20)) & MASK44;
+ v0 &= MASK44;
+ a0 += v0;
+ a1 += v1;
+ a2 += v2 + ((uint64_t)1 << 40);
+ MX(d0, c0, r0, u2, t1);
+ MX(d1, c1, r1, r0, t2);
+ MX(d2, c2, r2, r1, r0);
+ a0 = c0 + 20 * d2;
+ a1 = c1 + d0;
+ a2 = c2 + d1;
+
+ v0 = br_dec64le(buf + 48);
+ v1 = br_dec64le(buf + 56);
+ v2 = v1 >> 24;
+ v1 = ((v0 >> 44) | (v1 << 20)) & MASK44;
+ v0 &= MASK44;
+ a0 += v0;
+ a1 += v1;
+ a2 += v2 + ((uint64_t)1 << 40);
+ MX(d0, c0, r0, u2, t1);
+ MX(d1, c1, r1, r0, t2);
+ MX(d2, c2, r2, r1, r0);
+ a0 = c0 + 20 * d2;
+ a1 = c1 + d0;
+ a2 = c2 + d1;
+
+ a1 += a0 >> 44;
+ a0 &= MASK44;
+ a2 += a1 >> 44;
+ a1 &= MASK44;
+ a0 += 20 * (a2 >> 44);
+ a2 &= MASK44;
+
+ buf += 64;
+ len -= 64;
+ }
+ acc[0] = a0;
+ acc[1] = a1;
+ acc[2] = a2;
+
+#undef MX
+}
+
+static void
+poly1305_inner_small(uint64_t *acc, uint64_t *r, const void *data, size_t len)
+{
+ const unsigned char *buf;
+ uint64_t a0, a1, a2;
+ uint64_t r0, r1, r2, t1, t2, u2;
+
+ r0 = r[0];
+ r1 = r[1];
+ r2 = r[2];
+ t1 = r[3];
+ t2 = r[4];
+ u2 = r[5];
+ a0 = acc[0];
+ a1 = acc[1];
+ a2 = acc[2];
+ buf = data;
+
+ while (len > 0) {
+ uint64_t v0, v1, v2;
+ uint64_t c0, c1, c2, d0, d1, d2;
+ unsigned char tmp[16];
+
+ if (len < 16) {
+ memcpy(tmp, buf, len);
+ memset(tmp + len, 0, (sizeof tmp) - len);
+ buf = tmp;
+ len = 16;
+ }
+ v0 = br_dec64le(buf + 0);
+ v1 = br_dec64le(buf + 8);
+
+ v2 = v1 >> 24;
+ v1 = ((v0 >> 44) | (v1 << 20)) & MASK44;
+ v0 &= MASK44;
+
+ a0 += v0;
+ a1 += v1;
+ a2 += v2 + ((uint64_t)1 << 40);
+
+#define MX(hi, lo, m0, m1, m2) do { \
+ uint64_t mxhi, mxlo; \
+ MUL128(mxhi, mxlo, a0, m0); \
+ (hi) = mxhi; \
+ (lo) = mxlo >> 20; \
+ MUL128(mxhi, mxlo, a1, m1); \
+ (hi) += mxhi; \
+ (lo) += mxlo >> 20; \
+ MUL128(mxhi, mxlo, a2, m2); \
+ (hi) += mxhi; \
+ (lo) += mxlo >> 20; \
+ } while (0)
+
+ MX(d0, c0, r0, u2, t1);
+ MX(d1, c1, r1, r0, t2);
+ MX(d2, c2, r2, r1, r0);
+
+#undef MX
+
+ a0 = c0 + 20 * d2;
+ a1 = c1 + d0;
+ a2 = c2 + d1;
+
+ a1 += a0 >> 44;
+ a0 &= MASK44;
+ a2 += a1 >> 44;
+ a1 &= MASK44;
+ a0 += 20 * (a2 >> 44);
+ a2 &= MASK44;
+
+ buf += 16;
+ len -= 16;
+ }
+ acc[0] = a0;
+ acc[1] = a1;
+ acc[2] = a2;
+}
+
+static inline void
+poly1305_inner(uint64_t *acc, uint64_t *r, const void *data, size_t len)
+{
+ if (len >= 64) {
+ size_t len2;
+
+ len2 = len & ~(size_t)63;
+ poly1305_inner_big(acc, r, data, len2);
+ data = (const unsigned char *)data + len2;
+ len -= len2;
+ }
+ if (len > 0) {
+ poly1305_inner_small(acc, r, data, len);
+ }
+}
+
+/* see bearssl_block.h */
+void
+br_poly1305_ctmulq_run(const void *key, const void *iv,
+ void *data, size_t len, const void *aad, size_t aad_len,
+ void *tag, br_chacha20_run ichacha, int encrypt)
+{
+ unsigned char pkey[32], foot[16];
+ uint64_t r[6], acc[3], r0, r1;
+ uint32_t v0, v1, v2, v3, v4;
+ uint64_t w0, w1, w2, w3;
+ uint32_t ctl;
+
+ /*
+ * Compute the MAC key. The 'r' value is the first 16 bytes of
+ * pkey[].
+ */
+ memset(pkey, 0, sizeof pkey);
+ ichacha(key, iv, 0, pkey, sizeof pkey);
+
+ /*
+ * If encrypting, ChaCha20 must run first, followed by Poly1305.
+ * When decrypting, the operations are reversed.
+ */
+ if (encrypt) {
+ ichacha(key, iv, 1, data, len);
+ }
+
+ /*
+ * Run Poly1305. We must process the AAD, then ciphertext, then
+ * the footer (with the lengths). Note that the AAD and ciphertext
+ * are meant to be padded with zeros up to the next multiple of 16,
+ * and the length of the footer is 16 bytes as well.
+ */
+
+ /*
+ * Apply the "clamping" on r.
+ */
+ pkey[ 3] &= 0x0F;
+ pkey[ 4] &= 0xFC;
+ pkey[ 7] &= 0x0F;
+ pkey[ 8] &= 0xFC;
+ pkey[11] &= 0x0F;
+ pkey[12] &= 0xFC;
+ pkey[15] &= 0x0F;
+
+ /*
+ * Decode the 'r' value into 44-bit words, left-shifted by 20 bits.
+ * Also compute the u1 and u2 values.
+ */
+ r0 = br_dec64le(pkey + 0);
+ r1 = br_dec64le(pkey + 8);
+ r[0] = r0 << 20;
+ r[1] = ((r0 >> 24) | (r1 << 40)) & ~(uint64_t)0xFFFFF;
+ r[2] = (r1 >> 4) & ~(uint64_t)0xFFFFF;
+ r1 = 20 * (r[1] >> 20);
+ r[3] = r1 << 20;
+ r[5] = 20 * r[2];
+ r[4] = (r[5] + (r1 >> 24)) & ~(uint64_t)0xFFFFF;
+
+ /*
+ * Accumulator is 0.
+ */
+ acc[0] = 0;
+ acc[1] = 0;
+ acc[2] = 0;
+
+ /*
+ * Process the additional authenticated data, ciphertext, and
+ * footer in due order.
+ */
+ br_enc64le(foot, (uint64_t)aad_len);
+ br_enc64le(foot + 8, (uint64_t)len);
+ poly1305_inner(acc, r, aad, aad_len);
+ poly1305_inner(acc, r, data, len);
+ poly1305_inner_small(acc, r, foot, sizeof foot);
+
+ /*
+ * Finalise modular reduction. At that point, the value consists
+ * in three 44-bit values (the lowest one might be slightly above
+ * 2^44). Two loops shall be sufficient.
+ */
+ acc[1] += (acc[0] >> 44);
+ acc[0] &= MASK44;
+ acc[2] += (acc[1] >> 44);
+ acc[1] &= MASK44;
+ acc[0] += 5 * (acc[2] >> 42);
+ acc[2] &= MASK42;
+ acc[1] += (acc[0] >> 44);
+ acc[0] &= MASK44;
+ acc[2] += (acc[1] >> 44);
+ acc[1] &= MASK44;
+ acc[0] += 5 * (acc[2] >> 42);
+ acc[2] &= MASK42;
+
+ /*
+ * The value may still fall in the 2^130-5..2^130-1 range, in
+ * which case we must reduce it again. The code below selects,
+ * in constant-time, between 'acc' and 'acc-p'. We encode the
+ * value over four 32-bit integers to finish the operation.
+ */
+ v0 = (uint32_t)acc[0];
+ v1 = (uint32_t)(acc[0] >> 32) | ((uint32_t)acc[1] << 12);
+ v2 = (uint32_t)(acc[1] >> 20) | ((uint32_t)acc[2] << 24);
+ v3 = (uint32_t)(acc[2] >> 8);
+ v4 = (uint32_t)(acc[2] >> 40);
+
+ ctl = GT(v0, 0xFFFFFFFA);
+ ctl &= EQ(v1, 0xFFFFFFFF);
+ ctl &= EQ(v2, 0xFFFFFFFF);
+ ctl &= EQ(v3, 0xFFFFFFFF);
+ ctl &= EQ(v4, 0x00000003);
+ v0 = MUX(ctl, v0 + 5, v0);
+ v1 = MUX(ctl, 0, v1);
+ v2 = MUX(ctl, 0, v2);
+ v3 = MUX(ctl, 0, v3);
+
+ /*
+ * Add the "s" value. This is done modulo 2^128. Don't forget
+ * carry propagation...
+ */
+ w0 = (uint64_t)v0 + (uint64_t)br_dec32le(pkey + 16);
+ w1 = (uint64_t)v1 + (uint64_t)br_dec32le(pkey + 20) + (w0 >> 32);
+ w2 = (uint64_t)v2 + (uint64_t)br_dec32le(pkey + 24) + (w1 >> 32);
+ w3 = (uint64_t)v3 + (uint64_t)br_dec32le(pkey + 28) + (w2 >> 32);
+ v0 = (uint32_t)w0;
+ v1 = (uint32_t)w1;
+ v2 = (uint32_t)w2;
+ v3 = (uint32_t)w3;
+
+ /*
+ * Encode the tag.
+ */
+ br_enc32le((unsigned char *)tag + 0, v0);
+ br_enc32le((unsigned char *)tag + 4, v1);
+ br_enc32le((unsigned char *)tag + 8, v2);
+ br_enc32le((unsigned char *)tag + 12, v3);
+
+ /*
+ * If decrypting, then ChaCha20 runs _after_ Poly1305.
+ */
+ if (!encrypt) {
+ ichacha(key, iv, 1, data, len);
+ }
+}
+
+/* see bearssl_block.h */
+br_poly1305_run
+br_poly1305_ctmulq_get(void)
+{
+ return &br_poly1305_ctmulq_run;
+}
+
+#else
+
+/* see bearssl_block.h */
+br_poly1305_run
+br_poly1305_ctmulq_get(void)
+{
+ return 0;
+}
+
+#endif
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