X-Git-Url: https://pd.if.org/git/?a=blobdiff_plain;f=crypto%2Fchacha.c;fp=crypto%2Fchacha.c;h=50d9c7e4d6a7fb2a48c4c2f6448564f8a1e7cb0b;hb=66bc25938679f1d6a1d1200f329093d82a5e99b4;hp=0000000000000000000000000000000000000000;hpb=a52ee0733f420ca20224049260d6fc5cf7d8f621;p=zpackage

diff --git a/crypto/chacha.c b/crypto/chacha.c
new file mode 100644
index 0000000..50d9c7e
--- /dev/null
+++ b/crypto/chacha.c
@@ -0,0 +1,676 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "chacha.h"
+
+typedef unsigned char u8;
+typedef unsigned int u32;
+
+typedef struct chacha_ctx chacha_ctx;
+
+#define U8C(v) (v##U)
+#define U32C(v) (v##U)
+
+#define U8V(v) ((u8)(v) & U8C(0xFF))
+#define U32V(v) ((u32)(v) & U32C(0xFFFFFFFF))
+
+#define ROTL32(v, n) \
+  (U32V((v) << (n)) | ((v) >> (32 - (n))))
+
+#define U8TO32_LITTLE(p) \
+  (((u32)((p)[0])) | \
+   ((u32)((p)[1]) <<  8) | \
+   ((u32)((p)[2]) << 16) | \
+   ((u32)((p)[3]) << 24))
+
+#define U32TO8_LITTLE(p, v) \
+  do { \
+    (p)[0] = U8V((v)); \
+    (p)[1] = U8V((v) >>  8); \
+    (p)[2] = U8V((v) >> 16); \
+    (p)[3] = U8V((v) >> 24); \
+  } while (0)
+
+#define ROTATE(v,c) (ROTL32(v,c))
+#define XOR(v,w) ((v) ^ (w))
+#define PLUS(v,w) (U32V((v) + (w)))
+#define PLUSONE(v) (PLUS((v),1))
+
+#define QUARTERROUND(a,b,c,d) \
+  a = PLUS(a,b); d = ROTATE(XOR(d,a),16); \
+  c = PLUS(c,d); b = ROTATE(XOR(b,c),12); \
+  a = PLUS(a,b); d = ROTATE(XOR(d,a), 8); \
+  c = PLUS(c,d); b = ROTATE(XOR(b,c), 7);
+
+static const char sigma[] = "expand 32-byte k";
+static const char tau[] = "expand 16-byte k";
+
+void chacha_keysetup(chacha_ctx * x, const u8 * k, u32 kbits) {
+	const char *constants;
+
+	x->input[4] = U8TO32_LITTLE(k + 0);
+	x->input[5] = U8TO32_LITTLE(k + 4);
+	x->input[6] = U8TO32_LITTLE(k + 8);
+	x->input[7] = U8TO32_LITTLE(k + 12);
+	if (kbits == 256) {	/* recommended */
+		k += 16;
+		constants = sigma;
+	} else {		/* kbits == 128 */
+		constants = tau;
+	}
+	x->input[8] = U8TO32_LITTLE(k + 0);
+	x->input[9] = U8TO32_LITTLE(k + 4);
+	x->input[10] = U8TO32_LITTLE(k + 8);
+	x->input[11] = U8TO32_LITTLE(k + 12);
+	x->input[0] = U8TO32_LITTLE(constants + 0);
+	x->input[1] = U8TO32_LITTLE(constants + 4);
+	x->input[2] = U8TO32_LITTLE(constants + 8);
+	x->input[3] = U8TO32_LITTLE(constants + 12);
+}
+
+void chacha_key(chacha_ctx * x, u8 * k) {
+	U32TO8_LITTLE(k, x->input[4]);
+	U32TO8_LITTLE(k + 4, x->input[5]);
+	U32TO8_LITTLE(k + 8, x->input[6]);
+	U32TO8_LITTLE(k + 12, x->input[7]);
+
+	U32TO8_LITTLE(k + 16, x->input[8]);
+	U32TO8_LITTLE(k + 20, x->input[9]);
+	U32TO8_LITTLE(k + 24, x->input[10]);
+	U32TO8_LITTLE(k + 28, x->input[11]);
+}
+
+void chacha_nonce(chacha_ctx * x, u8 * nonce) {
+	U32TO8_LITTLE(nonce + 0, x->input[13]);
+	U32TO8_LITTLE(nonce + 4, x->input[14]);
+	U32TO8_LITTLE(nonce + 8, x->input[15]);
+}
+
+void chacha_ivsetup(chacha_ctx * x, const u8 * iv, const u8 * counter) {
+	x->input[12] =
+	    counter == NULL ? 0 : U8TO32_LITTLE(counter + 0);
+	x->input[13] =
+	    counter == NULL ? 0 : U8TO32_LITTLE(counter + 4);
+	if (iv) {
+		x->input[14] = U8TO32_LITTLE(iv + 0);
+		x->input[15] = U8TO32_LITTLE(iv + 4);
+	}
+}
+
+void chacha_ivsetup_96bitnonce(chacha_ctx * x, const u8 * iv,
+			       const u8 * counter) {
+	x->input[12] =
+	    counter == NULL ? 0 : U8TO32_LITTLE(counter + 0);
+	if (iv) {
+		x->input[13] = U8TO32_LITTLE(iv + 0);
+		x->input[14] = U8TO32_LITTLE(iv + 4);
+		x->input[15] = U8TO32_LITTLE(iv + 8);
+	}
+}
+
+void chacha_ivupdate(chacha_ctx * x, const uint8_t * iv,
+		     const uint8_t * aad, const uint8_t * counter) {
+	x->input[12] =
+	    counter == NULL ? 0 : U8TO32_LITTLE(counter + 0);
+	x->input[13] = U8TO32_LITTLE(iv + 0);
+	x->input[14] =
+	    U8TO32_LITTLE(iv +
+				       4) ^
+	    U8TO32_LITTLE(aad);
+	x->input[15] =
+	    U8TO32_LITTLE(iv +
+				       8) ^ U8TO32_LITTLE(aad
+								       +
+								       4);
+}
+
+void chacha_encrypt_bytes(chacha_ctx * x, const u8 * m, u8 * c, u32 bytes) {
+	u32 i;
+	u32 x0, x1, x2, x3, x4, x5, x6, x7;
+	u32 x8, x9, x10, x11, x12, x13, x14, x15;
+	u32 j0, j1, j2, j3, j4, j5, j6, j7;
+	u32 j8, j9, j10, j11, j12, j13, j14, j15;
+	u8 *ctarget = NULL;
+	u8 tmp[64];
+
+	if (!bytes) {
+		return;
+	}
+
+	j0 = x->input[0];
+	j1 = x->input[1];
+	j2 = x->input[2];
+	j3 = x->input[3];
+	j4 = x->input[4];
+	j5 = x->input[5];
+	j6 = x->input[6];
+	j7 = x->input[7];
+	j8 = x->input[8];
+	j9 = x->input[9];
+	j10 = x->input[10];
+	j11 = x->input[11];
+	j12 = x->input[12];
+	j13 = x->input[13];
+	j14 = x->input[14];
+	j15 = x->input[15];
+
+	for (;;) {
+		if (bytes < 64) {
+			for (i = 0; i < bytes; ++i) {
+				tmp[i] = m[i];
+			}
+			m = tmp;
+			ctarget = c;
+			c = tmp;
+		}
+		x0 = j0;
+		x1 = j1;
+		x2 = j2;
+		x3 = j3;
+		x4 = j4;
+		x5 = j5;
+		x6 = j6;
+		x7 = j7;
+		x8 = j8;
+		x9 = j9;
+		x10 = j10;
+		x11 = j11;
+		x12 = j12;
+		x13 = j13;
+		x14 = j14;
+		x15 = j15;
+		for (i = 20; i > 0; i -= 2) {
+			QUARTERROUND(x0, x4, x8, x12)
+			    QUARTERROUND(x1, x5, x9, x13)
+			    QUARTERROUND(x2, x6, x10, x14)
+			    QUARTERROUND(x3, x7, x11, x15)
+			    QUARTERROUND(x0, x5, x10, x15)
+			    QUARTERROUND(x1, x6, x11, x12)
+			    QUARTERROUND(x2, x7, x8, x13)
+			    QUARTERROUND(x3, x4, x9, x14)
+		}
+		x0 = PLUS(x0, j0);
+		x1 = PLUS(x1, j1);
+		x2 = PLUS(x2, j2);
+		x3 = PLUS(x3, j3);
+		x4 = PLUS(x4, j4);
+		x5 = PLUS(x5, j5);
+		x6 = PLUS(x6, j6);
+		x7 = PLUS(x7, j7);
+		x8 = PLUS(x8, j8);
+		x9 = PLUS(x9, j9);
+		x10 = PLUS(x10, j10);
+		x11 = PLUS(x11, j11);
+		x12 = PLUS(x12, j12);
+		x13 = PLUS(x13, j13);
+		x14 = PLUS(x14, j14);
+		x15 = PLUS(x15, j15);
+
+		if (bytes < 64) {
+			U32TO8_LITTLE(x->ks + 0, x0);
+			U32TO8_LITTLE(x->ks + 4, x1);
+			U32TO8_LITTLE(x->ks + 8, x2);
+			U32TO8_LITTLE(x->ks + 12, x3);
+			U32TO8_LITTLE(x->ks + 16, x4);
+			U32TO8_LITTLE(x->ks + 20, x5);
+			U32TO8_LITTLE(x->ks + 24, x6);
+			U32TO8_LITTLE(x->ks + 28, x7);
+			U32TO8_LITTLE(x->ks + 32, x8);
+			U32TO8_LITTLE(x->ks + 36, x9);
+			U32TO8_LITTLE(x->ks + 40, x10);
+			U32TO8_LITTLE(x->ks + 44, x11);
+			U32TO8_LITTLE(x->ks + 48, x12);
+			U32TO8_LITTLE(x->ks + 52, x13);
+			U32TO8_LITTLE(x->ks + 56, x14);
+			U32TO8_LITTLE(x->ks + 60, x15);
+		}
+
+		x0 = XOR(x0, U8TO32_LITTLE(m + 0));
+		x1 = XOR(x1, U8TO32_LITTLE(m + 4));
+		x2 = XOR(x2, U8TO32_LITTLE(m + 8));
+		x3 = XOR(x3, U8TO32_LITTLE(m + 12));
+		x4 = XOR(x4, U8TO32_LITTLE(m + 16));
+		x5 = XOR(x5, U8TO32_LITTLE(m + 20));
+		x6 = XOR(x6, U8TO32_LITTLE(m + 24));
+		x7 = XOR(x7, U8TO32_LITTLE(m + 28));
+		x8 = XOR(x8, U8TO32_LITTLE(m + 32));
+		x9 = XOR(x9, U8TO32_LITTLE(m + 36));
+		x10 = XOR(x10, U8TO32_LITTLE(m + 40));
+		x11 = XOR(x11, U8TO32_LITTLE(m + 44));
+		x12 = XOR(x12, U8TO32_LITTLE(m + 48));
+		x13 = XOR(x13, U8TO32_LITTLE(m + 52));
+		x14 = XOR(x14, U8TO32_LITTLE(m + 56));
+		x15 = XOR(x15, U8TO32_LITTLE(m + 60));
+
+		j12 = PLUSONE(j12);
+		if (!j12) {
+			j13 = PLUSONE(j13);
+			/*
+			 * Stopping at 2^70 bytes per nonce is the user's
+			 * responsibility.
+			 */
+		}
+
+		U32TO8_LITTLE(c + 0, x0);
+		U32TO8_LITTLE(c + 4, x1);
+		U32TO8_LITTLE(c + 8, x2);
+		U32TO8_LITTLE(c + 12, x3);
+		U32TO8_LITTLE(c + 16, x4);
+		U32TO8_LITTLE(c + 20, x5);
+		U32TO8_LITTLE(c + 24, x6);
+		U32TO8_LITTLE(c + 28, x7);
+		U32TO8_LITTLE(c + 32, x8);
+		U32TO8_LITTLE(c + 36, x9);
+		U32TO8_LITTLE(c + 40, x10);
+		U32TO8_LITTLE(c + 44, x11);
+		U32TO8_LITTLE(c + 48, x12);
+		U32TO8_LITTLE(c + 52, x13);
+		U32TO8_LITTLE(c + 56, x14);
+		U32TO8_LITTLE(c + 60, x15);
+
+		if (bytes <= 64) {
+			if (bytes < 64) {
+				for (i = 0; i < bytes; ++i)
+					ctarget[i] = c[i];
+			}
+			x->input[12] = j12;
+			x->input[13] = j13;
+			x->unused = 64 - bytes;
+			return;
+		}
+		bytes -= 64;
+		c += 64;
+		m += 64;
+	}
+}
+
+void chacha20_block(chacha_ctx * x, unsigned char *c, int len) {
+	int i;
+
+	unsigned int state[16];
+	for (i = 0; i < 16; i++)
+		state[i] = x->input[i];
+	for (i = 20; i > 0; i -= 2) {
+		QUARTERROUND(state[0], state[4], state[8], state[12])
+		    QUARTERROUND(state[1], state[5], state[9], state[13])
+		    QUARTERROUND(state[2], state[6], state[10], state[14])
+		    QUARTERROUND(state[3], state[7], state[11], state[15])
+		    QUARTERROUND(state[0], state[5], state[10], state[15])
+		    QUARTERROUND(state[1], state[6], state[11], state[12])
+		    QUARTERROUND(state[2], state[7], state[8], state[13])
+		    QUARTERROUND(state[3], state[4], state[9], state[14])
+	}
+
+	for (i = 0; i < 16; i++)
+		x->input[i] = PLUS(x->input[i], state[i]);
+
+	for (i = 0; i < len; i += 4) {
+		U32TO8_LITTLE(c + i, x->input[i / 4]);
+	}
+}
+
+int poly1305_generate_key(unsigned char *key256, unsigned char *nonce,
+			  unsigned int noncelen, unsigned char *poly_key,
+			  unsigned int counter) {
+	struct chacha_ctx ctx;
+	uint64_t ctr;
+	memset(&ctx, 0, sizeof(ctx));
+	chacha_keysetup(&ctx, key256, 256);
+	switch (noncelen) {
+	case 8:
+		ctr = counter;
+		chacha_ivsetup(&ctx, nonce, (unsigned char *) &ctr);
+		break;
+	case 12:
+		chacha_ivsetup_96bitnonce(&ctx, nonce,
+					  (unsigned char *) &counter);
+		break;
+	default:
+		return -1;
+	}
+	chacha20_block(&ctx, poly_key, POLY1305_KEYLEN);
+	return 0;
+}
+
+/* interpret four 8 bit unsigned integers as a 32 bit unsigned integer in
+ * little endian */
+static unsigned long U8TO32(const unsigned char *p) {
+	return
+	    (((unsigned long) (p[0] & 0xff)) |
+	     ((unsigned long) (p[1] & 0xff) << 8) |
+	     ((unsigned long) (p[2] & 0xff) << 16) |
+	     ((unsigned long) (p[3] & 0xff) << 24));
+}
+
+/* store a 32 bit unsigned integer as four 8 bit unsigned integers in little
+ * endian */
+static void U32TO8(unsigned char *p, unsigned long v) {
+	p[0] = (v) & 0xff;
+	p[1] = (v >> 8) & 0xff;
+	p[2] = (v >> 16) & 0xff;
+	p[3] = (v >> 24) & 0xff;
+}
+
+void tls_poly1305_init(struct poly1305_context *ctx,
+				const unsigned char key[32]) {
+	struct poly1305_context *st = (struct poly1305_context *) ctx;
+
+	/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
+	st->r[0] = (U8TO32(&key[0])) & 0x3ffffff;
+	st->r[1] = (U8TO32(&key[3]) >> 2) & 0x3ffff03;
+	st->r[2] = (U8TO32(&key[6]) >> 4) & 0x3ffc0ff;
+	st->r[3] = (U8TO32(&key[9]) >> 6) & 0x3f03fff;
+	st->r[4] = (U8TO32(&key[12]) >> 8) & 0x00fffff;
+
+	/* h = 0 */
+	st->h[0] = 0;
+	st->h[1] = 0;
+	st->h[2] = 0;
+	st->h[3] = 0;
+	st->h[4] = 0;
+
+	/* save pad for later */
+	st->pad[0] = U8TO32(&key[16]);
+	st->pad[1] = U8TO32(&key[20]);
+	st->pad[2] = U8TO32(&key[24]);
+	st->pad[3] = U8TO32(&key[28]);
+
+	st->leftover = 0;
+	st->final = 0;
+}
+
+void tls_poly1305_blocks(struct poly1305_context *st, const unsigned char *m,
+		size_t bytes) {
+	const unsigned long hibit = (st->final) ? 0 : (1UL << 24);	/* 1 << 128 */
+	unsigned long r0, r1, r2, r3, r4;
+	unsigned long s1, s2, s3, s4;
+	unsigned long h0, h1, h2, h3, h4;
+	unsigned long long d0, d1, d2, d3, d4;
+	unsigned long c;
+
+	r0 = st->r[0];
+	r1 = st->r[1];
+	r2 = st->r[2];
+	r3 = st->r[3];
+	r4 = st->r[4];
+
+	s1 = r1 * 5;
+	s2 = r2 * 5;
+	s3 = r3 * 5;
+	s4 = r4 * 5;
+
+	h0 = st->h[0];
+	h1 = st->h[1];
+	h2 = st->h[2];
+	h3 = st->h[3];
+	h4 = st->h[4];
+
+	while (bytes >= POLY1305_BLOCK_SIZE) {
+		/* h += m[i] */
+		h0 += (U8TO32(m + 0)) & 0x3ffffff;
+		h1 += (U8TO32(m + 3) >> 2) & 0x3ffffff;
+		h2 += (U8TO32(m + 6) >> 4) & 0x3ffffff;
+		h3 += (U8TO32(m + 9) >> 6) & 0x3ffffff;
+		h4 += (U8TO32(m + 12) >> 8) | hibit;
+
+		/* h *= r */
+		d0 = ((unsigned long long) h0 * r0) +
+		    ((unsigned long long) h1 * s4) +
+		    ((unsigned long long) h2 * s3) +
+		    ((unsigned long long) h3 * s2) +
+		    ((unsigned long long) h4 * s1);
+		d1 = ((unsigned long long) h0 * r1) +
+		    ((unsigned long long) h1 * r0) +
+		    ((unsigned long long) h2 * s4) +
+		    ((unsigned long long) h3 * s3) +
+		    ((unsigned long long) h4 * s2);
+		d2 = ((unsigned long long) h0 * r2) +
+		    ((unsigned long long) h1 * r1) +
+		    ((unsigned long long) h2 * r0) +
+		    ((unsigned long long) h3 * s4) +
+		    ((unsigned long long) h4 * s3);
+		d3 = ((unsigned long long) h0 * r3) +
+		    ((unsigned long long) h1 * r2) +
+		    ((unsigned long long) h2 * r1) +
+		    ((unsigned long long) h3 * r0) +
+		    ((unsigned long long) h4 * s4);
+		d4 = ((unsigned long long) h0 * r4) +
+		    ((unsigned long long) h1 * r3) +
+		    ((unsigned long long) h2 * r2) +
+		    ((unsigned long long) h3 * r1) +
+		    ((unsigned long long) h4 * r0);
+
+		/* (partial) h %= p */
+		c = (unsigned long) (d0 >> 26);
+		h0 = (unsigned long) d0 & 0x3ffffff;
+		d1 += c;
+		c = (unsigned long) (d1 >> 26);
+		h1 = (unsigned long) d1 & 0x3ffffff;
+		d2 += c;
+		c = (unsigned long) (d2 >> 26);
+		h2 = (unsigned long) d2 & 0x3ffffff;
+		d3 += c;
+		c = (unsigned long) (d3 >> 26);
+		h3 = (unsigned long) d3 & 0x3ffffff;
+		d4 += c;
+		c = (unsigned long) (d4 >> 26);
+		h4 = (unsigned long) d4 & 0x3ffffff;
+		h0 += c * 5;
+		c = (h0 >> 26);
+		h0 = h0 & 0x3ffffff;
+		h1 += c;
+
+		m += POLY1305_BLOCK_SIZE;
+		bytes -= POLY1305_BLOCK_SIZE;
+	}
+
+	st->h[0] = h0;
+	st->h[1] = h1;
+	st->h[2] = h2;
+	st->h[3] = h3;
+	st->h[4] = h4;
+}
+
+void tls_poly1305_finish(struct poly1305_context *ctx, unsigned char mac[16]) {
+	size_t i;
+	struct poly1305_context *st = (struct poly1305_context *) ctx;
+	unsigned long h0, h1, h2, h3, h4, c;
+	unsigned long g0, g1, g2, g3, g4;
+	unsigned long long f;
+	unsigned long mask;
+
+	/* process the remaining block */
+	if (st->leftover) {
+		i = st->leftover;
+		st->buffer[i++] = 1;
+		for (; i < POLY1305_BLOCK_SIZE; i++)
+			st->buffer[i] = 0;
+		st->final = 1;
+		tls_poly1305_blocks(st, st->buffer, POLY1305_BLOCK_SIZE);
+	}
+
+	/* fully carry h */
+	h0 = st->h[0];
+	h1 = st->h[1];
+	h2 = st->h[2];
+	h3 = st->h[3];
+	h4 = st->h[4];
+
+	c = h1 >> 26;
+	h1 = h1 & 0x3ffffff;
+	h2 += c;
+	c = h2 >> 26;
+	h2 = h2 & 0x3ffffff;
+	h3 += c;
+	c = h3 >> 26;
+	h3 = h3 & 0x3ffffff;
+	h4 += c;
+	c = h4 >> 26;
+	h4 = h4 & 0x3ffffff;
+	h0 += c * 5;
+	c = h0 >> 26;
+	h0 = h0 & 0x3ffffff;
+	h1 += c;
+
+	/* compute h + -p */
+	g0 = h0 + 5;
+	c = g0 >> 26;
+	g0 &= 0x3ffffff;
+	g1 = h1 + c;
+	c = g1 >> 26;
+	g1 &= 0x3ffffff;
+	g2 = h2 + c;
+	c = g2 >> 26;
+	g2 &= 0x3ffffff;
+	g3 = h3 + c;
+	c = g3 >> 26;
+	g3 &= 0x3ffffff;
+	g4 = h4 + c - (1UL << 26);
+
+	/* select h if h < p, or h + -p if h >= p */
+	mask = (g4 >> ((sizeof(unsigned long) * 8) - 1)) - 1;
+	g0 &= mask;
+	g1 &= mask;
+	g2 &= mask;
+	g3 &= mask;
+	g4 &= mask;
+	mask = ~mask;
+	h0 = (h0 & mask) | g0;
+	h1 = (h1 & mask) | g1;
+	h2 = (h2 & mask) | g2;
+	h3 = (h3 & mask) | g3;
+	h4 = (h4 & mask) | g4;
+
+	/* h = h % (2^128) */
+	h0 = ((h0) | (h1 << 26)) & 0xffffffff;
+	h1 = ((h1 >> 6) | (h2 << 20)) & 0xffffffff;
+	h2 = ((h2 >> 12) | (h3 << 14)) & 0xffffffff;
+	h3 = ((h3 >> 18) | (h4 << 8)) & 0xffffffff;
+
+	/* mac = (h + pad) % (2^128) */
+	f = (unsigned long long) h0 + st->pad[0];
+	h0 = (unsigned long) f;
+	f = (unsigned long long) h1 + st->pad[1] + (f >> 32);
+	h1 = (unsigned long) f;
+	f = (unsigned long long) h2 + st->pad[2] + (f >> 32);
+	h2 = (unsigned long) f;
+	f = (unsigned long long) h3 + st->pad[3] + (f >> 32);
+	h3 = (unsigned long) f;
+
+	U32TO8(mac + 0, h0);
+	U32TO8(mac + 4, h1);
+	U32TO8(mac + 8, h2);
+	U32TO8(mac + 12, h3);
+
+	/* zero out the state */
+	st->h[0] = 0;
+	st->h[1] = 0;
+	st->h[2] = 0;
+	st->h[3] = 0;
+	st->h[4] = 0;
+	st->r[0] = 0;
+	st->r[1] = 0;
+	st->r[2] = 0;
+	st->r[3] = 0;
+	st->r[4] = 0;
+	st->pad[0] = 0;
+	st->pad[1] = 0;
+	st->pad[2] = 0;
+	st->pad[3] = 0;
+}
+
+void tls_poly1305_update(struct poly1305_context *ctx, const unsigned char *m,
+		size_t bytes) {
+	struct poly1305_context *st = (struct poly1305_context *) ctx;
+	size_t i;
+	/* handle leftover */
+	if (st->leftover) {
+		size_t want = (POLY1305_BLOCK_SIZE - st->leftover);
+		if (want > bytes)
+			want = bytes;
+		for (i = 0; i < want; i++)
+			st->buffer[st->leftover + i] = m[i];
+		bytes -= want;
+		m += want;
+		st->leftover += want;
+		if (st->leftover < POLY1305_BLOCK_SIZE)
+			return;
+		tls_poly1305_blocks(st, st->buffer, POLY1305_BLOCK_SIZE);
+		st->leftover = 0;
+	}
+
+	/* process full blocks */
+	if (bytes >= POLY1305_BLOCK_SIZE) {
+		size_t want = (bytes & ~(POLY1305_BLOCK_SIZE - 1));
+		tls_poly1305_blocks(st, m, want);
+		m += want;
+		bytes -= want;
+	}
+
+	/* store leftover */
+	if (bytes) {
+		for (i = 0; i < bytes; i++)
+			st->buffer[st->leftover + i] = m[i];
+		st->leftover += bytes;
+	}
+}
+
+int poly1305_verify(const unsigned char mac1[16],
+		    const unsigned char mac2[16]) {
+	size_t i;
+	unsigned int dif = 0;
+	for (i = 0; i < 16; i++)
+		dif |= (mac1[i] ^ mac2[i]);
+	dif = (dif - 1) >> ((sizeof(unsigned int) * 8) - 1);
+	return (dif & 1);
+}
+
+void chacha20_poly1305_key(struct chacha_ctx *ctx,
+			   unsigned char *poly1305_key) {
+	unsigned char key[32];
+	unsigned char nonce[12];
+	chacha_key(ctx, key);
+	chacha_nonce(ctx, nonce);
+	poly1305_generate_key(key, nonce, sizeof(nonce), poly1305_key, 0);
+}
+
+static unsigned char zeropad[] =
+    { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
+
+int chacha20_poly1305_aead(struct chacha_ctx *ctx, unsigned char *pt,
+			   unsigned int len, unsigned char *aad,
+			   unsigned int aad_len, unsigned char *poly_key,
+			   unsigned char *out) {
+	if (aad_len > POLY1305_MAX_AAD) {
+		return -1;
+	}
+
+	unsigned int counter = 1;
+	chacha_ivsetup_96bitnonce(ctx, NULL, (unsigned char *) &counter);
+	chacha_encrypt_bytes(ctx, pt, out, len);
+
+	struct poly1305_context aead_ctx;
+	tls_poly1305_init(&aead_ctx, poly_key);
+	tls_poly1305_update(&aead_ctx, aad, aad_len);
+	int rem = aad_len % 16;
+	if (rem) {
+		tls_poly1305_update(&aead_ctx, zeropad, 16 - rem);
+	}
+	tls_poly1305_update(&aead_ctx, out, len);
+	rem = len % 16;
+	if (rem) {
+		tls_poly1305_update(&aead_ctx, zeropad, 16 - rem);
+	}
+
+	unsigned char trail[16];
+	U32TO8(&trail[0], aad_len);
+	*(int *) &trail[4] = 0;
+	U32TO8(&trail[8], len);
+	*(int *) &trail[12] = 0;
+
+	tls_poly1305_update(&aead_ctx, trail, 16);
+	tls_poly1305_finish(&aead_ctx, out + len);
+
+	return len + POLY1305_TAGLEN;
+}