libsec: add chacha cipher (from charles forsyth)

1 files changed, 175 insertions, 0 deletions

diff --git a/sys/src/libsec/port/chacha.c b/sys/src/libsec/port/chacha.c
new file mode 100644
index 000000000..e075c15e5
--- /dev/null
+++ b/sys/src/libsec/port/chacha.c
@@ -0,0 +1,175 @@
+/*
+Adapted from chacha-merged.c version 20080118
+D. J. Bernstein
+Public domain.
+
+modified for use in Plan 9 and Inferno (no algorithmic changes),
+and including the changes to block number and nonce defined in RFC7539
+*/
+
+#include <u.h>
+#include <libc.h>
+#include <libsec.h>
+
+enum{
+	Blockwords=	ChachaBsize/sizeof(u32int)
+};
+
+/* little-endian data order */
+#define GET4(p)	((((((p)[3]<<8) | (p)[2])<<8) | (p)[1])<<8 | (p)[0])
+#define PUT4(p, v)	(((p)[0]=v), (v>>=8), ((p)[1]=v), (v>>=8), ((p)[2]=v), (v>>=8), ((p)[3]=v))
+
+#define ROTATE(v,c) ((u32int)((v) << (c)) | ((v) >> (32 - (c))))
+
+#define QUARTERROUND(ia,ib,ic,id) { \
+	u32int a, b, c, d, t;\
+	a = x[ia]; b = x[ib]; c = x[ic]; d = x[id]; \
+	a += b; t = d^a; d = ROTATE(t,16); \
+	c += d; t = b^c; b = ROTATE(t,12); \
+	a += b; t = d^a; d = ROTATE(t, 8); \
+	c += d; t = b^c; b = ROTATE(t, 7); \
+	x[ia] = a; x[ib] = b; x[ic] = c; x[id] = d; \
+}
+
+#define ENCRYPT(s, x, y, d) {\
+	u32int v; \
+	uchar *sp, *dp; \
+	sp = (s); \
+	v = GET4(sp); \
+	v ^= (x)+(y); \
+	dp = (d); \
+	PUT4(dp, v); \
+}
+
+static uchar sigma[16] = "expand 32-byte k";
+static uchar tau[16] = "expand 16-byte k";
+
+static void
+load(u32int *d, uchar *s, int nw)
+{
+	int i;
+
+	for(i = 0; i < nw; i++, s+=4)
+		d[i] = GET4(s);
+}
+
+void
+setupChachastate(Chachastate *s, uchar *key, ulong keylen, uchar *iv, int rounds)
+{
+	if(keylen != 256/8 && keylen != 128/8)
+		sysfatal("invalid chacha key length");
+	if(rounds == 0)
+		rounds = 20;
+	s->rounds = rounds;
+	if(keylen == 256/8) { /* recommended */
+		load(&s->input[0], sigma, 4);
+		load(&s->input[4], key, 8);
+	}else{
+		load(&s->input[0], tau, 4);
+		load(&s->input[4], key, 4);
+		load(&s->input[8], key, 4);
+	}
+	s->input[12] = 0;
+	if(iv == nil){
+		s->input[13] = 0;
+		s->input[14] = 0;
+		s->input[15] = 0;
+	}else
+		load(&s->input[13], iv, 3);
+}
+
+void
+chacha_setblock(Chachastate *s, u32int blockno)
+{
+	s->input[12] = blockno;
+}
+
+static void
+encryptblock(Chachastate *s, uchar *src, uchar *dst)
+{
+	u32int x[Blockwords];
+	int i, rounds;
+
+	rounds = s->rounds;
+	x[0] = s->input[0];
+	x[1] = s->input[1];
+	x[2] = s->input[2];
+	x[3] = s->input[3];
+	x[4] = s->input[4];
+	x[5] = s->input[5];
+	x[6] = s->input[6];
+	x[7] = s->input[7];
+	x[8] = s->input[8];
+	x[9] = s->input[9];
+	x[10] = s->input[10];
+	x[11] = s->input[11];
+	x[12] = s->input[12];
+	x[13] = s->input[13];
+	x[14] = s->input[14];
+	x[15] = s->input[15];
+
+	for(i = rounds; 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)
+	}
+
+#ifdef FULL_UNROLL
+	ENCRYPT(src+0*4, x[0], s->input[0], dst+0*4);
+	ENCRYPT(src+1*4, x[1], s->input[1], dst+1*4);
+	ENCRYPT(src+2*4, x[2], s->input[2], dst+2*4);
+	ENCRYPT(src+3*4, x[3], s->input[3], dst+3*4);
+	ENCRYPT(src+4*4, x[4], s->input[4], dst+4*4);
+	ENCRYPT(src+5*4, x[5], s->input[5], dst+5*4);
+	ENCRYPT(src+6*4, x[6], s->input[6], dst+6*4);
+	ENCRYPT(src+7*4, x[7], s->input[7], dst+7*4);
+	ENCRYPT(src+8*4, x[8], s->input[8], dst+8*4);
+	ENCRYPT(src+9*4, x[9], s->input[9], dst+9*4);
+	ENCRYPT(src+10*4, x[10], s->input[10], dst+10*4);
+	ENCRYPT(src+11*4, x[11], s->input[11], dst+11*4);
+	ENCRYPT(src+12*4, x[12], s->input[12], dst+12*4);
+	ENCRYPT(src+13*4, x[13], s->input[13], dst+13*4);
+	ENCRYPT(src+14*4, x[14], s->input[14], dst+14*4);
+	ENCRYPT(src+15*4, x[15], s->input[15], dst+15*4);
+#else
+	for(i=0; i<nelem(x); i+=4){
+		ENCRYPT(src, x[i], s->input[i], dst);
+		ENCRYPT(src+4, x[i+1], s->input[i+1], dst+4);
+		ENCRYPT(src+8, x[i+2], s->input[i+2], dst+8);
+		ENCRYPT(src+12, x[i+3], s->input[i+3], dst+12);
+		src += 16;
+		dst += 16;
+	}
+#endif
+
+	s->input[12]++;
+}
+
+void
+chacha_encrypt2(uchar *src, uchar *dst, ulong bytes, Chachastate *s)
+{
+	uchar tmp[ChachaBsize];
+
+	for(; bytes >= ChachaBsize; bytes -= ChachaBsize){
+		encryptblock(s, src, dst);
+		src += ChachaBsize;
+		dst += ChachaBsize;
+	}
+	if(bytes > 0){
+		memmove(tmp, src, bytes);
+		encryptblock(s, tmp, tmp);
+		memmove(dst, tmp, bytes);
+	}
+}
+
+void
+chacha_encrypt(uchar *buf, ulong bytes, Chachastate *s)
+{
+	chacha_encrypt2(buf, buf, bytes, s);
+}