From c0e5d9280dd156631bd398463dbb6a65aff37d19 Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Thu, 15 Aug 2024 17:10:10 +0200
Subject: Implement SHA-1

---
 "c/sha1/sha1-na\303\257ve.c" | 140 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 "c/sha1/sha1-na\303\257ve.c"

(limited to 'c/sha1/sha1-naïve.c')

diff --git "a/c/sha1/sha1-na\303\257ve.c" "b/c/sha1/sha1-na\303\257ve.c"
new file mode 100644
index 0000000..6f1f257
--- /dev/null
+++ "b/c/sha1/sha1-na\303\257ve.c"
@@ -0,0 +1,140 @@
+#include <endian.h>
+#include <errno.h>
+#include <string.h>
+
+#include "sha1.h"
+
+#define lengthof(xs) (sizeof(xs) / sizeof(*(xs)))
+#define MIN(x, y)    ((x) < (y) ? (x) : (y))
+
+static void sha1hashblk(sha1_t *, const uint8_t *);
+
+static const uint32_t K[] = {
+	0x5A827999,
+	0x6ED9EBA1,
+	0x8F1BBCDC,
+	0xCA62C1D6,
+};
+
+static inline uint32_t
+rotl32(uint32_t x, uint8_t bits)
+{
+#if (__GNUC__ || __TINYC__) && __x86_64__
+	asm ("roll %1, %0" : "+r" (x) : "c" (bits) : "cc");
+	return x;
+#else
+	return (x << bits) | (x >> (32 - bits));
+#endif
+}
+
+void
+sha1init(sha1_t *s)
+{
+	static const uint32_t H[] = {
+		0x67452301,
+		0xEFCDAB89,
+		0x98BADCFE,
+		0x10325476,
+		0xC3D2E1F0,
+	};
+	memcpy(s->dgst, H, sizeof(H));
+	s->msgsz = s->bufsz = 0;
+}
+
+int
+sha1hash(sha1_t *s, const uint8_t *msg, size_t msgsz)
+{
+	if (s->msgsz + (msgsz * 8) < s->msgsz)
+		return EOVERFLOW;
+
+	s->msgsz += msgsz * 8;
+
+	while (msgsz != 0) {
+		size_t free_space = SHA1BLKSZ - s->bufsz;
+		size_t ncpy = MIN(msgsz, free_space);
+		memcpy(s->buf + s->bufsz, msg, ncpy);
+		s->bufsz += ncpy;
+		msg += ncpy;
+		msgsz -= ncpy;
+
+		if (s->bufsz == SHA1BLKSZ) {
+			sha1hashblk(s, s->buf);
+			s->bufsz = 0;
+		}
+	}
+
+	return 0;
+}
+
+void
+sha1end(sha1_t *s, uint8_t dgst[SHA1DGSTSZ])
+{
+	s->buf[s->bufsz++] = 0x80;
+
+	if (s->bufsz > SHA1BLKSZ - sizeof(uint64_t)) {
+		while (s->bufsz < SHA1BLKSZ)
+			s->buf[s->bufsz++] = 0;
+		sha1hashblk(s, s->buf);
+		s->bufsz = 0;
+	}
+
+	while (s->bufsz < 56)
+		s->buf[s->bufsz++] = 0;
+	((uint64_t *)s->buf)[SHA1BLKSZ/8 - 1] = htobe64(s->msgsz);
+
+	sha1hashblk(s, s->buf);
+
+	for (int i = 0; i < lengthof(s->dgst); i++)
+		((uint32_t *)dgst)[i] = htobe32(s->dgst[i]);
+}
+
+static void
+sha1hashblk(sha1_t *s, const uint8_t *blk)
+{
+	uint32_t w[80];
+	uint32_t a, b, c, d, e, tmp;
+
+	for (int i = 0; i < 16; i++)
+		w[i] = htobe32(((uint32_t *)blk)[i]);
+	for (int i = 16; i < 32; i++)
+		w[i] = rotl32(w[i-3] ^ w[i-8] ^ w[i-14] ^ w[i-16], 1);
+	for (int i = 32; i < 80; i++)
+		w[i] = rotl32(w[i-6] ^ w[i-16] ^ w[i-28] ^ w[i-32], 2);
+
+	a = s->dgst[0];
+	b = s->dgst[1];
+	c = s->dgst[2];
+	d = s->dgst[3];
+	e = s->dgst[4];
+
+	for (int i = 0; i < 80; i++) {
+		uint32_t f, k;
+
+		if (i < 20) {
+			f = b&c | ~b&d;
+			k = K[0];
+		} else if (i < 40) {
+			f = b ^ c ^ d;
+			k = K[1];
+		} else if (i < 60) {
+			f = b&c | b&d | c&d;
+			k = K[2];
+		} else {
+			f = b ^ c ^ d;
+			k = K[3];
+		}
+
+		tmp = rotl32(a, 5) + f + e + w[i] + k;
+		e = d;
+		d = c;
+		c = rotl32(b, 30);
+		b = a;
+		a = tmp;
+	}
+
+	s->dgst[0] += a;
+	s->dgst[1] += b;
+	s->dgst[2] += c;
+	s->dgst[3] += d;
+	s->dgst[4] += e;
+}
-- 
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