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+/*
+ *  md5.c - Compute MD5 checksum of strings according to the
+ *          definition of MD5 in RFC 1321 from April 1992.
+ *
+ *  Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.
+ *
+ *  Copyright (C) 1995-1999 Free Software Foundation, Inc.
+ *  Copyright (C) 2001 Manuel Novoa III
+ *  Copyright (C) 2003 Glenn L. McGrath
+ *  Copyright (C) 2003 Erik Andersen
+ *
+ *  Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ */
+
+#include <libubox/blob.h> /* TODO: better include for bswap_32 compat */
+#include "md5.h"
+
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+#define SWAP_LE32(x) (x)
+#else
+#define SWAP_LE32(x) bswap_32(x)
+#endif
+
+/* Initialize structure containing state of computation.
+ * (RFC 1321, 3.3: Step 3)
+ */
+void md5_begin(md5_ctx_t *ctx)
+{
+	ctx->A = 0x67452301;
+	ctx->B = 0xefcdab89;
+	ctx->C = 0x98badcfe;
+	ctx->D = 0x10325476;
+
+	ctx->total = 0;
+	ctx->buflen = 0;
+}
+
+/* These are the four functions used in the four steps of the MD5 algorithm
+ * and defined in the RFC 1321.  The first function is a little bit optimized
+ * (as found in Colin Plumbs public domain implementation).
+ * #define FF(b, c, d) ((b & c) | (~b & d))
+ */
+# define FF(b, c, d) (d ^ (b & (c ^ d)))
+# define FG(b, c, d) FF (d, b, c)
+# define FH(b, c, d) (b ^ c ^ d)
+# define FI(b, c, d) (c ^ (b | ~d))
+
+/* Hash a single block, 64 bytes long and 4-byte aligned. */
+static void md5_hash_block(const void *buffer, md5_ctx_t *ctx)
+{
+	uint32_t correct_words[16];
+	const uint32_t *words = buffer;
+
+	static const uint32_t C_array[] = {
+		/* round 1 */
+		0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
+		0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
+		0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
+		0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
+		/* round 2 */
+		0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
+		0xd62f105d, 0x2441453, 0xd8a1e681, 0xe7d3fbc8,
+		0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
+		0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
+		/* round 3 */
+		0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
+		0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
+		0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x4881d05,
+		0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
+		/* round 4 */
+		0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
+		0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
+		0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
+		0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
+	};
+
+	static const char P_array[] = {
+		0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,	/* 1 */
+		1, 6, 11, 0, 5, 10, 15, 4, 9, 14, 3, 8, 13, 2, 7, 12,	/* 2 */
+		5, 8, 11, 14, 1, 4, 7, 10, 13, 0, 3, 6, 9, 12, 15, 2,	/* 3 */
+		0, 7, 14, 5, 12, 3, 10, 1, 8, 15, 6, 13, 4, 11, 2, 9	/* 4 */
+	};
+
+	static const char S_array[] = {
+		7, 12, 17, 22,
+		5, 9, 14, 20,
+		4, 11, 16, 23,
+		6, 10, 15, 21
+	};
+
+	uint32_t A = ctx->A;
+	uint32_t B = ctx->B;
+	uint32_t C = ctx->C;
+	uint32_t D = ctx->D;
+
+	uint32_t *cwp = correct_words;
+
+#  define CYCLIC(w, s) (w = (w << s) | (w >> (32 - s)))
+
+	const uint32_t *pc;
+	const char *pp;
+	const char *ps;
+	int i;
+	uint32_t temp;
+
+	for (i = 0; i < 16; i++) {
+		cwp[i] = SWAP_LE32(words[i]);
+	}
+	words += 16;
+
+	pc = C_array;
+	pp = P_array;
+	ps = S_array;
+
+	for (i = 0; i < 16; i++) {
+		temp = A + FF(B, C, D) + cwp[(int) (*pp++)] + *pc++;
+		CYCLIC(temp, ps[i & 3]);
+		temp += B;
+		A = D;
+		D = C;
+		C = B;
+		B = temp;
+	}
+
+	ps += 4;
+	for (i = 0; i < 16; i++) {
+		temp = A + FG(B, C, D) + cwp[(int) (*pp++)] + *pc++;
+		CYCLIC(temp, ps[i & 3]);
+		temp += B;
+		A = D;
+		D = C;
+		C = B;
+		B = temp;
+	}
+	ps += 4;
+	for (i = 0; i < 16; i++) {
+		temp = A + FH(B, C, D) + cwp[(int) (*pp++)] + *pc++;
+		CYCLIC(temp, ps[i & 3]);
+		temp += B;
+		A = D;
+		D = C;
+		C = B;
+		B = temp;
+	}
+	ps += 4;
+	for (i = 0; i < 16; i++) {
+		temp = A + FI(B, C, D) + cwp[(int) (*pp++)] + *pc++;
+		CYCLIC(temp, ps[i & 3]);
+		temp += B;
+		A = D;
+		D = C;
+		C = B;
+		B = temp;
+	}
+
+
+	ctx->A += A;
+	ctx->B += B;
+	ctx->C += C;
+	ctx->D += D;
+}
+
+/* Feed data through a temporary buffer to call md5_hash_aligned_block()
+ * with chunks of data that are 4-byte aligned and a multiple of 64 bytes.
+ * This function's internal buffer remembers previous data until it has 64
+ * bytes worth to pass on.  Call md5_end() to flush this buffer. */
+
+void md5_hash(const void *buffer, size_t len, md5_ctx_t *ctx)
+{
+	char *buf = (char *)buffer;
+
+	/* RFC 1321 specifies the possible length of the file up to 2^64 bits,
+	 * Here we only track the number of bytes.  */
+
+	ctx->total += len;
+
+	// Process all input.
+
+	while (len) {
+		unsigned i = 64 - ctx->buflen;
+
+		// Copy data into aligned buffer.
+
+		if (i > len)
+			i = len;
+		memcpy(ctx->buffer + ctx->buflen, buf, i);
+		len -= i;
+		ctx->buflen += i;
+		buf += i;
+
+		// When buffer fills up, process it.
+
+		if (ctx->buflen == 64) {
+			md5_hash_block(ctx->buffer, ctx);
+			ctx->buflen = 0;
+		}
+	}
+}
+
+/* Process the remaining bytes in the buffer and put result from CTX
+ * in first 16 bytes following RESBUF.  The result is always in little
+ * endian byte order, so that a byte-wise output yields to the wanted
+ * ASCII representation of the message digest.
+ *
+ * IMPORTANT: On some systems it is required that RESBUF is correctly
+ * aligned for a 32 bits value.
+ */
+void md5_end(void *resbuf, md5_ctx_t *ctx)
+{
+	char *buf = ctx->buffer;
+	int i;
+
+	/* Pad data to block size.  */
+
+	buf[ctx->buflen++] = 0x80;
+	memset(buf + ctx->buflen, 0, 128 - ctx->buflen);
+
+	/* Put the 64-bit file length in *bits* at the end of the buffer.  */
+	ctx->total <<= 3;
+	if (ctx->buflen > 56)
+		buf += 64;
+
+	for (i = 0; i < 8; i++)
+		buf[56 + i] = ctx->total >> (i*8);
+
+	/* Process last bytes.  */
+	if (buf != ctx->buffer)
+		md5_hash_block(ctx->buffer, ctx);
+	md5_hash_block(buf, ctx);
+
+	/* Put result from CTX in first 16 bytes following RESBUF.  The result is
+	 * always in little endian byte order, so that a byte-wise output yields
+	 * to the wanted ASCII representation of the message digest.
+	 *
+	 * IMPORTANT: On some systems it is required that RESBUF is correctly
+	 * aligned for a 32 bits value.
+	 */
+	((uint32_t *) resbuf)[0] = SWAP_LE32(ctx->A);
+	((uint32_t *) resbuf)[1] = SWAP_LE32(ctx->B);
+	((uint32_t *) resbuf)[2] = SWAP_LE32(ctx->C);
+	((uint32_t *) resbuf)[3] = SWAP_LE32(ctx->D);
+}