new file mode 100644
--- /dev/null
+++ b/src/core/ngx_md5.c
@@ -0,0 +1,289 @@
+
+/*
+ * An internal implementation, based on Alexander Peslyak's
+ * public domain implementation:
+ * http://openwall.info/wiki/people/solar/software/public-domain-source-code/md5
+ * It is not expected to be optimal and is used only
+ * if no MD5 implementation was found in system.
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_md5.h>
+
+
+#if !(NGX_HAVE_MD5)
+
+static const u_char *ngx_md5_body(ngx_md5_t *ctx, const u_char *data,
+    size_t size);
+
+
+void
+ngx_md5_init(ngx_md5_t *ctx)
+{
+    ctx->a = 0x67452301;
+    ctx->b = 0xefcdab89;
+    ctx->c = 0x98badcfe;
+    ctx->d = 0x10325476;
+
+    ctx->bytes = 0;
+}
+
+
+void
+ngx_md5_update(ngx_md5_t *ctx, const u_char *data, size_t size)
+{
+    size_t  used, free;
+
+    used = ctx->bytes & 0x3f;
+    ctx->bytes += size;
+
+    if (used) {
+        free = 64 - used;
+
+        if (size < free) {
+            ngx_memcpy(&ctx->buffer[used], data, size);
+            return;
+        }
+
+        ngx_memcpy(&ctx->buffer[used], data, free);
+        data = (u_char *)data + free;
+        size -= free;
+        (void) ngx_md5_body(ctx, ctx->buffer, 64);
+    }
+
+    if (size >= 64) {
+        data = ngx_md5_body(ctx, data, size & ~(size_t) 0x3f);
+        size &= 0x3f;
+    }
+
+    ngx_memcpy(ctx->buffer, data, size);
+}
+
+
+void
+ngx_md5_final(u_char result[16], ngx_md5_t *ctx)
+{
+    size_t  used, free;
+
+    used = ctx->bytes & 0x3f;
+
+    ctx->buffer[used++] = 0x80;
+
+    free = 64 - used;
+
+    if (free < 8) {
+        ngx_memzero(&ctx->buffer[used], free);
+        (void) ngx_md5_body(ctx, ctx->buffer, 64);
+        used = 0;
+        free = 64;
+    }
+
+    ngx_memzero(&ctx->buffer[used], free - 8);
+
+    ctx->bytes <<= 3;
+    ctx->buffer[56] = ctx->bytes;
+    ctx->buffer[57] = ctx->bytes >> 8;
+    ctx->buffer[58] = ctx->bytes >> 16;
+    ctx->buffer[59] = ctx->bytes >> 24;
+    ctx->buffer[60] = ctx->bytes >> 32;
+    ctx->buffer[61] = ctx->bytes >> 40;
+    ctx->buffer[62] = ctx->bytes >> 48;
+    ctx->buffer[63] = ctx->bytes >> 56;
+
+    (void) ngx_md5_body(ctx, ctx->buffer, 64);
+
+    result[0] = ctx->a;
+    result[1] = ctx->a >> 8;
+    result[2] = ctx->a >> 16;
+    result[3] = ctx->a >> 24;
+    result[4] = ctx->b;
+    result[5] = ctx->b >> 8;
+    result[6] = ctx->b >> 16;
+    result[7] = ctx->b >> 24;
+    result[8] = ctx->c;
+    result[9] = ctx->c >> 8;
+    result[10] = ctx->c >> 16;
+    result[11] = ctx->c >> 24;
+    result[12] = ctx->d;
+    result[13] = ctx->d >> 8;
+    result[14] = ctx->d >> 16;
+    result[15] = ctx->d >> 24;
+
+    ngx_memzero(ctx, sizeof(*ctx));
+}
+
+
+/*
+ * The basic MD5 functions.
+ *
+ * F and G are optimized compared to their RFC 1321 definitions for
+ * architectures that lack an AND-NOT instruction, just like in
+ * Colin Plumb's implementation.
+ */
+
+#define F(x, y, z)  ((z) ^ ((x) & ((y) ^ (z))))
+#define G(x, y, z)  ((y) ^ ((z) & ((x) ^ (y))))
+#define H(x, y, z)  ((x) ^ (y) ^ (z))
+#define I(x, y, z)  ((y) ^ ((x) | ~(z)))
+
+/*
+ * The MD5 transformation for all four rounds.
+ */
+
+#define STEP(f, a, b, c, d, x, t, s)                                          \
+    (a) += f((b), (c), (d)) + (x) + (t);                                      \
+    (a) = (((a) << (s)) | (((a) & 0xffffffff) >> (32 - (s))));                \
+    (a) += (b)
+
+/*
+ * SET() reads 4 input bytes in little-endian byte order and stores them
+ * in a properly aligned word in host byte order.
+ *
+ * The check for little-endian architectures that tolerate unaligned
+ * memory accesses is just an optimization.  Nothing will break if it
+ * does not work.
+ */
+
+#if (NGX_HAVE_LITTLE_ENDIAN && NGX_HAVE_NONALIGNED)
+
+#define SET(n)      (*(uint32_t *) &p[n * 4])
+#define GET(n)      (*(uint32_t *) &p[n * 4])
+
+#else
+
+#define SET(n)                                                                \
+    (block[n] =                                                               \
+    (uint32_t) p[n * 4] |                                                     \
+    ((uint32_t) p[n * 4 + 1] << 8) |                                          \
+    ((uint32_t) p[n * 4 + 2] << 16) |                                         \
+    ((uint32_t) p[n * 4 + 3] << 24))
+
+#define GET(n)      block[n]
+
+#endif
+
+
+/*
+ * This processes one or more 64-byte data blocks, but does not update
+ * the bit counters.  There are no alignment requirements.
+ */
+
+static const u_char *
+ngx_md5_body(ngx_md5_t *ctx, const u_char *data, size_t size)
+{
+    uint32_t       a, b, c, d;
+    uint32_t       saved_a, saved_b, saved_c, saved_d;
+    const u_char  *p;
+#if !(NGX_HAVE_LITTLE_ENDIAN && NGX_HAVE_NONALIGNED)
+    uint32_t       block[16];
+#endif
+
+    p = data;
+
+    a = ctx->a;
+    b = ctx->b;
+    c = ctx->c;
+    d = ctx->d;
+
+    do {
+        saved_a = a;
+        saved_b = b;
+        saved_c = c;
+        saved_d = d;
+
+        /* Round 1 */
+
+        STEP(F, a, b, c, d, SET(0),  0xd76aa478, 7);
+        STEP(F, d, a, b, c, SET(1),  0xe8c7b756, 12);
+        STEP(F, c, d, a, b, SET(2),  0x242070db, 17);
+        STEP(F, b, c, d, a, SET(3),  0xc1bdceee, 22);
+        STEP(F, a, b, c, d, SET(4),  0xf57c0faf, 7);
+        STEP(F, d, a, b, c, SET(5),  0x4787c62a, 12);
+        STEP(F, c, d, a, b, SET(6),  0xa8304613, 17);
+        STEP(F, b, c, d, a, SET(7),  0xfd469501, 22);
+        STEP(F, a, b, c, d, SET(8),  0x698098d8, 7);
+        STEP(F, d, a, b, c, SET(9),  0x8b44f7af, 12);
+        STEP(F, c, d, a, b, SET(10), 0xffff5bb1, 17);
+        STEP(F, b, c, d, a, SET(11), 0x895cd7be, 22);
+        STEP(F, a, b, c, d, SET(12), 0x6b901122, 7);
+        STEP(F, d, a, b, c, SET(13), 0xfd987193, 12);
+        STEP(F, c, d, a, b, SET(14), 0xa679438e, 17);
+        STEP(F, b, c, d, a, SET(15), 0x49b40821, 22);
+
+        /* Round 2 */
+
+        STEP(G, a, b, c, d, GET(1),  0xf61e2562, 5);
+        STEP(G, d, a, b, c, GET(6),  0xc040b340, 9);
+        STEP(G, c, d, a, b, GET(11), 0x265e5a51, 14);
+        STEP(G, b, c, d, a, GET(0),  0xe9b6c7aa, 20);
+        STEP(G, a, b, c, d, GET(5),  0xd62f105d, 5);
+        STEP(G, d, a, b, c, GET(10), 0x02441453, 9);
+        STEP(G, c, d, a, b, GET(15), 0xd8a1e681, 14);
+        STEP(G, b, c, d, a, GET(4),  0xe7d3fbc8, 20);
+        STEP(G, a, b, c, d, GET(9),  0x21e1cde6, 5);
+        STEP(G, d, a, b, c, GET(14), 0xc33707d6, 9);
+        STEP(G, c, d, a, b, GET(3),  0xf4d50d87, 14);
+        STEP(G, b, c, d, a, GET(8),  0x455a14ed, 20);
+        STEP(G, a, b, c, d, GET(13), 0xa9e3e905, 5);
+        STEP(G, d, a, b, c, GET(2),  0xfcefa3f8, 9);
+        STEP(G, c, d, a, b, GET(7),  0x676f02d9, 14);
+        STEP(G, b, c, d, a, GET(12), 0x8d2a4c8a, 20);
+
+        /* Round 3 */
+
+        STEP(H, a, b, c, d, GET(5),  0xfffa3942, 4);
+        STEP(H, d, a, b, c, GET(8),  0x8771f681, 11);
+        STEP(H, c, d, a, b, GET(11), 0x6d9d6122, 16);
+        STEP(H, b, c, d, a, GET(14), 0xfde5380c, 23);
+        STEP(H, a, b, c, d, GET(1),  0xa4beea44, 4);
+        STEP(H, d, a, b, c, GET(4),  0x4bdecfa9, 11);
+        STEP(H, c, d, a, b, GET(7),  0xf6bb4b60, 16);
+        STEP(H, b, c, d, a, GET(10), 0xbebfbc70, 23);
+        STEP(H, a, b, c, d, GET(13), 0x289b7ec6, 4);
+        STEP(H, d, a, b, c, GET(0),  0xeaa127fa, 11);
+        STEP(H, c, d, a, b, GET(3),  0xd4ef3085, 16);
+        STEP(H, b, c, d, a, GET(6),  0x04881d05, 23);
+        STEP(H, a, b, c, d, GET(9),  0xd9d4d039, 4);
+        STEP(H, d, a, b, c, GET(12), 0xe6db99e5, 11);
+        STEP(H, c, d, a, b, GET(15), 0x1fa27cf8, 16);
+        STEP(H, b, c, d, a, GET(2),  0xc4ac5665, 23);
+
+        /* Round 4 */
+
+        STEP(I, a, b, c, d, GET(0),  0xf4292244, 6);
+        STEP(I, d, a, b, c, GET(7),  0x432aff97, 10);
+        STEP(I, c, d, a, b, GET(14), 0xab9423a7, 15);
+        STEP(I, b, c, d, a, GET(5),  0xfc93a039, 21);
+        STEP(I, a, b, c, d, GET(12), 0x655b59c3, 6);
+        STEP(I, d, a, b, c, GET(3),  0x8f0ccc92, 10);
+        STEP(I, c, d, a, b, GET(10), 0xffeff47d, 15);
+        STEP(I, b, c, d, a, GET(1),  0x85845dd1, 21);
+        STEP(I, a, b, c, d, GET(8),  0x6fa87e4f, 6);
+        STEP(I, d, a, b, c, GET(15), 0xfe2ce6e0, 10);
+        STEP(I, c, d, a, b, GET(6),  0xa3014314, 15);
+        STEP(I, b, c, d, a, GET(13), 0x4e0811a1, 21);
+        STEP(I, a, b, c, d, GET(4),  0xf7537e82, 6);
+        STEP(I, d, a, b, c, GET(11), 0xbd3af235, 10);
+        STEP(I, c, d, a, b, GET(2),  0x2ad7d2bb, 15);
+        STEP(I, b, c, d, a, GET(9),  0xeb86d391, 21);
+
+        a += saved_a;
+        b += saved_b;
+        c += saved_c;
+        d += saved_d;
+
+        p += 64;
+
+    } while (size -= 64);
+
+    ctx->a = a;
+    ctx->b = b;
+    ctx->c = c;
+    ctx->d = d;
+
+    return p;
+}
+
+#endif