Initial Digest support. At least partly working.

8 files changed, 657 insertions, 34 deletions

diff --git a/lib/Makefile.am b/lib/Makefile.am
index 62c5c55d9..b17bac198 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -67,7 +67,8 @@ getpass.c netrc.c telnet.h getinfo.c getinfo.h transfer.c strequal.c	\
 strequal.h easy.c security.h security.c krb4.c krb4.h memdebug.c	\
 memdebug.h inet_ntoa_r.h http_chunks.c http_chunks.h strtok.c strtok.h	\
 connect.c connect.h llist.c llist.h hash.c hash.h multi.c		\
-content_encoding.c content_encoding.h share.c share.h
+content_encoding.c content_encoding.h share.c share.h http_digest.c \
+md5.c md5.h http_digest.h
 
 noinst_HEADERS = setup.h transfer.h
 
diff --git a/lib/http.c b/lib/http.c
index a41d0b048..a7ad947e1 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -89,6 +89,7 @@
 #include "cookie.h"
 #include "strequal.h"
 #include "ssluse.h"
+#include "http_digest.h"
 
 #define _MPRINTF_REPLACE /* use our functions only */
 #include <curl/mprintf.h>
@@ -627,6 +628,7 @@ CURLcode Curl_http(struct connectdata *conn)
   char *host = conn->name;
   const char *te = ""; /* tranfer-encoding */
   char *ptr;
+  unsigned char *request;
 
   if(!conn->proto.http) {
     /* Only allocate this struct if we don't already have it! */
@@ -647,6 +649,12 @@ CURLcode Curl_http(struct connectdata *conn)
        data->set.upload) {
     data->set.httpreq = HTTPREQ_PUT;
   }
+
+  request = data->set.customrequest?data->set.customrequest:
+    (data->set.no_body?"HEAD":
+     ((HTTPREQ_POST == data->set.httpreq) ||
+      (HTTPREQ_POST_FORM == data->set.httpreq))?"POST":
+     (HTTPREQ_PUT == data->set.httpreq)?"PUT":"GET");
   
   /* The User-Agent string has been built in url.c already, because it might
      have been used in the proxy connect, but if we have got a header with
@@ -657,7 +665,12 @@ CURLcode Curl_http(struct connectdata *conn)
     conn->allocptr.uagent=NULL;
   }
 
-  if((conn->bits.user_passwd) && !checkheaders(data, "Authorization:")) {
+  if(data->state.digest.nonce) {
+    result = Curl_output_digest(conn, request, (unsigned char *)ppath);
+    if(result)
+      return result;
+  }
+  else if((conn->bits.user_passwd) && !checkheaders(data, "Authorization:")) {
     char *authorization;
 
     /* To prevent the user+password to get sent to other than the original
@@ -902,7 +915,7 @@ CURLcode Curl_http(struct connectdata *conn)
     /* add the main request stuff */
     add_bufferf(req_buffer,
                 "%s " /* GET/HEAD/POST/PUT */
-                "%s HTTP/%s\r\n" /* path */
+                "%s HTTP/%s\r\n" /* path + HTTP version */
                 "%s" /* proxyuserpwd */
                 "%s" /* userpwd */
                 "%s" /* range */
@@ -915,16 +928,12 @@ CURLcode Curl_http(struct connectdata *conn)
                 "%s" /* referer */
                 "%s",/* transfer-encoding */
 
-                data->set.customrequest?data->set.customrequest:
-                (data->set.no_body?"HEAD":
-                 ((HTTPREQ_POST == data->set.httpreq) ||
-                  (HTTPREQ_POST_FORM == data->set.httpreq))?"POST":
-                 (HTTPREQ_PUT == data->set.httpreq)?"PUT":"GET"),
-                ppath, httpstring,
+                request,
+                ppath,
+                httpstring,
                 (conn->bits.proxy_user_passwd &&
                  conn->allocptr.proxyuserpwd)?conn->allocptr.proxyuserpwd:"",
-                (conn->bits.user_passwd && conn->allocptr.userpwd)?
-                conn->allocptr.userpwd:"",
+                conn->allocptr.userpwd?conn->allocptr.userpwd:"",
                 (conn->bits.use_range && conn->allocptr.rangeline)?
                 conn->allocptr.rangeline:"",
                 (data->set.useragent && *data->set.useragent && conn->allocptr.uagent)?
diff --git a/lib/http_digest.c b/lib/http_digest.c
new file mode 100644
index 000000000..82ae1d2a8
--- /dev/null
+++ b/lib/http_digest.c
@@ -0,0 +1,210 @@
+/***************************************************************************
+ *                                  _   _ ____  _     
+ *  Project                     ___| | | |  _ \| |    
+ *                             / __| | | | |_) | |    
+ *                            | (__| |_| |  _ <| |___ 
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2003, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at http://curl.haxx.se/docs/copyright.html.
+ * 
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * $Id$
+ ***************************************************************************/
+#include "setup.h"
+
+#ifndef CURL_DISABLE_HTTP
+/* -- WIN32 approved -- */
+#include <stdio.h>
+#include <string.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <ctype.h>
+
+#include "urldata.h"
+#include "sendf.h"
+#include "strequal.h"
+
+#include "md5.h"
+#include "http_digest.h"
+
+#define _MPRINTF_REPLACE /* use our functions only */
+#include <curl/mprintf.h>
+
+/* The last #include file should be: */
+#ifdef MALLOCDEBUG
+#include "memdebug.h"
+#endif
+
+/* Test example header:
+
+WWW-Authenticate: Digest realm="testrealm", nonce="1053604598"
+
+*/
+
+CURLdigest Curl_input_digest(struct connectdata *conn,
+                             char *header) /* rest of the www-authenticate:
+                                              header */
+{
+  bool more = TRUE;
+  struct SessionHandle *data=conn->data;
+
+  /* skip initial whitespaces */
+  while(*header && isspace((int)*header))
+    header++;
+
+  if(checkprefix("Digest", header)) {
+    header += strlen("Digest");
+
+    data->state.digest.algo = CURLDIGESTALGO_MD5; /* default algorithm */
+
+    while(more) {
+      char value[32];
+      char content[128];
+      int totlen=0;
+
+      while(*header && isspace((int)*header))
+        header++;
+    
+      /* how big can these strings be? */
+      if(2 == sscanf(header, "%31[^=]=\"%127[^\"]\"",
+                     value, content)) {
+        if(strequal(value, "nonce")) {
+          data->state.digest.nonce = strdup(content);
+        }
+        else if(strequal(value, "cnonce")) {
+          data->state.digest.cnonce = strdup(content);
+        }
+        else if(strequal(value, "realm")) {
+          data->state.digest.realm = strdup(content);
+        }
+        else if(strequal(value, "algorithm")) {
+          if(strequal(content, "MD5-sess"))
+            data->state.digest.algo = CURLDIGESTALGO_MD5SESS;
+          /* else, remain using the default md5 */
+        }
+        else {
+          /* unknown specifier, ignore it! */
+        }
+        totlen = strlen(value)+strlen(content)+3;
+      }
+      else 
+        break; /* we're done here */
+        
+      header += totlen;
+      if(',' == *header)
+        /* allow the list to be comma-separated */
+        header++; 
+    }
+  }
+  else 
+    /* else not a digest, get out */
+    return CURLDIGEST_NONE;
+
+  return CURLDIGEST_FINE;
+}
+
+/* convert md5 chunk to RFC2617 (section 3.1.3) -suitable ascii string*/
+static void md5_to_ascii(unsigned char *source, /* 16 bytes */
+                         unsigned char *dest) /* 33 bytes */
+{
+  int i;
+  for(i=0; i<16; i++)
+    sprintf((char *)&dest[i*2], "%02x", source[i]);
+}
+
+CURLcode Curl_output_digest(struct connectdata *conn,
+                            unsigned char *request,
+                            unsigned char *uripath)
+{
+  /* We have a Digest setup for this, use it!
+     Now, to get all the details for this sorted out, I must urge you dear friend
+     to read up on the RFC2617 section 3.2.2, */
+  unsigned char md5buf[16]; /* 16 bytes/128 bits */
+  unsigned char ha1[33]; /* 32 digits and 1 zero byte */
+  unsigned char ha2[33];
+  unsigned char request_digest[33];
+  char *md5this;
+
+  struct SessionHandle *data = conn->data;
+
+  /*
+    if the algorithm is "MD5" or unspecified (which then defaults to MD5):
+    
+    A1 = unq(username-value) ":" unq(realm-value) ":" passwd
+
+    if the algorithm is "MD5-sess" then:
+
+    A1 = H( unq(username-value) ":" unq(realm-value) ":" passwd )
+         ":" unq(nonce-value) ":" unq(cnonce-value)
+  */
+  if(data->state.digest.algo == CURLDIGESTALGO_MD5SESS) {
+    md5this = aprintf("%s:%s:%s:%s:%s",
+                      data->state.user,
+                      data->state.digest.realm,
+                      data->state.passwd,
+                      data->state.digest.nonce,
+                      data->state.digest.cnonce);
+  }
+  else {
+    md5this = aprintf("%s:%s:%s",
+                      data->state.user,
+                      data->state.digest.realm,
+                      data->state.passwd);
+  }
+  Curl_md5it(md5buf, md5this);
+  free(md5this); /* free this again */
+  md5_to_ascii(md5buf, ha1);
+
+  /*
+    A2 = Method ":" digest-uri-value
+    
+    (The "Method" value is the HTTP request method as specified in section
+    5.1.1 of RFC 2616)
+  */
+
+  md5this = aprintf("%s:%s", request, uripath);
+  Curl_md5it(md5buf, md5this);
+  free(md5this); /* free this again */
+  md5_to_ascii(md5buf, ha2);
+
+  md5this = aprintf("%s:%s:%s",
+                    ha1,
+                    data->state.digest.nonce,
+                    ha2);
+  Curl_md5it(md5buf, md5this);
+  free(md5this); /* free this again */
+  md5_to_ascii(md5buf, request_digest);
+
+  /* for test case 64 (snooped from a Mozilla 1.3a request)
+
+    Authorization: Digest username="testuser", realm="testrealm", \
+    nonce="1053604145", uri="/64", response="c55f7f30d83d774a3d2dcacf725abaca"
+  */
+
+  conn->allocptr.userpwd =
+    aprintf( "Authorization: Digest "
+             "username=\"%s\", "
+             "realm=\"%s\", "
+             "nonce=\"%s\", "
+             "uri=\"%s\", "
+             "response=\"%s\"\r\n",
+             data->state.user,
+             data->state.digest.realm,
+             data->state.digest.nonce,
+             uripath, /* this is the PATH part of the URL */ 
+             request_digest );
+
+  return CURLE_OK;
+}
+
+#endif
diff --git a/lib/http_digest.h b/lib/http_digest.h
new file mode 100644
index 000000000..f4204c40d
--- /dev/null
+++ b/lib/http_digest.h
@@ -0,0 +1,43 @@
+/***************************************************************************
+ *                                  _   _ ____  _     
+ *  Project                     ___| | | |  _ \| |    
+ *                             / __| | | | |_) | |    
+ *                            | (__| |_| |  _ <| |___ 
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2003, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at http://curl.haxx.se/docs/copyright.html.
+ * 
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * $Id$
+ ***************************************************************************/
+
+typedef enum {
+  CURLDIGEST_NONE, /* not a digest */
+  CURLDIGEST_BAD,  /* a digest, but one we don't like */
+  CURLDIGEST_FINE, /* a digest we act on */
+
+  CURLDIGEST_LAST  /* last entry in this enum, don't use */
+} CURLdigest;
+
+enum {
+  CURLDIGESTALGO_MD5,
+  CURLDIGESTALGO_MD5SESS
+};
+
+/* this is for digest header input */
+CURLdigest Curl_input_digest(struct connectdata *conn, char *header);
+
+/* this is for creating digest header output */
+CURLcode Curl_output_digest(struct connectdata *conn,
+                            unsigned char *request,
+                            unsigned char *uripath);
diff --git a/lib/md5.c b/lib/md5.c
new file mode 100644
index 000000000..f6abde9e5
--- /dev/null
+++ b/lib/md5.c
@@ -0,0 +1,320 @@
+/* Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
+rights reserved.
+
+License to copy and use this software is granted provided that it
+is identified as the "RSA Data Security, Inc. MD5 Message-Digest
+Algorithm" in all material mentioning or referencing this software
+or this function.
+
+License is also granted to make and use derivative works provided
+that such works are identified as "derived from the RSA Data
+Security, Inc. MD5 Message-Digest Algorithm" in all material
+mentioning or referencing the derived work.
+
+RSA Data Security, Inc. makes no representations concerning either
+the merchantability of this software or the suitability of this
+software for any particular purpose. It is provided "as is"
+without express or implied warranty of any kind.
+
+These notices must be retained in any copies of any part of this
+documentation and/or software.
+ */
+
+#include <string.h>
+
+/* UINT2 defines a two byte word */
+typedef unsigned short int UINT2;
+
+/* UINT4 defines a four byte word */
+typedef unsigned long int UINT4;
+
+/* MD5 context. */
+struct md5_ctx {
+  UINT4 state[4];                                   /* state (ABCD) */
+  UINT4 count[2];        /* number of bits, modulo 2^64 (lsb first) */
+  unsigned char buffer[64];                         /* input buffer */
+};
+
+static void MD5Init(struct md5_ctx *);
+static void MD5Update(struct md5_ctx *, unsigned char *, unsigned int);
+static void MD5Final(unsigned char [16], struct md5_ctx *);
+
+/* Constants for MD5Transform routine.
+ */
+
+#define S11 7
+#define S12 12
+#define S13 17
+#define S14 22
+#define S21 5
+#define S22 9
+#define S23 14
+#define S24 20
+#define S31 4
+#define S32 11
+#define S33 16
+#define S34 23
+#define S41 6
+#define S42 10
+#define S43 15
+#define S44 21
+
+static void MD5Transform(UINT4 [4], unsigned char [64]);
+static void Encode(unsigned char *, UINT4 *, unsigned int);
+static void Decode(UINT4 *, unsigned char *, unsigned int);
+
+#define MD5_memcpy(dst,src,len) memcpy(dst,src,len)
+#define MD5_memset(dst,val,len) memset(dst,val,len)
+
+static unsigned char PADDING[64] = {
+  0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+};
+
+/* F, G, H and I are basic MD5 functions.
+ */
+#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
+#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
+#define H(x, y, z) ((x) ^ (y) ^ (z))
+#define I(x, y, z) ((y) ^ ((x) | (~z)))
+
+/* ROTATE_LEFT rotates x left n bits.
+ */
+#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
+
+/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
+Rotation is separate from addition to prevent recomputation.
+ */
+#define FF(a, b, c, d, x, s, ac) { \
+ (a) += F ((b), (c), (d)) + (x) + (UINT4)(ac); \
+ (a) = ROTATE_LEFT ((a), (s)); \
+ (a) += (b); \
+  }
+#define GG(a, b, c, d, x, s, ac) { \
+ (a) += G ((b), (c), (d)) + (x) + (UINT4)(ac); \
+ (a) = ROTATE_LEFT ((a), (s)); \
+ (a) += (b); \
+  }
+#define HH(a, b, c, d, x, s, ac) { \
+ (a) += H ((b), (c), (d)) + (x) + (UINT4)(ac); \
+ (a) = ROTATE_LEFT ((a), (s)); \
+ (a) += (b); \
+  }
+#define II(a, b, c, d, x, s, ac) { \
+ (a) += I ((b), (c), (d)) + (x) + (UINT4)(ac); \
+ (a) = ROTATE_LEFT ((a), (s)); \
+ (a) += (b); \
+  }
+
+/* MD5 initialization. Begins an MD5 operation, writing a new context.
+ */
+static void MD5Init (context)
+struct md5_ctx *context;                                        /* context */
+{
+  context->count[0] = context->count[1] = 0;
+  /* Load magic initialization constants.
+*/
+  context->state[0] = 0x67452301;
+  context->state[1] = 0xefcdab89;
+  context->state[2] = 0x98badcfe;
+  context->state[3] = 0x10325476;
+}
+
+/* MD5 block update operation. Continues an MD5 message-digest
+  operation, processing another message block, and updating the
+  context.
+ */
+static void MD5Update (context, input, inputLen)
+struct md5_ctx *context;                                        /* context */
+unsigned char *input;                                /* input block */
+unsigned int inputLen;                     /* length of input block */
+{
+  unsigned int i, index, partLen;
+
+  /* Compute number of bytes mod 64 */
+  index = (unsigned int)((context->count[0] >> 3) & 0x3F);
+
+  /* Update number of bits */
+  if ((context->count[0] += ((UINT4)inputLen << 3))
+      < ((UINT4)inputLen << 3))
+    context->count[1]++;
+  context->count[1] += ((UINT4)inputLen >> 29);
+  
+  partLen = 64 - index;
+
+  /* Transform as many times as possible. */
+  if (inputLen >= partLen) {
+    MD5_memcpy((void *)&context->buffer[index], (void *)input, partLen);
+    MD5Transform(context->state, context->buffer);
+    
+    for (i = partLen; i + 63 < inputLen; i += 64)
+      MD5Transform(context->state, &input[i]);
+    
+    index = 0;
+  }
+  else
+    i = 0;
+
+  /* Buffer remaining input */
+  MD5_memcpy((void *)&context->buffer[index], (void *)&input[i],
+             inputLen-i);
+}
+
+/* MD5 finalization. Ends an MD5 message-digest operation, writing the
+  the message digest and zeroizing the context.
+ */
+static void MD5Final (digest, context)
+unsigned char digest[16];                         /* message digest */
+struct md5_ctx *context;                                       /* context */
+{
+  unsigned char bits[8];
+  unsigned int index, padLen;
+
+  /* Save number of bits */
+  Encode (bits, context->count, 8);
+
+  /* Pad out to 56 mod 64. */
+  index = (unsigned int)((context->count[0] >> 3) & 0x3f);
+  padLen = (index < 56) ? (56 - index) : (120 - index);
+  MD5Update (context, PADDING, padLen);
+
+  /* Append length (before padding) */
+  MD5Update (context, bits, 8);
+
+  /* Store state in digest */
+  Encode (digest, context->state, 16);
+
+  /* Zeroize sensitive information. */
+  MD5_memset ((void *)context, 0, sizeof (*context));
+}
+
+/* MD5 basic transformation. Transforms state based on block. */
+static void MD5Transform (state, block)
+UINT4 state[4];
+unsigned char block[64];
+{
+  UINT4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];
+
+  Decode (x, block, 64);
+
+  /* Round 1 */
+  FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
+  FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
+  FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
+  FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
+  FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
+  FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
+  FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
+  FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
+  FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
+  FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
+  FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
+  FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
+  FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
+  FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
+  FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
+  FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */
+
+ /* Round 2 */
+  GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
+  GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
+  GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
+  GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
+  GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
+  GG (d, a, b, c, x[10], S22,  0x2441453); /* 22 */
+  GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
+  GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
+  GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
+  GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
+  GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
+  GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
+  GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
+  GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
+  GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
+  GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */
+
+  /* Round 3 */
+  HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
+  HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
+  HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
+  HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
+  HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
+  HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
+  HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
+  HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
+  HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
+  HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
+  HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
+  HH (b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */
+  HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
+  HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
+  HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
+  HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */
+
+  /* Round 4 */
+  II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
+  II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
+  II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
+  II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
+  II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
+  II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
+  II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
+  II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
+  II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
+  II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
+  II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
+  II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
+  II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
+  II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
+  II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
+  II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */
+
+  state[0] += a;
+  state[1] += b;
+  state[2] += c;
+  state[3] += d;
+
+  /* Zeroize sensitive information. */
+  MD5_memset ((void *)x, 0, sizeof (x));
+}
+
+/* Encodes input (UINT4) into output (unsigned char). Assumes len is
+  a multiple of 4.
+ */
+static void Encode (unsigned char *output,
+                    UINT4 *input,
+                    unsigned int len)
+{
+  unsigned int i, j;
+
+  for (i = 0, j = 0; j < len; i++, j += 4) {
+    output[j] = (unsigned char)(input[i] & 0xff);
+    output[j+1] = (unsigned char)((input[i] >> 8) & 0xff);
+    output[j+2] = (unsigned char)((input[i] >> 16) & 0xff);
+    output[j+3] = (unsigned char)((input[i] >> 24) & 0xff);
+  }
+}
+
+/* Decodes input (unsigned char) into output (UINT4). Assumes len is
+   a multiple of 4.
+*/
+static void Decode (UINT4 *output,
+                    unsigned char *input,
+                    unsigned int len)
+{
+  unsigned int i, j;
+
+  for (i = 0, j = 0; j < len; i++, j += 4)
+    output[i] = ((UINT4)input[j]) | (((UINT4)input[j+1]) << 8) |
+      (((UINT4)input[j+2]) << 16) | (((UINT4)input[j+3]) << 24);
+}
+
+void Curl_md5it(unsigned char *outbuffer, /* 16 bytes */
+                unsigned char *input)
+{
+  struct md5_ctx ctx;
+  MD5Init(&ctx);
+  MD5Update(&ctx, input, strlen((char *)input));
+  MD5Final(outbuffer, &ctx);
+}
diff --git a/lib/md5.h b/lib/md5.h
new file mode 100644
index 000000000..df7587e8c
--- /dev/null
+++ b/lib/md5.h
@@ -0,0 +1,4 @@
+
+void Curl_md5it(unsigned char *output,
+                unsigned char *input);
+
diff --git a/lib/transfer.c b/lib/transfer.c
index 9befa5585..c8c127348 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -95,6 +95,7 @@
 #include "url.h"
 #include "getinfo.h"
 #include "ssluse.h"
+#include "http_digest.h"
 
 #define _MPRINTF_REPLACE /* use our functions only */
 #include <curl/mprintf.h>
@@ -701,31 +702,51 @@ CURLcode Curl_readwrite(struct connectdata *conn,
               if(data->set.get_filetime)
                 data->info.filetime = k->timeofdoc;
             }
+            else if(checkprefix("WWW-Authenticate:", k->p) &&
+                    (401 == k->httpcode) &&
+                    1 /* TODO: replace with a check for Digest authentication
+                         activated */) {
+              CURLdigest dig = Curl_input_digest(conn, k->p+
+                                                 strlen("WWW-Authenticate:"));
+              if(CURLDIGEST_FINE == dig) {
+                /* We act on it. Store our new url, which happens to be
+                   the same one we already use! */
+                conn->newurl = strdup(data->change.url); /* clone string */
+              }
+            }
             else if ((k->httpcode >= 300 && k->httpcode < 400) &&
-                     (data->set.http_follow_location) &&
                      checkprefix("Location:", k->p)) {
-              /* this is the URL that the server advices us to get instead */
-              char *ptr;
-              char *start=k->p;
-              char backup;
-
-              start += 9; /* pass "Location:" */
-
-              /* Skip spaces and tabs. We do this to support multiple
-                 white spaces after the "Location:" keyword. */
-              while(*start && isspace((int)*start ))
-                start++;
-              ptr = start; /* start scanning here */
-
-              /* scan through the string to find the end */
-              while(*ptr && !isspace((int)*ptr))
-                ptr++;
-              backup = *ptr; /* store the ending letter */
-              if(ptr != start) {
-                *ptr = '\0';   /* zero terminate */
-                conn->newurl = strdup(start); /* clone string */
-                *ptr = backup; /* restore ending letter */
+              if(data->set.http_follow_location) {
+                /* this is the URL that the server advices us to get instead */
+                char *ptr;
+                char *start=k->p;
+                char backup;
+
+                start += 9; /* pass "Location:" */
+
+                /* Skip spaces and tabs. We do this to support multiple
+                   white spaces after the "Location:" keyword. */
+                while(*start && isspace((int)*start ))
+                  start++;
+                ptr = start; /* start scanning here */
+
+                /* scan through the string to find the end */
+                while(*ptr && !isspace((int)*ptr))
+                  ptr++;
+                backup = *ptr; /* store the ending letter */
+                if(ptr != start) {
+                  *ptr = '\0';   /* zero terminate */
+                  conn->newurl = strdup(start); /* clone string */
+                  *ptr = backup; /* restore ending letter */
+                }
               }
+#if 0 /* for consideration */
+              else {
+                /* This is a Location: but we have not been instructed to
+                   follow it */
+                infof(data, "We ignore this location header as instructed\n");
+              }
+#endif
             }
 
             /*
@@ -1554,8 +1575,15 @@ CURLcode Curl_follow(struct SessionHandle *data,
    * differently based on exactly what return code there was.
    * Discussed on the curl mailing list and posted about on the 26th
    * of January 2001.
+   *
+   * News from 7.10.6: we can also get here on a 401, in case we need to
+   * do Digest authentication.
    */
   switch(data->info.httpcode) {
+  case 401:
+    /* Act on a digest authentication, we keep on moving and do the
+       Authorization: Digest header in the HTTP request code snippet */
+    break;
   case 300: /* Multiple Choices */
   case 306: /* Not used */
   case 307: /* Temporary Redirect */
diff --git a/lib/urldata.h b/lib/urldata.h
index efd73b2cf..31a755355 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -152,6 +152,13 @@ struct curl_ssl_session {
   struct ssl_config_data ssl_config; /* setup for this session */
 };
 
+/* Struct used for Digest challenge-response authentication */
+struct digestdata {
+  char *nonce;
+  char *cnonce;
+  char *realm;
+  int algo;
+};
 
 /****************************************************************************
  * HTTP unique setup
@@ -327,7 +334,6 @@ struct Curl_transfer_keeper {
                        and we're uploading the last chunk */
 };
 
-
 /*
  * The connectdata struct contains all fields and variables that should be
  * unique for an entire connection.
@@ -619,6 +625,8 @@ struct UrlState {
 #endif
   bool allow_port; /* Is set.use_port allowed to take effect or not. This
                       is always set TRUE when curl_easy_perform() is called. */
+
+  struct digestdata digest;
 };