A patch to simplify some digest-auth code

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For the ChangeLog:

 Factored out code to produce hexadecimal MD5 digests into one
 function (soup_md5_final_hex); eliminated use of sprintf().

Some more explanation:

My linker complains bitterly when I link something that references
sprintf() (because it's easy to write a buffer overflow --- the
linker suggests that I use snprintf() instead). Libsoup's use of
sprintf() appears safe, but while looking at it I decided to merge
the two identical copies of digest_hex() into one function in the
md5 utilities file.  I think this makes the code slightly more
maintainable. It definitely reduces the warning-message clutter when
linking on OpenBSD.

-- 
  Wim Lewis <[email protected]>, Seattle, WA, USA. PGP keyID 27F772C1

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Index: soup-server-auth.c
===================================================================
RCS file: /cvs/gnome/libsoup/libsoup/soup-server-auth.c,v
retrieving revision 1.9
diff -u -r1.9 soup-server-auth.c
--- soup-server-auth.c	10 Sep 2003 18:14:18 -0000	1.9
+++ soup-server-auth.c	1 Aug 2005 07:18:45 -0000
@@ -70,16 +70,6 @@
 	return scheme->type;
 }
 
-static void
-digest_hex (guchar *digest, guchar hex[33])
-{
-	guchar *s, *p;
-
-	/* lowercase hexify that bad-boy... */
-	for (s = digest, p = hex; p < hex + 32; s++, p += 2)
-		sprintf (p, "%.2x", *s);
-}
-
 static gboolean 
 check_digest_passwd (SoupServerAuthDigest *digest,
 		     gchar                *passwd)
@@ -111,8 +101,7 @@
 	}
 
 	/* hexify A1 */
-	soup_md5_final (&ctx, d);
-	digest_hex (d, hex_a1);
+	soup_md5_final_hex (&ctx, hex_a1);
 
 	/* compute A2 */
 	soup_md5_init (&ctx);
@@ -129,8 +118,7 @@
 	}
 
 	/* hexify A2 */
-	soup_md5_final (&ctx, d);
-	digest_hex (d, hex_a2);
+	soup_md5_final_hex (&ctx, hex_a2);
 
 	/* compute KD */
 	soup_md5_init (&ctx);
@@ -156,9 +144,7 @@
 	soup_md5_update (&ctx, ":", 1);
 
 	soup_md5_update (&ctx, hex_a2, 32);
-	soup_md5_final (&ctx, d);
-
-	digest_hex (d, o);
+	soup_md5_final_hex (&ctx, o);
 
 	return strcmp (o, digest->digest_response) == 0;
 }
Index: soup-auth-digest.c
===================================================================
RCS file: /cvs/gnome/libsoup/libsoup/soup-auth-digest.c,v
retrieving revision 1.8
diff -u -r1.8 soup-auth-digest.c
--- soup-auth-digest.c	19 Apr 2005 06:21:31 -0000	1.8
+++ soup-auth-digest.c	1 Aug 2005 07:18:45 -0000
@@ -243,16 +243,6 @@
 }
 
 static void
-digest_hex (guchar *digest, guchar hex[33])
-{
-	guchar *s, *p;
-
-	/* lowercase hexify that bad-boy... */
-	for (s = digest, p = hex; p < hex + 32; s++, p += 2)
-		sprintf (p, "%.2x", *s);
-}
-
-static void
 authenticate (SoupAuth *auth, const char *username, const char *password)
 {
 	SoupAuthDigestPrivate *priv = SOUP_AUTH_DIGEST_GET_PRIVATE (auth);
@@ -300,8 +290,7 @@
 	}
 
 	/* hexify A1 */
-	soup_md5_final (&ctx, d);
-	digest_hex (d, priv->hex_a1);
+	soup_md5_final_hex (&ctx, priv->hex_a1);
 }
 
 static gboolean
@@ -314,7 +303,6 @@
 compute_response (SoupAuthDigestPrivate *priv, SoupMessage *msg)
 {
 	guchar hex_a2[33], o[33];
-	guchar d[16];
 	SoupMD5Context md5;
 	char *url;
 	const SoupUri *uri;
@@ -338,8 +326,7 @@
 	}
 
 	/* now hexify A2 */
-	soup_md5_final (&md5, d);
-	digest_hex (d, hex_a2);
+	soup_md5_final_hex (&md5, hex_a2);
 
 	/* compute KD */
 	soup_md5_init (&md5);
@@ -373,9 +360,7 @@
 	}
 
 	soup_md5_update (&md5, hex_a2, 32);
-	soup_md5_final (&md5, d);
-
-	digest_hex (d, o);
+	soup_md5_final_hex (&md5, o);
 
 	return g_strdup (o);
 }
Index: soup-md5-utils.c
===================================================================
RCS file: /cvs/gnome/libsoup/libsoup/soup-md5-utils.c,v
retrieving revision 1.1
diff -u -r1.1 soup-md5-utils.c
--- soup-md5-utils.c	10 Sep 2003 18:14:18 -0000	1.1
+++ soup-md5-utils.c	1 Aug 2005 07:18:46 -0000
@@ -20,6 +20,7 @@
  * Written March 1993 by Branko Lankester
  * Modified June 1993 by Colin Plumb for altered md5.c.
  * Modified October 1995 by Erik Troan for RPM
+ * Modified July 2005 by Wim Lewis for libsoup
  */
 
 
@@ -131,7 +132,8 @@
  * @digest: 16 bytes buffer
  * @ctx: context containing the calculated md5
  * 
- * copy the final md5 hash to a bufer
+ * Performs the final md5 transformation on the context, and
+ * then copies the resulting md5 hash to a buffer
  **/
 void 
 soup_md5_final (SoupMD5Context *ctx, guchar digest[16])
@@ -179,6 +181,34 @@
 
 
 
+/**
+ * soup_md5_final_hex: copy the final md5 hash to a bufer
+ * @digest: 33 bytes buffer (32 hex digits plus NUL)
+ * @ctx: context containing the calculated md5
+ * 
+ * As soup_md5_final(), but copies the final md5 hash
+ * to a buffer as a NUL-terminated hexadecimal string
+ **/
+void 
+soup_md5_final_hex (SoupMD5Context *ctx, guchar hex_digest[33])
+{
+	static const guchar hexdigits[16] =  {
+		'0', '1', '2', '3', '4', '5', '6', '7',
+		'8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
+	};
+	int p;
+
+	soup_md5_final (ctx, hex_digest);
+
+	/* lowercase hexify that bad-boy... */
+	hex_digest[32] = 0;
+	for (p = 15; p >= 0; p --) {
+		guchar b = hex_digest[p];
+		hex_digest[p*2+1] = hexdigits[ (b & 0x0F ) ];
+		hex_digest[p*2  ] = hexdigits[ (b & 0xF0 ) >> 4 ];
+	}
+}
+
 
 /* The four core functions - F1 is optimized somewhat */
 
@@ -280,3 +310,4 @@
 	buf[2] += c;
 	buf[3] += d;
 }
+
Index: soup-md5-utils.h
===================================================================
RCS file: /cvs/gnome/libsoup/libsoup/soup-md5-utils.h,v
retrieving revision 1.2
diff -u -r1.2 soup-md5-utils.h
--- soup-md5-utils.h	14 Jun 2005 15:34:21 -0000	1.2
+++ soup-md5-utils.h	1 Aug 2005 07:18:46 -0000
@@ -20,6 +20,7 @@
  * Written March 1993 by Branko Lankester
  * Modified June 1993 by Colin Plumb for altered md5.c.
  * Modified October 1995 by Erik Troan for RPM
+ * Modified July 2005 by Wim Lewis for libsoup
  */
 
 
@@ -42,6 +43,8 @@
 		      guint32         len);
 void soup_md5_final  (SoupMD5Context *ctx,
 		      guchar          digest[16]);
+void soup_md5_final_hex  (SoupMD5Context *ctx,
+		          guchar          digest[33]);
 
 
 #endif	/* SOUP_MD5_UTILS_H */

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