[crypto] Add implementation of MS-CHAPv2 authentication

Add an implementation of the authentication portions of the MS-CHAPv2
algorithm as defined in RFC 2759, along with the single test vector
provided therein.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/mschapv2.h

@@ -0,0 +1,59 @@
+#ifndef _IPXE_MSCHAPV2_H
+#define _IPXE_MSCHAPV2_H
+
+/** @file
+ *
+ * MS-CHAPv2 authentication
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+
+/** An MS-CHAPv2 challenge */
+struct mschapv2_challenge {
+	/** Raw bytes */
+	uint8_t byte[16];
+} __attribute__ (( packed ));
+
+/** An MS-CHAPv2 NT response */
+struct mschapv2_nt_response {
+	/** DES-encrypted blocks */
+	uint8_t block[3][8];
+} __attribute__ (( packed ));
+
+/** An MS-CHAPv2 challenge response */
+struct mschapv2_response {
+	/** Peer challenge */
+	struct mschapv2_challenge peer;
+	/** Reserved, must be zero */
+	uint8_t reserved[8];
+	/** NT response */
+	struct mschapv2_nt_response nt;
+	/** Flags, must be zero */
+	uint8_t flags;
+} __attribute__ (( packed ));
+
+/** An MS-CHAPv2 authenticator response */
+struct mschapv2_auth {
+	/** Authenticator response string
+	 *
+	 * This is an unterminated 42-byte string of the form
+	 * "S=<auth_string>" where <auth_string> is the upper-cased
+	 * hexadecimal encoding of the actual authenticator response
+	 * value.  Joy.
+	 */
+	char wtf[42];
+} __attribute__ (( packed ));
+
+extern void mschapv2_response ( const char *username, const char *password,
+				const struct mschapv2_challenge *challenge,
+				const struct mschapv2_challenge *peer,
+				struct mschapv2_response *response );
+extern void mschapv2_auth ( const char *username, const char *password,
+			    const struct mschapv2_challenge *challenge,
+			    const struct mschapv2_response *response,
+			    struct mschapv2_auth *auth );
+
+#endif /* _IPXE_MSCHAPV2_H */