From 6f232ed6b5343dea62abdbbd7d38b48858bee373 Mon Sep 17 00:00:00 2001
From: "Eric S. Raymond" <esr@thyrsus.com>
Date: Tue, 8 Jun 1999 07:20:17 +0000
Subject: CRAM-MD5 authentication support a la RFC2195.

svn path=/trunk/; revision=2485
---
 imap.c | 136 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 136 insertions(+)

(limited to 'imap.c')

diff --git a/imap.c b/imap.c
index 1b62f65b..94e4da30 100644
--- a/imap.c
+++ b/imap.c
@@ -37,6 +37,8 @@
 #include <gssapi/gssapi_generic.h>
 #endif
 
+#include "md5.h"
+
 #if OPIE
 #include <opie.h>
 #endif /* OPIE */
@@ -588,6 +590,127 @@ static int do_gssauth(int sock, char *hostname, char *username)
 }	
 #endif /* GSSAPI */
 
+static void hmac_md5 (unsigned char *password,  size_t pass_len,
+                      unsigned char *challenge, size_t chal_len,
+                      unsigned char *response,  size_t resp_len)
+{
+    int i;
+    unsigned char ipad[64];
+    unsigned char opad[64];
+    unsigned char hash_passwd[16];
+
+    MD5_CTX ctx;
+    
+    if (resp_len != 16)
+        return;
+
+    if (pass_len > sizeof (ipad))
+    {
+        MD5Init (&ctx);
+        MD5Update (&ctx, password, pass_len);
+        MD5Final (hash_passwd, &ctx);
+        password = hash_passwd; pass_len = sizeof (hash_passwd);
+    }
+
+    memset (ipad, 0, sizeof (ipad));
+    memset (opad, 0, sizeof (opad));
+    memcpy (ipad, password, pass_len);
+    memcpy (opad, password, pass_len);
+
+    for (i=0; i<64; i++) {
+        ipad[i] ^= 0x36;
+        opad[i] ^= 0x5c;
+    }
+
+    MD5Init (&ctx);
+    MD5Update (&ctx, ipad, sizeof (ipad));
+    MD5Update (&ctx, challenge, chal_len);
+    MD5Final (response, &ctx);
+
+    MD5Init (&ctx);
+    MD5Update (&ctx, opad, sizeof (opad));
+    MD5Update (&ctx, response, resp_len);
+    MD5Final (response, &ctx);
+}
+
+
+static int do_cram_md5 (int sock, struct query *ctl)
+/* authenticate as per RFC2195 */
+{
+    int result;
+    int len;
+    unsigned char buf1[1024];
+    unsigned char msg_id[768];
+    unsigned char response[16];
+    unsigned char reply[1024];
+
+    gen_send (sock, "AUTHENTICATE CRAM-MD5");
+
+    /* From RFC2195:
+     * The data encoded in the first ready response contains an
+     * presumptively arbitrary string of random digits, a timestamp, and the
+     * fully-qualified primary host name of the server.  The syntax of the
+     * unencoded form must correspond to that of an RFC 822 'msg-id'
+     * [RFC822] as described in [POP3].
+     */
+
+    if (result = gen_recv (sock, buf1, sizeof (buf1))) {
+	return result;
+    }
+
+    len = from64tobits (msg_id, buf1);
+    if (len < 0) {
+	report (stderr, _("could not decode BASE64 challenge\n"));
+	return PS_AUTHFAIL;
+    } else if (len < sizeof (msg_id)) {
+        msg_id[len] = 0;
+    } else {
+        msg_id[sizeof (msg_id)-1] = 0;
+    }
+    if (outlevel >= O_DEBUG) {
+        report (stdout, "decoded as %s\n", msg_id);
+    }
+
+    /* The client makes note of the data and then responds with a string
+     * consisting of the user name, a space, and a 'digest'.  The latter is
+     * computed by applying the keyed MD5 algorithm from [KEYED-MD5] where
+     * the key is a shared secret and the digested text is the timestamp
+     * (including angle-brackets).
+     */
+
+    hmac_md5 (ctl->password, strlen (ctl->password),
+              msg_id, strlen (msg_id),
+              response, sizeof (response));
+
+    snprintf (reply, sizeof (reply),
+              "%s %02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x", 
+              ctl->remotename,
+              response[0], response[1], response[2], response[3],
+              response[4], response[5], response[6], response[7],
+              response[8], response[9], response[10], response[11],
+              response[12], response[13], response[14], response[15]);
+
+    if (outlevel >= O_DEBUG) {
+        report (stdout, "replying with %s\n", reply);
+    }
+
+    to64frombits (buf1, reply, strlen (reply));
+    if (outlevel >= O_MONITOR) {
+	report (stdout, "IMAP> %s\n", buf1);
+    }
+    SockWrite (sock, buf1, strlen (buf1));
+    SockWrite (sock, "\r\n", 2);
+
+    if (result = gen_recv (sock, buf1, sizeof (buf1)))
+	return result;
+
+    if (strstr (buf1, "OK")) {
+        return PS_SUCCESS;
+    } else {
+	return PS_AUTHFAIL;
+    }
+}
+
 int imap_canonicalize(char *result, char *passwd)
 /* encode an IMAP password as per RFC1730's quoting conventions */
 {
@@ -695,6 +818,19 @@ int imap_getauth(int sock, struct query *ctl, char *greeting)
     }
 #endif /* KERBEROS_V4 */
 
+    if (strstr (capabilities, "AUTH=CRAM-MD5"))
+    {
+        if (outlevel >= O_DEBUG)
+            report (stdout, _("CRAM-MD5 authentication is supported\n"));
+        if ((ok = do_cram_md5 (sock, ctl)))
+        {
+            if (outlevel >= O_MONITOR)
+                report (stdout, "IMAP> *\n");
+            SockWrite (sock, "*\r\n", 3);
+        }
+        return ok;
+    }
+
 #ifdef __UNUSED__	/* The Cyrus IMAP4rev1 server chokes on this */
     /* this handles either AUTH=LOGIN or AUTH-LOGIN */
     if ((imap_version >= IMAP4rev1) && (!strstr(capabilities, "LOGIN"))) {
-- 
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