From c7132be603c07e7851a3a374dc9b6be59ce3c919 Mon Sep 17 00:00:00 2001
From: "Eric S. Raymond" <esr@thyrsus.com>
Date: Sun, 11 Feb 2001 04:57:31 +0000
Subject: Initial revision

svn path=/trunk/; revision=3041
---
 cram.c | 150 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 150 insertions(+)
 create mode 100644 cram.c

diff --git a/cram.c b/cram.c
new file mode 100644
index 00000000..ae8800d1
--- /dev/null
+++ b/cram.c
@@ -0,0 +1,150 @@
+/*
+ * cram.c -- CRAM-MD5 authentication (see RFC 2195)
+ *
+ * For license terms, see the file COPYING in this directory.
+ */
+
+#include  "config.h"
+#include  <stdio.h>
+#include  <string.h>
+#include  <ctype.h>
+#if defined(STDC_HEADERS)
+#include  <stdlib.h>
+#endif
+#include  "fetchmail.h"
+#include  "socket.h"
+
+#include  "i18n.h"
+#include "md5.h"
+
+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);
+}
+
+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));
+
+#ifdef HAVE_SNPRINTF
+    snprintf (reply, sizeof (reply),
+#else
+    sprintf(reply,
+#endif
+              "%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, "CRAM> %s\n", buf1);
+    }
+
+    /* PMDF5.2 IMAP has a bug that requires this to be a single write */
+    strcat (buf1, "\r\n");
+    SockWrite (sock, buf1, strlen (buf1));
+
+    if ((result = gen_recv (sock, buf1, sizeof (buf1))))
+	return result;
+
+    /*
+     * Ugh.  This has to recognize all kinds of success lines.
+     * These two tests will catch IMAP and POP OK or SMTP-like
+     * protocols that use 2xx as a success indication.
+     */
+    if (buf1[0] = '2' || strstr(buf1, "OK"))
+	return(PS_SUCCESS);
+    else 
+	return(PS_AUTHFAIL);
+}
+
+/* cram.c ends here */
-- 
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