Initial revision

svn path=/trunk/; revision=3074

1 files changed, 271 insertions, 0 deletions

diff --git a/kerberos.c b/kerberos.c
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+++ b/kerberos.c
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+/*
+ * kerberos.c -- Kerberos authentication (see RFC 1731).
+ *
+ * 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"
+
+#ifdef KERBEROS_V4
+
+#  ifdef KERBEROS_V5
+#    include <kerberosIV/des.h>
+#    include <kerberosIV/krb.h>
+#  else
+#    if defined (__bsdi__)
+#       include <des.h>
+#       define krb_get_err_text(e) (krb_err_txt[e])
+#    endif
+#    if defined(__NetBSD__) || (__FreeBSD__) || defined(__linux__)
+#       define krb_get_err_text(e) (krb_err_txt[e])
+#    endif
+#    include <krb.h>
+#  endif
+
+#if SIZEOF_INT == 4
+typedef	int	int32;
+#elif SIZEOF_SHORT == 4
+typedef	short	int32;
+#elif SIZEOF_LONG == 4
+typedef	long	int32;
+#else
+#error Cannot deduce a 32-bit-type
+#endif
+
+int do_rfc1731(int sock, char *command, char *truename)
+/* authenticate as per RFC1731 -- note 32-bit integer requirement here */
+{
+    int result = 0, len;
+    char buf1[4096], buf2[4096];
+    union {
+      int32 cint;
+      char cstr[4];
+    } challenge1, challenge2;
+    char srvinst[INST_SZ];
+    char *p;
+    char srvrealm[REALM_SZ];
+    KTEXT_ST authenticator;
+    CREDENTIALS credentials;
+    char tktuser[MAX_K_NAME_SZ+1+INST_SZ+1+REALM_SZ+1];
+    char tktinst[INST_SZ];
+    char tktrealm[REALM_SZ];
+    des_cblock session;
+    des_key_schedule schedule;
+
+    gen_send(sock, "%s KERBEROS_V4", command);
+
+    /* The data encoded in the first ready response contains a random
+     * 32-bit number in network byte order.  The client should respond
+     * with a Kerberos ticket and an authenticator for the principal
+     * "imap.hostname@realm", where "hostname" is the first component
+     * of the host name of the server with all letters in lower case
+     * and where "realm" is the Kerberos realm of the server.  The
+     * encrypted checksum field included within the Kerberos
+     * authenticator should contain the server provided 32-bit number
+     * in network byte order.
+     */
+
+    if (result = gen_recv(sock, buf1, sizeof buf1)) {
+	return result;
+    }
+
+    len = from64tobits(challenge1.cstr, buf1);
+    if (len < 0) {
+	report(stderr, _("could not decode initial BASE64 challenge\n"));
+	return PS_AUTHFAIL;
+    }
+
+    /* this patch by Dan Root <dar@thekeep.org> solves an endianess
+     * problem. */
+    {
+	char tmp[4];
+
+	*(int *)tmp = ntohl(*(int *) challenge1.cstr);
+	memcpy(challenge1.cstr, tmp, sizeof(tmp));
+    }
+
+    /* Client responds with a Kerberos ticket and an authenticator for
+     * the principal "imap.hostname@realm" where "hostname" is the
+     * first component of the host name of the server with all letters
+     * in lower case and where "realm" is the Kerberos realm of the
+     * server.  The encrypted checksum field included within the
+     * Kerberos authenticator should contain the server-provided
+     * 32-bit number in network byte order.
+     */
+
+    strncpy(srvinst, truename, (sizeof srvinst)-1);
+    srvinst[(sizeof srvinst)-1] = '\0';
+    for (p = srvinst; *p; p++) {
+      if (isupper(*p)) {
+	*p = tolower(*p);
+      }
+    }
+
+    strncpy(srvrealm, (char *)krb_realmofhost(srvinst), (sizeof srvrealm)-1);
+    srvrealm[(sizeof srvrealm)-1] = '\0';
+    if (p = strchr(srvinst, '.')) {
+      *p = '\0';
+    }
+
+    result = krb_mk_req(&authenticator, "imap", srvinst, srvrealm, 0);
+    if (result) {
+	report(stderr, "krb_mq_req: %s\n", krb_get_err_text(result));
+	return PS_AUTHFAIL;
+    }
+
+    result = krb_get_cred("imap", srvinst, srvrealm, &credentials);
+    if (result) {
+	report(stderr, "krb_get_cred: %s\n", krb_get_err_text(result));
+	return PS_AUTHFAIL;
+    }
+
+    memcpy(session, credentials.session, sizeof session);
+    memset(&credentials, 0, sizeof credentials);
+    des_key_sched(session, schedule);
+
+    result = krb_get_tf_fullname(TKT_FILE, tktuser, tktinst, tktrealm);
+    if (result) {
+	report(stderr, "krb_get_tf_fullname: %s\n", krb_get_err_text(result));
+	return PS_AUTHFAIL;
+    }
+
+#ifdef __UNUSED__
+    /*
+     * Andrew H. Chatham <andrew.chatham@duke.edu> alleges that this check
+     * is not necessary and has consistently been messing him up.
+     */
+    if (strcmp(tktuser, user) != 0) {
+	report(stderr, 
+	       _("principal %s in ticket does not match -u %s\n"), tktuser,
+		user);
+	return PS_AUTHFAIL;
+    }
+#endif /* __UNUSED__ */
+
+    if (tktinst[0]) {
+	report(stderr, 
+	       _("non-null instance (%s) might cause strange behavior\n"),
+		tktinst);
+	strcat(tktuser, ".");
+	strcat(tktuser, tktinst);
+    }
+
+    if (strcmp(tktrealm, srvrealm) != 0) {
+	strcat(tktuser, "@");
+	strcat(tktuser, tktrealm);
+    }
+
+    result = krb_mk_req(&authenticator, "imap", srvinst, srvrealm,
+	    challenge1.cint);
+    if (result) {
+	report(stderr, "krb_mq_req: %s\n", krb_get_err_text(result));
+	return PS_AUTHFAIL;
+    }
+
+    to64frombits(buf1, authenticator.dat, authenticator.length);
+    if (outlevel >= O_MONITOR) {
+	report(stdout, "IMAP> %s\n", buf1);
+    }
+    strcat(buf1, "\r\n");
+    SockWrite(sock, buf1, strlen(buf1));
+
+    /* Upon decrypting and verifying the ticket and authenticator, the
+     * server should verify that the contained checksum field equals
+     * the original server provided random 32-bit number.  Should the
+     * verification be successful, the server must add one to the
+     * checksum and construct 8 octets of data, with the first four
+     * octets containing the incremented checksum in network byte
+     * order, the fifth octet containing a bit-mask specifying the
+     * protection mechanisms supported by the server, and the sixth
+     * through eighth octets containing, in network byte order, the
+     * maximum cipher-text buffer size the server is able to receive.
+     * The server must encrypt the 8 octets of data in the session key
+     * and issue that encrypted data in a second ready response.  The
+     * client should consider the server authenticated if the first
+     * four octets the un-encrypted data is equal to one plus the
+     * checksum it previously sent.
+     */
+    
+    if (result = gen_recv(sock, buf1, sizeof buf1))
+	return result;
+
+    /* The client must construct data with the first four octets
+     * containing the original server-issued checksum in network byte
+     * order, the fifth octet containing the bit-mask specifying the
+     * selected protection mechanism, the sixth through eighth octets
+     * containing in network byte order the maximum cipher-text buffer
+     * size the client is able to receive, and the following octets
+     * containing a user name string.  The client must then append
+     * from one to eight octets so that the length of the data is a
+     * multiple of eight octets. The client must then PCBC encrypt the
+     * data with the session key and respond to the second ready
+     * response with the encrypted data.  The server decrypts the data
+     * and verifies the contained checksum.  The username field
+     * identifies the user for whom subsequent IMAP operations are to
+     * be performed; the server must verify that the principal
+     * identified in the Kerberos ticket is authorized to connect as
+     * that user.  After these verifications, the authentication
+     * process is complete.
+     */
+
+    len = from64tobits(buf2, buf1);
+    if (len < 0) {
+	report(stderr, _("could not decode BASE64 ready response\n"));
+	return PS_AUTHFAIL;
+    }
+
+    des_ecb_encrypt((des_cblock *)buf2, (des_cblock *)buf2, schedule, 0);
+    memcpy(challenge2.cstr, buf2, 4);
+    if (ntohl(challenge2.cint) != challenge1.cint + 1) {
+	report(stderr, _("challenge mismatch\n"));
+	return PS_AUTHFAIL;
+    }	    
+
+    memset(authenticator.dat, 0, sizeof authenticator.dat);
+
+    result = htonl(challenge1.cint);
+    memcpy(authenticator.dat, &result, sizeof result);
+
+    /* The protection mechanisms and their corresponding bit-masks are as
+     * follows:
+     *
+     * 1 No protection mechanism
+     * 2 Integrity (krb_mk_safe) protection
+     * 4 Privacy (krb_mk_priv) protection
+     */
+    authenticator.dat[4] = 1;
+
+    len = strlen(tktuser);
+    strncpy(authenticator.dat+8, tktuser, len);
+    authenticator.length = len + 8 + 1;
+    while (authenticator.length & 7) {
+	authenticator.length++;
+    }
+    des_pcbc_encrypt((des_cblock *)authenticator.dat,
+	    (des_cblock *)authenticator.dat, authenticator.length, schedule,
+	    &session, 1);
+
+    to64frombits(buf1, authenticator.dat, authenticator.length);
+
+    /* ship down the response, accept the server's error/ok indication */
+    suppress_tags = TRUE;
+    result = gen_transact(sock, buf1, strlen(buf1));
+    suppress_tags = FALSE;
+    if (result)
+	return(result);
+    else
+	return(PS_SUCCESS);
+}
+#endif /* KERBEROS_V4 */
+
+/* kerberos.c ends here */
+