I have been working on deploying an imap server using EXTERNAL+TLS
authentication. Everything is working fine and then I discover that
there is no support CRLs in imapd; from my point of view this is a Bad
Thing(tm).
I searched the mailing list and found a discussion of this in 2005/02
with the final word being (I'll paraphrase) "sounds interesting, patches
welcome."
All right, the attached implements CRL checking via a 'tls_crl' option
in imapd.conf. Just point it at a PEM encoded CRL file. The file can
contain multiple CRLs if you have more than one CA you care about.
What it doesn't do is:
- implement crl_path
- implement CRL checking in the TLS client code
It also suffers from the fact that this code is ran at initialisation
time. When the CRL expires you need to get a fresh CRL, you need to
restart imapd; but this is the same behavior as Apache httpd and sendmail.
-stacy
--- imap/tls.c.orig 2008-11-14 15:24:38.000000000 -0700
+++ imap/tls.c 2010-05-27 08:32:39.000000000 -0600
@@ -308,6 +308,9 @@
case X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD:
syslog(LOG_NOTICE, "cert has expired");
break;
+ case X509_V_ERR_CERT_REVOKED:
+ syslog(LOG_NOTICE, "cert has been revoked");
+ break;
}
return (ok);
@@ -629,10 +632,15 @@
const char *cipher_list;
const char *CApath;
const char *CAfile;
+ const char *CAcrl;
const char *s_cert_file;
const char *s_key_file;
int requirecert;
int timeout;
+ BIO *crl_file;
+ X509_CRL *crl;
+ X509_STORE *store;
+
if (tls_serverengine)
return (0); /* already running */
@@ -719,6 +727,7 @@
CAfile = config_getstring(IMAPOPT_TLS_CA_FILE);
CApath = config_getstring(IMAPOPT_TLS_CA_PATH);
+ CAcrl = config_getstring(IMAPOPT_TLS_CRL);
if ((!SSL_CTX_load_verify_locations(s_ctx, CAfile, CApath)) ||
(!SSL_CTX_set_default_verify_paths(s_ctx))) {
@@ -760,6 +769,25 @@
SSL_CTX_set_client_CA_list(s_ctx, SSL_load_client_CA_file(CAfile));
}
}
+ if(CAcrl != NULL) {
+ store = SSL_CTX_get_cert_store(s_ctx);
+ if((crl_file = BIO_new(BIO_s_file_internal())) != NULL) {
+ if (BIO_read_filename(crl_file, CAcrl) >= 0) {
+ while((crl = PEM_read_bio_X509_CRL(crl_file,
NULL, NULL, NULL))) {
+ X509_STORE_add_crl(store, crl);
+ X509_CRL_free(crl);
+ }
+ X509_STORE_set_flags(store,
X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
+ } else {
+ syslog(LOG_ERR, "TLS server engine: Can't load
CRL.");
+ /* should we bail? */
+ }
+
+ BIO_free(crl_file);
+ } else {
+ syslog(LOG_ERR, "TLS server engine: Can't load CRL.
BIO_new failed.");
+ }
+ }
tls_serverengine = 1;
return (0);
--- lib/imapopts.c.orig 2009-12-21 06:17:55.000000000 -0700
+++ lib/imapopts.c 2010-05-27 07:18:26.000000000 -0600
@@ -736,6 +736,9 @@
{ IMAPOPT_TLS_CA_PATH, "tls_ca_path", 0, OPT_STRING,
{(void *)(NULL)},
{ { NULL, IMAP_ENUM_ZERO } } },
+ { IMAPOPT_TLS_CRL, "tls_crl", 0, OPT_STRING,
+ {(void *)(NULL)},
+ { { NULL, IMAP_ENUM_ZERO } } },
{ IMAPOPT_TLSCACHE_DB, "tlscache_db", 0, OPT_STRINGLIST,
{(void*)("berkeley-nosync")},
{ { "berkeley" , IMAP_ENUM_ZERO },
--- lib/imapopts.h.orig 2009-12-21 06:17:55.000000000 -0700
+++ lib/imapopts.h 2010-05-27 07:14:52.000000000 -0600
@@ -219,6 +219,7 @@
IMAPOPT_TIMEOUT,
IMAPOPT_TLS_CA_FILE,
IMAPOPT_TLS_CA_PATH,
+ IMAPOPT_TLS_CRL,
IMAPOPT_TLSCACHE_DB,
IMAPOPT_TLS_CERT_FILE,
IMAPOPT_TLS_CIPHER_LIST,
----
Cyrus Home Page: http://cyrusimap.web.cmu.edu/
Cyrus Wiki/FAQ: http://cyrusimap.web.cmu.edu/twiki
List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html
