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acl/lib_tls/tls/tls_scache.c

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/*++
* NAME
* tls_scache 3
* SUMMARY
* TLS session cache manager
* SYNOPSIS
* #include <tls_scache.h>
*
* TLS_SCACHE *tls_scache_open(dbname, cache_label, verbose, timeout)
* const char *dbname
* const char *cache_label;
* int verbose;
* int timeout;
*
* void tls_scache_close(cache)
* TLS_SCACHE *cache;
*
* int tls_scache_lookup(cache, cache_id, out_session)
* TLS_SCACHE *cache;
* const char *cache_id;
* ACL_VSTRING *out_session;
*
* int tls_scache_update(cache, cache_id, session, session_len)
* TLS_SCACHE *cache;
* const char *cache_id;
* const char *session;
* ssize_t session_len;
*
* int tls_scache_sequence(cache, first_next, out_cache_id,
* ACL_VSTRING *out_session)
* TLS_SCACHE *cache;
* int first_next;
* char **out_cache_id;
* ACL_VSTRING *out_session;
*
* int tls_scache_delete(cache, cache_id)
* TLS_SCACHE *cache;
* const char *cache_id;
* DESCRIPTION
* This module maintains Postfix TLS session cache files.
* each session is stored under a lookup key (hostname or
* session ID).
*
* tls_scache_open() opens the specified TLS session cache
* and returns a handle that must be used for subsequent
* access.
*
* tls_scache_close() closes the specified TLS session cache
* and releases memory that was allocated by tls_scache_open().
*
* tls_scache_lookup() looks up the specified session in the
* specified cache, and applies session timeout restrictions.
* Entries that are too old are silently deleted.
*
* tls_scache_update() updates the specified TLS session cache
* with the specified session information.
*
* tls_scache_sequence() iterates over the specified TLS session
* cache and either returns the first or next entry that has not
* timed out, or returns no data. Entries that are too old are
* silently deleted. Specify TLS_SCACHE_SEQUENCE_NOTHING as the
* third and last argument to disable saving of cache entry
* content or cache entry ID information. This is useful when
* purging expired entries. A result value of zero means that
* the end of the cache was reached.
*
* tls_scache_delete() removes the specified cache entry from
* the specified TLS session cache.
*
* Arguments:
* .IP dbname
* The base name of the session cache file.
* .IP cache_label
* A string that is used in logging and error messages.
* .IP verbose
* Do verbose logging of cache operations? (zero == no)
* .IP timeout
* The time after wich a session cache entry is considered too old.
* .IP first_next
* One of DICT_SEQ_FUN_FIRST (first cache element) or DICT_SEQ_FUN_NEXT
* (next cache element).
* .IP cache_id
* Session cache lookup key.
* .IP session
* Storage for session information.
* .IP session_len
* The size of the session information in bytes.
* .IP out_cache_id
* .IP out_session
* Storage for saving the cache_id or session information of the
* current cache entry.
*
* Specify TLS_SCACHE_DONT_NEED_CACHE_ID to avoid saving
* the session cache ID of the cache entry.
*
* Specify TLS_SCACHE_DONT_NEED_SESSION to avoid
* saving the session information in the cache entry.
* DIAGNOSTICS
* These routines terminate with a fatal run-time error
* for unrecoverable database errors. This allows the
* program to restart and reset the database to an
* empty initial state.
*
* tls_scache_open() never returns on failure. All other
* functions return non-zero on success, zero when the
* operation could not be completed.
* LICENSE
* .ad
* .fi
* The Secure Mailer license must be distributed with this software.
* AUTHOR(S)
* Wietse Venema
* IBM T.J. Watson Research
* P.O. Box 704
* Yorktown Heights, NY 10598, USA
*--*/
#include "StdAfx.h"
#ifdef USE_TLS
#include <string.h>
#include <stddef.h>
#include "dict.h"
/* Global library. */
/* TLS library. */
#include "tls_scache.h"
/* Application-specific. */
/*
* Session cache entry format.
*/
typedef struct {
time_t timestamp; /* time when saved */
char session[1]; /* actually a bunch of bytes */
} TLS_SCACHE_ENTRY;
/*
* SLMs.
*/
#define STR(x) acl_vstring_str(x)
#define LEN(x) ACL_VSTRING_LEN(x)
/* tls_scache_encode - encode TLS session cache entry */
static ACL_VSTRING *tls_scache_encode(TLS_SCACHE *cp, const char *cache_id,
const char *session, ssize_t session_len)
{
TLS_SCACHE_ENTRY *entry;
ACL_VSTRING *hex_data;
ssize_t binary_data_len;
/*
* Assemble the TLS session cache entry.
*
* We could eliminate some copying by using incremental encoding, but
* sessions are so small that it really does not matter.
*/
binary_data_len = session_len + offsetof(TLS_SCACHE_ENTRY, session);
entry = (TLS_SCACHE_ENTRY *) acl_mymalloc(binary_data_len);
entry->timestamp = time((time_t *) 0);
memcpy(entry->session, session, session_len);
/*
* Encode the TLS session cache entry.
*/
hex_data = acl_vstring_alloc(2 * binary_data_len + 1);
acl_hex_encode(hex_data, (char *) entry, binary_data_len);
/*
* Logging.
*/
if (cp->verbose)
acl_msg_info("write %s TLS cache entry %s: time=%ld [data %ld bytes]",
cp->cache_label, cache_id, (long) entry->timestamp,
(long) session_len);
/*
* Clean up.
*/
acl_myfree(entry);
return (hex_data);
}
/* tls_scache_decode - decode TLS session cache entry */
static int tls_scache_decode(TLS_SCACHE *cp, const char *cache_id,
const char *hex_data, ssize_t hex_data_len, ACL_VSTRING *out_session)
{
const char *myname = "tls+scache_decode";
TLS_SCACHE_ENTRY *entry;
ACL_VSTRING *bin_data;
/*
* Sanity check.
*/
if (hex_data_len < (ssize_t) (2 * (offsetof(TLS_SCACHE_ENTRY, session)))) {
acl_msg_warn("%s: %s TLS cache: truncated entry for %s: %.100s",
myname, cp->cache_label, cache_id, hex_data);
return (0);
}
/*
* Disassemble the TLS session cache entry.
*
* No early returns or we have a memory leak.
*/
#define FREE_AND_RETURN(ptr, x) { acl_vstring_free(ptr); return (x); }
bin_data = acl_vstring_alloc(hex_data_len / 2 + 1);
if (acl_hex_decode(bin_data, hex_data, hex_data_len) == 0) {
acl_msg_warn("%s: %s TLS cache: malformed entry for %s: %.100s",
myname, cp->cache_label, cache_id, hex_data);
FREE_AND_RETURN(bin_data, 0);
}
entry = (TLS_SCACHE_ENTRY *) STR(bin_data);
/*
* Logging.
*/
if (cp->verbose)
acl_msg_info("read %s TLS cache entry %s: time=%ld [data %ld bytes]",
cp->cache_label, cache_id, (long) entry->timestamp,
(long) (LEN(bin_data) - offsetof(TLS_SCACHE_ENTRY, session)));
/*
* Other mandatory restrictions.
*/
if (entry->timestamp + cp->timeout < time((time_t *) 0))
FREE_AND_RETURN(bin_data, 0);
/*
* Optional output.
*/
if (out_session != 0)
acl_vstring_memcpy(out_session, entry->session,
LEN(bin_data) - offsetof(TLS_SCACHE_ENTRY, session));
/*
* Clean up.
*/
FREE_AND_RETURN(bin_data, 1);
}
/* tls_scache_lookup - load session from cache */
int tls_scache_lookup(TLS_SCACHE *cp, char *cache_id, ACL_VSTRING *session)
{
char *hex_data;
size_t size;
/*
* Logging.
*/
if (cp->verbose)
acl_msg_info("lookup %s session id=%s", cp->cache_label, cache_id);
/*
* Initialize. Don't leak data.
*/
if (session)
ACL_VSTRING_RESET(session);
/*
* Search the cache database.
*/
if ((DICT_GET(cp->db, cache_id, strlen(cache_id), &hex_data, &size)) == 0)
return (0);
/*
* Decode entry and delete if expired or malformed.
*/
if (tls_scache_decode(cp, cache_id, hex_data, (int) strlen(hex_data), session) == 0) {
tls_scache_delete(cp, cache_id);
acl_myfree(hex_data);
return (0);
} else {
acl_myfree(hex_data);
return (1);
}
}
/* tls_scache_update - save session to cache */
int tls_scache_update(TLS_SCACHE *cp, char *cache_id, const char *buf, ssize_t len)
{
ACL_VSTRING *hex_data;
/*
* Logging.
*/
if (cp->verbose)
acl_msg_info("put %s session id=%s [data %ld bytes]",
cp->cache_label, cache_id, (long) len);
/*
* Encode the cache entry.
*/
hex_data = tls_scache_encode(cp, cache_id, buf, len);
/*
* Store the cache entry.
*
* XXX Berkeley DB supports huge database keys and values. SDBM seems to
* have a finite limit, and DBM simply can't be used at all.
*/
DICT_PUT(cp->db, cache_id, strlen(cache_id), STR(hex_data), LEN(hex_data));
/*
* Clean up.
*/
acl_vstring_free(hex_data);
return (1);
}
/* tls_scache_sequence - get first/next TLS session cache entry */
int tls_scache_sequence(TLS_SCACHE *cp, int first_next,
char **out_cache_id, ACL_VSTRING *out_session)
{
char *member;
char *value;
char *saved_cursor;
int found_entry;
int keep_entry = 0;
char *saved_member = 0;
size_t key_size, val_size;
/*
* XXX Deleting entries while enumerating a map can he tricky. Some map
* types have a concept of cursor and support a "delete the current
* element" operation. Some map types without cursors don't behave well
* when the current first/next entry is deleted (example: with Berkeley
* DB < 2, the "next" operation produces garbage). To avoid trouble, we
* delete an expired entry after advancing the current first/next
* position beyond it, and ignore client requests to delete the current
* entry.
*/
/*
* Find the first or next database entry. Activate the passivated entry
* and check the time stamp. Schedule the entry for deletion if it is too
* old.
*
* Save the member (cache id) so that it will not be clobbered by the
* tls_scache_lookup() call below.
*/
found_entry = (DICT_SEQ(cp->db, first_next, &member, &key_size, &value, &val_size) == 0);
if (found_entry) {
keep_entry = tls_scache_decode(cp, member, value, (int) strlen(value),
out_session);
if (keep_entry && out_cache_id)
*out_cache_id = acl_mystrdup(member);
saved_member = acl_mystrdup(member);
acl_myfree(member);
acl_myfree(value);
}
/*
* Delete behind. This is a no-op if an expired cache entry was updated
* in the mean time. Use the saved lookup criteria so that the "delete
* behind" operation works as promised.
*/
if (cp->flags & TLS_SCACHE_FLAG_DEL_SAVED_CURSOR) {
cp->flags &= ~TLS_SCACHE_FLAG_DEL_SAVED_CURSOR;
saved_cursor = cp->saved_cursor;
cp->saved_cursor = 0;
tls_scache_lookup(cp, saved_cursor, (ACL_VSTRING *) 0);
acl_myfree(saved_cursor);
}
/*
* Otherwise, clean up if this is not the first iteration.
*/
else {
if (cp->saved_cursor)
acl_myfree(cp->saved_cursor);
cp->saved_cursor = 0;
}
/*
* Protect the current first/next entry against explicit or implied
* client delete requests, and schedule a bad or expired entry for
* deletion. Save the lookup criteria so that the "delete behind"
* operation will work as promised.
*/
if (found_entry) {
cp->saved_cursor = saved_member;
if (keep_entry == 0)
cp->flags |= TLS_SCACHE_FLAG_DEL_SAVED_CURSOR;
}
return (found_entry);
}
/* tls_scache_delete - delete session from cache */
int tls_scache_delete(TLS_SCACHE *cp, char *cache_id)
{
/*
* Logging.
*/
if (cp->verbose)
acl_msg_info("delete %s session id=%s", cp->cache_label, cache_id);
/*
* Do it, unless we would delete the current first/next entry. Some map
* types don't have cursors, and some of those don't behave when the
* "current" entry is deleted.
*/
return ((cp->saved_cursor != 0 && strcmp(cp->saved_cursor, cache_id) == 0)
|| DICT_DEL(cp->db, cache_id, strlen(cache_id)) == 0);
}
/* tls_scache_init - init dict */
void tls_scache_init()
{
dict_open_init();
}
/* tls_scache_open - open TLS session cache file */
TLS_SCACHE *tls_scache_open(const char *dbname, const char *cache_label,
int verbose, int timeout)
{
const char *myname = "tls_scache_open";
TLS_SCACHE *cp;
DICT *dict;
/*
* Logging.
*/
if (verbose)
acl_msg_info("open %s TLS cache %s", cache_label, dbname);
/*
* Open the dictionary with O_TRUNC, so that we never have to worry about
* opening a damaged file after some process terminated abnormally.
*/
#ifdef SINGLE_UPDATER
#define DICT_FLAGS (DICT_FLAG_DUP_REPLACE)
#elif defined(ACL_UNIX)
#define DICT_FLAGS \
(DICT_FLAG_DUP_REPLACE | DICT_FLAG_LOCK | DICT_FLAG_SYNC_UPDATE)
#elif defined(WIN32)
#define DICT_FLAGS \
(DICT_FLAG_DUP_REPLACE | DICT_FLAG_SYNC_UPDATE)
#endif
dict = dict_open(dbname, O_RDWR | O_CREAT | O_TRUNC, DICT_FLAGS);
/*
* Sanity checks.
*/
if (dict->lock_fd < 0)
acl_msg_fatal("%s: dictionary %s is not a regular file", myname, dbname);
#ifdef SINGLE_UPDATER
if (acl_myflock(dict->lock_fd, INTERNAL_LOCK,
MYFLOCK_OP_EXCLUSIVE | MYFLOCK_OP_NOWAIT) < 0)
acl_msg_fatal("%s: cannot lock dictionary %s for exclusive use: %s",
myname, dbname, acl_last_serror());
#endif
if (dict->update == 0)
acl_msg_fatal("%s: dictionary %s does not support update operations", myname, dbname);
if (dict->delete_it == 0)
acl_msg_fatal("%s: dictionary %s does not support delete operations", myname, dbname);
if (dict->sequence == 0)
acl_msg_fatal("%s: dictionary %s does not support sequence operations", myname, dbname);
/*
* Create the TLS_SCACHE object.
*/
cp = (TLS_SCACHE *) acl_mymalloc(sizeof(*cp));
cp->flags = 0;
cp->db = dict;
cp->cache_label = acl_mystrdup(cache_label);
cp->verbose = verbose;
cp->timeout = timeout;
cp->saved_cursor = 0;
return (cp);
}
/* tls_scache_close - close TLS session cache file */
void tls_scache_close(TLS_SCACHE *cp)
{
const char *myname = "tls_scache_close";
/*
* Logging.
*/
if (cp->verbose)
acl_msg_info("%s: close %s TLS cache %s",
myname, cp->cache_label, cp->db->name);
/*
* Destroy the TLS_SCACHE object.
*/
DICT_CLOSE(cp->db);
acl_myfree(cp->cache_label);
if (cp->saved_cursor)
acl_myfree(cp->saved_cursor);
acl_myfree(cp);
}
#endif
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