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Obscure the cached passphrases.

This commit is contained in:
Werner Koch 2010-09-02 10:46:23 +00:00
parent a0b9ebfb7d
commit 90a4599c5e
10 changed files with 215 additions and 160 deletions
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18
agent/ChangeLog
View File

@ -1,3 +1,21 @@
2010-09-02 Werner Koch <wk@g10code.com>
* cache.c (new_data): Change arg and callers to use a string and
explicity return an error code. We never used raw binary data and
thus it is easier to use a string. Adjust callers.
(initialize_module_cache, deinitialize_module_cache): New.
(new_data): Encrypt the cached data.
(struct cache_item_s): Remove field LOCKCOUNT. Change all users
accordingly.
(agent_unlock_cache_entry): Remove.
(agent_get_cache): Return an allocated string and remove CACHE_ID.
* genkey.c (agent_genkey): Remove cache marker stuff.
* findkey.c (unprotect): Ditto.
* cvt-openpgp.c (convert_openpgp): Ditto.
* command.c (cmd_get_passphrase): Ditto.
* gpg-agent.c (main, cleanup): Initialize and deinitialize the
cache module.
2010-09-01 Werner Koch <wk@g10code.com>
* call-pinentry.c (start_pinentry): Disable pinentry logging.

6
agent/agent.h
View File

@ -264,12 +264,12 @@ void agent_popup_message_stop (ctrl_t ctrl);
/*-- cache.c --*/
void initialize_module_cache (void);
void deinitialize_module_cache (void);
void agent_flush_cache (void);
int agent_put_cache (const char *key, cache_mode_t cache_mode,
const char *data, int ttl);
const char *agent_get_cache (const char *key, cache_mode_t cache_mode,
void **cache_id);
void agent_unlock_cache_entry (void **cache_id);
char *agent_get_cache (const char *key, cache_mode_t cache_mode);
/*-- pksign.c --*/

293
agent/cache.c
View File

@ -24,13 +24,31 @@
#include <string.h>
#include <time.h>
#include <assert.h>
#include <pth.h>
#include "agent.h"
/* The size of the encryption key in bytes. */
#define ENCRYPTION_KEYSIZE (128/8)
/* A mutex used to protect the encryption. This is required because
we use one context to do all encryption and decryption. */
static pth_mutex_t encryption_lock;
/* The encryption context. This is the only place where the
encryption key for all cached entries is available. It would nice
to keep this (or just the key) in some hardware device, for example
a TPM. Libgcrypt could be extended to provide such a service.
With the current scheme it is easy to retrieve the cached entries
if access to Libgcrypt's memory is available. The encryption
merely avoids grepping for clear texts in the memory. Nevertheless
the encryption provides the necessary infrastructure to make it
more secure. */
static gcry_cipher_hd_t encryption_handle;
struct secret_data_s {
int totallen; /* this includes the padding */
int datalen; /* actual data length */
char data[1];
int totallen; /* This includes the padding and space for AESWRAP. */
char data[1]; /* A string. */
};
typedef struct cache_item_s *ITEM;
@ -39,47 +57,116 @@ struct cache_item_s {
time_t created;
time_t accessed;
int ttl; /* max. lifetime given in seconds, -1 one means infinite */
int lockcount;
struct secret_data_s *pw;
cache_mode_t cache_mode;
char key[1];
};
/* The cache himself. */
static ITEM thecache;
/* This function must be called once to initialize this module. It
has to be done before a second thread is spawned. */
void
initialize_module_cache (void)
{
static int initialized;
gpg_error_t err;
void *key;
if (!pth_mutex_init (&encryption_lock))
err = gpg_error_from_syserror ();
else
err = gcry_cipher_open (&encryption_handle, GCRY_CIPHER_AES128,
GCRY_CIPHER_MODE_AESWRAP, GCRY_CIPHER_SECURE);
if (!err)
{
key = gcry_random_bytes (ENCRYPTION_KEYSIZE, GCRY_STRONG_RANDOM);
if (!key)
err = gpg_error_from_syserror ();
else
{
err = gcry_cipher_setkey (encryption_handle, key, ENCRYPTION_KEYSIZE);
xfree (key);
}
}
if (err)
log_fatal ("error initializing cache encryption context: %s\n",
gpg_strerror (err));
initialized = 1;
}
void
deinitialize_module_cache (void)
{
gcry_cipher_close (encryption_handle);
encryption_handle = NULL;
}
static void
release_data (struct secret_data_s *data)
{
xfree (data);
}
static struct secret_data_s *
new_data (const void *data, size_t length)
static gpg_error_t
new_data (const char *string, struct secret_data_s **r_data)
{
struct secret_data_s *d;
gpg_error_t err;
struct secret_data_s *d, *d_enc;
size_t length;
int total;
*r_data = NULL;
/* we pad the data to 32 bytes so that it get more complicated
if (!encryption_handle)
return gpg_error (GPG_ERR_NOT_INITIALIZED);
length = strlen (string) + 1;
/* We pad the data to 32 bytes so that it get more complicated
finding something out by watching allocation patterns. This is
usally not possible but we better assume nothing about our
secure storage provider*/
total = length + 32 - (length % 32);
usally not possible but we better assume nothing about our secure
storage provider. To support the AESWRAP mode we need to add 8
extra bytes as well. */
total = (length + 8) + 32 - ((length+8) % 32);
d = gcry_malloc_secure (sizeof *d + total - 1);
if (d)
d = xtrymalloc_secure (sizeof *d + total - 1);
if (!d)
return gpg_error_from_syserror ();
memcpy (d->data, string, length);
d_enc = xtrymalloc (sizeof *d_enc + total - 1);
if (!d_enc)
{
d->totallen = total;
d->datalen = length;
memcpy (d->data, data, length);
err = gpg_error_from_syserror ();
xfree (d);
return err;
}
return d;
d_enc->totallen = total;
if (!pth_mutex_acquire (&encryption_lock, 0, NULL))
log_fatal ("failed to acquire cache encryption mutex\n");
err = gcry_cipher_encrypt (encryption_handle, d_enc->data, total,
d->data, total - 8);
xfree (d);
if (!pth_mutex_release (&encryption_lock))
log_fatal ("failed to release cache encryption mutex\n");
if (err)
{
xfree (d_enc);
return err;
}
*r_data = d_enc;
return 0;
}
/* check whether there are items to expire */
/* Check whether there are items to expire. */
static void
housekeeping (void)
{
@ -89,8 +176,7 @@ housekeeping (void)
/* First expire the actual data */
for (r=thecache; r; r = r->next)
{
if (!r->lockcount && r->pw
&& r->ttl >= 0 && r->accessed + r->ttl < current)
if (r->pw && r->ttl >= 0 && r->accessed + r->ttl < current)
{
if (DBG_CACHE)
log_debug (" expired `%s' (%ds after last access)\n",
@ -112,7 +198,7 @@ housekeeping (void)
case CACHE_MODE_SSH: maxttl = opt.max_cache_ttl_ssh; break;
default: maxttl = opt.max_cache_ttl; break;
}
if (!r->lockcount && r->pw && r->created + maxttl < current)
if (r->pw && r->created + maxttl < current)
{
if (DBG_CACHE)
log_debug (" expired `%s' (%lus after creation)\n",
@ -129,28 +215,16 @@ housekeeping (void)
{
if (!r->pw && r->ttl >= 0 && r->accessed + 60*30 < current)
{
if (r->lockcount)
{
log_error ("can't remove unused cache entry `%s' (mode %d) due to"
" lockcount=%d\n",
r->key, r->cache_mode, r->lockcount);
r->accessed += 60*10; /* next error message in 10 minutes */
rprev = r;
r = r->next;
}
ITEM r2 = r->next;
if (DBG_CACHE)
log_debug (" removed `%s' (mode %d) (slot not used for 30m)\n",
r->key, r->cache_mode);
xfree (r);
if (!rprev)
thecache = r2;
else
{
ITEM r2 = r->next;
if (DBG_CACHE)
log_debug (" removed `%s' (mode %d) (slot not used for 30m)\n",
r->key, r->cache_mode);
xfree (r);
if (!rprev)
thecache = r2;
else
rprev->next = r2;
r = r2;
}
rprev->next = r2;
r = r2;
}
else
{
@ -171,7 +245,7 @@ agent_flush_cache (void)
for (r=thecache; r; r = r->next)
{
if (!r->lockcount && r->pw)
if (r->pw)
{
if (DBG_CACHE)
log_debug (" flushing `%s'\n", r->key);
@ -179,28 +253,22 @@ agent_flush_cache (void)
r->pw = NULL;
r->accessed = 0;
}
else if (r->lockcount && r->pw)
{
if (DBG_CACHE)
log_debug (" marked `%s' for flushing\n", r->key);
r->accessed = 0;
r->ttl = 0;
}
}
}
/* Store DATA of length DATALEN in the cache under KEY and mark it
with a maximum lifetime of TTL seconds. If there is already data
under this key, it will be replaced. Using a DATA of NULL deletes
the entry. A TTL of 0 is replaced by the default TTL and a TTL of
-1 set infinite timeout. CACHE_MODE is stored with the cache entry
/* Store the string DATA in the cache under KEY and mark it with a
maximum lifetime of TTL seconds. If there is already data under
this key, it will be replaced. Using a DATA of NULL deletes the
entry. A TTL of 0 is replaced by the default TTL and a TTL of -1
set infinite timeout. CACHE_MODE is stored with the cache entry
and used to select different timeouts. */
int
agent_put_cache (const char *key, cache_mode_t cache_mode,
const char *data, int ttl)
{
gpg_error_t err = 0;
ITEM r;
if (DBG_CACHE)
@ -221,15 +289,14 @@ agent_put_cache (const char *key, cache_mode_t cache_mode,
for (r=thecache; r; r = r->next)
{
if (!r->lockcount
&& ((cache_mode != CACHE_MODE_USER
&& cache_mode != CACHE_MODE_NONCE)
|| r->cache_mode == cache_mode)
if (((cache_mode != CACHE_MODE_USER
&& cache_mode != CACHE_MODE_NONCE)
|| r->cache_mode == cache_mode)
&& !strcmp (r->key, key))
break;
}
if (r)
{ /* replace */
if (r) /* Replace. */
{
if (r->pw)
{
release_data (r->pw);
@ -240,46 +307,47 @@ agent_put_cache (const char *key, cache_mode_t cache_mode,
r->created = r->accessed = gnupg_get_time ();
r->ttl = ttl;
r->cache_mode = cache_mode;
r->pw = new_data (data, strlen (data)+1);
if (!r->pw)
log_error ("out of core while allocating new cache item\n");
err = new_data (data, &r->pw);
if (err)
log_error ("error replacing cache item: %s\n", gpg_strerror (err));
}
}
else if (data)
{ /* simply insert */
else if (data) /* Insert. */
{
r = xtrycalloc (1, sizeof *r + strlen (key));
if (!r)
log_error ("out of core while allocating new cache control\n");
err = gpg_error_from_syserror ();
else
{
strcpy (r->key, key);
r->created = r->accessed = gnupg_get_time ();
r->ttl = ttl;
r->cache_mode = cache_mode;
r->pw = new_data (data, strlen (data)+1);
if (!r->pw)
{
log_error ("out of core while allocating new cache item\n");
xfree (r);
}
err = new_data (data, &r->pw);
if (err)
xfree (r);
else
{
r->next = thecache;
thecache = r;
}
}
if (err)
log_error ("error inserting cache item: %s\n", gpg_strerror (err));
}
return 0;
return err;
}
/* Try to find an item in the cache. Note that we currently don't
make use of CACHE_MODE except for CACHE_MODE_NONCE and
CACHE_MODE_USER. */
const char *
agent_get_cache (const char *key, cache_mode_t cache_mode, void **cache_id)
char *
agent_get_cache (const char *key, cache_mode_t cache_mode)
{
gpg_error_t err;
ITEM r;
char *value = NULL;
if (cache_mode == CACHE_MODE_IGNORE)
return NULL;
@ -288,67 +356,46 @@ agent_get_cache (const char *key, cache_mode_t cache_mode, void **cache_id)
log_debug ("agent_get_cache `%s' (mode %d) ...\n", key, cache_mode);
housekeeping ();
/* first try to find one with no locks - this is an updated cache
entry: We might have entries with a lockcount and without a
lockcount. */
for (r=thecache; r; r = r->next)
{
if (!r->lockcount && r->pw
if (r->pw
&& ((cache_mode != CACHE_MODE_USER
&& cache_mode != CACHE_MODE_NONCE)
|| r->cache_mode == cache_mode)
&& !strcmp (r->key, key))
{
/* put_cache does only put strings into the cache, so we
don't need the lengths */
r->accessed = gnupg_get_time ();
if (DBG_CACHE)
log_debug ("... hit\n");
r->lockcount++;
*cache_id = r;
return r->pw->data;
}
}
/* again, but this time get even one with a lockcount set */
for (r=thecache; r; r = r->next)
{
if (r->pw
&& ((cache_mode != CACHE_MODE_USER
&& cache_mode != CACHE_MODE_NONCE)
|| r->cache_mode == cache_mode)
&& !strcmp (r->key, key))
{
r->accessed = gnupg_get_time ();
if (DBG_CACHE)
log_debug ("... hit (locked)\n");
r->lockcount++;
*cache_id = r;
return r->pw->data;
if (r->pw->totallen < 32)
err = gpg_error (GPG_ERR_INV_LENGTH);
else if (!encryption_handle)
err = gpg_error (GPG_ERR_NOT_INITIALIZED);
else if (!(value = xtrymalloc_secure (r->pw->totallen - 8)))
err = gpg_error_from_syserror ();
else
{
if (!pth_mutex_acquire (&encryption_lock, 0, NULL))
log_fatal ("failed to acquire cache encryption mutex\n");
err = gcry_cipher_decrypt (encryption_handle,
value, r->pw->totallen - 8,
r->pw->data, r->pw->totallen);
if (!pth_mutex_release (&encryption_lock))
log_fatal ("failed to release cache encryption mutex\n");
}
if (err)
{
xfree (value);
value = NULL;
log_error ("retrieving cache entry `%s' failed: %s\n",
key, gpg_strerror (err));
}
return value;
}
}
if (DBG_CACHE)
log_debug ("... miss\n");
*cache_id = NULL;
return NULL;
}
void
agent_unlock_cache_entry (void **cache_id)
{
ITEM r;
for (r=thecache; r; r = r->next)
{
if (r == *cache_id)
{
if (!r->lockcount)
log_error ("trying to unlock non-locked cache entry `%s'\n",
r->key);
else
r->lockcount--;
return;
}
}
}

8
agent/command.c
View File

@ -1069,12 +1069,11 @@ cmd_get_passphrase (assuan_context_t ctx, char *line)
{
ctrl_t ctrl = assuan_get_pointer (ctx);
int rc;
const char *pw;
char *pw;
char *response;
char *cacheid = NULL, *desc = NULL, *prompt = NULL, *errtext = NULL;
const char *desc2 = _("Please re-enter this passphrase");
char *p;
void *cache_marker;
int opt_data, opt_check, opt_no_ask, opt_qualbar;
int opt_repeat = 0;
char *repeat_errtext = NULL;
@ -1135,12 +1134,11 @@ cmd_get_passphrase (assuan_context_t ctx, char *line)
if (!strcmp (desc, "X"))
desc = NULL;
pw = cacheid ? agent_get_cache (cacheid, CACHE_MODE_NORMAL, &cache_marker)
: NULL;
pw = cacheid ? agent_get_cache (cacheid, CACHE_MODE_NORMAL) : NULL;
if (pw)
{
rc = send_back_passphrase (ctx, opt_data, pw);
agent_unlock_cache_entry (&cache_marker);
xfree (pw);
}
else if (opt_no_ask)
rc = gpg_error (GPG_ERR_NO_DATA);

8
agent/cvt-openpgp.c
View File

@ -766,16 +766,14 @@ convert_openpgp (ctrl_t ctrl, gcry_sexp_t s_pgp,
err = gpg_error (GPG_ERR_BAD_PASSPHRASE);
if (cache_nonce)
{
void *cache_marker = NULL;
const char *cache_value;
char *cache_value;
cache_value = agent_get_cache (cache_nonce, CACHE_MODE_NONCE,
&cache_marker);
cache_value = agent_get_cache (cache_nonce, CACHE_MODE_NONCE);
if (cache_value)
{
if (strlen (cache_value) < pi->max_length)
strcpy (pi->pin, cache_value);
agent_unlock_cache_entry (&cache_marker);
xfree (cache_value);
}
if (*pi->pin)
err = try_do_unprotect_cb (pi);

14
agent/findkey.c
View File

@ -291,14 +291,13 @@ unprotect (ctrl_t ctrl, const char *cache_nonce, const char *desc_text,
/* Initially try to get it using a cache nonce. */
if (cache_nonce)
{
void *cache_marker;
const char *pw;
char *pw;
pw = agent_get_cache (cache_nonce, CACHE_MODE_NONCE, &cache_marker);
pw = agent_get_cache (cache_nonce, CACHE_MODE_NONCE);
if (pw)
{
rc = agent_unprotect (*keybuf, pw, NULL, &result, &resultlen);
agent_unlock_cache_entry (&cache_marker);
xfree (pw);
if (!rc)
{
xfree (*keybuf);
@ -312,15 +311,14 @@ unprotect (ctrl_t ctrl, const char *cache_nonce, const char *desc_text,
unprotect it, we fall back to ask the user */
if (cache_mode != CACHE_MODE_IGNORE)
{
void *cache_marker;
const char *pw;
char *pw;
retry:
pw = agent_get_cache (hexgrip, cache_mode, &cache_marker);
pw = agent_get_cache (hexgrip, cache_mode);
if (pw)
{
rc = agent_unprotect (*keybuf, pw, NULL, &result, &resultlen);
agent_unlock_cache_entry (&cache_marker);
xfree (pw);
if (!rc)
{
xfree (*keybuf);

18
agent/genkey.c
View File

@ -359,7 +359,7 @@ agent_genkey (ctrl_t ctrl, const char *cache_nonce,
membuf_t *outbuf)
{
gcry_sexp_t s_keyparam, s_key, s_private, s_public;
char *passphrase = NULL;
char *passphrase;
int rc;
size_t len;
char *buf;
@ -372,21 +372,7 @@ agent_genkey (ctrl_t ctrl, const char *cache_nonce,
}
/* Get the passphrase now, cause key generation may take a while. */
if (cache_nonce)
{
void *cache_marker = NULL;
const char *cache_value;
cache_value = agent_get_cache (cache_nonce, CACHE_MODE_NONCE,
&cache_marker);
if (cache_value)
{
passphrase = xtrymalloc_secure (strlen (cache_value)+1);
if (passphrase)
strcpy (passphrase, cache_value);
agent_unlock_cache_entry (&cache_marker);
}
}
passphrase = cache_nonce? agent_get_cache (cache_nonce, CACHE_MODE_NONCE):NULL;
if (passphrase)
rc = 0;
else

2
agent/gpg-agent.c
View File

@ -440,6 +440,7 @@ remove_socket (char *name)
static void
cleanup (void)
{
deinitialize_module_cache ();
remove_socket (socket_name);
remove_socket (socket_name_ssh);
}
@ -842,6 +843,7 @@ main (int argc, char **argv )
exit (1);
}
initialize_module_cache ();
initialize_module_call_pinentry ();
initialize_module_call_scd ();
initialize_module_trustlist ();

4
common/ChangeLog
View File

@ -1,3 +1,7 @@
2010-09-02 Werner Koch <wk@g10code.com>
* util.h (GPG_ERR_NOT_INITIALIZED): Define if not defined.
2010-09-01 Marcus Brinkmann <marcus@g10code.de>
* estream.c (_es_set_std_fd): Disable debug output.

4
common/util.h
View File

@ -30,6 +30,10 @@
#ifndef GPG_ERR_LIMIT_REACHED
#define GPG_ERR_LIMIT_REACHED 183
#endif
#ifndef GPG_ERR_NOT_INITIALIZED
#define GPG_ERR_NOT_INITIALIZED 184
#endif
/* Hash function used with libksba. */
#define HASH_FNC ((void (*)(void *, const void*,size_t))gcry_md_write)