/* Unprotect the canconical encoded S-expression key in KEYBUF. GRIP
should be the hex encoded keygrip of that key to be used with the
caching mechanism. DESC_TEXT may be set to override the default
description used for the pinentry. If LOOKUP_TTL is given this
function is used to lookup the default ttl. */
static int
unprotect (ctrl_t ctrl, const char *desc_text,
unsigned char **keybuf, const unsigned char *grip,
cache_mode_t cache_mode, lookup_ttl_t lookup_ttl)
{
struct pin_entry_info_s *pi;
struct try_unprotect_arg_s arg;
int rc;
unsigned char *result;
size_t resultlen;
char hexgrip[40+1];
bin2hex (grip, 20, hexgrip);
/* First try to get it from the cache - if there is none or we can't
unprotect it, we fall back to ask the user */
if (cache_mode != CACHE_MODE_IGNORE)
{
void *cache_marker;
const char *pw;
retry:
pw = agent_get_cache (hexgrip, cache_mode, &cache_marker);
if (pw)
{
rc = agent_unprotect (*keybuf, pw, NULL, &result, &resultlen);
agent_unlock_cache_entry (&cache_marker);
if (!rc)
{
xfree (*keybuf);
*keybuf = result;
return 0;
}
rc = 0;
}
/* If the pinentry is currently in use, we wait up to 60 seconds
for it to close and check the cache again. This solves a common
situation where several requests for unprotecting a key have
been made but the user is still entering the passphrase for
the first request. Because all requests to agent_askpin are
serialized they would then pop up one after the other to
request the passphrase - despite that the user has already
entered it and is then available in the cache. This
implementation is not race free but in the worst case the
user has to enter the passphrase only once more. */
if (pinentry_active_p (ctrl, 0))
{
/* Active - wait */
if (!pinentry_active_p (ctrl, 60))
{
/* We need to give the other thread a chance to actually put
it into the cache. */
pth_sleep (1);
goto retry;
}
/* Timeout - better call pinentry now the plain way. */
}
}
pi = gcry_calloc_secure (1, sizeof (*pi) + 100);
if (!pi)
return gpg_error_from_syserror ();
pi->max_length = 100;
pi->min_digits = 0; /* we want a real passphrase */
pi->max_digits = 16;
pi->max_tries = 3;
pi->check_cb = try_unprotect_cb;
arg.ctrl = ctrl;
arg.protected_key = *keybuf;
arg.unprotected_key = NULL;
arg.change_required = 0;
pi->check_cb_arg = &arg;
rc = agent_askpin (ctrl, desc_text, NULL, NULL, pi);
if (!rc)
{
assert (arg.unprotected_key);
if (arg.change_required)
{
size_t canlen, erroff;
gcry_sexp_t s_skey;
assert (arg.unprotected_key);
canlen = gcry_sexp_canon_len (arg.unprotected_key, 0, NULL, NULL);
rc = gcry_sexp_sscan (&s_skey, &erroff,
(char*)arg.unprotected_key, canlen);
if (rc)
{
log_error ("failed to build S-Exp (off=%u): %s\n",
(unsigned int)erroff, gpg_strerror (rc));
wipememory (arg.unprotected_key, canlen);
xfree (arg.unprotected_key);
xfree (pi);
return rc;
}
rc = agent_protect_and_store (ctrl, s_skey);
gcry_sexp_release (s_skey);
if (rc)
{
log_error ("changing the passphrase failed: %s\n",
gpg_strerror (rc));
wipememory (arg.unprotected_key, canlen);
xfree (arg.unprotected_key);
xfree (pi);
return rc;
}
}
else
agent_put_cache (hexgrip, cache_mode, pi->pin,
lookup_ttl? lookup_ttl (hexgrip) : 0);
xfree (*keybuf);
*keybuf = arg.unprotected_key;
}
xfree (pi);
return rc;
}
/* Return the secret key as an S-Exp in RESULT after locating it using
the GRIP. If the operation shall be diverted to a token, an
allocated S-expression with the shadow_info part from the file is
stored at SHADOW_INFO; if not NULL will be stored at SHADOW_INFO.
CACHE_MODE defines now the cache shall be used. DESC_TEXT may be
set to present a custom description for the pinentry. LOOKUP_TTL
is an optional function to convey a TTL to the cache manager; we do
not simply pass the TTL value because the value is only needed if
an unprotect action was needed and looking up the TTL may have some
overhead (e.g. scanning the sshcontrol file). If a CACHE_NONCE is
given that cache item is first tried to get a passphrase. If
R_PASSPHRASE is not NULL, the function succeeded and the key was
protected the used passphrase (entered or from the cache) is stored
there; if not NULL will be stored. The caller needs to free the
returned passphrase. */
gpg_error_t
agent_key_from_file (ctrl_t ctrl, const char *cache_nonce,
const char *desc_text,
const unsigned char *grip, unsigned char **shadow_info,
cache_mode_t cache_mode, lookup_ttl_t lookup_ttl,
gcry_sexp_t *result, char **r_passphrase)
{
int rc;
unsigned char *buf;
size_t len, buflen, erroff;
gcry_sexp_t s_skey;
*result = NULL;
if (shadow_info)
*shadow_info = NULL;
if (r_passphrase)
*r_passphrase = NULL;
rc = read_key_file (grip, &s_skey);
if (rc)
{
if (gpg_err_code (rc) == GPG_ERR_ENOENT)
rc = gpg_error (GPG_ERR_NO_SECKEY);
return rc;
}
/* For use with the protection functions we also need the key as an
canonical encoded S-expression in a buffer. Create this buffer
now. */
rc = make_canon_sexp (s_skey, &buf, &len);
if (rc)
return rc;
switch (agent_private_key_type (buf))
{
case PRIVATE_KEY_CLEAR:
break; /* no unprotection needed */
case PRIVATE_KEY_OPENPGP_NONE:
{
unsigned char *buf_new;
size_t buf_newlen;
rc = agent_unprotect (ctrl, buf, "", NULL, &buf_new, &buf_newlen);
if (rc)
log_error ("failed to convert unprotected openpgp key: %s\n",
gpg_strerror (rc));
else
{
xfree (buf);
buf = buf_new;
}
}
break;
case PRIVATE_KEY_PROTECTED:
{
char *desc_text_final;
char *comment = NULL;
/* Note, that we will take the comment as a C string for
display purposes; i.e. all stuff beyond a Nul character is
ignored. */
{
gcry_sexp_t comment_sexp;
comment_sexp = gcry_sexp_find_token (s_skey, "comment", 0);
if (comment_sexp)
comment = gcry_sexp_nth_string (comment_sexp, 1);
gcry_sexp_release (comment_sexp);
}
desc_text_final = NULL;
if (desc_text)
rc = modify_description (desc_text, comment? comment:"", s_skey,
&desc_text_final);
gcry_free (comment);
if (!rc)
{
rc = unprotect (ctrl, cache_nonce, desc_text_final, &buf, grip,
cache_mode, lookup_ttl, r_passphrase);
if (rc)
log_error ("failed to unprotect the secret key: %s\n",
gpg_strerror (rc));
}
xfree (desc_text_final);
}
break;
case PRIVATE_KEY_SHADOWED:
if (shadow_info)
{
const unsigned char *s;
size_t n;
rc = agent_get_shadow_info (buf, &s);
if (!rc)
{
n = gcry_sexp_canon_len (s, 0, NULL,NULL);
assert (n);
*shadow_info = xtrymalloc (n);
if (!*shadow_info)
rc = out_of_core ();
else
{
memcpy (*shadow_info, s, n);
rc = 0;
}
}
if (rc)
log_error ("get_shadow_info failed: %s\n", gpg_strerror (rc));
}
else
rc = gpg_error (GPG_ERR_UNUSABLE_SECKEY);
break;
default:
log_error ("invalid private key format\n");
rc = gpg_error (GPG_ERR_BAD_SECKEY);
break;
}
gcry_sexp_release (s_skey);
s_skey = NULL;
if (rc)
{
xfree (buf);
if (r_passphrase)
{
xfree (*r_passphrase);
*r_passphrase = NULL;
}
return rc;
}
buflen = gcry_sexp_canon_len (buf, 0, NULL, NULL);
rc = gcry_sexp_sscan (&s_skey, &erroff, (char*)buf, buflen);
wipememory (buf, buflen);
xfree (buf);
if (rc)
{
log_error ("failed to build S-Exp (off=%u): %s\n",
(unsigned int)erroff, gpg_strerror (rc));
if (r_passphrase)
{
xfree (*r_passphrase);
*r_passphrase = NULL;
}
return rc;
}
*result = s_skey;
return 0;
}
/* Callback function to try the unprotection from the passpharse query
code. */
static int
try_unprotect_cb (struct pin_entry_info_s *pi)
{
struct try_unprotect_arg_s *arg = pi->check_cb_arg;
size_t dummy;
gpg_error_t err;
gnupg_isotime_t now, protected_at, tmptime;
char *desc = NULL;
assert (!arg->unprotected_key);
arg->change_required = 0;
err = agent_unprotect (arg->protected_key, pi->pin, protected_at,
&arg->unprotected_key, &dummy);
if (err)
return err;
if (!opt.max_passphrase_days || arg->ctrl->in_passwd)
return 0; /* No regular passphrase change required. */
if (!*protected_at)
{
/* No protection date known - must force passphrase change. */
desc = xtrystrdup (_("Note: This passphrase has never been changed.%0A"
"Please change it now."));
if (!desc)
return gpg_error_from_syserror ();
}
else
{
gnupg_get_isotime (now);
gnupg_copy_time (tmptime, protected_at);
err = add_days_to_isotime (tmptime, opt.max_passphrase_days);
if (err)
return err;
if (strcmp (now, tmptime) > 0 )
{
/* Passphrase "expired". */
desc = xtryasprintf
(_("This passphrase has not been changed%%0A"
"since %.4s-%.2s-%.2s. Please change it now."),
protected_at, protected_at+4, protected_at+6);
if (!desc)
return gpg_error_from_syserror ();
}
}
if (desc)
{
/* Change required. */
if (opt.enforce_passphrase_constraints)
{
err = agent_get_confirmation (arg->ctrl, desc,
_("Change passphrase"), NULL, 0);
if (!err)
arg->change_required = 1;
}
else
{
err = agent_get_confirmation (arg->ctrl, desc,
_("Change passphrase"),
_("I'll change it later"), 0);
if (!err)
arg->change_required = 1;
else if (gpg_err_code (err) == GPG_ERR_CANCELED)
err = 0;
}
xfree (desc);
}
return 0;
}
/* Unprotect the canconical encoded S-expression key in KEYBUF. GRIP
should be the hex encoded keygrip of that key to be used with the
caching mechanism. DESC_TEXT may be set to override the default
description used for the pinentry. If LOOKUP_TTL is given this
function is used to lookup the default ttl. If R_PASSPHRASE is not
NULL, the function succeeded and the key was protected the used
passphrase (entered or from the cache) is stored there; if not NULL
will be stored. The caller needs to free the returned
passphrase. */
static int
unprotect (ctrl_t ctrl, const char *cache_nonce, const char *desc_text,
unsigned char **keybuf, const unsigned char *grip,
cache_mode_t cache_mode, lookup_ttl_t lookup_ttl,
char **r_passphrase)
{
struct pin_entry_info_s *pi;
struct try_unprotect_arg_s arg;
int rc;
unsigned char *result;
size_t resultlen;
char hexgrip[40+1];
if (r_passphrase)
*r_passphrase = NULL;
bin2hex (grip, 20, hexgrip);
/* Initially try to get it using a cache nonce. */
if (cache_nonce)
{
char *pw;
pw = agent_get_cache (cache_nonce, CACHE_MODE_NONCE);
if (pw)
{
rc = agent_unprotect (ctrl, *keybuf, pw, NULL, &result, &resultlen);
if (!rc)
{
if (r_passphrase)
*r_passphrase = pw;
else
xfree (pw);
xfree (*keybuf);
*keybuf = result;
return 0;
}
xfree (pw);
}
}
/* First try to get it from the cache - if there is none or we can't
unprotect it, we fall back to ask the user */
if (cache_mode != CACHE_MODE_IGNORE)
{
char *pw;
retry:
pw = agent_get_cache (hexgrip, cache_mode);
if (pw)
{
rc = agent_unprotect (ctrl, *keybuf, pw, NULL, &result, &resultlen);
if (!rc)
{
if (cache_mode == CACHE_MODE_NORMAL)
agent_store_cache_hit (hexgrip);
if (r_passphrase)
*r_passphrase = pw;
else
xfree (pw);
xfree (*keybuf);
*keybuf = result;
return 0;
}
xfree (pw);
rc = 0;
}
else if (cache_mode == CACHE_MODE_NORMAL)
{
/* The standard use of GPG keys is to have a signing and an
encryption subkey. Commonly both use the same
passphrase. We try to help the user to enter the
passphrase only once by silently trying the last
correctly entered passphrase. Checking one additional
passphrase should be acceptable; despite the S2K
introduced delays. The assumed workflow is:
1. Read encrypted message in a MUA and thus enter a
passphrase for the encryption subkey.
2. Reply to that mail with an encrypted and signed
mail, thus entering the passphrase for the signing
subkey.
We can often avoid the passphrase entry in the second
step. We do this only in normal mode, so not to
interfere with unrelated cache entries. */
pw = agent_get_cache (NULL, cache_mode);
if (pw)
{
rc = agent_unprotect (ctrl, *keybuf, pw, NULL,
&result, &resultlen);
if (!rc)
{
if (r_passphrase)
*r_passphrase = pw;
else
xfree (pw);
xfree (*keybuf);
*keybuf = result;
return 0;
}
xfree (pw);
rc = 0;
}
}
/* If the pinentry is currently in use, we wait up to 60 seconds
for it to close and check the cache again. This solves a common
situation where several requests for unprotecting a key have
been made but the user is still entering the passphrase for
the first request. Because all requests to agent_askpin are
serialized they would then pop up one after the other to
request the passphrase - despite that the user has already
entered it and is then available in the cache. This
implementation is not race free but in the worst case the
user has to enter the passphrase only once more. */
if (pinentry_active_p (ctrl, 0))
{
/* Active - wait */
if (!pinentry_active_p (ctrl, 60))
{
/* We need to give the other thread a chance to actually put
it into the cache. */
npth_sleep (1);
goto retry;
}
/* Timeout - better call pinentry now the plain way. */
}
}
pi = gcry_calloc_secure (1, sizeof (*pi) + MAX_PASSPHRASE_LEN + 1);
if (!pi)
return gpg_error_from_syserror ();
pi->max_length = MAX_PASSPHRASE_LEN + 1;
pi->min_digits = 0; /* we want a real passphrase */
pi->max_digits = 16;
pi->max_tries = 3;
pi->check_cb = try_unprotect_cb;
arg.ctrl = ctrl;
arg.protected_key = *keybuf;
arg.unprotected_key = NULL;
arg.change_required = 0;
pi->check_cb_arg = &arg;
rc = agent_askpin (ctrl, desc_text, NULL, NULL, pi, hexgrip, cache_mode);
if (!rc)
{
assert (arg.unprotected_key);
if (arg.change_required)
{
/* The callback told as that the user should change their
passphrase. Present the dialog to do. */
size_t canlen, erroff;
gcry_sexp_t s_skey;
assert (arg.unprotected_key);
canlen = gcry_sexp_canon_len (arg.unprotected_key, 0, NULL, NULL);
rc = gcry_sexp_sscan (&s_skey, &erroff,
(char*)arg.unprotected_key, canlen);
if (rc)
{
log_error ("failed to build S-Exp (off=%u): %s\n",
(unsigned int)erroff, gpg_strerror (rc));
wipememory (arg.unprotected_key, canlen);
xfree (arg.unprotected_key);
xfree (pi);
return rc;
}
rc = agent_protect_and_store (ctrl, s_skey, NULL);
gcry_sexp_release (s_skey);
if (rc)
{
log_error ("changing the passphrase failed: %s\n",
gpg_strerror (rc));
wipememory (arg.unprotected_key, canlen);
xfree (arg.unprotected_key);
xfree (pi);
return rc;
}
}
else
{
/* Passphrase is fine. */
agent_put_cache (hexgrip, cache_mode, pi->pin,
lookup_ttl? lookup_ttl (hexgrip) : 0);
agent_store_cache_hit (hexgrip);
if (r_passphrase && *pi->pin)
*r_passphrase = xtrystrdup (pi->pin);
}
xfree (*keybuf);
*keybuf = arg.unprotected_key;
}
xfree (pi);
return rc;
}
