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agent: Ignore passphrase constraints for a generated passphrase.

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* agent/agent.h (PINENTRY_STATUS_PASSWORD_GENERATED): New.
(MAX_GENPIN_TRIES): Remove.
* agent/call-pinentry.c (struct entry_parm_s):
(struct inq_cb_parm_s): Add genpinhash and genpinhas_valid.
(is_generated_pin): New.
(inq_cb): Suppress constraints checking for a generated passphrase.
No more need for several tries to generate the passphrase.
(do_getpin): Store a generated passphrase/pin in the status field.
(agent_askpin): Suppress constraints checking for a generated
passphrase.
(agent_get_passphrase): Ditto.
* agent/command.c (cmd_get_passphrase): Ditto.
--

A generated passphrase has enough entropy so that all kind of extra
checks would only reduce the actual available entropy.  We thus detect
if a passphrase has been generated (and not changed) and skip all
passphrase constraints checking.
This commit is contained in:
Werner Koch 2021-08-18 18:24:35 +02:00
parent 8ed7910347
commit b89b1f35c2
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
4 changed files with 74 additions and 35 deletions
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3
agent/agent.h
View File

@ -296,7 +296,8 @@ enum
{
PINENTRY_STATUS_CLOSE_BUTTON = 1 << 0,
PINENTRY_STATUS_PIN_REPEATED = 1 << 8,
PINENTRY_STATUS_PASSWORD_FROM_CACHE = 1 << 9
PINENTRY_STATUS_PASSWORD_FROM_CACHE = 1 << 9,
PINENTRY_STATUS_PASSWORD_GENERATED = 1 << 10
};
/* Information pertaining to pinentry requests. */

87
agent/call-pinentry.c
View File

@ -53,8 +53,6 @@
time. */
#define LOCK_TIMEOUT (1*60)
/* Define the maximum tries to generate a pin for the GENPIN inquire */
#define MAX_GENPIN_TRIES 10
/* Define the number of bits to use for a generated pin. The
* passphrase will be rendered as zbase32 which results for 150 bits
* in a string of 30 characters. That fits nicely into the 5
@ -882,9 +880,32 @@ struct inq_cb_parm_s
{
assuan_context_t ctx;
unsigned int flags; /* CHECK_CONSTRAINTS_... */
int genpinhash_valid;
char genpinhash[32]; /* Hash of the last generated pin. */
};
/* Return true if PIN is indentical to the last generated pin. */
static int
is_generated_pin (struct inq_cb_parm_s *parm, const char *pin)
{
char hashbuf[32];
if (!parm->genpinhash_valid)
return 0;
if (!*pin)
return 0;
/* Note that we compare the hash so that we do not need to save the
* generated PIN longer than needed. */
gcry_md_hash_buffer (GCRY_MD_SHA256, hashbuf, pin, strlen (pin));
if (!memcmp (hashbuf, parm->genpinhash, 32))
return 1; /* yes, it is the same. */
return 0;
}
static gpg_error_t
inq_cb (void *opaque, const char *line)
{
@ -929,7 +950,8 @@ inq_cb (void *opaque, const char *line)
err = gpg_error_from_syserror ();
else
{
if (check_passphrase_constraints (NULL, pin, parm->flags, &errtext))
if (!is_generated_pin (parm, pin)
&& check_passphrase_constraints (NULL, pin,parm->flags, &errtext))
{
if (errtext)
{
@ -954,32 +976,24 @@ inq_cb (void *opaque, const char *line)
}
else if ((s = has_leading_keyword (line, "GENPIN")))
{
int tries;
int wasconf;
for (tries = 0; tries < MAX_GENPIN_TRIES; tries ++)
parm->genpinhash_valid = 0;
pin = generate_pin ();
if (!pin)
{
pin = generate_pin ();
if (!pin)
{
log_error ("failed to generate a passphrase\n");
err = gpg_error (GPG_ERR_GENERAL);
goto leave;
}
if (!check_passphrase_constraints (NULL, pin, parm->flags, NULL))
{
int wasconf = assuan_get_flag (entry_ctx, ASSUAN_CONFIDENTIAL);
assuan_begin_confidential (parm->ctx);
err = assuan_send_data (parm->ctx, pin, strlen (pin));
if (!wasconf)
assuan_end_confidential (parm->ctx);
xfree (pin);
goto leave;
}
xfree (pin);
log_error ("failed to generate a passphrase\n");
err = gpg_error (GPG_ERR_GENERAL);
goto leave;
}
log_error ("failed to generate a passphrase after %i tries\n",
MAX_GENPIN_TRIES);
err = gpg_error (GPG_ERR_GENERAL);
wasconf = assuan_get_flag (entry_ctx, ASSUAN_CONFIDENTIAL);
assuan_begin_confidential (parm->ctx);
err = assuan_send_data (parm->ctx, pin, strlen (pin));
if (!wasconf)
assuan_end_confidential (parm->ctx);
gcry_md_hash_buffer (GCRY_MD_SHA256, parm->genpinhash, pin, strlen (pin));
parm->genpinhash_valid = 1;
xfree (pin);
}
else
{
@ -1376,6 +1390,7 @@ do_getpin (ctrl_t ctrl, struct entry_parm_s *parm)
inq_cb_parm.ctx = entry_ctx;
inq_cb_parm.flags = parm->constraints_flags;
inq_cb_parm.genpinhash_valid = 0;
wasconf = assuan_get_flag (entry_ctx, ASSUAN_CONFIDENTIAL);
assuan_begin_confidential (entry_ctx);
@ -1385,6 +1400,11 @@ do_getpin (ctrl_t ctrl, struct entry_parm_s *parm)
if (!wasconf)
assuan_end_confidential (entry_ctx);
if (!rc && parm->buffer && is_generated_pin (&inq_cb_parm, parm->buffer))
parm->status |= PINENTRY_STATUS_PASSWORD_GENERATED;
else
parm->status &= ~PINENTRY_STATUS_PASSWORD_GENERATED;
/* Most pinentries out in the wild return the old Assuan error code
for canceled which gets translated to an assuan Cancel error and
not to the code for a user cancel. Fix this here. */
@ -1417,6 +1437,7 @@ agent_askpin (ctrl_t ctrl,
struct entry_parm_s parm;
const char *errtext = NULL;
int is_pin = 0;
int is_generated;
if (opt.batch)
return 0; /* fixme: we should return BAD PIN */
@ -1562,13 +1583,15 @@ agent_askpin (ctrl_t ctrl,
rc = do_getpin (ctrl, &parm);
pininfo->status = parm.status;
is_generated = !!(parm.status & PINENTRY_STATUS_PASSWORD_GENERATED);
if (gpg_err_code (rc) == GPG_ERR_ASS_TOO_MUCH_DATA)
errtext = is_pin? L_("PIN too long")
: L_("Passphrase too long");
else if (rc)
return unlock_pinentry (ctrl, rc);
if (!errtext && pininfo->min_digits)
if (!errtext && pininfo->min_digits && !is_generated)
{
/* do some basic checks on the entered PIN. */
if (!all_digitsp (pininfo->pin))
@ -1580,7 +1603,7 @@ agent_askpin (ctrl_t ctrl,
errtext = L_("PIN too short");
}
if (!errtext && pininfo->check_cb)
if (!errtext && pininfo->check_cb && !is_generated)
{
/* More checks by utilizing the optional callback. */
pininfo->cb_errtext = NULL;
@ -1639,6 +1662,7 @@ agent_get_passphrase (ctrl_t ctrl,
{
int rc;
int is_pin;
int is_generated;
char line[ASSUAN_LINELENGTH];
struct entry_parm_s parm;
@ -1793,6 +1817,7 @@ agent_get_passphrase (ctrl_t ctrl,
for (;pininfo->failed_tries < pininfo->max_tries; pininfo->failed_tries++)
{
memset (&parm, 0, sizeof parm);
parm.constraints_flags = pininfo->constraints_flags;
parm.size = pininfo->max_length;
parm.buffer = (unsigned char*)pininfo->pin;
*pininfo->pin = 0; /* Reset the PIN. */
@ -1822,13 +1847,15 @@ agent_get_passphrase (ctrl_t ctrl,
rc = do_getpin (ctrl, &parm);
pininfo->status = parm.status;
is_generated = !!(parm.status & PINENTRY_STATUS_PASSWORD_GENERATED);
if (gpg_err_code (rc) == GPG_ERR_ASS_TOO_MUCH_DATA)
errtext = is_pin? L_("PIN too long")
: L_("Passphrase too long");
else if (rc)
return unlock_pinentry (ctrl, rc);
if (!errtext && pininfo->min_digits)
if (!errtext && pininfo->min_digits && !is_generated)
{
/* do some basic checks on the entered PIN. */
if (!all_digitsp (pininfo->pin))
@ -1840,7 +1867,7 @@ agent_get_passphrase (ctrl_t ctrl,
errtext = L_("PIN too short");
}
if (!errtext && pininfo->check_cb)
if (!errtext && pininfo->check_cb && !is_generated)
{
/* More checks by utilizing the optional callback. */
pininfo->cb_errtext = NULL;

13
agent/command.c
View File

@ -1760,6 +1760,7 @@ cmd_get_passphrase (assuan_context_t ctx, char *line)
char *entry_errtext = NULL;
struct pin_entry_info_s *pi = NULL;
struct pin_entry_info_s *pi2 = NULL;
int is_generated;
if (ctrl->restricted)
return leave_cmd (ctx, gpg_error (GPG_ERR_FORBIDDEN));
@ -1892,10 +1893,13 @@ cmd_get_passphrase (assuan_context_t ctx, char *line)
goto leave;
xfree (entry_errtext);
entry_errtext = NULL;
is_generated = !!(pi->status & PINENTRY_STATUS_PASSWORD_GENERATED);
/* We don't allow an empty passpharse in this mode. */
if (check_passphrase_constraints (ctrl, pi->pin,
pi->constraints_flags,
&entry_errtext))
if (!is_generated
&& check_passphrase_constraints (ctrl, pi->pin,
pi->constraints_flags,
&entry_errtext))
{
pi->failed_tries = 0;
pi2->failed_tries = 0;
@ -1951,11 +1955,14 @@ cmd_get_passphrase (assuan_context_t ctx, char *line)
opt_qualbar, cacheid, CACHE_MODE_USER, NULL);
xfree (entry_errtext);
entry_errtext = NULL;
is_generated = !!(pi->status & PINENTRY_STATUS_PASSWORD_GENERATED);
if (!rc)
{
int i;
if (opt_check
&& !is_generated
&& check_passphrase_constraints
(ctrl, response,
(opt_newsymkey? CHECK_CONSTRAINTS_NEW_SYMKEY:0),

6
doc/gpg-agent.texi
View File

@ -476,7 +476,11 @@ user for a new passphrase and masking of the passphrase is turned off.
If passphrase formatting is enabled, then all non-breaking space characters
are stripped from the entered passphrase. Passphrase formatting is mostly
useful in combination with passphrases generated with the GENPIN command.
useful in combination with passphrases generated with the GENPIN
feature of some Pinentries. Note that such a generated
passphrase, if not modified by the user, skips all passphrase
constraints checking because such constraints would actually weaken
the generated passphrase.
@item --pinentry-program @var{filename}
@opindex pinentry-program