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gpg: Improve passphrase caching.

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* agent/cache.c (last_stored_cache_key): New.
(agent_get_cache): Allow NULL for KEY.
(agent_store_cache_hit): New.
* agent/findkey.c (unprotect): Call new function and try to use the
last stored key.

* g10/revoke.c (create_revocation): Add arg CACHE_NONCE and pass to
make_keysig_packet.
(gen_standard_revoke): Add arg CACHE_NONCE and pass to
create_revocation.
* g10/keygen.c (do_generate_keypair): Call gen_standard_revoke with
cache nonce.
--

This patch adds two features:

1. The key for the last passphrase successfully used for unprotecting
a key is stored away.  On a cache miss the stored away passphrase is
tried as well.  This helps for the common GPG use case of having a
signing and encryption (sub)key with the same passphrase.  See the
code for more comments.

2. The now auto-generated revocation certificate does not anymore
popup a passphrase prompt.  Thus for standard key generation the
passphrase needs to be given only once (well, two with the
confirmation).
This commit is contained in:
Werner Koch 2014-09-17 15:12:08 +02:00
parent 83c2d2396c
commit 457bce5cd3
6 changed files with 81 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

42
agent/findkey.c
View file

@ -372,6 +372,8 @@ unprotect (ctrl_t ctrl, const char *cache_nonce, const char *desc_text,
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
@ -383,6 +385,45 @@ unprotect (ctrl_t ctrl, const char *cache_nonce, const char *desc_text,
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
@ -460,6 +501,7 @@ unprotect (ctrl_t ctrl, const char *cache_nonce, const char *desc_text,
{
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);
}