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core: Do not leak the override session key to ps(1).

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* src/engine-gpg.c (struct engine_gpg): New field
override_session_key.
(gpg_release): Free that field.
(gpg_decrypt): With gnupg 2.1.16 use --override-session-key-fd.

* tests/run-decrypt.c (main): Fix setting over the override key.
--

Note that this works only with gnupg 2.1.16 and later.

Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2016-11-16 10:12:19 +01:00
parent 5730647421
commit 9fc92a15bd
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
3 changed files with 34 additions and 5 deletions
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4
doc/gpgme.texi
View File

@ -2910,7 +2910,9 @@ not exported.
The string given in @var{value} is passed to the GnuPG engine to override
the session key for decryption. The format of that session key is
specific to GnuPG and can be retrieved during a decrypt operation when
the context flag "export-session-key" is enabled.
the context flag "export-session-key" is enabled. Please be aware that
using this feature with GnuPG < 2.1.16 will leak the session key on
many platforms via ps(1).
@end table

26
src/engine-gpg.c
View File

@ -139,6 +139,9 @@ struct engine_gpg
struct gpgme_io_cbs io_cbs;
gpgme_pinentry_mode_t pinentry_mode;
/* NULL or the data object fed to --override_session_key-fd. */
gpgme_data_t override_session_key;
};
typedef struct engine_gpg *engine_gpg_t;
@ -441,6 +444,8 @@ gpg_release (void *engine)
if (gpg->cmd.keyword)
free (gpg->cmd.keyword);
gpgme_data_release (gpg->override_session_key);
free (gpg);
}
@ -1563,10 +1568,31 @@ gpg_decrypt (void *engine, gpgme_data_t ciph, gpgme_data_t plain,
if (!err && override_session_key && *override_session_key)
{
if (have_gpg_version (gpg, "2.1.16"))
{
gpgme_data_release (gpg->override_session_key);
TRACE2 (DEBUG_ENGINE, "override", gpg, "seskey='%s' len=%zu\n",
override_session_key,
strlen (override_session_key));
err = gpgme_data_new_from_mem (&gpg->override_session_key,
override_session_key,
strlen (override_session_key), 1);
if (!err)
{
err = add_arg (gpg, "--override-session-key-fd");
if (!err)
err = add_data (gpg, gpg->override_session_key, -2, 0);
}
}
else
{
/* Using that option may leak the session key via ps(1). */
err = add_arg (gpg, "--override-session-key");
if (!err)
err = add_arg (gpg, override_session_key);
}
}
/* Tell the gpg object about the data. */
if (!err)

3
tests/run-decrypt.c
View File

@ -185,7 +185,8 @@ main (int argc, char **argv)
}
if (override_session_key)
{
err = gpgme_set_ctx_flag (ctx, "overrride-session-key", "1");
err = gpgme_set_ctx_flag (ctx, "override-session-key",
override_session_key);
if (err)
{
fprintf (stderr, PGM ": error overriding session key: %s\n",