Author: des
Date: Sun Nov 20 15:18:49 2011
New Revision: 227757
URL: http://svn.freebsd.org/changeset/base/227757
Log:
key_load_private() ignores the passphrase argument if the private key
is unencrypted. This defeats the nullok check, because it means a
non-null passphrase will successfully unlock the key.
To address this, try at first to load the key without a passphrase.
If this succeeds and the user provided a non-empty passphrase *or*
nullok is false, reject the key.
MFC after: 1 week
Noticed by: Guy Helmer <guy.hel...@palisadesystems.com>
Modified:
head/lib/libpam/modules/pam_ssh/pam_ssh.c
Modified: head/lib/libpam/modules/pam_ssh/pam_ssh.c
==============================================================================
--- head/lib/libpam/modules/pam_ssh/pam_ssh.c Sun Nov 20 15:06:39 2011
(r227756)
+++ head/lib/libpam/modules/pam_ssh/pam_ssh.c Sun Nov 20 15:18:49 2011
(r227757)
@@ -93,7 +93,8 @@ static char *const pam_ssh_agent_envp[]
* struct pam_ssh_key containing the key and its comment.
*/
static struct pam_ssh_key *
-pam_ssh_load_key(const char *dir, const char *kfn, const char *passphrase)
+pam_ssh_load_key(const char *dir, const char *kfn, const char *passphrase,
+ int nullok)
{
struct pam_ssh_key *psk;
char fn[PATH_MAX];
@@ -103,7 +104,21 @@ pam_ssh_load_key(const char *dir, const
if (snprintf(fn, sizeof(fn), "%s/%s", dir, kfn) > (int)sizeof(fn))
return (NULL);
comment = NULL;
- key = key_load_private(fn, passphrase, &comment);
+ /*
+ * If the key is unencrypted, OpenSSL ignores the passphrase, so
+ * it will seem like the user typed in the right one. This allows
+ * a user to circumvent nullok by providing a dummy passphrase.
+ * Verify that the key really *is* encrypted by trying to load it
+ * with an empty passphrase, and if the key is not encrypted,
+ * accept only an empty passphrase.
+ */
+ key = key_load_private(fn, NULL, &comment);
+ if (key != NULL && !(*passphrase == '\0' && nullok)) {
+ key_free(key);
+ return (NULL);
+ }
+ if (key == NULL)
+ key = key_load_private(fn, passphrase, &comment);
if (key == NULL) {
openpam_log(PAM_LOG_DEBUG, "failed to load key from %s", fn);
return (NULL);
@@ -170,9 +185,6 @@ pam_sm_authenticate(pam_handle_t *pamh,
if (pam_err != PAM_SUCCESS)
return (pam_err);
- if (*passphrase == '\0' && !nullok)
- goto skip_keys;
-
/* switch to user credentials */
pam_err = openpam_borrow_cred(pamh, pwd);
if (pam_err != PAM_SUCCESS)
@@ -180,7 +192,7 @@ pam_sm_authenticate(pam_handle_t *pamh,
/* try to load keys from all keyfiles we know of */
for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
- psk = pam_ssh_load_key(pwd->pw_dir, *kfn, passphrase);
+ psk = pam_ssh_load_key(pwd->pw_dir, *kfn, passphrase, nullok);
if (psk != NULL) {
pam_set_data(pamh, *kfn, psk, pam_ssh_free_key);
++nkeys;
@@ -190,7 +202,6 @@ pam_sm_authenticate(pam_handle_t *pamh,
/* switch back to arbitrator credentials */
openpam_restore_cred(pamh);
- skip_keys:
/*
* If we tried an old token and didn't get anything, and
* try_first_pass was specified, try again after prompting the
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