Date: Sun, 20 Nov 2011 15:18:49 +0000 (UTC) From: Dag-Erling Smorgrav <des@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r227757 - head/lib/libpam/modules/pam_ssh Message-ID: <201111201518.pAKFInfS097994@svn.freebsd.org>
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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.helmer@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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