From 8acdac217755805993ce2e7c747f38a4b2a75ba7 Mon Sep 17 00:00:00 2001 From: des Date: Sun, 11 Dec 2011 17:32:37 +0000 Subject: [PATCH] MFH r228410: check for null passphrases, since openssl doesn't Approved by: re (kib) Security: prevents users with unencrypted ssh keys (prohibited unless the nullok option is specified) from logging in by providing a bogus non-null passphrase. git-svn-id: svn://svn.freebsd.org/base/releng/9.0@228414 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f --- lib/libpam/modules/pam_ssh/pam_ssh.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) diff --git a/lib/libpam/modules/pam_ssh/pam_ssh.c b/lib/libpam/modules/pam_ssh/pam_ssh.c index bec9892b..f051dd4b 100644 --- a/lib/libpam/modules/pam_ssh/pam_ssh.c +++ b/lib/libpam/modules/pam_ssh/pam_ssh.c @@ -91,7 +91,8 @@ static char *const pam_ssh_agent_envp[] = { NULL }; * 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]; @@ -101,7 +102,21 @@ pam_ssh_load_key(const char *dir, const char *kfn, const char *passphrase) 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); @@ -168,9 +183,6 @@ pam_sm_authenticate(pam_handle_t *pamh, int flags __unused, 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) @@ -178,7 +190,7 @@ pam_sm_authenticate(pam_handle_t *pamh, int flags __unused, /* 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; @@ -188,7 +200,6 @@ pam_sm_authenticate(pam_handle_t *pamh, int flags __unused, /* 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 -- 2.42.0