path: root/libpam/
diff options
authorDmitry V. Levin <>2014-01-24 15:32:08 +0000
committerDmitry V. Levin <>2014-01-27 15:42:11 +0000
commitb0ec5d1e472a0cd74972bfe9575dcf6a3d0cad1c (patch)
treefe7f03043c1a60bfe982936eae981667c3bb27dc /libpam/
parent47db675c910a065fa9602753a904b050b0322f29 (diff)
Introduce pam_modutil_sanitize_helper_fds
This change introduces pam_modutil_sanitize_helper_fds - a new function that redirects standard descriptors and closes all other descriptors. pam_modutil_sanitize_helper_fds supports three types of input and output redirection: - PAM_MODUTIL_IGNORE_FD: do not redirect at all. - PAM_MODUTIL_PIPE_FD: redirect to a pipe. For stdin, it is implemented by creating a pipe, closing its write end, and redirecting stdin to its read end. Likewise, for stdout/stderr it is implemented by creating a pipe, closing its read end, and redirecting to its write end. Unlike stdin redirection, stdout/stderr redirection to a pipe has a side effect that a process writing to such descriptor should be prepared to handle SIGPIPE appropriately. - PAM_MODUTIL_NULL_FD: redirect to /dev/null. For stdin, it is implemented via PAM_MODUTIL_PIPE_FD because there is no functional difference. For stdout/stderr, it is classic redirection to /dev/null. PAM_MODUTIL_PIPE_FD is usually more suitable due to linux kernel security restrictions, but when the helper process might be writing to the corresponding descriptor and termination of the helper process by SIGPIPE is not desirable, one should choose PAM_MODUTIL_NULL_FD. * libpam/pam_modutil_sanitize.c: New file. * libpam/ (libpam_la_SOURCES): Add it. * libpam/include/security/pam_modutil.h (pam_modutil_redirect_fd, pam_modutil_sanitize_helper_fds): New declarations. * libpam/ (LIBPAM_MODUTIL_1.1.9): New interface. * modules/pam_exec/pam_exec.c (call_exec): Use pam_modutil_sanitize_helper_fds. * modules/pam_mkhomedir/pam_mkhomedir.c (create_homedir): Likewise. * modules/pam_unix/pam_unix_acct.c (_unix_run_verify_binary): Likewise. * modules/pam_unix/pam_unix_passwd.c (_unix_run_update_binary): Likewise. * modules/pam_unix/support.c (_unix_run_helper_binary): Likewise. * modules/pam_xauth/pam_xauth.c (run_coprocess): Likewise. * modules/pam_unix/support.h (MAX_FD_NO): Remove.
Diffstat (limited to 'libpam/')
1 files changed, 5 insertions, 0 deletions
diff --git a/libpam/ b/libpam/
index b0885d65..d6835b47 100644
--- a/libpam/
+++ b/libpam/
@@ -67,3 +67,8 @@ LIBPAM_MODUTIL_1.1.3 {
+ global:
+ pam_modutil_sanitize_helper_fds;