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authorSteve Langasek <vorlon@debian.org>2019-01-22 14:54:11 -0800
committerSteve Langasek <vorlon@debian.org>2019-01-22 14:54:11 -0800
commitf00afb1ef201b2eef7f9ddbe5a0c6ca802cf49bb (patch)
tree402838c53047b0e21466a653ae88d86a8e4b7b65 /libpam/pam_modutil_sanitize.c
parent795badba7f95e737f979917859cd32c9bd47bcad (diff)
parent1cad9fb2a0d729c5b5e5aa7297c521df7d5a2d33 (diff)
New upstream version 1.3.0
Diffstat (limited to 'libpam/pam_modutil_sanitize.c')
-rw-r--r--libpam/pam_modutil_sanitize.c175
1 files changed, 175 insertions, 0 deletions
diff --git a/libpam/pam_modutil_sanitize.c b/libpam/pam_modutil_sanitize.c
new file mode 100644
index 00000000..65f85d01
--- /dev/null
+++ b/libpam/pam_modutil_sanitize.c
@@ -0,0 +1,175 @@
+/*
+ * This file implements the following functions:
+ * pam_modutil_sanitize_helper_fds:
+ * redirects standard descriptors, closes all other descriptors.
+ */
+
+#include "pam_modutil_private.h"
+#include <security/pam_ext.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <syslog.h>
+#include <sys/resource.h>
+
+/*
+ * Creates a pipe, closes its write end, redirects fd to its read end.
+ * Returns fd on success, -1 otherwise.
+ */
+static int
+redirect_in_pipe(pam_handle_t *pamh, int fd, const char *name)
+{
+ int in[2];
+
+ if (pipe(in) < 0) {
+ pam_syslog(pamh, LOG_ERR, "Could not create pipe: %m");
+ return -1;
+ }
+
+ close(in[1]);
+
+ if (in[0] == fd)
+ return fd;
+
+ if (dup2(in[0], fd) != fd) {
+ pam_syslog(pamh, LOG_ERR, "dup2 of %s failed: %m", name);
+ fd = -1;
+ }
+
+ close(in[0]);
+ return fd;
+}
+
+/*
+ * Creates a pipe, closes its read end, redirects fd to its write end.
+ * Returns fd on success, -1 otherwise.
+ */
+static int
+redirect_out_pipe(pam_handle_t *pamh, int fd, const char *name)
+{
+ int out[2];
+
+ if (pipe(out) < 0) {
+ pam_syslog(pamh, LOG_ERR, "Could not create pipe: %m");
+ return -1;
+ }
+
+ close(out[0]);
+
+ if (out[1] == fd)
+ return fd;
+
+ if (dup2(out[1], fd) != fd) {
+ pam_syslog(pamh, LOG_ERR, "dup2 of %s failed: %m", name);
+ fd = -1;
+ }
+
+ close(out[1]);
+ return fd;
+}
+
+/*
+ * Opens /dev/null for writing, redirects fd there.
+ * Returns fd on success, -1 otherwise.
+ */
+static int
+redirect_out_null(pam_handle_t *pamh, int fd, const char *name)
+{
+ int null = open("/dev/null", O_WRONLY);
+
+ if (null < 0) {
+ pam_syslog(pamh, LOG_ERR, "open of %s failed: %m", "/dev/null");
+ return -1;
+ }
+
+ if (null == fd)
+ return fd;
+
+ if (dup2(null, fd) != fd) {
+ pam_syslog(pamh, LOG_ERR, "dup2 of %s failed: %m", name);
+ fd = -1;
+ }
+
+ close(null);
+ return fd;
+}
+
+static int
+redirect_out(pam_handle_t *pamh, enum pam_modutil_redirect_fd mode,
+ int fd, const char *name)
+{
+ switch (mode) {
+ case PAM_MODUTIL_PIPE_FD:
+ if (redirect_out_pipe(pamh, fd, name) < 0)
+ return -1;
+ break;
+ case PAM_MODUTIL_NULL_FD:
+ if (redirect_out_null(pamh, fd, name) < 0)
+ return -1;
+ break;
+ case PAM_MODUTIL_IGNORE_FD:
+ break;
+ }
+ return fd;
+}
+
+/* Closes all descriptors after stderr. */
+static void
+close_fds(void)
+{
+ /*
+ * An arbitrary upper limit for the maximum file descriptor number
+ * returned by RLIMIT_NOFILE.
+ */
+ const int MAX_FD_NO = 65535;
+
+ /* The lower limit is the same as for _POSIX_OPEN_MAX. */
+ const int MIN_FD_NO = 20;
+
+ int fd;
+ struct rlimit rlim;
+
+ if (getrlimit(RLIMIT_NOFILE, &rlim) || rlim.rlim_max > MAX_FD_NO)
+ fd = MAX_FD_NO;
+ else if (rlim.rlim_max < MIN_FD_NO)
+ fd = MIN_FD_NO;
+ else
+ fd = rlim.rlim_max - 1;
+
+ for (; fd > STDERR_FILENO; --fd)
+ close(fd);
+}
+
+int
+pam_modutil_sanitize_helper_fds(pam_handle_t *pamh,
+ enum pam_modutil_redirect_fd stdin_mode,
+ enum pam_modutil_redirect_fd stdout_mode,
+ enum pam_modutil_redirect_fd stderr_mode)
+{
+ if (stdin_mode != PAM_MODUTIL_IGNORE_FD &&
+ redirect_in_pipe(pamh, STDIN_FILENO, "stdin") < 0) {
+ return -1;
+ }
+
+ if (redirect_out(pamh, stdout_mode, STDOUT_FILENO, "stdout") < 0)
+ return -1;
+
+ /*
+ * If stderr should not be ignored and
+ * redirect mode for stdout and stderr are the same,
+ * optimize by redirecting stderr to stdout.
+ */
+ if (stderr_mode != PAM_MODUTIL_IGNORE_FD &&
+ stdout_mode == stderr_mode) {
+ if (dup2(STDOUT_FILENO, STDERR_FILENO) != STDERR_FILENO) {
+ pam_syslog(pamh, LOG_ERR,
+ "dup2 of %s failed: %m", "stderr");
+ return -1;
+ }
+ } else {
+ if (redirect_out(pamh, stderr_mode, STDERR_FILENO, "stderr") < 0)
+ return -1;
+ }
+
+ close_fds();
+ return 0;
+}