[continued from previous message]

++ retval = inst_init(polyptr, "tmpfs", idata, 1);
++ goto cleanup;
+ }
+
+- if (stat(polyptr->dir, &statbuf) < 0) {
+- pam_syslog(idata->pamh, LOG_ERR, "Error stating %s: %m",
+- polyptr->dir);
+- return PAM_SESSION_ERR;
++ if (fstat(dfd_pptrdir, &statbuf) < 0) {
++ pam_syslog(idata->pamh, LOG_ERR, "Error stating %s: %m", polyptr->dir);
++ goto error_out;
+ }
+
+ /*
+@@ -1693,15 +1933,16 @@ static int ns_setup(struct polydir_s *polyptr,
+ * security policy.
+ */
+ #ifdef WITH_SELINUX
+- retval = poly_name(polyptr, &instname, &instcontext,
+- &origcontext, idata);
++ retval = poly_name(polyptr, &instcontext, &origcontext, idata);
+ #else
+- retval = poly_name(polyptr, &instname, idata);
++ retval = poly_name(polyptr, idata);
+ #endif
+
+ if (retval != PAM_SUCCESS) {
+- if (retval != PAM_IGNORE)
++ if (retval != PAM_IGNORE) {
+ pam_syslog(idata->pamh, LOG_ERR, "Error getting instance name");
++ goto error_out;
++ }
+ goto cleanup;
+ } else {
+ #ifdef WITH_SELINUX
+@@ -1712,22 +1953,33 @@ static int ns_setup(struct polydir_s *polyptr,
+ #endif
+ }
+
+- if (asprintf(&inst_dir, "%s%s", polyptr->instance_prefix, instname) < 0) +- goto error_out;
+-
+- if (idata->flags & PAMNS_DEBUG)
+- pam_syslog(idata->pamh, LOG_DEBUG, "instance_dir %s",
+- inst_dir);
++ /*
++ * Gets a fd in a secure manner (we may be operating on a path under
++ * user control), and check it's compliant.
++ * Then, we should *always* operate on *this* fd and a relative path
++ * to be protected against race conditions.
++ */
++ dfd_iparent = secure_opendir(polyptr->instance_parent,
++ SECURE_OPENDIR_PROTECT | SECURE_OPENDIR_MKDIR, 0, idata);
++ if (dfd_iparent == -1) {
++ pam_syslog(idata->pamh, LOG_ERR,
++ "polyptr->instance_parent %s access error",
++ polyptr->instance_parent);
++ goto error_out;
++ }
++ if (check_inst_parent(dfd_iparent, idata)) {
++ goto error_out;
++ }
+
+ /*
+ * Create instance directory with appropriate security
+ * contexts, owner, group and mode bits.
+ */
+ #ifdef WITH_SELINUX
+- retval = create_instance(polyptr, inst_dir, &statbuf, instcontext,
+- origcontext, idata);
++ retval = create_instance(polyptr, dfd_iparent, &statbuf, instcontext,
++ origcontext, idata);
+ #else
+- retval = create_instance(polyptr, inst_dir, &statbuf, idata);
++ retval = create_instance(polyptr, dfd_iparent, &statbuf, idata);
+ #endif
+
+ if (retval == PAM_IGNORE) {
+@@ -1739,19 +1991,48 @@ static int ns_setup(struct polydir_s *polyptr,
+ goto error_out;
+ }
+
++ /*
++ * Instead of getting a new secure fd, we reuse the fd opened on directory
++ * polyptr->instance_parent to ensure we are working on the same dir as ++ * previously, and thus ensure that previous checks (e.g. check_inst_parent())
++ * are still relevant.
++ */
++ dfd_ipath = openat(dfd_iparent, polyptr->instname,
++ O_PATH | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
++ if (dfd_ipath == -1) {
++ pam_syslog(idata->pamh, LOG_ERR, "Error openat on %s, %m",
++ polyptr->instname);
++ goto error_out;
++ }
++
++ if (pam_sprintf(s_ipath, "/proc/self/fd/%d", dfd_ipath) < 0) {
++ pam_syslog(idata->pamh, LOG_ERR, "Error pam_sprintf s_ipath");
++ goto error_out;
++ }
++
++ if (pam_sprintf(s_pptrdir, "/proc/self/fd/%d", dfd_pptrdir) < 0) {
++ pam_syslog(idata->pamh, LOG_ERR, "Error pam_sprintf s_pptrdir");
++ goto error_out;
++ }
++
+ /*
+ * Bind mount instance directory on top of the polyinstantiated
+ * directory to provide an instance of polyinstantiated directory
+ * based on polyinstantiated method.
++ *
++ * Operates on magic links created from two fd obtained securely
++ * to protect against race conditions and symlink attacks. Indeed,
++ * the source and destination can be in a user controled path.
+ */
+- if (mount(inst_dir, polyptr->dir, NULL, MS_BIND, NULL) < 0) {
+- pam_syslog(idata->pamh, LOG_ERR, "Error mounting %s on %s, %m",
+- inst_dir, polyptr->dir);
++ if(mount(s_ipath, s_pptrdir, NULL, MS_BIND, NULL) < 0) {
++ pam_syslog(idata->pamh, LOG_ERR,
++ "Error mounting %s on %s (%s on %s), %m",
++ s_ipath, s_pptrdir, polyptr->instance_absolute, polyptr->dir);
+ goto error_out;
+ }
+
+ if (!(polyptr->flags & POLYDIR_NOINIT))
+- retval = inst_init(polyptr, inst_dir, idata, newdir);
++ retval = inst_init(polyptr, polyptr->instance_absolute, idata, newdir); +
+ goto cleanup;
+
+@@ -1763,8 +2044,12 @@ error_out:
+ retval = PAM_SESSION_ERR;
+
+ cleanup:
+- free(inst_dir);
+- free(instname);
++ if (dfd_iparent != -1)
++ close(dfd_iparent);
++ if (dfd_ipath != -1)
++ close(dfd_ipath);
++ if (dfd_pptrdir != -1)
++ close(dfd_pptrdir);
+ #ifdef WITH_SELINUX
+ freecon(instcontext);
+ freecon(origcontext);
+@@ -1803,6 +2088,7 @@ static int cleanup_tmpdirs(struct instance_data *idata) + {
+ struct polydir_s *pptr;
+ pid_t rc, pid;
++ int dfd = -1;
+ struct sigaction newsa, oldsa;
+ int status;
+
+@@ -1814,7 +2100,17 @@ static int cleanup_tmpdirs(struct instance_data *idata) + }
+
+ for (pptr = idata->polydirs_ptr; pptr; pptr = pptr->next) {
+- if (pptr->method == TMPDIR && access(pptr->instance_prefix, F_OK) == 0) {
++ if (pptr->method == TMPDIR) {
++
++ dfd = secure_opendir_stateless(pptr->instance_parent);
++ if (dfd == -1)
++ continue;
++
++ if (faccessat(dfd, pptr->instname, F_OK, AT_SYMLINK_NOFOLLOW) != 0) {
++ close(dfd);
++ continue;
++ }
++
+ pid = fork();
+ if (pid == 0) {
+ static char *envp[] = { NULL };
+@@ -1824,10 +2120,21 @@ static int cleanup_tmpdirs(struct instance_data *idata)
+ _exit(1);
+ }
+ #endif
++ if (fchdir(dfd) == -1) {
++ pam_syslog(idata->pamh, LOG_ERR, "Failed fchdir to %s: %m",
++ pptr->instance_absolute);
++ _exit(1);
++ }
++
+ close_fds_pre_exec(idata);
+- if (execle("/bin/rm", "/bin/rm", "-rf", pptr->instance_prefix, NULL, envp) < 0)
+- _exit(1);
++
++ execle("/bin/rm", "/bin/rm", "-rf", pptr->instname, NULL, envp);
++ _exit(1);
+ } else if (pid > 0) {
++
++ if (dfd != -1)
++ close(dfd);
++
+ while (((rc = waitpid(pid, &status, 0)) == (pid_t)-1) &&
+ (errno == EINTR));
+ if (rc == (pid_t)-1) {
+@@ -1840,6 +2147,10 @@ static int cleanup_tmpdirs(struct instance_data *idata) + "Error removing %s", pptr->instance_prefix);
+ }
+ } else if (pid < 0) {
++
++ if (dfd != -1)
++ close(dfd);
++
+ pam_syslog(idata->pamh, LOG_ERR,
+ "Cannot fork to cleanup temporary directory, %m");
+ rc = PAM_SESSION_ERR;
+@@ -1863,6 +2174,7 @@ out:
+ static int setup_namespace(struct instance_data *idata, enum unmnt_op unmnt) + {
+ int retval = 0, need_poly = 0, changing_dir = 0;
++ int dfd = -1;
+ char *cptr, *fptr, poly_parent[PATH_MAX];
+ struct polydir_s *pptr;
+
+@@ -1978,13 +2290,21 @@ static int setup_namespace(struct instance_data *idata, enum unmnt_op unmnt)
+ strcpy(poly_parent, "/");
+ else if (cptr)
+ *cptr = '\0';
+- if (chdir(poly_parent) < 0) {
++
++ dfd = secure_opendir_stateless(poly_parent);
++ if (dfd == -1) {
+ pam_syslog(idata->pamh, LOG_ERR,
+- "Can't chdir to %s, %m", poly_parent);
++ "Failed opening %s to fchdir: %m", poly_parent); + }
++ else if (fchdir(dfd) == -1) {
++ pam_syslog(idata->pamh, LOG_ERR,
++ "Failed fchdir to %s: %m", poly_parent);
++ }
++ if (dfd != -1)
++ close(dfd);
+ }
+
+- if (umount(pptr->rdir) < 0) {
++ if (secure_umount(pptr->rdir) < 0) {
+ int saved_errno = errno;
+ pam_syslog(idata->pamh, LOG_ERR, "Unmount of %s failed, %m",
+ pptr->rdir);
+@@ -2054,7 +2374,7 @@ static int orig_namespace(struct instance_data *idata)
+ "Unmounting instance dir for user %d & dir %s",
+ idata->uid, pptr->dir);
+
+- if (umount(pptr->dir) < 0) {
++ if (secure_umount(pptr->dir) < 0) {
+ pam_syslog(idata->pamh, LOG_ERR, "Unmount of %s failed, %m", + pptr->dir);
+ return PAM_SESSION_ERR;
+diff --git a/modules/pam_namespace/pam_namespace.h b/modules/pam_namespace/pam_namespace.h
+index 1799938..8a7a66b 100644
+--- a/modules/pam_namespace/pam_namespace.h
++++ b/modules/pam_namespace/pam_namespace.h
+@@ -44,21 +44,17 @@
+ #include <stdlib.h>
+ #include <errno.h>
+ #include <syslog.h>
+-#include <dlfcn.h>
+-#include <stdarg.h>
+ #include <pwd.h>
+ #include <grp.h>
+ #include <limits.h>
+ #include <sys/types.h>
+ #include <sys/stat.h>
+-#include <sys/resource.h>
+ #include <sys/mount.h>
+ #include <sys/wait.h>
+ #include <libgen.h>
+ #include <fcntl.h>
+ #include <sched.h>
+ #include <glob.h>
+-#include <locale.h>
+ #include "security/pam_modules.h"
+ #include "security/pam_modutil.h"
+ #include "security/pam_ext.h"
+@@ -126,6 +122,13 @@
+ #define NAMESPACE_POLYDIR_DATA "pam_namespace:polydir_data"
+ #define NAMESPACE_PROTECT_DATA "pam_namespace:protect_data"
+
++/*
++ * Operation mode for function secure_opendir()
++ */
++#define SECURE_OPENDIR_PROTECT 0x00000001
++#define SECURE_OPENDIR_MKDIR 0x00000002
++#define SECURE_OPENDIR_FULL_FD 0x00000004
++
+ /*
+ * Polyinstantiation method options, based on user, security context
+ * or both
+@@ -163,6 +166,9 @@ struct polydir_s {
+ char dir[PATH_MAX]; /* directory to polyinstantiate */
+ char rdir[PATH_MAX]; /* directory to unmount (based on RUSER) */
+ char instance_prefix[PATH_MAX]; /* prefix for instance dir path name */ ++ char instance_absolute[PATH_MAX]; /* absolute path to the instance dir (instance_parent + instname) */
++ char instance_parent[PATH_MAX]; /* parent dir of the instance dir */
++ char *instname; /* last segment of the path to the instance dir */
+ enum polymethod method; /* method used to polyinstantiate */
+ unsigned int num_uids; /* number of override uids */
+ uid_t *uid; /* list of override uids */ diff --git a/debian/patches/upstream/0022-pam_access-rework-resolving-of-tokens-as-hostname.patch b/debian/patches/upstream/0022-pam_access-rework-resolving-of-tokens-as-hostname.patch
new file mode 100644
index 00000000..f08cf0ad
--- /dev/null
+++ b/debian/patches/upstream/0022-pam_access-rework-resolving-of-tokens-as-hostname.patch
@@ -0,0 +1,223 @@
+From: Thorsten Kukuk <[email protected]>
+Date: Thu, 14 Nov 2024 10:27:28 +0100
+Subject: pam_access: rework resolving of tokens as hostname
+
+* modules/pam_access/pam_access.c: separate resolving of IP addresses
+ from hostnames. Don't resolve TTYs or display variables as hostname
+ (#834).
+ Add "nodns" option to disallow resolving of tokens as hostname.
+* modules/pam_access/pam_access.8.xml: document nodns option
+* modules/pam_access/access.conf.5.xml: document that hostnames should
+ be written as FQHN.
+
+(cherry picked from commit 940747f88c16e029b69a74e80a2e94f65cb3e628)
+---
+ modules/pam_access/access.conf.5.xml | 4 ++
+ modules/pam_access/pam_access.8.xml | 46 +++++++++++++++--------
+ modules/pam_access/pam_access.c | 72 +++++++++++++++++++++++++++++++++++-
+ 3 files changed, 105 insertions(+), 17 deletions(-)
+
+diff --git a/modules/pam_access