diff -Nru cifs-utils-6.11/debian/changelog cifs-utils-6.11/debian/changelog --- cifs-utils-6.11/debian/changelog 2021-04-17 18:31:22.000000000 +0200 +++ cifs-utils-6.11/debian/changelog 2021-05-06 21:24:29.000000000 +0200 @@ -1,3 +1,10 @@ +cifs-utils (2:6.11-3) unstable; urgency=high + + * CVE-2021-20208: cifs.upcall kerberos auth leak in container + (Closes: #987308) + + -- Mathieu Parent Thu, 06 May 2021 21:24:29 +0200 + cifs-utils (2:6.11-2) unstable; urgency=medium [ Sergio Durigan Junior ] diff -Nru cifs-utils-6.11/debian/patches/0010-CVE-2021-20208.patch cifs-utils-6.11/debian/patches/0010-CVE-2021-20208.patch --- cifs-utils-6.11/debian/patches/0010-CVE-2021-20208.patch 1970-01-01 01:00:00.000000000 +0100 +++ cifs-utils-6.11/debian/patches/0010-CVE-2021-20208.patch 2021-05-06 21:23:15.000000000 +0200 @@ -0,0 +1,264 @@ +From e461afd8cfa6d0781ae0c5c10e89b6ef1ca6da32 Mon Sep 17 00:00:00 2001 +From: Alastair Houghton +Date: Tue, 29 Dec 2020 14:02:39 +0000 +Subject: [PATCH] cifs.upcall: try to use container ipc/uts/net/pid/mnt/user + namespaces + +In certain scenarios (e.g. kerberos multimount), when a process does +syscalls, the kernel sometimes has to query information or trigger +some actions in userspace. To do so it calls the cifs.upcall binary +with information on the process that triggered the syscall in the +first place. + +ls(pid=10) ====> open("foo") ====> kernel + + that user doesn't have an SMB + session, lets create one using his + kerberos credential cache + + call cifs.upcall and ask for krb info + for whoever owns pid=10 + | + cifs.upcall --pid 10 <=================+ + + ...gather info... + return binary blob used + when establishing SMB session + ===================> kernel + open SMB session, handle + open() syscall +ls <=================================== return open() result to ls + +On a system using containers, the kernel is still calling the host +cifs.upcall and using the host configuration (for network, pid, etc). + +This patch changes the behaviour of cifs.upcall so that it uses the +calling process namespaces (ls in the example) when doing its +job. + +Note that the kernel still calls the binary in the host, but the +binary will place itself the contexts of the calling process +namespaces. + +This code makes use of (but shouldn't require) the following kernel +config options and syscall flags: + +approx. year | +introduced | config/flags +---------------+---------------- +2008 | CONFIG_NAMESPACES=y +2007 | CONFIG_UTS_NS=y +2020 | CONFIG_TIME_NS=y +2006 | CONFIG_IPC_NS=y +2007 | CONFIG_USER_NS +2008 | CONFIG_PID_NS=y +2007 | CONFIG_NET_NS=y +2007 | CONFIG_CGROUPS +2016 | CLONE_NEWCGROUP setns() flag + +Signed-off-by: Aurelien Aptel +Signed-off-by: Alastair Houghton +--- + cifs.upcall.c | 172 ++++++++++++++++++++++++++++++++++++++++++++++++++ + 1 file changed, 172 insertions(+) + +diff --git a/cifs.upcall.c b/cifs.upcall.c +index 400b42d..e413934 100644 +--- a/cifs.upcall.c ++++ b/cifs.upcall.c +@@ -51,6 +51,7 @@ + #include + #include + #include ++#include + + #include "data_blob.h" + #include "spnego.h" +@@ -240,6 +241,164 @@ err_cache: + return credtime; + } + ++static struct namespace_file { ++ int nstype; ++ const char *name; ++ int fd; ++} namespace_files[] = { ++ ++#ifdef CLONE_NEWCGROUP ++ { CLONE_NEWCGROUP, "cgroup", -1 }, ++#endif ++ ++#ifdef CLONE_NEWIPC ++ { CLONE_NEWIPC, "ipc", -1 }, ++#endif ++ ++#ifdef CLONE_NEWUTS ++ { CLONE_NEWUTS, "uts", -1 }, ++#endif ++ ++#ifdef CLONE_NEWNET ++ { CLONE_NEWNET, "net", -1 }, ++#endif ++ ++#ifdef CLONE_NEWPID ++ { CLONE_NEWPID, "pid", -1 }, ++#endif ++ ++#ifdef CLONE_NEWTIME ++ { CLONE_NEWTIME, "time", -1 }, ++#endif ++ ++#ifdef CLONE_NEWNS ++ { CLONE_NEWNS, "mnt", -1 }, ++#endif ++ ++#ifdef CLONE_NEWUSER ++ { CLONE_NEWUSER, "user", -1 }, ++#endif ++}; ++ ++#define NS_PATH_FMT "/proc/%d/ns/%s" ++#define NS_PATH_MAXLEN (6 + 10 + 4 + 6 + 1) ++ ++/** ++ * in_same_user_ns - return true if two processes are in the same user ++ * namespace. ++ * @pid_a: the pid of the first process ++ * @pid_b: the pid of the second process ++ * ++ * Works by comparing the inode numbers for /proc//user. ++ */ ++static int ++in_same_user_ns(pid_t pid_a, pid_t pid_b) ++{ ++ char path[NS_PATH_MAXLEN]; ++ ino_t a_ino, b_ino; ++ struct stat st; ++ ++ snprintf(path, sizeof(path), NS_PATH_FMT, pid_a, "user"); ++ if (stat(path, &st) != 0) ++ return 0; ++ a_ino = st.st_ino; ++ ++ snprintf(path, sizeof(path), NS_PATH_FMT, pid_b, "user"); ++ if (stat(path, &st) != 0) ++ return 0; ++ b_ino = st.st_ino; ++ ++ return a_ino == b_ino; ++} ++ ++/** ++ * switch_to_process_ns - change the namespace to the one for the specified ++ * process. ++ * @pid: initiating pid value from the upcall string ++ * ++ * Uses setns() to switch process namespace. ++ * This ensures that we have the same access and configuration as the ++ * process that triggered the lookup. ++ */ ++static int ++switch_to_process_ns(pid_t pid) ++{ ++ int count = sizeof(namespace_files) / sizeof(struct namespace_file); ++ int n, err = 0; ++ int rc = 0; ++ ++ /* First, open all the namespace fds. We do this first because ++ the namespace changes might prohibit us from opening them. */ ++ for (n = 0; n < count; ++n) { ++ char nspath[NS_PATH_MAXLEN]; ++ int ret, fd; ++ ++#ifdef CLONE_NEWUSER ++ if (namespace_files[n].nstype == CLONE_NEWUSER ++ && in_same_user_ns(getpid(), pid)) { ++ /* Switching to the same user namespace is forbidden, ++ because switching to a user namespace grants all ++ capabilities in that namespace regardless of uid. */ ++ namespace_files[n].fd = -1; ++ continue; ++ } ++#endif ++ ++ ret = snprintf(nspath, NS_PATH_MAXLEN, NS_PATH_FMT, ++ pid, namespace_files[n].name); ++ if (ret >= NS_PATH_MAXLEN) { ++ syslog(LOG_DEBUG, "%s: unterminated path!\n", __func__); ++ err = ENAMETOOLONG; ++ rc = -1; ++ goto out; ++ } ++ ++ fd = open(nspath, O_RDONLY); ++ if (fd < 0 && errno != ENOENT) { ++ /* ++ * don't stop on non-existing ns ++ * but stop for other errors ++ */ ++ err = errno; ++ rc = -1; ++ goto out; ++ } ++ ++ namespace_files[n].fd = fd; ++ } ++ ++ /* Next, call setns for each of them */ ++ for (n = 0; n < count; ++n) { ++ /* skip non-existing ns */ ++ if (namespace_files[n].fd < 0) ++ continue; ++ ++ rc = setns(namespace_files[n].fd, namespace_files[n].nstype); ++ ++ if (rc < 0) { ++ syslog(LOG_DEBUG, "%s: setns() failed for %s\n", ++ __func__, namespace_files[n].name); ++ err = errno; ++ goto out; ++ } ++ } ++ ++out: ++ /* Finally, close all the fds */ ++ for (n = 0; n < count; ++n) { ++ if (namespace_files[n].fd != -1) { ++ close(namespace_files[n].fd); ++ namespace_files[n].fd = -1; ++ } ++ } ++ ++ if (rc != 0) { ++ errno = err; ++ } ++ ++ return rc; ++} ++ + #define ENV_PATH_FMT "/proc/%d/environ" + #define ENV_PATH_MAXLEN (6 + 10 + 8 + 1) + +@@ -1109,6 +1268,19 @@ int main(const int argc, char *const argv[]) + env_cachename = + get_cachename_from_process_env(env_probe ? arg.pid : 0); + ++ /* ++ * Change to the process's namespace. This means that things will work ++ * acceptably in containers, because we'll be looking at the correct ++ * filesystem and have the correct network configuration. ++ */ ++ rc = switch_to_process_ns(arg.pid); ++ if (rc == -1) { ++ syslog(LOG_ERR, "unable to switch to process namespace: %s", ++ strerror(errno)); ++ rc = 1; ++ goto out; ++ } ++ + rc = setuid(uid); + if (rc == -1) { + syslog(LOG_ERR, "setuid: %s", strerror(errno)); +-- +2.25.1 + diff -Nru cifs-utils-6.11/debian/patches/series cifs-utils-6.11/debian/patches/series --- cifs-utils-6.11/debian/patches/series 2020-11-13 09:32:31.000000000 +0100 +++ cifs-utils-6.11/debian/patches/series 2021-05-06 21:23:29.000000000 +0200 @@ -1,3 +1,4 @@ 0001-Fix-fPIE-casing.patch 0002-Install-hook-relative-to-DESTDIR.patch 0003-Change-script-shbangs-to-python3.patch +0010-CVE-2021-20208.patch