diff options
Diffstat (limited to 'poky/meta/recipes-extended/shadow/files/CVE-2018-7169.patch')
| -rw-r--r-- | poky/meta/recipes-extended/shadow/files/CVE-2018-7169.patch | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/poky/meta/recipes-extended/shadow/files/CVE-2018-7169.patch b/poky/meta/recipes-extended/shadow/files/CVE-2018-7169.patch new file mode 100644 index 000000000..36887d44e --- /dev/null +++ b/poky/meta/recipes-extended/shadow/files/CVE-2018-7169.patch @@ -0,0 +1,186 @@ +From fb28c99b8a66ff2605c5cb96abc0a4d975f92de0 Mon Sep 17 00:00:00 2001 +From: Aleksa Sarai <asarai@suse.de> +Date: Thu, 15 Feb 2018 23:49:40 +1100 +Subject: [PATCH] newgidmap: enforce setgroups=deny if self-mapping a group + +This is necessary to match the kernel-side policy of "self-mapping in a +user namespace is fine, but you cannot drop groups" -- a policy that was +created in order to stop user namespaces from allowing trivial privilege +escalation by dropping supplementary groups that were "blacklisted" from +certain paths. + +This is the simplest fix for the underlying issue, and effectively makes +it so that unless a user has a valid mapping set in /etc/subgid (which +only administrators can modify) -- and they are currently trying to use +that mapping -- then /proc/$pid/setgroups will be set to deny. This +workaround is only partial, because ideally it should be possible to set +an "allow_setgroups" or "deny_setgroups" flag in /etc/subgid to allow +administrators to further restrict newgidmap(1). + +We also don't write anything in the "allow" case because "allow" is the +default, and users may have already written "deny" even if they +technically are allowed to use setgroups. And we don't write anything if +the setgroups policy is already "deny". + +Ref: https://bugs.launchpad.net/ubuntu/+source/shadow/+bug/1729357 +Fixes: CVE-2018-7169 + +Upstream-Status: Backport [https://github.com/shadow-maint/shadow/commit/fb28c99b8a66ff2605c5cb96abc0a4d975f92de0] +Reported-by: Craig Furman <craig.furman89@gmail.com> +Signed-off-by: Aleksa Sarai <asarai@suse.de> +Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa@mvista.com> +--- + src/newgidmap.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++------ + 1 file changed, 80 insertions(+), 9 deletions(-) + +diff --git a/src/newgidmap.c b/src/newgidmap.c +index b1e33513..59a2e75c 100644 +--- a/src/newgidmap.c ++++ b/src/newgidmap.c +@@ -46,32 +46,37 @@ + */ + const char *Prog; + +-static bool verify_range(struct passwd *pw, struct map_range *range) ++ ++static bool verify_range(struct passwd *pw, struct map_range *range, bool *allow_setgroups) + { + /* An empty range is invalid */ + if (range->count == 0) + return false; + +- /* Test /etc/subgid */ +- if (have_sub_gids(pw->pw_name, range->lower, range->count)) ++ /* Test /etc/subgid. If the mapping is valid then we allow setgroups. */ ++ if (have_sub_gids(pw->pw_name, range->lower, range->count)) { ++ *allow_setgroups = true; + return true; ++ } + +- /* Allow a process to map it's own gid */ +- if ((range->count == 1) && (pw->pw_gid == range->lower)) ++ /* Allow a process to map its own gid. */ ++ if ((range->count == 1) && (pw->pw_gid == range->lower)) { ++ /* noop -- if setgroups is enabled already we won't disable it. */ + return true; ++ } + + return false; + } + + static void verify_ranges(struct passwd *pw, int ranges, +- struct map_range *mappings) ++ struct map_range *mappings, bool *allow_setgroups) + { + struct map_range *mapping; + int idx; + + mapping = mappings; + for (idx = 0; idx < ranges; idx++, mapping++) { +- if (!verify_range(pw, mapping)) { ++ if (!verify_range(pw, mapping, allow_setgroups)) { + fprintf(stderr, _( "%s: gid range [%lu-%lu) -> [%lu-%lu) not allowed\n"), + Prog, + mapping->upper, +@@ -89,6 +94,70 @@ static void usage(void) + exit(EXIT_FAILURE); + } + ++void write_setgroups(int proc_dir_fd, bool allow_setgroups) ++{ ++ int setgroups_fd; ++ char *policy, policy_buffer[4096]; ++ ++ /* ++ * Default is "deny", and any "allow" will out-rank a "deny". We don't ++ * forcefully write an "allow" here because the process we are writing ++ * mappings for may have already set themselves to "deny" (and "allow" ++ * is the default anyway). So allow_setgroups == true is a noop. ++ */ ++ policy = "deny\n"; ++ if (allow_setgroups) ++ return; ++ ++ setgroups_fd = openat(proc_dir_fd, "setgroups", O_RDWR|O_CLOEXEC); ++ if (setgroups_fd < 0) { ++ /* ++ * If it's an ENOENT then we are on too old a kernel for the setgroups ++ * code to exist. Emit a warning and bail on this. ++ */ ++ if (ENOENT == errno) { ++ fprintf(stderr, _("%s: kernel doesn't support setgroups restrictions\n"), Prog); ++ goto out; ++ } ++ fprintf(stderr, _("%s: couldn't open process setgroups: %s\n"), ++ Prog, ++ strerror(errno)); ++ exit(EXIT_FAILURE); ++ } ++ ++ /* ++ * Check whether the policy is already what we want. /proc/self/setgroups ++ * is write-once, so attempting to write after it's already written to will ++ * fail. ++ */ ++ if (read(setgroups_fd, policy_buffer, sizeof(policy_buffer)) < 0) { ++ fprintf(stderr, _("%s: failed to read setgroups: %s\n"), ++ Prog, ++ strerror(errno)); ++ exit(EXIT_FAILURE); ++ } ++ if (!strncmp(policy_buffer, policy, strlen(policy))) ++ goto out; ++ ++ /* Write the policy. */ ++ if (lseek(setgroups_fd, 0, SEEK_SET) < 0) { ++ fprintf(stderr, _("%s: failed to seek setgroups: %s\n"), ++ Prog, ++ strerror(errno)); ++ exit(EXIT_FAILURE); ++ } ++ if (dprintf(setgroups_fd, "%s", policy) < 0) { ++ fprintf(stderr, _("%s: failed to setgroups %s policy: %s\n"), ++ Prog, ++ policy, ++ strerror(errno)); ++ exit(EXIT_FAILURE); ++ } ++ ++out: ++ close(setgroups_fd); ++} ++ + /* + * newgidmap - Set the gid_map for the specified process + */ +@@ -103,6 +172,7 @@ int main(int argc, char **argv) + struct stat st; + struct passwd *pw; + int written; ++ bool allow_setgroups = false; + + Prog = Basename (argv[0]); + +@@ -145,7 +215,7 @@ int main(int argc, char **argv) + (unsigned long) getuid ())); + return EXIT_FAILURE; + } +- ++ + /* Get the effective uid and effective gid of the target process */ + if (fstat(proc_dir_fd, &st) < 0) { + fprintf(stderr, _("%s: Could not stat directory for target %u\n"), +@@ -177,8 +247,9 @@ int main(int argc, char **argv) + if (!mappings) + usage(); + +- verify_ranges(pw, ranges, mappings); ++ verify_ranges(pw, ranges, mappings, &allow_setgroups); + ++ write_setgroups(proc_dir_fd, allow_setgroups); + write_mapping(proc_dir_fd, ranges, mappings, "gid_map"); + sub_gid_close(); + +-- +2.13.3 + |
