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enable landlock access to files to allow forking and name resolution

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This commit is contained in:
Yves Rutschle 2024-01-05 13:21:55 +01:00
parent 940461de18
commit 39184b5622
1 changed files with 39 additions and 1 deletions
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40
landlock.c
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@ -59,6 +59,36 @@ static inline int landlock_restrict_self(const int ruleset_fd,
} }
#endif #endif
typedef enum {
LL_TREE,
LL_FILE
} ll_obj_type;
static int add_path_ro(int ruleset_fd, ll_obj_type otype, const char* path)
{
int fd = open(path, O_PATH | O_CLOEXEC);
if (fd < 0) {
print_message(msg_config_error, "Landlock: Failed to open %s: %s\n", path, strerror(errno));
return -1;
}
struct landlock_path_beneath_attr path_beneath = {
.allowed_access = (otype == LL_TREE ? LANDLOCK_ACCESS_FS_READ_DIR : 0 ) |
LANDLOCK_ACCESS_FS_READ_FILE,
.parent_fd = fd,
};
int res = landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH, &path_beneath, 0);
if (res) {
print_message(msg_config_error, "Landlock: Failed to update the ruleset with \"%s\": %s\n",
path, strerror(errno));
close(path_beneath.parent_fd);
return -1;
}
return 0;
}
void setup_landlock(void) void setup_landlock(void)
{ {
@ -90,7 +120,15 @@ void setup_landlock(void)
return; return;
} }
/* No call to landlock_add_rule: we retain no rights whatsoever */ /* Access to libraries, to be able to fork */
add_path_ro(ruleset_fd, LL_TREE, "/lib");
add_path_ro(ruleset_fd, LL_TREE, "/usr/lib");
add_path_ro(ruleset_fd, LL_FILE, "/etc/ld.so.cache"); /* To avoid searching all libs... */
/* Files to resolve names (required when dynamic resolution is used) */
add_path_ro(ruleset_fd, LL_FILE, "/etc/hosts");
add_path_ro(ruleset_fd, LL_FILE, "/etc/resolv.conf");
add_path_ro(ruleset_fd, LL_FILE, "/etc/nsswitch.conf");
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) { if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
print_message(msg_config_error, "Landlock: Failed to restrict privileges"); print_message(msg_config_error, "Landlock: Failed to restrict privileges");