feat: special presets (handle fileless exec)

KubeArmor/BPF/anonmapexec.bpf.c

@@ -0,0 +1,126 @@
+// +build ignore
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright 2023 Authors of KubeArmor */
+
+#include "shared.h"
+
+#define PROT_EXEC 0x4  /* page can be executed */
+#define MAP_ANONYMOUS 0x20
+#define MAP_ANON MAP_ANONYMOUS
+
+#define S_IFIFO 0010000
+
+struct {
+  __uint(type, BPF_MAP_TYPE_RINGBUF);
+  __uint(max_entries, 1 << 24);
+} events SEC(".maps");
+
+typedef struct {
+  u64 ts;
+
+  u32 pid_id;
+  u32 mnt_id;
+
+  u32 host_ppid;
+  u32 host_pid;
+
+  u32 ppid;
+  u32 pid;
+  u32 uid;
+
+  u32 event_id;
+  s64 retval;
+
+  u8 comm[TASK_COMM_LEN];
+
+  unsigned long args[6];
+} mmap_event;
+
+static __always_inline u32 init_mmap_context(mmap_event *event_data) {
+  struct task_struct *task = (struct task_struct *)bpf_get_current_task();
+
+  event_data->ts = bpf_ktime_get_ns();
+
+  event_data->host_ppid = get_task_ppid(task);
+  event_data->host_pid = bpf_get_current_pid_tgid() >> 32;
+
+  u32 pid = get_task_ns_tgid(task);
+  if (event_data->host_pid == pid) { // host
+    event_data->pid_id = 0;
+    event_data->mnt_id = 0;
+
+    event_data->ppid = get_task_ppid(task);
+    event_data->pid = bpf_get_current_pid_tgid() >> 32;
+  } else { // container
+    event_data->pid_id = get_task_pid_ns_id(task);
+    event_data->mnt_id = get_task_mnt_ns_id(task);
+
+    event_data->ppid = get_task_ns_ppid(task);
+    event_data->pid = pid;
+  }
+
+  event_data->uid = bpf_get_current_uid_gid();
+
+  // Clearing array to avoid garbage values
+  __builtin_memset(event_data->comm, 0, sizeof(event_data->comm));
+  bpf_get_current_comm(&event_data->comm, sizeof(event_data->comm));
+
+  return 0;
+}
+
+
+// Force emitting struct mmap_event into the ELF.
+const mmap_event *unused __attribute__((unused));
+
+struct preset_map anon_map_exec_preset_containers SEC(".maps");
+
+
+SEC("lsm/mmap_file")
+int BPF_PROG(enforce_mmap_file, struct file *file, unsigned long reqprot,
+	 unsigned long prot, unsigned long flags){
+
+  struct task_struct *t = (struct task_struct *)bpf_get_current_task();
+
+  struct outer_key okey;
+  get_outer_key(&okey, t);
+
+  u32 *present = bpf_map_lookup_elem(&anon_map_exec_preset_containers, &okey);
+
+  if (!present) {
+    return 0;
+  }
+
+  // only if PROT_EXEC is assigned
+  if (prot & PROT_EXEC) {
+    if (flags & MAP_ANONYMOUS) {
+      mmap_event *event_data;
+      event_data = bpf_ringbuf_reserve(&events, sizeof(mmap_event), 0);
+
+      if (!event_data) {
+      return 0;
+      }
+
+      init_mmap_context(event_data);
+
+      __builtin_memset(event_data->args, 0, sizeof(event_data->args));
+
+      event_data->args[0] = reqprot;
+      event_data->args[1] = prot;
+      event_data->args[2] = flags;
+      event_data->event_id = ANON_MAP_EXEC;
+      if (*present == BLOCK) {
+        event_data->retval = -13;
+      } else {
+        event_data->retval = 0;
+      }
+      bpf_ringbuf_submit(event_data, 0);
+      // mapping not backed by any file with executable permission, denying mapping
+      if (*present == BLOCK) {
+        return -13;
+      } else {
+        return 0;
+      }
+    }
+  }
+  return 0;
+}

KubeArmor/BPF/filelessexec.bpf.c

@@ -0,0 +1,143 @@
+// +build ignore
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright 2023 Authors of KubeArmor */
+
+#include "shared.h"
+
+
+struct {
+  __uint(type, BPF_MAP_TYPE_RINGBUF);
+  __uint(max_entries, 1 << 24);
+} events SEC(".maps");
+
+
+// Force emitting struct mmap_event into the ELF.
+const event *unused __attribute__((unused));
+
+struct preset_map fileless_exec_preset_containers SEC(".maps");
+
+#define MEMFD "memfd:"
+
+static __always_inline int is_memfd(char *name) {
+  char memfd[] = MEMFD;
+  int i = 0;
+  while (i < sizeof(MEMFD) - 1 && name[i] != '\0' && name[i] == memfd[i]) {
+    i++;
+  }
+
+  if (i == sizeof(MEMFD) - 1) {
+    return 1;
+  }
+
+  return 0;
+}
+
+#define RUN_SHM "/run/shm/"
+
+static __always_inline int is_run_shm(char *name) {
+  char run_shm[] = RUN_SHM;
+  int i = 0;
+  while (i < sizeof(RUN_SHM) - 1 && name[i] != '\0' && name[i] == run_shm[i]) {
+    i++;
+  }
+
+  if (i == sizeof(RUN_SHM) - 1) {
+    return 1;
+  }
+
+  return 0;
+}
+
+#define DEV_SHM "/dev/shm/"
+
+static __always_inline int is_dev_shm(char *name) {
+  char dev_shm[] = DEV_SHM;
+  int i = 0;
+  while (i < sizeof(DEV_SHM) - 1 && name[i] != '\0' && name[i] == dev_shm[i]) {
+    i++;
+  }
+
+  if (i == sizeof(DEV_SHM) - 1) {
+    return 1;
+  }
+
+  return 0;
+}
+
+struct pathname {
+  char path[256];
+};
+
+SEC("lsm/bprm_check_security")
+int BPF_PROG(enforce_bprm_check_security, struct linux_binprm *bprm){
+
+  struct task_struct *t = (struct task_struct *)bpf_get_current_task();
+
+  struct outer_key okey;
+  get_outer_key(&okey, t);
+
+  u32 *present = bpf_map_lookup_elem(&fileless_exec_preset_containers, &okey);
+
+  if (!present) {
+    return 0;
+  }
+
+  struct pathname path_data = {};
+
+  struct file *file = BPF_CORE_READ(bprm, file);
+  if (file == NULL)
+    return 0;
+
+  bufs_t *path_buf = get_buf(PATH_BUFFER);
+  if (path_buf == NULL)
+    return 0;
+
+  // prepend path is needed to capture /dev/shm and /run/shm paths
+  if (!prepend_path(&(file->f_path), path_buf)){
+    // memfd files have no path in the filesystem -> extract their name
+    struct dentry *dentry = BPF_CORE_READ(&file->f_path, dentry);
+    struct qstr d_name = BPF_CORE_READ(dentry, d_name);
+    bpf_probe_read_kernel_str(path_data.path, MAX_STRING_SIZE, (void *) d_name.name);
+  } else {
+    u32 *path_offset = get_buf_off(PATH_BUFFER);
+    if (path_offset == NULL)
+      return 0;
+
+    void *path_ptr = &path_buf->buf[*path_offset];
+    bpf_probe_read_str(path_data.path, MAX_STRING_SIZE, path_ptr);
+  }
+
+  const char *filename = BPF_CORE_READ(bprm, filename);
+
+  if (is_memfd(path_data.path) || is_run_shm(path_data.path) || is_dev_shm(path_data.path)) {
+    event *event_data;
+    event_data = bpf_ringbuf_reserve(&events, sizeof(event), 0);
+
+    if (!event_data) {
+      return 0;
+    }
+
+    __builtin_memset(event_data->data.path, 0, sizeof(event_data->data.path));
+    __builtin_memset(event_data->data.source, 0, sizeof(event_data->data.source));
+
+    bpf_probe_read_str(event_data->data.path, MAX_STRING_SIZE, path_data.path);
+    bpf_probe_read_str(event_data->data.source, MAX_STRING_SIZE, filename);
+
+    init_context(event_data);
+    event_data->event_id = FILELESS_EXEC;
+
+    // mapping not backed by any file with executable permission, denying mapping
+    if (*present == BLOCK) {
+      event_data->retval = -13;
+      bpf_ringbuf_submit(event_data, 0);
+      // bpf_printk("[bprm] fileless execution detected with pid %d, denying execution", event_data->pid);
+      return -13;
+    } else {
+      event_data->retval = 0;
+      bpf_ringbuf_submit(event_data, 0);
+      return 0;
+    }
+  }
+
+  return 0;
+}

KubeArmor/BPF/protectenv.bpf.c

@@ -0,0 +1,108 @@
+// +build ignore
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright 2023 Authors of KubeArmor */
+
+#include "shared.h"
+
+typedef struct {
+  u32 pid;
+  u32 pid_ns;
+  u32 mnt_ns;
+  char comm[80];
+} pevent;
+
+const pevent *unused __attribute__((unused));
+
+struct {
+  __uint(type, BPF_MAP_TYPE_RINGBUF);
+  __uint(max_entries, 1 << 24);
+} events SEC(".maps");
+
+struct preset_map protectenv_preset_containers SEC(".maps");
+
+#define DIR_PROC "/proc/"
+
+static __always_inline int isProcDir(char *path) {
+  char procDir[] = DIR_PROC;
+  int i = 0;
+  while (i < sizeof(DIR_PROC) - 1 && path[i] != '\0' && path[i] == procDir[i]) {
+    i++;
+  }
+
+  if (i == sizeof(DIR_PROC) - 1) {
+    return 1;
+  }
+
+  return 0;
+}
+
+#define FILE_ENVIRON "/environ"
+
+static __always_inline int isEnviron(char *path) {
+  char envFile[] = FILE_ENVIRON;
+  int i = 0;
+  while (i < sizeof(FILE_ENVIRON) - 1 && path[i] != '\0' &&
+         path[i] == envFile[i]) {
+    i++;
+  }
+
+  if (i == sizeof(FILE_ENVIRON) - 1) {
+    return 1;
+  }
+
+  return 0;
+}
+
+SEC("lsm/file_open")
+int BPF_PROG(enforce_file, struct file *file) {
+
+  struct task_struct *t = (struct task_struct *)bpf_get_current_task();
+
+  struct outer_key okey;
+  get_outer_key(&okey, t);
+
+  u32 *present = bpf_map_lookup_elem(&protectenv_preset_containers, &okey);
+
+  if (!present) {
+    return 0;
+  }
+
+  u64 id = bpf_get_current_pid_tgid();
+  u32 tgid = id >> 32;
+
+  char path[80];
+  bpf_d_path(&file->f_path, path, 80);
+
+  if (!isProcDir(path)) {
+    return 0;
+  }
+
+  long envpid;
+  int count = bpf_strtol(path + sizeof(DIR_PROC) - 1, 10, 0, &envpid);
+  if (count < 0) {
+    return 0;
+  }
+  u8 envstart = sizeof(DIR_PROC) + count - 1;
+  if (envstart < 80 && !isEnviron(path + envstart)) {
+    return 0;
+  }
+
+  long pid = get_task_ns_tgid(t);
+
+  if (envpid != pid) {
+
+    pevent *task_info;
+
+    task_info = bpf_ringbuf_reserve(&events, sizeof(pevent), 0);
+    if (!task_info) {
+      return 0;
+    }
+    task_info->pid = pid;
+    task_info->pid_ns = okey.pid_ns;
+    task_info->mnt_ns = okey.mnt_ns;
+    bpf_ringbuf_submit(task_info, 0);
+    return -13;
+  }
+
+  return 0;
+}