hotdog: CVE-2022-0071

Signed-off-by: Arnaldo Garcia Rincon <agarrcia@amazon.com>

packages/hotdog/0001-poststart-hook-silently-exit-under-certain-condition.patch

@@ -0,0 +1,66 @@
+From 6ce5ac28431bfb18a0ba0233636e238fc18082d6 Mon Sep 17 00:00:00 2001
+From: Arnaldo Garcia Rincon <agarrcia@amazon.com>
+Date: Wed, 23 Feb 2022 19:55:25 +0000
+Subject: [PATCH 1/9] poststart-hook: silently exit under certain conditions
+
+Since hotdog patches java processes on a best-effort basis, the hotdog
+poststart hook won't exit with a non-zero error code if:
+
+- The process fails to constrain itself
+- An error occurred while reading the container's capabilities
+- An error occurred while the hotpatch was applied
+
+Signed-off-by: Arnaldo Garcia Rincon <agarrcia@amazon.com>
+Reviewed-by: Ben Cressey <bcressey@amazon.com>
+Reviewed-by: Samuel Karp <skarp@amazon.com>
+---
+ cmd/hotdog-poststart-hook/main.go | 14 +++++++++++---
+ 1 file changed, 11 insertions(+), 3 deletions(-)
+
+diff --git a/cmd/hotdog-poststart-hook/main.go b/cmd/hotdog-poststart-hook/main.go
+index 49b3606..2e559d4 100644
+--- a/cmd/hotdog-poststart-hook/main.go
++++ b/cmd/hotdog-poststart-hook/main.go
+@@ -20,6 +20,7 @@ func main() {
+ }
+
+ func _main() error {
++	// Fail if an error occurs while the container's state or config are retrieved
+ 	state, err := hook.State()
+ 	if err != nil {
+ 		return err
+@@ -28,21 +29,28 @@ func _main() error {
+ 	if err != nil {
+ 		return err
+ 	}
++	// Silently exit if:
++	// - The process fails to constrain itself
++	// - An error occurred while reading the container's capabilities
++	// - An error occurred while the hotpatch was applied
++	// We don't send these errors to the STDOUT because the runtime
++	// only reads it when the hook errors out
+ 	if spec.Process.SelinuxLabel != "" {
+ 		runtime.LockOSThread()
+ 		defer runtime.UnlockOSThread()
+ 		if err := selinux.SetExecLabel(spec.Process.SelinuxLabel); err != nil {
+-			return err
++			return nil
+ 		}
+ 	}
+ 	capJSON, err := json.Marshal(spec.Process.Capabilities)
+ 	if err != nil {
+-		return err
++		return nil
+ 	}
+ 	hotpatch := exec.Command("nsenter",
+ 		"-t", strconv.Itoa(state.Pid),
+ 		"-m", "-n", "-i", "-u", "-p",
+ 		filepath.Join(hotdog.ContainerDir, hotdog.HotpatchBinary))
+ 	hotpatch.Env = []string{hotdog.EnvCapability + "=" + string(capJSON)}
+-	return hotpatch.Start()
++	hotpatch.Start()
++	return nil
+ }
+-- 
+2.33.1
+

packages/hotdog/0002-poststart-hook-enter-container-s-cgroups.patch

@@ -0,0 +1,168 @@
+From 84a8080e1a8754d605bad861fc528d61d7792ff9 Mon Sep 17 00:00:00 2001
+From: Arnaldo Garcia Rincon <agarrcia@amazon.com>
+Date: Thu, 27 Jan 2022 22:29:30 +0000
+Subject: [PATCH 2/9] poststart-hook: enter container's cgroups
+
+The poststart-hooks processes have to be bound to the resource limits
+set to the container to prevent them from consuming all the host's
+resources.
+
+Signed-off-by: Arnaldo Garcia Rincon <agarrcia@amazon.com>
+Reviewed-by: Ben Cressey <bcressey@amazon.com>
+Reviewed-by: Samuel Karp <skarp@amazon.com>
+---
+ cgroups/utils.go                  | 74 +++++++++++++++++++++++++++++++
+ cmd/hotdog-poststart-hook/main.go | 32 +++++++++----
+ 2 files changed, 98 insertions(+), 8 deletions(-)
+ create mode 100644 cgroups/utils.go
+
+diff --git a/cgroups/utils.go b/cgroups/utils.go
+new file mode 100644
+index 0000000..fc321d0
+--- /dev/null
++++ b/cgroups/utils.go
+@@ -0,0 +1,74 @@
++package cgroups
++
++import (
++	"bufio"
++	"fmt"
++	"os"
++	"path/filepath"
++	"strconv"
++	"strings"
++)
++
++// EnterCgroups writes the current process into the cgroups of
++// the target process
++func EnterCgroups(targetPID string) error {
++	cgroups, err := parseCgroupFile(filepath.Join("/proc", targetPID, "/cgroup"))
++	if err != nil {
++		return nil
++	}
++	pid := os.Getpid()
++
++	for sub, path := range cgroups {
++		if err := os.WriteFile(filepath.Join("/sys/fs/cgroup/", sub, path, "tasks"), []byte(strconv.Itoa(pid)), 0); err != nil {
++			return err
++		}
++	}
++	return nil
++}
++
++// parseCgroupFile returns a map of strings, with the keys being the names of the cgroups
++// controllers, and the values the path name of the control group in the hierarchy
++// to which the process belongs.
++func parseCgroupFile(path string) (map[string]string, error) {
++	f, err := os.Open(path)
++	if err != nil {
++		return nil, err
++	}
++	defer f.Close()
++
++	s := bufio.NewScanner(f)
++	cgroups := make(map[string]string)
++
++	for s.Scan() {
++		text := s.Text()
++		// from cgroups(7):
++		// /proc/[pid]/cgroup
++		// ...
++		// For each cgroup hierarchy ... there is one entry
++		// containing three colon-separated fields of the form:
++		//     hierarchy-ID:subsystem-list:cgroup-path
++		parts := strings.SplitN(text, ":", 3)
++		if len(parts) < 3 {
++			return nil, fmt.Errorf("invalid cgroup entry: must contain at least two colons: %v", text)
++		}
++		subsystem := parts[1]
++		path := parts[2]
++		// The `cgroup` file contains lines with empty subsystems
++		if subsystem == "" {
++			continue
++		}
++		// There are subsystems with the form `name=<sub>`
++		if strings.Contains(subsystem, "=") {
++			subParts := strings.SplitN(subsystem, "=", 2)
++			if len(subParts) < 2 {
++				return nil, fmt.Errorf("invalid subsystem format, must have subsystem name: %s", parts[1])
++			}
++			subsystem = subParts[1]
++		}
++		cgroups[subsystem] = path
++	}
++	if err := s.Err(); err != nil {
++		return nil, err
++	}
++	return cgroups, nil
++}
+diff --git a/cmd/hotdog-poststart-hook/main.go b/cmd/hotdog-poststart-hook/main.go
+index 2e559d4..fc5d9d1 100644
+--- a/cmd/hotdog-poststart-hook/main.go
++++ b/cmd/hotdog-poststart-hook/main.go
+@@ -8,9 +8,11 @@ import (
+ 	"strconv"
+
+ 	"github.com/bottlerocket/hotdog"
++	"github.com/bottlerocket/hotdog/cgroups"
+ 	"github.com/bottlerocket/hotdog/hook"
+
+-	selinux "github.com/opencontainers/selinux/go-selinux"
++	"github.com/opencontainers/runtime-spec/specs-go"
++	"github.com/opencontainers/selinux/go-selinux"
+ )
+
+ func main() {
+@@ -29,28 +31,42 @@ func _main() error {
+ 	if err != nil {
+ 		return err
+ 	}
++	targetPID := strconv.Itoa(state.Pid)
++	runtime.LockOSThread()
++	defer runtime.UnlockOSThread()
++
+ 	// Silently exit if:
+ 	// - The process fails to constrain itself
+ 	// - An error occurred while reading the container's capabilities
+ 	// - An error occurred while the hotpatch was applied
+ 	// We don't send these errors to the STDOUT because the runtime
+ 	// only reads it when the hook errors out
+-	if spec.Process.SelinuxLabel != "" {
+-		runtime.LockOSThread()
+-		defer runtime.UnlockOSThread()
+-		if err := selinux.SetExecLabel(spec.Process.SelinuxLabel); err != nil {
+-			return nil
+-		}
++	if err := constrainProcess(spec, targetPID); err != nil {
++		return nil
+ 	}
+ 	capJSON, err := json.Marshal(spec.Process.Capabilities)
+ 	if err != nil {
+ 		return nil
+ 	}
+ 	hotpatch := exec.Command("nsenter",
+-		"-t", strconv.Itoa(state.Pid),
++		"-t", targetPID,
+ 		"-m", "-n", "-i", "-u", "-p",
+ 		filepath.Join(hotdog.ContainerDir, hotdog.HotpatchBinary))
+ 	hotpatch.Env = []string{hotdog.EnvCapability + "=" + string(capJSON)}
+ 	hotpatch.Start()
+ 	return nil
+ }
++
++// constrainProcess sets the SELinux label of the running process, and changes
++// its cgroups to be the same as the target container.
++func constrainProcess(spec specs.Spec, targetPID string) error {
++	if err := cgroups.EnterCgroups(targetPID); err != nil {
++		return err
++	}
++	if spec.Process.SelinuxLabel != "" {
++		if err := selinux.SetExecLabel(spec.Process.SelinuxLabel); err != nil {
++			return err
++		}
++	}
++	return nil
++}
+-- 
+2.33.1
+

packages/hotdog/0003-poststart-hook-set-NO_NEW_PRIVS-in-poststart-process.patch

@@ -0,0 +1,52 @@
+From 71ac992149a17862a495552f38e747a6d297fb43 Mon Sep 17 00:00:00 2001
+From: Arnaldo Garcia Rincon <agarrcia@amazon.com>
+Date: Thu, 3 Feb 2022 22:55:40 +0000
+Subject: [PATCH 3/9] poststart-hook: set `NO_NEW_PRIVS` in poststart process
+
+The `NO_NEW_PRIVS` flag will prevent the poststart process and its
+children from getting more privileges than what they were granted.
+
+Signed-off-by: Arnaldo Garcia Rincon <agarrcia@amazon.com>
+Reviewed-by: Ben Cressey <bcressey@amazon.com>
+Reviewed-by: Samuel Karp <skarp@amazon.com>
+---
+ cmd/hotdog-poststart-hook/main.go | 10 ++++++++--
+ 1 file changed, 8 insertions(+), 2 deletions(-)
+
+diff --git a/cmd/hotdog-poststart-hook/main.go b/cmd/hotdog-poststart-hook/main.go
+index fc5d9d1..ac9d33c 100644
+--- a/cmd/hotdog-poststart-hook/main.go
++++ b/cmd/hotdog-poststart-hook/main.go
+@@ -13,6 +13,7 @@ import (
+
+ 	"github.com/opencontainers/runtime-spec/specs-go"
+ 	"github.com/opencontainers/selinux/go-selinux"
++	"golang.org/x/sys/unix"
+ )
+
+ func main() {
+@@ -57,8 +58,10 @@ func _main() error {
+ 	return nil
+ }
+
+-// constrainProcess sets the SELinux label of the running process, and changes
+-// its cgroups to be the same as the target container.
++// constrainProcess sets the SELinux label of the running process, changes
++// its cgroups to be the same as the target container, and sets the
++// `NO_NEW_PRIVS` flags to prevent the current process to get more
++// privileges.
+ func constrainProcess(spec specs.Spec, targetPID string) error {
+ 	if err := cgroups.EnterCgroups(targetPID); err != nil {
+ 		return err
+@@ -68,5 +71,8 @@ func constrainProcess(spec specs.Spec, targetPID string) error {
+ 			return err
+ 		}
+ 	}
++	if err := unix.Prctl(unix.PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); err != nil {
++		return err
++	}
+ 	return nil
+ }
+-- 
+2.33.1
+