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pkg/subscriptions: Modernize FIPS mounts
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/etc/system-fips is deprecated in CentOS Stream 9 and has been removed
from CentOS Stream 10. UBI8 containers still contain /etc/system-fips ->
/run/secrets/system-fips, but UBI9 containers do not, so creating
/run/secrets/system-fips on UBI9 (or later) does not serve a useful
purpose. See [1, 2].

Instead of checking /etc/system-fips to determine whether FIPS mode is
enabled on the host, read /proc/sys/crypto/fips_enabled, which works for
all supported RHEL versions and likely even earlier.

In CentOS 10 Stream, the crypto-policies package does now contain
/usr/share/crypto-policies/default-fips-config, which is meant to serve
as a file to bind-mount over /etc/crypto-policies/config when in FIPS
mode [3]. Manual creation of this file is thus no longer required in
containers/common for modern containers. Using this file as a source
also enables improvements in crypto-policies tooling which will now
 - unmount the two bind mounts when a user manually changes the policy
   using update-crypto-policies --set, something which was previously
   broken in containers because /etc/crypto-policies/config was
   a read-only bind-mount, and
 - unmount and restore the two bind-mounts when the crypto-policies
   package is updated.
The crypto-policies package will only do these steps if the the bind
mounts for crypto-policies use the
  /usr/share/crypto-policies/default-fips-config
file as source, so it makes sense for containers/common to switch to
that.

[1]: https://gitlab.com/redhat-crypto/fedora-crypto-policies/-/merge_requests/111
[2]: https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/9/html/9.0_release_notes/deprecated_functionality#deprecated-functionality_security
[3]: https://gitlab.com/redhat-crypto/fedora-crypto-policies/-/commit/04ceadccfc07e5946b08157d06ca5c0d5a229d92

Closes: #2130
Related: https://issues.redhat.com/browse/CRYPTO-13556
Signed-off-by: Clemens Lang <[email protected]>
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@neverpanic
neverpanic committed Oct 31, 2024
1 parent a44f1f1 commit abf2f6b
Showing 1 changed file with 145 additions and 61 deletions.
206 changes: 145 additions & 61 deletions pkg/subscriptions/subscriptions.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -155,6 +155,25 @@ func getMountsMap(path string) (string, string, error) { //nolint
return "", "", fmt.Errorf("unable to get host and container dir from path: %s", path)
}

// Return true iff the system is in FIPS mode as determined by reading
// /proc/sys/crypto/fips_enabled.
func shouldAddFIPSMounts() bool {
fips_enabled, err := os.ReadFile("/proc/sys/crypto/fips_enabled")
if err != nil {
if !errors.Is(err, os.ErrNotExist) {
logrus.Errorf("Failed to read /proc/sys/crypto/fips_enabled to determine FIPS state: %v", err)
}
return false
}

if strings.TrimSpace(string(fips_enabled)) != "1" {
logrus.Debug("/proc/sys/crypto/fips_enabled does not contain '1', not adding FIPS mode bind mounts")
return false
}

return true
}

// MountsWithUIDGID copies, adds, and mounts the subscriptions to the container root filesystem
// mountLabel: MAC/SELinux label for container content
// containerRunDir: Private data for storing subscriptions on the host mounted in container.
Expand Down Expand Up @@ -194,22 +213,16 @@ func MountsWithUIDGID(mountLabel, containerRunDir, mountFile, mountPoint string,
}
}

// Only add FIPS subscription mount if disableFips=false
if disableFips {
// Only add FIPS subscription mount if disableFips is false and
// /proc/sys/crypto/fips_enabled contains "1"
if disableFips || !shouldAddFIPSMounts() {
return subscriptionMounts
}
// Add FIPS mode subscription if /etc/system-fips exists on the host
err := fileutils.Exists("/etc/system-fips")
switch {
case err == nil:
if err := addFIPSModeSubscription(&subscriptionMounts, containerRunDir, mountPoint, mountLabel, uid, gid); err != nil {
logrus.Errorf("Adding FIPS mode subscription to container: %v", err)
}
case errors.Is(err, os.ErrNotExist):
logrus.Debug("/etc/system-fips does not exist on host, not mounting FIPS mode subscription")
default:
logrus.Errorf("stat /etc/system-fips failed for FIPS mode subscription: %v", err)

if err := addFIPSMounts(&subscriptionMounts, containerRunDir, mountPoint, mountLabel, uid, gid); err != nil {
logrus.Errorf("Adding FIPS mode bind mounts to container: %v", err)
}

return subscriptionMounts
}

Expand Down Expand Up @@ -306,43 +319,97 @@ func addSubscriptionsFromMountsFile(filePath, mountLabel, containerRunDir string
return mounts, nil
}

// addFIPSModeSubscription adds mounts to the `mounts` slice that are needed for the container to run openssl in FIPs mode
// (i.e: be FIPs compliant).
// It should only be called if /etc/system-fips exists on host.
// It primarily does two things:
// - creates /run/secrets/system-fips in the container root filesystem, and adds it to the `mounts` slice.
// - If `/etc/crypto-policies/back-ends` already exists inside of the container, it creates
// `/usr/share/crypto-policies/back-ends/FIPS` inside the container as well.
// It is done from within the container to ensure to avoid policy incompatibility between the container and host.
func addFIPSModeSubscription(mounts *[]rspec.Mount, containerRunDir, mountPoint, mountLabel string, uid, gid int) error {
func containerHasEtcSystemFips(subscriptionsDir, mountPoint string) (bool, error) {
containerEtc, err := securejoin.SecureJoin(mountPoint, "etc")
if err != nil {
return false, fmt.Errorf("Container /etc resolution error: %w", err)
}
if fileutils.Lexists(filepath.Join(containerEtc, "system-fips")) != nil {
logrus.Debug("/etc/system-fips does not exist in the container, not creating /run/secrets/system-fips")
return false, nil
}

fipsFileTarget, err := securejoin.SecureJoin(mountPoint, "etc/system-fips")
if err != nil {
return false, fmt.Errorf("Container /etc/system-fips resolution error: %w", err)
}
if fipsFileTarget != filepath.Join(mountPoint, subscriptionsDir, "system-fips") {
logrus.Warnf("/etc/system-fips exists in the container, but is not a symlink to %[1]v/system-fips; not creating %[1]v/system-fips", subscriptionsDir)
return false, nil
}

return true, nil
}

// addFIPSMounts adds mounts to the `mounts` slice that are needed
// for the container to run cryptographic libraries (openssl, gnutls, NSS, ...)
// in FIPS mode (i.e: be FIPS compliant).
// It should only be called if /proc/sys/crypto/fips_enabled on the host
// contains '1'.
// It does three things:
// - creates /run/secrets/system-fips in the container root filesystem if
// /etc/system-fips exists and is a symlink to /run/secrets/system-fips,
// and adds it to the `mounts` slice. This is, for example, the case on
// RHEL 8, but not on newer RHEL, since /etc/system-fips is deprecated.
// - Bind-mounts `/usr/share/crypto-policies/back-ends/FIPS` over
// `/etc/crypto-policies/back-ends` if the former exists inside of the
// container. This is done from within the container to avoid policy
// incompatibility between container and host.
// - If a bind mount for `/etc/crypto-policies/back-ends` was created,
// bind-mounts `/usr/share/crypto-policies/default-fips-config` over
// `/etc/crypto-policies/config` if the former exists inside of the
// container. If it does not exist, creates a new temporary file containing
// "FIPS\n", and bind-mounts that over `/etc/crypto-policies/config`.
//
// Starting in CentOS 10 Stream, the crypto-policies package gracefully recognizes the two bind mounts
//
// - /etc/crypto-policies/config -> /usr/share/crypto-policies/default-fips-config
// - /etc/crypto-policies/back-ends/FIPS -> /usr/share/crypto-policies/back-ends/FIPS
//
// and unmounts them when users manually change the policy, or removes and
// restores the mounts when the crypto-policies package is upgraded.
func addFIPSMounts(mounts *[]rspec.Mount, containerRunDir, mountPoint, mountLabel string, uid, gid int) error {
// Check whether $container/etc/system-fips exists and is a symlink to /run/secrets/system-fips
subscriptionsDir := "/run/secrets"
ctrDirOnHost := filepath.Join(containerRunDir, subscriptionsDir)
if err := fileutils.Exists(ctrDirOnHost); errors.Is(err, os.ErrNotExist) {
if err = idtools.MkdirAllAs(ctrDirOnHost, 0o755, uid, gid); err != nil { //nolint
return err
}
if err = label.Relabel(ctrDirOnHost, mountLabel, false); err != nil {
return fmt.Errorf("applying correct labels on %q: %w", ctrDirOnHost, err)
}

createSystemFipsSecret, err := containerHasEtcSystemFips(subscriptionsDir, mountPoint)
if err != nil {
return err
}
fipsFile := filepath.Join(ctrDirOnHost, "system-fips")
// In the event of restart, it is possible for the FIPS mode file to already exist
if err := fileutils.Exists(fipsFile); errors.Is(err, os.ErrNotExist) {
file, err := os.Create(fipsFile)
if err != nil {
return fmt.Errorf("creating system-fips file in container for FIPS mode: %w", err)
if createSystemFipsSecret {
// This container contains
// /etc/system-fips -> /run/secrets/system-fips
// and expects podman to create this file if the container should
// be in FIPS mode
ctrDirOnHost := filepath.Join(containerRunDir, subscriptionsDir)
if err := fileutils.Exists(ctrDirOnHost); errors.Is(err, os.ErrNotExist) {
if err = idtools.MkdirAllAs(ctrDirOnHost, 0o755, uid, gid); err != nil { //nolint
return err
}
if err = label.Relabel(ctrDirOnHost, mountLabel, false); err != nil {
return fmt.Errorf("applying correct labels on %q: %w", ctrDirOnHost, err)
}
}
file.Close()
}
fipsFile := filepath.Join(ctrDirOnHost, "system-fips")

if !mountExists(*mounts, subscriptionsDir) {
m := rspec.Mount{
Source: ctrDirOnHost,
Destination: subscriptionsDir,
Type: "bind",
Options: []string{"bind", "rprivate"},
// In the event of restart, it is possible for the FIPS mode file to already exist
if err := fileutils.Exists(fipsFile); errors.Is(err, os.ErrNotExist) {
file, err := os.Create(fipsFile)
if err != nil {
return fmt.Errorf("creating system-fips file in container for FIPS mode: %w", err)
}
file.Close()
}

if !mountExists(*mounts, subscriptionsDir) {
m := rspec.Mount{
Source: ctrDirOnHost,
Destination: subscriptionsDir,
Type: "bind",
Options: []string{"bind", "rprivate"},
}
*mounts = append(*mounts, m)
}
*mounts = append(*mounts, m)
}

srcBackendDir := "/usr/share/crypto-policies/back-ends/FIPS"
Expand Down Expand Up @@ -370,27 +437,44 @@ func addFIPSModeSubscription(mounts *[]rspec.Mount, containerRunDir, mountPoint,

// Make sure we set the config to FIPS so that the container does not overwrite
// /etc/crypto-policies/back-ends when crypto-policies-scripts is reinstalled.
cryptoPoliciesConfigFile := filepath.Join(containerRunDir, "fips-config")
file, err := os.Create(cryptoPoliciesConfigFile)
//
// Starting in CentOS 10 Stream, crypto-policies provides
// /usr/share/crypto-policies/default-fips-config as bind mount source
// file and the crypto-policies tooling gracefully deals with the two bind-mounts
// /etc/crypto-policies/back-ends -> /usr/share/crypto-policies/back-ends/FIPS
// /etc/crypto-policies/config -> /usr/share/crypto-policies/default-fips-config
// if they both exist.
srcPolicyConfig := "/usr/share/crypto-policies/default-fips-config"
destPolicyConfig := "/etc/crypto-policies/config"
srcPolicyConfigOnHost, err := securejoin.SecureJoin(mountPoint, srcPolicyConfig)
if err != nil {
return fmt.Errorf("creating fips config file in container for FIPS mode: %w", err)
}
defer file.Close()
if _, err := file.WriteString("FIPS\n"); err != nil {
return fmt.Errorf("writing fips config file in container for FIPS mode: %w", err)
}
if err = label.Relabel(cryptoPoliciesConfigFile, mountLabel, false); err != nil {
return fmt.Errorf("applying correct labels on fips-config file: %w", err)
return fmt.Errorf("Could not expand %q in container: %w", srcPolicyConfig, err)
}
if err := file.Chown(uid, gid); err != nil {
return fmt.Errorf("chown fips-config file: %w", err)

if err = fileutils.Exists(srcPolicyConfigOnHost); err != nil {
if !errors.Is(err, os.ErrNotExist) {
return fmt.Errorf("Could not check whether %q exists in container: %w", srcPolicyConfig, err)
}

// /usr/share/crypto-policies/default-fips-config does not exist, let's create it ourselves
cryptoPoliciesConfigFile := filepath.Join(containerRunDir, "fips-config")
if err := os.WriteFile(cryptoPoliciesConfigFile, []byte("FIPS\n"), 0o644); err != nil {
return fmt.Errorf("Failed to write fips config file in container for FIPS mode: %w", err)
}
if err = label.Relabel(cryptoPoliciesConfigFile, mountLabel, false); err != nil {
return fmt.Errorf("Failed to apply correct labels on fips config file: %w", err)
}
if err := os.Chown(cryptoPoliciesConfigFile, uid, gid); err != nil {
return fmt.Errorf("Failed to chown fips config file: %w", err)
}

srcPolicyConfigOnHost = cryptoPoliciesConfigFile
}

policyConfig := "/etc/crypto-policies/config"
if !mountExists(*mounts, policyConfig) {
if !mountExists(*mounts, destPolicyConfig) {
m := rspec.Mount{
Source: cryptoPoliciesConfigFile,
Destination: policyConfig,
Source: srcPolicyConfigOnHost,
Destination: destPolicyConfig,
Type: "bind",
Options: []string{"bind", "rprivate"},
}
Expand Down

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