Securitypolicy: Move fragment extraction

Move inject and load fragment into the securitypolicy pkg

Signed-off-by: Mahati Chamarthy <[email protected]>

Author: MahatiC

internal/gcs-sidecar/host.go

@@ -5,17 +5,10 @@ package bridge
 
 import (
 	"context"
-	"crypto/sha256"
-	"encoding/base64"
 	"fmt"
 	"io"
-	"os"
-	"path/filepath"
 	"sync"
-	"time"
 
-	"github.com/Microsoft/cosesign1go/pkg/cosesign1"
-	didx509resolver "github.com/Microsoft/didx509go/pkg/did-x509-resolver"
 	"github.com/Microsoft/hcsshim/internal/bridgeutils/gcserr"
 	hcsschema "github.com/Microsoft/hcsshim/internal/hcs/schema2"
 	"github.com/Microsoft/hcsshim/internal/log"
@@ -75,61 +68,15 @@ func NewHost(initialEnforcer securitypolicy.SecurityPolicyEnforcer) *Host {
 // security policy (done in the regoby LoadFragment)
 func (h *Host) InjectFragment(ctx context.Context, fragment *guestresource.LCOWSecurityPolicyFragment) (err error) {
 	log.G(ctx).WithField("fragment", fmt.Sprintf("%+v", fragment)).Debug("GCS Host.InjectFragment")
-
-	raw, err := base64.StdEncoding.DecodeString(fragment.Fragment)
-	if err != nil {
-		return err
-	}
-	blob := []byte(fragment.Fragment)
-	// keep a copy of the fragment, so we can manually figure out what went wrong
-	// will be removed eventually. Give it a unique name to avoid any potential
-	// race conditions.
-	sha := sha256.New()
-	sha.Write(blob)
-	timestamp := time.Now()
-	fragmentPath := fmt.Sprintf("fragment-%x-%d.blob", sha.Sum(nil), timestamp.UnixMilli())
-	_ = os.WriteFile(filepath.Join(os.TempDir(), fragmentPath), blob, 0644)
-
-	unpacked, err := cosesign1.UnpackAndValidateCOSE1CertChain(raw)
-	if err != nil {
-		return fmt.Errorf("InjectFragment failed COSE validation: %w", err)
-	}
-
-	payloadString := string(unpacked.Payload[:])
-	issuer := unpacked.Issuer
-	feed := unpacked.Feed
-	chainPem := unpacked.ChainPem
-
-	log.G(ctx).WithFields(logrus.Fields{
-		"issuer":   issuer, // eg the DID:x509:blah....
-		"feed":     feed,
-		"cty":      unpacked.ContentType,
-		"chainPem": chainPem,
-	}).Debugf("unpacked COSE1 cert chain")
-
-	log.G(ctx).WithFields(logrus.Fields{
-		"payload": payloadString,
-	}).Tracef("unpacked COSE1 payload")
-
-	if len(issuer) == 0 || len(feed) == 0 { // must both be present
-		return fmt.Errorf("either issuer and feed must both be provided in the COSE_Sign1 protected header")
-	}
-
-	// Resolve returns a did doc that we don't need
-	// we only care if there was an error or not
-	_, err = didx509resolver.Resolve(unpacked.ChainPem, issuer, true)
+	issuer, feed, payloadString, err := securitypolicy.ExtractAndVerifyFragment(ctx, fragment)
 	if err != nil {
-		log.G(ctx).Printf("Badly formed fragment - did resolver failed to match fragment did:x509 from chain with purported issuer %s, feed %s - err %s", issuer, feed, err.Error())
 		return err
 	}
-
 	// now offer the payload fragment to the policy
 	err = h.securityPolicyEnforcer.LoadFragment(ctx, issuer, feed, payloadString)
 	if err != nil {
-		return fmt.Errorf("InjectFragment failed policy load: %w", err)
+		return fmt.Errorf("error loading security policy fragment: %w", err)
 	}
-	log.G(ctx).Printf("passed fragment into the enforcer.")
-
 	return nil
 }
 

internal/guest/runtime/hcsv2/uvm.go

@@ -6,8 +6,6 @@ package hcsv2
 import (
 	"bufio"
 	"context"
-	"crypto/sha256"
-	"encoding/base64"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -20,8 +18,6 @@ import (
 	"syscall"
 	"time"
 
-	"github.com/Microsoft/cosesign1go/pkg/cosesign1"
-	didx509resolver "github.com/Microsoft/didx509go/pkg/did-x509-resolver"
 	"github.com/Microsoft/hcsshim/internal/bridgeutils/gcserr"
 	"github.com/Microsoft/hcsshim/internal/debug"
 	"github.com/Microsoft/hcsshim/internal/guest/policy"
@@ -166,61 +162,15 @@ func (h *Host) SetConfidentialUVMOptions(ctx context.Context, r *guestresource.L
 // security policy (done in the regoby LoadFragment)
 func (h *Host) InjectFragment(ctx context.Context, fragment *guestresource.LCOWSecurityPolicyFragment) (err error) {
 	log.G(ctx).WithField("fragment", fmt.Sprintf("%+v", fragment)).Debug("GCS Host.InjectFragment")
-
-	raw, err := base64.StdEncoding.DecodeString(fragment.Fragment)
-	if err != nil {
-		return err
-	}
-	blob := []byte(fragment.Fragment)
-	// keep a copy of the fragment, so we can manually figure out what went wrong
-	// will be removed eventually. Give it a unique name to avoid any potential
-	// race conditions.
-	sha := sha256.New()
-	sha.Write(blob)
-	timestamp := time.Now()
-	fragmentPath := fmt.Sprintf("fragment-%x-%d.blob", sha.Sum(nil), timestamp.UnixMilli())
-	_ = os.WriteFile(filepath.Join("/tmp", fragmentPath), blob, 0644)
-
-	unpacked, err := cosesign1.UnpackAndValidateCOSE1CertChain(raw)
-	if err != nil {
-		return fmt.Errorf("InjectFragment failed COSE validation: %w", err)
-	}
-
-	payloadString := string(unpacked.Payload[:])
-	issuer := unpacked.Issuer
-	feed := unpacked.Feed
-	chainPem := unpacked.ChainPem
-
-	log.G(ctx).WithFields(logrus.Fields{
-		"issuer":   issuer, // eg the DID:x509:blah....
-		"feed":     feed,
-		"cty":      unpacked.ContentType,
-		"chainPem": chainPem,
-	}).Debugf("unpacked COSE1 cert chain")
-
-	log.G(ctx).WithFields(logrus.Fields{
-		"payload": payloadString,
-	}).Tracef("unpacked COSE1 payload")
-
-	if len(issuer) == 0 || len(feed) == 0 { // must both be present
-		return fmt.Errorf("either issuer and feed must both be provided in the COSE_Sign1 protected header")
-	}
-
-	// Resolve returns a did doc that we don't need
-	// we only care if there was an error or not
-	_, err = didx509resolver.Resolve(unpacked.ChainPem, issuer, true)
+	issuer, feed, payloadString, err := securitypolicy.ExtractAndVerifyFragment(ctx, fragment)
 	if err != nil {
-		log.G(ctx).Printf("Badly formed fragment - did resolver failed to match fragment did:x509 from chain with purported issuer %s, feed %s - err %s", issuer, feed, err.Error())
 		return err
 	}
-
 	// now offer the payload fragment to the policy
 	err = h.securityPolicyEnforcer.LoadFragment(ctx, issuer, feed, payloadString)
 	if err != nil {
-		return fmt.Errorf("InjectFragment failed policy load: %w", err)
+		return fmt.Errorf("error loading security policy fragment: %w", err)
 	}
-	log.G(ctx).Printf("passed fragment into the enforcer.")
-
 	return nil
 }
 

pkg/securitypolicy/securitypolicyenforcer.go

@@ -2,12 +2,22 @@ package securitypolicy
 
 import (
 	"context"
+	"crypto/sha256"
+	"encoding/base64"
 	"fmt"
+	"os"
+	"path/filepath"
 	"syscall"
+	"time"
 
+	"github.com/Microsoft/cosesign1go/pkg/cosesign1"
+	didx509resolver "github.com/Microsoft/didx509go/pkg/did-x509-resolver"
+	"github.com/Microsoft/hcsshim/internal/log"
 	"github.com/Microsoft/hcsshim/internal/protocol/guestrequest"
+	"github.com/Microsoft/hcsshim/internal/protocol/guestresource"
 	oci "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 )
 
 type createEnforcerFunc func(base64EncodedPolicy string, criMounts, criPrivilegedMounts []oci.Mount, maxErrorMessageLength int) (SecurityPolicyEnforcer, error)
@@ -121,7 +131,7 @@ type SecurityPolicyEnforcer interface {
 	EnforceGetPropertiesPolicy(ctx context.Context) error
 	EnforceDumpStacksPolicy(ctx context.Context) error
 	EnforceRuntimeLoggingPolicy(ctx context.Context) (err error)
-	LoadFragment(ctx context.Context, issuer string, feed string, code string) error
+	LoadFragment(ctx context.Context, issuer string, feed string, rego string) error
 	EnforceScratchMountPolicy(ctx context.Context, scratchPath string, encrypted bool) (err error)
 	EnforceScratchUnmountPolicy(ctx context.Context, scratchPath string) (err error)
 	GetUserInfo(spec *oci.Process, rootPath string) (IDName, []IDName, string, error)
@@ -142,6 +152,69 @@ func (s stringSet) contains(item string) bool {
 	return contains
 }
 
+// Fragment extends current security policy with additional constraints
+// from the incoming fragment. Note that it is base64 encoded over the bridge/
+//
+// There are three checking steps:
+// 1 - Unpack the cose document and check it was actually signed with the cert
+// chain inside its header
+// 2 - Check that the issuer field did:x509 identifier is for that cert chain
+// (ie fingerprint of a non leaf cert and the subject matches the leaf cert)
+// 3 - Check that this issuer/feed match the requirement of the user provided
+// security policy (done in the regoby LoadFragment)
+func ExtractAndVerifyFragment(ctx context.Context, fragment *guestresource.LCOWSecurityPolicyFragment) (issuer string, feed string, payloadString string, err error) {
+	log.G(ctx).WithField("fragment", fmt.Sprintf("%+v", fragment)).Debug("VerifyAndExtractFragment")
+
+	raw, err := base64.StdEncoding.DecodeString(fragment.Fragment)
+	if err != nil {
+		return "", "", "", fmt.Errorf("failed to decode fragment: %w", err)
+	}
+	blob := []byte(fragment.Fragment)
+	// keep a copy of the fragment, so we can manually figure out what went wrong
+	// will be removed eventually. Give it a unique name to avoid any potential
+	// race conditions.
+	sha := sha256.New()
+	sha.Write(blob)
+	timestamp := time.Now()
+	fragmentPath := fmt.Sprintf("fragment-%x-%d.blob", sha.Sum(nil), timestamp.UnixMilli())
+	_ = os.WriteFile(filepath.Join(os.TempDir(), fragmentPath), blob, 0644)
+
+	unpacked, err := cosesign1.UnpackAndValidateCOSE1CertChain(raw)
+	if err != nil {
+		return "", "", "", fmt.Errorf("InjectFragment failed COSE validation: %w", err)
+	}
+
+	payloadString = string(unpacked.Payload[:])
+	issuer = unpacked.Issuer
+	feed = unpacked.Feed
+	chainPem := unpacked.ChainPem
+
+	log.G(ctx).WithFields(logrus.Fields{
+		"issuer":   issuer, // eg the DID:x509:blah....
+		"feed":     feed,
+		"cty":      unpacked.ContentType,
+		"chainPem": chainPem,
+	}).Debugf("unpacked COSE1 cert chain")
+
+	log.G(ctx).WithFields(logrus.Fields{
+		"payload": payloadString,
+	}).Tracef("unpacked COSE1 payload")
+
+	if len(issuer) == 0 || len(feed) == 0 { // must both be present
+		return "", "", "", fmt.Errorf("either issuer and feed must both be provided in the COSE_Sign1 protected header")
+	}
+
+	// Resolve returns a did doc that we don't need
+	// we only care if there was an error or not
+	_, err = didx509resolver.Resolve(unpacked.ChainPem, issuer, true)
+	if err != nil {
+		log.G(ctx).Printf("Badly formed fragment - did resolver failed to match fragment did:x509 from chain with purported issuer %s, feed %s - err %s", issuer, feed, err.Error())
+		return "", "", "", err
+	}
+
+	return issuer, feed, payloadString, nil
+}
+
 // CreateSecurityPolicyEnforcer returns an appropriate enforcer for input
 // parameters.  Returns an error if the requested `enforcer` implementation
 // isn't registered.

pkg/securitypolicy/securitypolicyenforcer_rego.go

@@ -59,17 +59,6 @@ type regoEnforcer struct {
 
 var _ SecurityPolicyEnforcer = (*regoEnforcer)(nil)
 
-//nolint:unused
-/*func (sp SecurityPolicy) toInternal() (*securityPolicyInternal, error) {
-	policy := new(securityPolicyInternal)
-	var err error
-	if policy.Containers, err = sp.Containers.toInternal(); err != nil {
-		return nil, err
-	}
-
-	return policy, nil
-}*/
-
 func toStringSet(items []string) stringSet {
 	s := make(stringSet)
 	for _, item := range items {