Added --client-signing-algorithms flag

Signed-off-by: Riccardo Schirone <[email protected]>

cmd/rekor-server/app/root.go

@@ -20,10 +20,14 @@ import (
 	"net/http"
 	"net/http/pprof"
 	"os"
+	"sort"
+	"strings"
 	"time"
 
 	homedir "github.com/mitchellh/go-homedir"
+	"github.com/sigstore/rekor/pkg/api"
 	"github.com/sigstore/rekor/pkg/log"
+	"github.com/sigstore/sigstore/pkg/signature"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 
@@ -131,6 +135,18 @@ Memory and file-based signers should only be used for testing.`)
 	rootCmd.PersistentFlags().Int("search_index.mysql.max_open_connections", 0, "maximum open connections")
 	rootCmd.PersistentFlags().Int("search_index.mysql.max_idle_connections", 0, "maximum idle connections")
 
+	keyAlgorithmTypes := []string{}
+	for _, keyAlgorithm := range api.AllowedClientSigningAlgorithms {
+		keyFlag, err := signature.FormatSignatureAlgorithmFlag(keyAlgorithm)
+		if err != nil {
+			panic(err)
+		}
+		keyAlgorithmTypes = append(keyAlgorithmTypes, keyFlag)
+	}
+	sort.Strings(keyAlgorithmTypes)
+	keyAlgorithmHelp := fmt.Sprintf("signing algorithm to use for signing/hashing (allowed %s)", strings.Join(keyAlgorithmTypes, ", "))
+	rootCmd.PersistentFlags().StringSlice("client-signing-algorithms", keyAlgorithmTypes, keyAlgorithmHelp)
+
 	if err := viper.BindPFlags(rootCmd.PersistentFlags()); err != nil {
 		log.Logger.Fatal(err)
 	}

go.mod

@@ -26,7 +26,6 @@ require (
 	github.com/rs/cors v1.10.1
 	github.com/sassoftware/relic v7.2.1+incompatible
 	github.com/secure-systems-lab/go-securesystemslib v0.8.0
-	github.com/sigstore/sigstore v1.8.1
 	github.com/spf13/cobra v1.8.0
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.18.2
@@ -63,7 +62,8 @@ require (
 	github.com/jmoiron/sqlx v1.3.5
 	github.com/redis/go-redis/v9 v9.4.0
 	github.com/sassoftware/relic/v7 v7.6.1
-	github.com/sigstore/protobuf-specs v0.2.1
+	github.com/sigstore/protobuf-specs v0.3.0-beta.2
+	github.com/sigstore/sigstore v1.6.4
 	github.com/sigstore/sigstore/pkg/signature/kms/aws v1.8.1
 	github.com/sigstore/sigstore/pkg/signature/kms/azure v1.8.1
 	github.com/sigstore/sigstore/pkg/signature/kms/gcp v1.8.1
@@ -164,7 +164,7 @@ require (
 	github.com/godbus/dbus/v5 v5.1.0 // indirect
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/golang/protobuf v1.5.3 // indirect
-	github.com/google/go-containerregistry v0.17.0 // indirect
+	github.com/google/go-containerregistry v0.18.0 // indirect
 	github.com/google/uuid v1.5.0 // indirect
 	github.com/google/wire v0.5.0 // indirect
 	github.com/googleapis/enterprise-certificate-proxy v0.3.2 // indirect
@@ -204,3 +204,5 @@ require (
 	gopkg.in/yaml.v2 v2.4.0
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
+
+replace github.com/sigstore/sigstore => github.com/trail-of-forks/sigstore v0.0.0-20240129055912-d89eade746d5

go.sum

@@ -215,8 +215,8 @@ github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
-github.com/google/go-containerregistry v0.17.0 h1:5p+zYs/R4VGHkhyvgWurWrpJ2hW4Vv9fQI+GzdcwXLk=
-github.com/google/go-containerregistry v0.17.0/go.mod h1:u0qB2l7mvtWVR5kNcbFIhFY1hLbf8eeGapA+vbFDCtQ=
+github.com/google/go-containerregistry v0.18.0 h1:ShE7erKNPqRh5ue6Z9DUOlk04WsnFWPO6YGr3OxnfoQ=
+github.com/google/go-containerregistry v0.18.0/go.mod h1:u0qB2l7mvtWVR5kNcbFIhFY1hLbf8eeGapA+vbFDCtQ=
 github.com/google/go-replayers/grpcreplay v1.1.0 h1:S5+I3zYyZ+GQz68OfbURDdt/+cSMqCK1wrvNx7WBzTE=
 github.com/google/go-replayers/grpcreplay v1.1.0/go.mod h1:qzAvJ8/wi57zq7gWqaE6AwLM6miiXUQwP1S+I9icmhk=
 github.com/google/go-replayers/httpreplay v1.2.0 h1:VM1wEyyjaoU53BwrOnaf9VhAyQQEEioJvFYxYcLRKzk=
@@ -387,10 +387,8 @@ github.com/secure-systems-lab/go-securesystemslib v0.8.0 h1:mr5An6X45Kb2nddcFlbm
 github.com/secure-systems-lab/go-securesystemslib v0.8.0/go.mod h1:UH2VZVuJfCYR8WgMlCU1uFsOUU+KeyrTWcSS73NBOzU=
 github.com/shibumi/go-pathspec v1.3.0 h1:QUyMZhFo0Md5B8zV8x2tesohbb5kfbpTi9rBnKh5dkI=
 github.com/shibumi/go-pathspec v1.3.0/go.mod h1:Xutfslp817l2I1cZvgcfeMQJG5QnU2lh5tVaaMCl3jE=
-github.com/sigstore/protobuf-specs v0.2.1 h1:KIoM7E3C4uaK092q8YoSj/XSf9720f8dlsbYwwOmgEA=
-github.com/sigstore/protobuf-specs v0.2.1/go.mod h1:xPqQGnH/HllKuZ4VFPz/g+78epWM/NLRGl7Fuy45UdE=
-github.com/sigstore/sigstore v1.8.1 h1:mAVposMb14oplk2h/bayPmIVdzbq2IhCgy4g6R0ZSjo=
-github.com/sigstore/sigstore v1.8.1/go.mod h1:02SL1158BSj15bZyOFz7m+/nJzLZfFd9A8ab3Kz7w/E=
+github.com/sigstore/protobuf-specs v0.3.0-beta.2 h1:neHS0O1z7qz4q21vyXqSaKuKYxA0upzJERT88NrgYlM=
+github.com/sigstore/protobuf-specs v0.3.0-beta.2/go.mod h1:ynKzXpqr3dUj2Xk9O/5ZUhjnpi0F53DNi5AdH6pS3jc=
 github.com/sigstore/sigstore/pkg/signature/kms/aws v1.8.1 h1:rEDdUefulkIQaMJyzLwtgPDLNXBIltBABiFYfb0YmgQ=
 github.com/sigstore/sigstore/pkg/signature/kms/aws v1.8.1/go.mod h1:RCdYCc1IxCYWzh2IdzdA6Yf7JIY0cMRqH08fpQYechw=
 github.com/sigstore/sigstore/pkg/signature/kms/azure v1.8.1 h1:DvRWG99QGWZC5mp42SEde2Xke/Q384Idnj2da7yB+Mk=
@@ -432,6 +430,8 @@ github.com/theupdateframework/go-tuf v0.7.0 h1:CqbQFrWo1ae3/I0UCblSbczevCCbS31Qv
 github.com/theupdateframework/go-tuf v0.7.0/go.mod h1:uEB7WSY+7ZIugK6R1hiBMBjQftaFzn7ZCDJcp1tCUug=
 github.com/titanous/rocacheck v0.0.0-20171023193734-afe73141d399 h1:e/5i7d4oYZ+C1wj2THlRK+oAhjeS/TRQwMfkIuet3w0=
 github.com/titanous/rocacheck v0.0.0-20171023193734-afe73141d399/go.mod h1:LdwHTNJT99C5fTAzDz0ud328OgXz+gierycbcIx2fRs=
+github.com/trail-of-forks/sigstore v0.0.0-20240129055912-d89eade746d5 h1:G0g5M0EnhCixAnBMMpilo6IlNDkK67BNStUUOt5/arc=
+github.com/trail-of-forks/sigstore v0.0.0-20240129055912-d89eade746d5/go.mod h1:CO6jK1y+gQzIQBTV3/qZG7Nqem6Kxy+YQR4cOi2axLk=
 github.com/transparency-dev/merkle v0.0.2 h1:Q9nBoQcZcgPamMkGn7ghV8XiTZ/kRxn1yCG81+twTK4=
 github.com/transparency-dev/merkle v0.0.2/go.mod h1:pqSy+OXefQ1EDUVmAJ8MUhHB9TXGuzVAT58PqBoHz1A=
 github.com/ulikunitz/xz v0.5.11 h1:kpFauv27b6ynzBNT/Xy+1k+fK4WswhN/6PN5WhFAGw8=

pkg/api/api.go

@@ -30,6 +30,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials/insecure"
 
+	v1 "github.com/sigstore/protobuf-specs/gen/pb-go/common/v1"
 	"github.com/sigstore/rekor/pkg/indexstorage"
 	"github.com/sigstore/rekor/pkg/log"
 	"github.com/sigstore/rekor/pkg/pubsub"
@@ -70,8 +71,21 @@ type API struct {
 	// Publishes notifications when new entries are added to the log. May be
 	// nil if no publisher is configured.
 	newEntryPublisher pubsub.Publisher
+	algorithmRegistry *signature.AlgorithmRegistryConfig
 }
 
+var AllowedClientSigningAlgorithms = []v1.KnownSignatureAlgorithm{
+	v1.KnownSignatureAlgorithm_RSA_SIGN_PKCS1_2048_SHA256,
+	v1.KnownSignatureAlgorithm_RSA_SIGN_PKCS1_3072_SHA256,
+	v1.KnownSignatureAlgorithm_RSA_SIGN_PKCS1_4096_SHA256,
+	v1.KnownSignatureAlgorithm_ECDSA_SHA2_256_NISTP256,
+	v1.KnownSignatureAlgorithm_ECDSA_SHA2_384_NISTP384,
+	v1.KnownSignatureAlgorithm_ECDSA_SHA2_512_NISTP521,
+	v1.KnownSignatureAlgorithm_ED25519,
+	v1.KnownSignatureAlgorithm_ED25519_PH,
+}
+var DefaultClientSigningAlgorithms = AllowedClientSigningAlgorithms[:]
+
 func NewAPI(treeID uint) (*API, error) {
 	logRPCServer := fmt.Sprintf("%s:%d",
 		viper.GetString("trillian_log_server.address"),
@@ -102,6 +116,32 @@ func NewAPI(treeID uint) (*API, error) {
 	log.Logger.Infof("Starting Rekor server with active tree %v", tid)
 	ranges.SetActive(tid)
 
+	algorithms_str := viper.GetStringSlice("client-signing-algorithms")
+	var algorithms []v1.KnownSignatureAlgorithm
+	if algorithms_str == nil {
+		algorithms = DefaultClientSigningAlgorithms
+	} else {
+		for _, a := range algorithms_str {
+			algorithm, err := signature.ParseSignatureAlgorithmFlag(a)
+			if err != nil {
+				return nil, fmt.Errorf("parsing signature algorithm flag: %w", err)
+			}
+			algorithms = append(algorithms, algorithm)
+		}
+	}
+	algorithmsStr := make([]string, len(algorithms))
+	for i, a := range algorithms {
+		algorithmsStr[i], err = signature.FormatSignatureAlgorithmFlag(a)
+		if err != nil {
+			return nil, fmt.Errorf("formatting signature algorithm flag: %w", err)
+		}
+	}
+	algorithmRegistry, err := signature.NewAlgorithmRegistryConfig(algorithms)
+	if err != nil {
+		return nil, fmt.Errorf("getting algorithm registry: %w", err)
+	}
+	log.Logger.Infof("Allowed client signing algorithms: %v", algorithmsStr)
+
 	rekorSigner, err := signer.New(ctx, viper.GetString("rekor_server.signer"),
 		viper.GetString("rekor_server.signer-passwd"))
 	if err != nil {
@@ -142,6 +182,7 @@ func NewAPI(treeID uint) (*API, error) {
 		signer:     rekorSigner,
 		// Utility functionality not required for operation of the core service
 		newEntryPublisher: newEntryPublisher,
+		algorithmRegistry: algorithmRegistry,
 	}, nil
 }
 

pkg/api/entries.go

@@ -18,11 +18,17 @@ package api
 import (
 	"bytes"
 	"context"
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/rsa"
+	"crypto/x509"
 	"encoding/hex"
 	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
+	"strings"
 
 	"github.com/cyberphone/json-canonicalization/go/src/webpki.org/jsoncanonicalizer"
 	"github.com/go-openapi/runtime"
@@ -177,12 +183,78 @@ func GetLogEntryByIndexHandler(params entries.GetLogEntryByIndexParams) middlewa
 	return entries.NewGetLogEntryByIndexOK().WithPayload(logEntry)
 }
 
+func checkEntryAlgorithms(entry types.EntryImpl) (bool, error) {
+	verifiers, err := entry.Verifiers()
+	if err != nil {
+		return false, fmt.Errorf("getting verifiers: %w", err)
+	}
+	// Get artifact hash from entry
+	artifactHash, err := entry.ArtifactHash()
+	if err != nil {
+		return false, fmt.Errorf("getting artifact hash: %w", err)
+	}
+	artifactHashAlgorithm := artifactHash[:strings.Index(artifactHash, ":")]
+	var artifactHashValue crypto.Hash
+	switch artifactHashAlgorithm {
+	case "sha256":
+		artifactHashValue = crypto.SHA256
+	case "sha384":
+		artifactHashValue = crypto.SHA384
+	case "sha512":
+		artifactHashValue = crypto.SHA512
+	default:
+		return false, fmt.Errorf("unsupported artifact hash algorithm %s", artifactHashAlgorithm)
+	}
+
+	// Check if all the verifiers public keys (together with the ArtifactHash)
+	// are allowed according to the policy
+	for _, v := range verifiers {
+		identities, err := v.Identities()
+		if err != nil {
+			return false, fmt.Errorf("getting identities: %w", err)
+		}
+
+		for _, identity := range identities {
+			var publicKey crypto.PublicKey
+			switch identityCrypto := identity.Crypto.(type) {
+			case *x509.Certificate:
+				publicKey = identityCrypto.PublicKey
+			case *rsa.PublicKey:
+				publicKey = identityCrypto
+			case *ecdsa.PublicKey:
+				publicKey = identityCrypto
+			case ed25519.PublicKey:
+				publicKey = identityCrypto
+			default:
+				continue
+			}
+			isPermitted, err := api.algorithmRegistry.IsAlgorithmPermitted(publicKey, artifactHashValue)
+			if err != nil {
+				return false, fmt.Errorf("checking if algorithm is permitted: %w", err)
+			}
+			if !isPermitted {
+				return false, nil
+			}
+		}
+	}
+	return true, nil
+}
+
 func createLogEntry(params entries.CreateLogEntryParams) (models.LogEntry, middleware.Responder) {
 	ctx := params.HTTPRequest.Context()
 	entry, err := types.CreateVersionedEntry(params.ProposedEntry)
 	if err != nil {
 		return nil, handleRekorAPIError(params, http.StatusBadRequest, err, fmt.Sprintf(validationError, err))
 	}
+
+	areEntryAlgorithmsAllowed, err := checkEntryAlgorithms(entry)
+	if err != nil {
+		return nil, handleRekorAPIError(params, http.StatusBadRequest, err, fmt.Sprintf(validationError, err))
+	}
+	if !areEntryAlgorithmsAllowed {
+		return nil, handleRekorAPIError(params, http.StatusBadRequest, errors.New("entry algorithms are not allowed"), fmt.Sprintf(validationError, "entry algorithms are not allowed"))
+	}
+
 	leaf, err := types.CanonicalizeEntry(ctx, entry)
 	if err != nil {
 		if _, ok := (err).(types.ValidationError); ok {