forked from jcmturner/grpckrb
/
client.go
105 lines (95 loc) · 2.98 KB
/
client.go
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package grpc_krb
import (
"context"
"encoding/base64"
"net"
"strings"
"github.com/jcmturner/gokrb5/v8/client"
"github.com/jcmturner/gokrb5/v8/crypto"
"github.com/jcmturner/gokrb5/v8/messages"
"github.com/jcmturner/gokrb5/v8/types"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/status"
)
type KRBClientInterceptor struct {
KRBClient *client.Client
DefaultSPN string
MethodSPNs map[string]string
}
func (i *KRBClientInterceptor) Unary() grpc.UnaryClientInterceptor {
return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
ctx, err := i.attachKrbToken(ctx, cc, method)
if err != nil {
return status.Error(codes.Unknown, err.Error())
}
return invoker(ctx, method, req, reply, cc, opts...)
}
}
func (i *KRBClientInterceptor) Stream() grpc.StreamClientInterceptor {
return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
ctx, err := i.attachKrbToken(ctx, cc, method)
if err != nil {
cs, e := streamer(ctx, desc, cc, method, opts...)
if e != nil {
return cs, status.Errorf(codes.Unknown, "streamer error: %v attach krb token error: %v", e, err)
}
return cs, status.Error(codes.Unknown, err.Error())
}
return streamer(ctx, desc, cc, method, opts...)
}
}
func (i *KRBClientInterceptor) attachKrbToken(ctx context.Context, cc *grpc.ClientConn, method string) (context.Context, error) {
err := i.KRBClient.AffirmLogin()
if err != nil {
return ctx, err
}
spn := i.resolveSPN(cc, method)
tkt, key, err := i.KRBClient.GetServiceTicket(spn)
if err != nil {
return ctx, err
}
auth, err := types.NewAuthenticator(i.KRBClient.Credentials.Realm(), i.KRBClient.Credentials.CName())
if err != nil {
return ctx, err
}
etype, err := crypto.GetEtype(key.KeyType)
if err != nil {
return ctx, err
}
err = auth.GenerateSeqNumberAndSubKey(key.KeyType, etype.GetKeyByteSize())
if err != nil {
return ctx, err
}
auth.Cksum = types.Checksum{
CksumType: 32772, // using an unassigned id as this is not used here
Checksum: []byte(method), // putting the method being called in the authenticator checksum. Server side can check this matches that being called.
}
apReq, err := messages.NewAPReq(tkt, key, auth)
if err != nil {
return ctx, err
}
b, err := apReq.Marshal()
if err != nil {
return ctx, err
}
b64 := base64.StdEncoding.EncodeToString(b)
return metadata.AppendToOutgoingContext(ctx, MDField, b64), nil
}
func (i *KRBClientInterceptor) resolveSPN(cc *grpc.ClientConn, method string) string {
if spn, ok := i.MethodSPNs[method]; ok {
return spn
}
if i.DefaultSPN != "" {
return i.DefaultSPN
}
host, _, err := net.SplitHostPort(cc.Target())
if err != nil {
return ""
}
var spn strings.Builder
spn.WriteString("GRPC/")
spn.WriteString(host)
return spn.String()
}