token-server: Delegation config import, validation and evaluation.

tokenserver/appengine/delegation/rpc_mint_delegation_token.go

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package delegation
 
 import (
+        "fmt"
+        "strings"
+        "time"
+
+        "github.com/golang/protobuf/jsonpb"
         "golang.org/x/net/context"
         "google.golang.org/grpc"
         "google.golang.org/grpc/codes"
 
+        "github.com/luci/luci-go/common/errors"
+        "github.com/luci/luci-go/common/logging"
+        "github.com/luci/luci-go/server/auth"
+        "github.com/luci/luci-go/server/auth/identity"
         "github.com/luci/luci-go/server/auth/signing"
-        minter "github.com/luci/luci-go/tokenserver/api/minter/v1"
+
+        "github.com/luci/luci-go/tokenserver/api/minter/v1"
+        "github.com/luci/luci-go/tokenserver/appengine/utils/identityset"
 )
 
 // MintDelegationTokenRPC implements TokenMinter.MintDelegationToken RPC method.
 type MintDelegationTokenRPC struct {
         // Signer is mocked in tests.
         //
         // In prod it is gaesigner.Signer.
         Signer signing.Signer
+
+        // ConfigLoader loads delegation config on demand.
+        //
+        // In prod it is DelegationConfigLoader.
+        ConfigLoader func(context.Context) (*DelegationConfig, error)
 }
 
 // MintDelegationToken generates a new bearer delegation token.
 func (r *MintDelegationTokenRPC) MintDelegationToken(c context.Context, req *minter.MintDelegationTokenRequest) (*minter.MintDelegationTokenResponse, error) {
+        state := auth.GetState(c)
+
+        // Dump the whole request and relevant auth state to the debug log.
+        if logging.IsLogging(c, logging.Debug) {
+                m := jsonpb.Marshaler{Indent: "  "}
+                dump, _ := m.MarshalToString(req)
+                logging.Debugf(c, "PeerIdentity: %s", state.PeerIdentity())
+                logging.Debugf(c, "MintDelegationTokenRequest:\n%s", dump)
+        }
+
+        // Validate the request authentication context: not an anonymous call, no
+        // delegation is used.
+        callerID := state.User().Identity
+        if callerID != state.PeerIdentity() {
+                logging.Errorf(c, "Trying to use delegation, it's forbidden")
+                return nil, grpc.Errorf(codes.PermissionDenied, "delegation is forbidden for this API call")
+        }
+        if callerID == identity.AnonymousIdentity {
+                logging.Errorf(c, "Unauthenticated request")
+                return nil, grpc.Errorf(codes.Unauthenticated, "authentication required")
+        }
+
+        cfg, err := r.ConfigLoader(c)
+        if err != nil {
+                // Don't put error details in the message, it may be returned to
+                // unauthorized callers. ConfigLoader logs the error already.
+                return nil, grpc.Errorf(codes.Internal, "failed to load delegation config")
+        }
+
+        // Make sure the caller is mentioned in the config before doing anything else.
+        // This rejects unauthorized callers early. Passing this check doesn't mean
+        // that there's a matching rule though, so the request still can be rejected
+        // later.
+        switch ok, err := cfg.IsAuthorizedRequestor(c, callerID); {
+        case err != nil:
+                logging.WithError(err).Errorf(c, "IsAuthorizedRequestor failed")
+                return nil, grpc.Errorf(codes.Internal, "failed to check authorization")
+        case !ok:
+                logging.Errorf(c, "Didn't pass initial authorization")
+                return nil, grpc.Errorf(codes.PermissionDenied, "not authorized")
+        }
+
+        // Validate and normalize the request. This may do relatively expensive calls
+        // to resolve "https://<service-url>" entries to "service:<id>" entries.
+        query, err := buildRulesQuery(c, req, callerID)
+        if err != nil {
+                if errors.IsTransient(err) {
+                        logging.WithError(err).Errorf(c, "buildRulesQuery failed")
+                        return nil, grpc.Errorf(codes.Internal, "failure when resolving target service ID - %s", err)
+                }
+                logging.WithError(err).Errorf(c, "Bad request")
+                return nil, grpc.Errorf(codes.InvalidArgument, "bad request - %s", err)
+        }
+
+        // Consult the config to find the rule that allows this operation (if any).
+        rule, err := cfg.FindMatchingRule(c, query)
+        if err != nil {
+                if errors.IsTransient(err) {
+                        logging.WithError(err).Errorf(c, "FindMatchingRule failed")
+                        return nil, grpc.Errorf(codes.Internal, "failure when checking rules - %s", err)
+                }
+                logging.WithError(err).Errorf(c, "Didn't pass rules check")
+                return nil, grpc.Errorf(codes.PermissionDenied, "forbidden - %s", err)
+        }
+        logging.Infof(c, "Found the matching rule %q in the config rev %s", rule.Name, cfg.Revision)
+
+        // TODO(vadimsh): Make the token, record it in the audit log.
+
         return nil, grpc.Errorf(codes.Unimplemented, "Not implemented yet")
 }
+
+// buildRulesQuery validates the request, extracts and normalizes relevant
+// fields into RulesQuery object.
+//
+// May return transient errors.
+func buildRulesQuery(c context.Context, req *minter.MintDelegationTokenRequest, requestor identity.Identity) (*RulesQuery, error) {
+        // Validate 'delegated_identity'.
+        var err error
+        var delegatee identity.Identity
+        if req.DelegatedIdentity == "" {
+                return nil, fmt.Errorf("'delegated_identity' is required")
+        }
+        if req.DelegatedIdentity == Requestor {
+                delegatee = requestor // the requestor is delegating its own identity
+        } else {
+                if delegatee, err = identity.MakeIdentity(req.DelegatedIdentity); err != nil {
+                        return nil, fmt.Errorf("bad 'delegated_identity' - %s", err)
+                }
+        }
+
+        // Validate 'audience', convert it into a set.
+        if len(req.Audience) == 0 {
+                return nil, fmt.Errorf("'audience' is required")
+        }
+        audienceSet, err := identityset.FromStrings(req.Audience, skipRequestor)
+        if err != nil {
+                return nil, fmt.Errorf("bad 'audience' - %s", err)
+        }
+        if sliceHasString(req.Audience, Requestor) {
+                audienceSet.AddIdentity(requestor)
+        }
+
+        // Split 'services' into two lists: URLs and everything else (which is
+        // "service:..." and "*" presumably, validated below).
+        if len(req.Services) == 0 {
+                return nil, fmt.Errorf("'services' is required")
+        }
+        urls := make([]string, 0, len(req.Services))
+        rest := make([]string, 0, len(req.Services))
+        for _, srv := range req.Services {
+                if strings.HasPrefix(srv, "https://") {
+                        urls = append(urls, srv)
+                } else {
+                        rest = append(rest, srv)
+                }
+        }
+
+        // Convert the list into a set, verify it contains only services (or "*").
+        servicesSet, err := identityset.FromStrings(rest, nil)
+        if err != nil {
+                return nil, fmt.Errorf("bad 'services' - %s", err)
+        }
+        if len(servicesSet.Groups) != 0 {
+                return nil, fmt.Errorf("bad 'services' - can't specify groups")
+        }
+        for ident := range servicesSet.IDs {
+                if ident.Kind() != identity.Service {
+                        return nil, fmt.Errorf("bad 'services' - %q is not a service ID", ident)
+                }
+        }
+
+        // Resolve URLs into app IDs. This may involve URL fetch calls (if the cache
+        // is cold), so skip this expensive call if already specifying the universal
+        // set of all services.
+        if !servicesSet.All && len(urls) != 0 {
+                if err = resolveServiceIDs(c, urls, servicesSet); err != nil {
+                        return nil, err
+                }
+        }
+
+        // Done!
+        return &RulesQuery{
+                Requestor: requestor,
+                Delegatee: delegatee,
+                Audience:  audienceSet,
+                Services:  servicesSet,
+        }, nil
+}
+
+// resolveServiceIDs takes a bunch of service URLs and resolves them to
+// 'service:<app-id>' identities, putting them in the 'out' set.
+//
+// May return transient errors.
+func resolveServiceIDs(c context.Context, urls []string, out *identityset.Set) error {
+        // URL fetch calls below should be extra fast. If they get stuck, something is
+        // horribly wrong, better to abort soon.
+        c, abort := context.WithTimeout(c, 5*time.Second)
+        defer abort()
+
+        type Result struct {
+                URL string
+                ID  identity.Identity
+                Err error
+        }
+
+        ch := make(chan Result, len(urls))
+
+        for _, url := range urls {
+                go func(url string) {
+                        id, err := signing.FetchLUCIServiceIdentity(c, url)
+                        ch <- Result{url, id, err}
+                }(url)
+        }
+
+        for i := 0; i < len(urls); i++ {
+                result := <-ch
+                if result.Err != nil {
+                        if errors.IsTransient(result.Err) {
+                                return result.Err
+                        }
+                        return fmt.Errorf("could not resolve %q to service ID - %s", result.URL, result.Err)
+                }
+                out.AddIdentity(result.ID)
+        }
+
+        return nil
+}