nuts-foundation/nuts-node

/*
 * Copyright (C) 2023 Nuts community
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 */

package didnuts

import (
    "errors"
    "fmt"
    "github.com/nuts-foundation/go-did/did"
    "github.com/nuts-foundation/nuts-node/vdr/didnuts/didstore"
    "github.com/nuts-foundation/nuts-node/vdr/resolver"
)

const maxControllerDepth = 5

// ErrNestedDocumentsTooDeep is returned when a DID Document contains a multiple services with the same type
var ErrNestedDocumentsTooDeep = errors.New("DID Document controller structure has too many indirections")

// Resolver implements the DIDResolver interface for resolving did:nuts documents.
type Resolver struct {
    Store didstore.Store
}

func (d Resolver) Resolve(id did.DID, metadata *resolver.ResolveMetadata) (*did.Document, *resolver.DocumentMetadata, error) {
    if metadata != nil && metadata.AllowDeactivated {
        // No need to check whether controllers are active if we allow deactivated documents
        return d.Store.Resolve(id, metadata)
    }
    return resolve(d.Store, id, metadata, 0)
}

func resolve(didResolver resolver.DIDResolver, id did.DID, metadata *resolver.ResolveMetadata, depth int) (*did.Document, *resolver.DocumentMetadata, error) {
    if depth >= maxControllerDepth {
        return nil, nil, ErrNestedDocumentsTooDeep
    }

    doc, meta, err := didResolver.Resolve(id, metadata)
    if err != nil {
        return nil, nil, err
    }

    // has the doc controllers, should we check for controller deactivation?
    if len(doc.Controller) > 0 && (metadata == nil || !metadata.AllowDeactivated) {
        // also check if the controller is not deactivated
        // since ResolveControllers calls Resolve and propagates the metadata
        controllers, err := resolveControllers(didResolver, *doc, metadata, depth+1)
        if err != nil {
            return nil, nil, err
        }
        // doc should have controllers, but no results, so they are not active, return error:
        if len(controllers) == 0 {
            return nil, nil, resolver.ErrNoActiveController
        }
    }

    return doc, meta, nil
}

// ResolveControllers finds the DID Document controllers
func ResolveControllers(resolver resolver.DIDResolver, doc did.Document, metadata *resolver.ResolveMetadata) ([]did.Document, error) {
    return resolveControllers(resolver, doc, metadata, 0)
}

func resolveControllers(didResolver resolver.DIDResolver, doc did.Document, metadata *resolver.ResolveMetadata, depth int) ([]did.Document, error) {
    var leaves []did.Document
    var refsToResolve []did.DID

    if len(doc.Controller) == 0 && len(doc.CapabilityInvocation) > 0 {
        // no controller -> doc is its own controller
        leaves = append(leaves, doc)
    } else {
        for _, ctrlDID := range doc.Controller {
            if doc.ID.Equals(ctrlDID) {
                if len(doc.CapabilityInvocation) > 0 {
                    // doc is its own controller
                    leaves = append(leaves, doc)
                }
            } else {
                // add did to be resolved later
                refsToResolve = append(refsToResolve, ctrlDID)
            }
        }
    }

    // resolve all unresolved doc
    for _, ref := range refsToResolve {
        node, _, err := resolve(didResolver, ref, metadata, depth)
        if errors.Is(err, resolver.ErrDeactivated) || errors.Is(err, resolver.ErrNoActiveController) || errors.Is(err, resolver.ErrNotFound) || errors.Is(err, resolver.ErrDIDMethodNotSupported) {
            continue
        }
        if errors.Is(err, ErrNestedDocumentsTooDeep) {
            return nil, err
        }
        if err != nil {
            return nil, fmt.Errorf("unable to resolve controller ref: %w", err)
        }
        leaves = append(leaves, *node)
    }

    // filter deactivated
    j := 0
    for _, leaf := range leaves {
        if !resolver.IsDeactivated(leaf) {
            leaves[j] = leaf
            j++
        }
    }

    return leaves[:j], nil
}