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 policy

import (
    "context"
    "encoding/json"
    "fmt"
    "github.com/nuts-foundation/nuts-node/core"
    "github.com/nuts-foundation/nuts-node/vcr/pe"
    v2 "github.com/nuts-foundation/nuts-node/vcr/pe/schema/v2"
    "io"
    "os"
    "strings"
)

var _ PDPBackend = (*LocalPDP)(nil)

// New creates a new local policy backend
func New() *LocalPDP {
    return &LocalPDP{}
}

// LocalPDP is a backend for presentation definitions
// It loads a file with the mapping from oauth scope to PEX Policy.
// It allows access when the requester can present a submission according to the Presentation Definition.
type LocalPDP struct {
    config Config
    // mapping holds the oauth scope to PEX Policy mapping
    mapping map[string]validatingWalletOwnerMapping
}

func (b *LocalPDP) Name() string {
    return ModuleName
}

func (b *LocalPDP) Configure(_ core.ServerConfig) error {
    // check if directory exists
    if b.config.Directory != "" {
        _, err := os.Stat(b.config.Directory)
        if err != nil {
            if os.IsNotExist(err) && b.config.Directory == defaultConfig().Directory {
                // assume this is the default config value and remove it
                b.config.Directory = ""
            } else {
                return fmt.Errorf("failed to load policy from directory: %w", err)
            }
        }
    }
    if b.config.Directory != "" {
        if err := b.loadFromDirectory(b.config.Directory); err != nil {
            return fmt.Errorf("failed to load policy from directory: %w", err)
        }
    }

    return nil
}

func (b *LocalPDP) Config() interface{} {
    return &b.config
}

func (b *LocalPDP) PresentationDefinitions(_ context.Context, scope string) (pe.WalletOwnerMapping, error) {
    result := pe.WalletOwnerMapping{}
    mapping, exists := b.mapping[scope]
    if !exists {
        return nil, ErrNotFound
    }
    for walletOwnerType, policy := range mapping {
        result[walletOwnerType] = policy
    }
    return result, nil
}

// loadFromDirectory traverses all .json files in the given directory and loads them
func (b *LocalPDP) loadFromDirectory(directory string) error {
    // open the directory
    dir, err := os.Open(directory)
    if err != nil {
        return err
    }
    defer dir.Close()

    // read all the files in the directory
    files, err := dir.Readdir(0)
    if err != nil {
        return err
    }

    // load all the files
    for _, file := range files {
        if file.IsDir() {
            continue
        }
        if !strings.HasSuffix(file.Name(), ".json") {
            continue
        }
        err := b.loadFromFile(fmt.Sprintf("%s/%s", directory, file.Name()))
        if err != nil {
            return err
        }
    }
    return nil
}

// LoadFromFile loads the mapping from the given file
func (b *LocalPDP) loadFromFile(filename string) error {
    // read the bytes from the file
    reader, err := os.Open(filename)
    if err != nil {
        return err
    }
    defer reader.Close()
    bytes, err := io.ReadAll(reader)
    if err != nil {
        return err
    }

    // unmarshal the bytes into the mapping
    result := make(map[string]validatingWalletOwnerMapping)
    err = json.Unmarshal(bytes, &result)
    if err != nil {
        return fmt.Errorf("failed to unmarshal PEX Policy mapping file %s: %w", filename, err)
    }
    if b.mapping == nil {
        b.mapping = make(map[string]validatingWalletOwnerMapping)
    }
    for scope, defs := range result {
        if _, exists := b.mapping[scope]; exists {
            return fmt.Errorf("mapping for scope '%s' already exists (file=%s)", scope, filename)
        }
        b.mapping[scope] = defs
    }
    return nil
}

// validatingPresentationDefinition is an alias for PresentationDefinition that validates the JSON on unmarshal.
type validatingWalletOwnerMapping pe.WalletOwnerMapping

func (v *validatingWalletOwnerMapping) UnmarshalJSON(data []byte) error {
    if err := v2.Validate(data, v2.WalletOwnerMapping); err != nil {
        return err
    }
    return json.Unmarshal(data, (*pe.WalletOwnerMapping)(v))
}