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103 lines
3.0 KiB
103 lines
3.0 KiB
// Copyright 2018 clair authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package pagination implements a series of utilities for dealing with
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// paginating lists of objects for an API.
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package pagination
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import (
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"bytes"
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"encoding/json"
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"errors"
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"time"
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"github.com/fernet/fernet-go"
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)
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// ErrInvalidToken is returned when a token fails to Unmarshal because it was
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// invalid or expired.
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var ErrInvalidToken = errors.New("invalid or expired pagination token")
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// ErrInvalidKeyString is returned when the string representing a key is malformed.
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var ErrInvalidKeyString = errors.New("invalid pagination key string: must be 32-byte URL-safe base64")
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// Key represents the key used to cryptographically secure the token
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// being used to keep track of pages.
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type Key struct {
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fkey *fernet.Key
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}
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// Token represents an opaque pagination token keeping track of a user's
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// progress iterating through a list of results.
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type Token string
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// FirstPageToken is used to represent the first page of content.
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var FirstPageToken = Token("")
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// NewKey generates a new random pagination key.
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func NewKey() (k Key, err error) {
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k.fkey = new(fernet.Key)
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err = k.fkey.Generate()
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return k, err
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}
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// KeyFromString creates the key for a given string.
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//
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// Strings must be 32-byte URL-safe base64 representations of the key bytes.
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func KeyFromString(keyString string) (k Key, err error) {
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var fkey *fernet.Key
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fkey, err = fernet.DecodeKey(keyString)
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if err != nil {
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return Key{}, ErrInvalidKeyString
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}
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return Key{fkey}, err
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}
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// Must is a helper that wraps calls returning a Key and and error and panics
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// if the error is non-nil.
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func Must(k Key, err error) Key {
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if err != nil {
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panic(err)
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}
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return k
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}
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// String implements the fmt.Stringer interface for Key.
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func (k Key) String() string {
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return k.fkey.Encode()
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}
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// MarshalToken encodes an interface into JSON bytes and produces a Token.
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func (k Key) MarshalToken(v interface{}) (Token, error) {
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var buf bytes.Buffer
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err := json.NewEncoder(&buf).Encode(v)
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if err != nil {
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return Token(""), err
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}
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tokenBytes, err := fernet.EncryptAndSign(buf.Bytes(), k.fkey)
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return Token(tokenBytes), err
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}
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// UnmarshalToken decrypts a Token using provided key and decodes the result
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// into the provided interface.
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func (k Key) UnmarshalToken(t Token, v interface{}) error {
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msg := fernet.VerifyAndDecrypt([]byte(t), time.Hour, []*fernet.Key{k.fkey})
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if msg == nil {
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return ErrInvalidToken
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}
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return json.NewDecoder(bytes.NewBuffer(msg)).Decode(&v)
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}
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