timestampcache.go

Documentation: github.com/sassoftware/relic/lib/pkcs9/timestampcache

     1  // Copyright © SAS Institute Inc.
     2  // Licensed under the Apache License, Version 2.0 (the "License");
     3  // you may not use this file except in compliance with the License.
     4  // You may obtain a copy of the License at
     5  //
     6  //     http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package timestampcache
    15  
    16  import (
    17  	"context"
    18  	"crypto/sha256"
    19  	"fmt"
    20  	"log"
    21  	"time"
    22  
    23  	"github.com/bradfitz/gomemcache/memcache"
    24  	"github.com/pkg/errors"
    25  	"github.com/sassoftware/relic/lib/pkcs7"
    26  	"github.com/sassoftware/relic/lib/pkcs9"
    27  )
    28  
    29  const (
    30  	memcacheTimeout = 1 * time.Second
    31  	memcacheExpiry  = 7 * 24 * time.Hour
    32  )
    33  
    34  type timestampCache struct {
    35  	Timestamper pkcs9.Timestamper
    36  	Memcache    *memcache.Client
    37  }
    38  
    39  func New(t pkcs9.Timestamper, servers []string) (pkcs9.Timestamper, error) {
    40  	selector := new(memcache.ServerList)
    41  	if err := selector.SetServers(servers...); err != nil {
    42  		return nil, errors.Wrap(err, "parsing memcache servers")
    43  	}
    44  	mc := memcache.NewFromSelector(selector)
    45  	mc.Timeout = memcacheTimeout
    46  	return &timestampCache{t, mc}, nil
    47  }
    48  
    49  func (c *timestampCache) Timestamp(ctx context.Context, req *pkcs9.Request) (*pkcs7.ContentInfoSignedData, error) {
    50  	key := cacheKey(req)
    51  	item, err := c.Memcache.Get(key)
    52  	if err == nil {
    53  		token, err := pkcs7.Unmarshal(item.Value)
    54  		if err == nil {
    55  			return token, nil
    56  		}
    57  		log.Printf("warning: failed to parse cached value for timestamp with key %s: %s", key, err)
    58  		// bad cached value, fall through
    59  	}
    60  	token, err := c.Timestamper.Timestamp(ctx, req)
    61  	if err == nil {
    62  		blob, err := token.Marshal()
    63  		if err != nil {
    64  			return nil, err
    65  		}
    66  		if err := c.Memcache.Set(&memcache.Item{
    67  			Key:        key,
    68  			Value:      blob,
    69  			Expiration: int32(memcacheExpiry / time.Second),
    70  		}); err != nil {
    71  			log.Printf("warning: failed to save cached timestamp value: %s", err)
    72  		}
    73  	}
    74  	return token, err
    75  }
    76  
    77  func cacheKey(req *pkcs9.Request) string {
    78  	d := sha256.New()
    79  	d.Write(req.EncryptedDigest)
    80  	prefix := "pkcs9"
    81  	if req.Legacy {
    82  		prefix = "msft"
    83  	}
    84  	return fmt.Sprintf("%s-%d-%x", prefix, req.Hash, d.Sum(nil))
    85  }
    86
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