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middleware.go
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middleware.go
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// Package middleware - cloudfront wrapper for storage libs
// N.B. currently only works with S3, not arbitrary sites
package middleware
import (
"context"
"crypto/x509"
"encoding/pem"
"fmt"
"io/ioutil"
"net/url"
"strings"
"time"
"github.com/aws/aws-sdk-go/service/cloudfront/sign"
dcontext "github.com/docker/distribution/context"
storagedriver "github.com/docker/distribution/registry/storage/driver"
storagemiddleware "github.com/docker/distribution/registry/storage/driver/middleware"
)
// cloudFrontStorageMiddleware provides a simple implementation of layerHandler that
// constructs temporary signed CloudFront URLs from the storagedriver layer URL,
// then issues HTTP Temporary Redirects to this CloudFront content URL.
type cloudFrontStorageMiddleware struct {
storagedriver.StorageDriver
awsIPs *awsIPs
urlSigner *sign.URLSigner
baseURL string
duration time.Duration
}
var _ storagedriver.StorageDriver = &cloudFrontStorageMiddleware{}
// newCloudFrontLayerHandler constructs and returns a new CloudFront
// LayerHandler implementation.
// Required options: baseurl, privatekey, keypairid
// Optional options: ipFilteredBy, awsregion
// ipfilteredby: valid value "none|aws|awsregion". "none", do not filter any IP, default value. "aws", only aws IP goes
//
// to S3 directly. "awsregion", only regions listed in awsregion options goes to S3 directly
//
// awsregion: a comma separated string of AWS regions.
func newCloudFrontStorageMiddleware(storageDriver storagedriver.StorageDriver, options map[string]interface{}) (storagedriver.StorageDriver, error) {
// parse baseurl
base, ok := options["baseurl"]
if !ok {
return nil, fmt.Errorf("no baseurl provided")
}
baseURL, ok := base.(string)
if !ok {
return nil, fmt.Errorf("baseurl must be a string")
}
if !strings.Contains(baseURL, "://") {
baseURL = "https://" + baseURL
}
if !strings.HasSuffix(baseURL, "/") {
baseURL += "/"
}
if _, err := url.Parse(baseURL); err != nil {
return nil, fmt.Errorf("invalid baseurl: %v", err)
}
// parse privatekey to get pkPath
pk, ok := options["privatekey"]
if !ok {
return nil, fmt.Errorf("no privatekey provided")
}
pkPath, ok := pk.(string)
if !ok {
return nil, fmt.Errorf("privatekey must be a string")
}
// parse keypairid
kpid, ok := options["keypairid"]
if !ok {
return nil, fmt.Errorf("no keypairid provided")
}
keypairID, ok := kpid.(string)
if !ok {
return nil, fmt.Errorf("keypairid must be a string")
}
// get urlSigner from the file specified in pkPath
pkBytes, err := ioutil.ReadFile(pkPath)
if err != nil {
return nil, fmt.Errorf("failed to read privatekey file: %s", err)
}
block, _ := pem.Decode(pkBytes)
if block == nil {
return nil, fmt.Errorf("failed to decode private key as an rsa private key")
}
privateKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
if err != nil {
return nil, err
}
urlSigner := sign.NewURLSigner(keypairID, privateKey)
// parse duration
duration := 20 * time.Minute
if d, ok := options["duration"]; ok {
switch d := d.(type) {
case time.Duration:
duration = d
case string:
dur, err := time.ParseDuration(d)
if err != nil {
return nil, fmt.Errorf("invalid duration: %s", err)
}
duration = dur
}
}
// parse updatefrenquency
updateFrequency := defaultUpdateFrequency
if u, ok := options["updatefrenquency"]; ok {
switch u := u.(type) {
case time.Duration:
updateFrequency = u
case string:
updateFreq, err := time.ParseDuration(u)
if err != nil {
return nil, fmt.Errorf("invalid updatefrenquency: %s", err)
}
duration = updateFreq
}
}
// parse iprangesurl
ipRangesURL := defaultIPRangesURL
if i, ok := options["iprangesurl"]; ok {
if iprangeurl, ok := i.(string); ok {
ipRangesURL = iprangeurl
} else {
return nil, fmt.Errorf("iprangesurl must be a string")
}
}
// parse ipfilteredby
var awsIPs *awsIPs
if i, ok := options["ipfilteredby"]; ok {
if ipFilteredBy, ok := i.(string); ok {
switch strings.ToLower(strings.TrimSpace(ipFilteredBy)) {
case "", "none":
awsIPs = nil
case "aws":
awsIPs = newAWSIPs(ipRangesURL, updateFrequency, nil)
case "awsregion":
var awsRegion []string
if i, ok := options["awsregion"]; ok {
if regions, ok := i.(string); ok {
for _, awsRegions := range strings.Split(regions, ",") {
awsRegion = append(awsRegion, strings.ToLower(strings.TrimSpace(awsRegions)))
}
awsIPs = newAWSIPs(ipRangesURL, updateFrequency, awsRegion)
} else {
return nil, fmt.Errorf("awsRegion must be a comma separated string of valid aws regions")
}
} else {
return nil, fmt.Errorf("awsRegion is not defined")
}
default:
return nil, fmt.Errorf("ipfilteredby only allows a string the following value: none|aws|awsregion")
}
} else {
return nil, fmt.Errorf("ipfilteredby only allows a string with the following value: none|aws|awsregion")
}
}
return &cloudFrontStorageMiddleware{
StorageDriver: storageDriver,
urlSigner: urlSigner,
baseURL: baseURL,
duration: duration,
awsIPs: awsIPs,
}, nil
}
// S3BucketKeyer is any type that is capable of returning the S3 bucket key
// which should be cached by AWS CloudFront.
type S3BucketKeyer interface {
S3BucketKey(path string) string
}
// URLFor attempts to find a url which may be used to retrieve the file at the given path.
// Returns an error if the file cannot be found.
func (lh *cloudFrontStorageMiddleware) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
// TODO(endophage): currently only supports S3
keyer, ok := lh.StorageDriver.(S3BucketKeyer)
if !ok {
dcontext.GetLogger(ctx).Warn("the CloudFront middleware does not support this backend storage driver")
return lh.StorageDriver.URLFor(ctx, path, options)
}
if eligibleForS3(ctx, lh.awsIPs) {
return lh.StorageDriver.URLFor(ctx, path, options)
}
// Get signed cloudfront url.
cfURL, err := lh.urlSigner.Sign(lh.baseURL+keyer.S3BucketKey(path), time.Now().Add(lh.duration))
if err != nil {
return "", err
}
return cfURL, nil
}
// init registers the cloudfront layerHandler backend.
func init() {
storagemiddleware.Register("cloudfront", storagemiddleware.InitFunc(newCloudFrontStorageMiddleware))
}