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authorNiall Sheridan <nsheridan@gmail.com>2016-06-05 22:18:24 +0100
committerNiall Sheridan <nsheridan@gmail.com>2016-06-05 23:00:46 +0100
commitb8af9fe60f27353bdd5933ed37508b30d4290046 (patch)
treefcc12e2f39f9fe4d7aa7d37fd4114309d3362c38
parenta52d19e9e78d08643ffd4aee0483515d8bae2939 (diff)
Add AWS S3 and Google GCS virtual filesystems.
This allows the signing key to be read directly from S3 using a path like /s3/<bucket>/<path/to/signing.key> or /gcs/<bucket>/<path/to/signing.key>.
-rw-r--r--README.md13
-rw-r--r--cmd/cashierd/main.go2
-rw-r--r--example-server.conf11
-rw-r--r--server/config/config.go15
-rw-r--r--server/fs/s3.go152
-rw-r--r--server/signer/signer.go6
6 files changed, 195 insertions, 4 deletions
diff --git a/README.md b/README.md
index 70186c8..2d0be20 100644
--- a/README.md
+++ b/README.md
@@ -70,7 +70,7 @@ A working SSH agent.
I have only tested this on Linux & OSX.
# Configuration
-Configuration is divided into three sections: `server`, `auth`, and `ssh`.
+Configuration is divided into different sections: `server`, `auth`, `ssh`, and `aws`.
### server
- `use_tls` : boolean. If set `tls_key` and `tls_cert` are required.
@@ -110,11 +110,20 @@ Example:
Supported options:
### ssh
-- `signing_key`: string. Path to the signing ssh private key you created earlier.
+- `signing_key`: string. Path to the signing ssh private key you created earlier. This can be a S3 or GCS path using `/s3/<bucket>/<path/to/key>` or `/gcs/<bucket>/<path/to/key>` as appropriate. For S3 you should add an [aws](#aws) config as needed.
- `additional_principals`: array of string. By default certificates will have one principal set - the username portion of the requester's email address. If `additional_principals` is set, these will be added to the certificate e.g. if your production machines use shared user accounts.
- `max_age`: string. If set the server will not issue certificates with an expiration value longer than this, regardless of what the client requests. Must be a valid Go [`time.Duration`](https://golang.org/pkg/time/#ParseDuration) string.
- `permissions`: array of string. Actions the certificate can perform. See the [`-O` option to `ssh-keygen(1)`](http://man.openbsd.org/OpenBSD-current/man1/ssh-keygen.1) for a complete list.
+### aws
+AWS configuration is only needed for accessing signing keys stored on S3, and isn't required even then.
+The S3 client can be configured using any of [the usual AWS-SDK means](https://github.com/aws/aws-sdk-go/wiki/configuring-sdk) - environment variables, IAM roles etc.
+It's strongly recommended that signing keys stored on S3 be locked down to specific IAM roles and encrypted using KMS.
+
+- `region`: string. AWS region the bucket resides in, e.g. `us-east-1`.
+- `access_key`: string. AWS Access Key ID.
+- `secret_key`: string. AWS Secret Key.
+
## Configuring ssh
The client needs no special configuration, just a running ssh-agent.
The ssh server needs to trust the public part of the CA signing key. Add something like the following to your sshd_config:
diff --git a/cmd/cashierd/main.go b/cmd/cashierd/main.go
index 1b1035c..9a162d7 100644
--- a/cmd/cashierd/main.go
+++ b/cmd/cashierd/main.go
@@ -24,6 +24,7 @@ import (
"github.com/nsheridan/cashier/server/auth/github"
"github.com/nsheridan/cashier/server/auth/google"
"github.com/nsheridan/cashier/server/config"
+ "github.com/nsheridan/cashier/server/fs"
"github.com/nsheridan/cashier/server/signer"
"github.com/nsheridan/cashier/templates"
)
@@ -199,6 +200,7 @@ func main() {
if err != nil {
log.Fatal(err)
}
+ fs.Register(&config.AWS)
signer, err := signer.New(config.SSH)
if err != nil {
log.Fatal(err)
diff --git a/example-server.conf b/example-server.conf
index 94c6b69..5a88615 100644
--- a/example-server.conf
+++ b/example-server.conf
@@ -1,3 +1,4 @@
+# Server config
server {
use_tls = true # Optional. If this is set then `tls_key` and `tls_cert` must be set
tls_key = "server.key" # Path to TLS key
@@ -6,6 +7,7 @@ server {
cookie_secret = "supersecret" # Authentication key for the client cookie
}
+# Oauth2 configuration
auth {
provider = "google" # Oauth provider to use
oauth_client_id = "nnnnnnnnnnnnnnnn.apps.googleusercontent.com" # Oauth client ID
@@ -16,9 +18,18 @@ auth {
}
}
+# Configuration for the certificate signer.
ssh {
signing_key = "signing_key" # Path to the CA signing secret key
additional_principals = ["ec2-user", "ubuntu"] # Additional principals to allow
max_age = "720h" # Maximum lifetime of a ssh certificate
permissions = ["permit-pty", "permit-X11-forwarding", "permit-agent-forwarding", "permit-port-forwarding", "permit-user-rc"] # Permissions associated with a certificate.
}
+
+# Optional AWS config. if an aws config is present, the signing key can be read from S3 using the syntax `/s3/bucket/path/to/signing.key`.
+# These can also be set configured using the standard aws-sdk environment variables, IAM roles etc. https://github.com/aws/aws-sdk-go/wiki/configuring-sdk
+aws {
+ region = "eu-west-1"
+ access_key = "abcdef"
+ secret_key = "xyz123"
+}
diff --git a/server/config/config.go b/server/config/config.go
index fae823b..648cf46 100644
--- a/server/config/config.go
+++ b/server/config/config.go
@@ -13,6 +13,7 @@ type Config struct {
Server `mapstructure:"server"`
Auth `mapstructure:"auth"`
SSH `mapstructure:"ssh"`
+ AWS `mapstructure:"aws"`
}
// unmarshalled holds the raw config.
@@ -20,6 +21,7 @@ type unmarshalled struct {
Server []Server `mapstructure:"server"`
Auth []Auth `mapstructure:"auth"`
SSH []SSH `mapstructure:"ssh"`
+ AWS []AWS `mapstructure:"aws"`
}
// Server holds the configuration specific to the web server and sessions.
@@ -48,6 +50,14 @@ type SSH struct {
Permissions []string `mapstructure:"permissions"`
}
+// AWS holds Amazon AWS configuration.
+// AWS can also be configured using SDK methods.
+type AWS struct {
+ Region string `mapstructure:"region"`
+ AccessKey string `mapstructure:"access_key"`
+ SecretKey string `mapstructure:"secret_key"`
+}
+
func verifyConfig(u *unmarshalled) error {
var err error
if len(u.SSH) == 0 {
@@ -59,6 +69,10 @@ func verifyConfig(u *unmarshalled) error {
if len(u.Server) == 0 {
err = multierror.Append(errors.New("missing server config block"))
}
+ if len(u.AWS) == 0 {
+ // AWS config is optional
+ u.AWS = append(u.AWS, AWS{})
+ }
return err
}
@@ -80,5 +94,6 @@ func ReadConfig(r io.Reader) (*Config, error) {
Server: u.Server[0],
Auth: u.Auth[0],
SSH: u.SSH[0],
+ AWS: u.AWS[0],
}, nil
}
diff --git a/server/fs/s3.go b/server/fs/s3.go
new file mode 100644
index 0000000..4e82bb4
--- /dev/null
+++ b/server/fs/s3.go
@@ -0,0 +1,152 @@
+package fs
+
+import (
+ "bytes"
+ "errors"
+ "io/ioutil"
+ "os"
+ "path"
+ "strings"
+ "time"
+
+ "go4.org/wkfs"
+
+ "github.com/aws/aws-sdk-go/aws"
+ "github.com/aws/aws-sdk-go/aws/awserr"
+ "github.com/aws/aws-sdk-go/aws/credentials"
+ "github.com/aws/aws-sdk-go/aws/session"
+ "github.com/aws/aws-sdk-go/service/s3"
+ "github.com/nsheridan/cashier/server/config"
+)
+
+func Register(config *config.AWS) {
+ ac := &aws.Config{}
+ // If region is unset the SDK will attempt to read the region from the environment.
+ if config.Region != "" {
+ ac.Region = aws.String(config.Region)
+ }
+ // Attempt to get credentials from the cashier config.
+ // Otherwise check for standard credentials. If neither are present register the fs as broken.
+ // TODO: implement this as a provider.
+ if config.AccessKey != "" && config.SecretKey != "" {
+ ac.Credentials = credentials.NewStaticCredentials(config.AccessKey, config.SecretKey, "")
+ } else {
+ _, err := session.New().Config.Credentials.Get()
+ if err != nil {
+ registerBrokenFS(errors.New("aws credentials not found"))
+ return
+ }
+ }
+ sc := s3.New(session.New(ac))
+ if aws.StringValue(sc.Config.Region) == "" {
+ registerBrokenFS(errors.New("aws region configuration not found"))
+ return
+ }
+ wkfs.RegisterFS("/s3/", &s3FS{
+ sc: sc,
+ })
+}
+
+func registerBrokenFS(err error) {
+ wkfs.RegisterFS("/s3/", &s3FS{
+ err: err,
+ })
+}
+
+type s3FS struct {
+ sc *s3.S3
+ err error
+}
+
+func (fs *s3FS) parseName(name string) (bucket, fileName string, err error) {
+ if fs.err != nil {
+ return "", "", fs.err
+ }
+ name = strings.TrimPrefix(name, "/s3/")
+ i := strings.Index(name, "/")
+ if i < 0 {
+ return name, "", nil
+ }
+ return name[:i], name[i+1:], nil
+}
+
+// Open opens the named file for reading.
+func (fs *s3FS) Open(name string) (wkfs.File, error) {
+ bucket, fileName, err := fs.parseName(name)
+ if err != nil {
+ return nil, err
+ }
+ obj, err := fs.sc.GetObject(&s3.GetObjectInput{
+ Bucket: &bucket,
+ Key: &fileName,
+ })
+ if err != nil {
+ return nil, err
+ }
+ defer obj.Body.Close()
+ slurp, err := ioutil.ReadAll(obj.Body)
+ if err != nil {
+ return nil, err
+ }
+ return &file{
+ name: name,
+ Reader: bytes.NewReader(slurp),
+ }, nil
+}
+
+func (fs *s3FS) Stat(name string) (os.FileInfo, error) { return fs.Lstat(name) }
+func (fs *s3FS) Lstat(name string) (os.FileInfo, error) {
+ bucket, fileName, err := fs.parseName(name)
+ if err != nil {
+ return nil, err
+ }
+ obj, err := fs.sc.GetObject(&s3.GetObjectInput{
+ Bucket: &bucket,
+ Key: &fileName,
+ })
+ if err != nil {
+ if awsErr, ok := err.(awserr.Error); ok {
+ if awsErr.Code() == "NoSuchKey" {
+ return nil, os.ErrNotExist
+ }
+ }
+ }
+ if err != nil {
+ return nil, err
+ }
+ return &statInfo{
+ name: path.Base(fileName),
+ size: *obj.ContentLength,
+ }, nil
+}
+
+func (fs *s3FS) MkdirAll(path string, perm os.FileMode) error { return nil }
+
+func (fs *s3FS) OpenFile(name string, flag int, perm os.FileMode) (wkfs.FileWriter, error) {
+ return nil, errors.New("not implemented")
+}
+
+type statInfo struct {
+ name string
+ size int64
+ isDir bool
+ modtime time.Time
+}
+
+func (si *statInfo) IsDir() bool { return si.isDir }
+func (si *statInfo) ModTime() time.Time { return si.modtime }
+func (si *statInfo) Mode() os.FileMode { return 0644 }
+func (si *statInfo) Name() string { return path.Base(si.name) }
+func (si *statInfo) Size() int64 { return si.size }
+func (si *statInfo) Sys() interface{} { return nil }
+
+type file struct {
+ name string
+ *bytes.Reader
+}
+
+func (*file) Close() error { return nil }
+func (f *file) Name() string { return path.Base(f.name) }
+func (f *file) Stat() (os.FileInfo, error) {
+ panic("Stat not implemented on /s3/ files yet")
+}
diff --git a/server/signer/signer.go b/server/signer/signer.go
index 8be5cad..1be6d75 100644
--- a/server/signer/signer.go
+++ b/server/signer/signer.go
@@ -4,11 +4,13 @@ import (
"crypto/md5"
"crypto/rand"
"fmt"
- "io/ioutil"
"log"
"strings"
"time"
+ "go4.org/wkfs"
+ _ "go4.org/wkfs/gcs" // Register "/gcs/" as a wkfs.
+
"github.com/nsheridan/cashier/lib"
"github.com/nsheridan/cashier/server/config"
"golang.org/x/crypto/ssh"
@@ -71,7 +73,7 @@ func makeperms(perms []string) map[string]string {
// New creates a new KeySigner from the supplied configuration.
func New(conf config.SSH) (*KeySigner, error) {
- data, err := ioutil.ReadFile(conf.SigningKey)
+ data, err := wkfs.ReadFile(conf.SigningKey)
if err != nil {
return nil, fmt.Errorf("unable to read CA key %s: %v", conf.SigningKey, err)
}