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ds.go
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ds.go
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package unicreds
import (
"encoding/base64"
"errors"
"fmt"
"time"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/dynamodb"
"github.com/aws/aws-sdk-go/service/dynamodb/dynamodbiface"
)
const (
// Table the name of the dynamodb table
Table = "credential-store"
// DefaultKmsKey default KMS key alias name
DefaultKmsKey = "alias/credstash"
// CreatedAtNotAvailable returned to indicate the created at field is missing
// from the secret
CreatedAtNotAvailable = "Not Available"
tableCreateTimeout = 30 * time.Second
)
var (
dynamoSvc dynamodbiface.DynamoDBAPI
// ErrSecretNotFound returned when unable to find the specified secret in dynamodb
ErrSecretNotFound = errors.New("Secret Not Found")
// ErrHmacValidationFailed returned when the hmac signature validation fails
ErrHmacValidationFailed = errors.New("Secret HMAC validation failed")
// ErrTimeout timeout occured waiting for dynamodb table to create
ErrTimeout = errors.New("Timed out waiting for dynamodb table to become active")
)
func init() {
dynamoSvc = dynamodb.New(session.New(), aws.NewConfig())
}
// SetDynamoDBConfig override the default aws configuration
func SetDynamoDBConfig(config *aws.Config) {
dynamoSvc = dynamodb.New(session.New(), config)
}
// Credential managed credential information
type Credential struct {
Name string `ds:"name"`
Version string `ds:"version"`
Key string `ds:"key"`
Contents string `ds:"contents"`
Hmac string `ds:"hmac"`
CreatedAt int64 `ds:"created_at"`
}
// CreatedAtDate convert the timestamp field to a date string
func (c *Credential) CreatedAtDate() string {
if c.CreatedAt == 0 {
return CreatedAtNotAvailable
}
tm := time.Unix(c.CreatedAt, 0)
return tm.String()
}
// DecryptedCredential managed credential information
type DecryptedCredential struct {
*Credential
Secret string
}
// Setup create the table which stores credentials
func Setup() (err error) {
res, err := dynamoSvc.CreateTable(&dynamodb.CreateTableInput{
AttributeDefinitions: []*dynamodb.AttributeDefinition{
{
AttributeName: aws.String("name"),
AttributeType: aws.String("S"),
},
{
AttributeName: aws.String("version"),
AttributeType: aws.String("S"),
},
},
KeySchema: []*dynamodb.KeySchemaElement{
{
AttributeName: aws.String("name"),
KeyType: aws.String(dynamodb.KeyTypeHash),
},
{
AttributeName: aws.String("version"),
KeyType: aws.String(dynamodb.KeyTypeRange),
},
},
ProvisionedThroughput: &dynamodb.ProvisionedThroughput{
ReadCapacityUnits: aws.Int64(1),
WriteCapacityUnits: aws.Int64(1),
},
TableName: aws.String(Table),
})
if err != nil {
return
}
fmt.Printf("res = %+v\n", res)
err = waitForTable()
return
}
// GetSecret retrieve the secret from dynamodb using the name
func GetSecret(name string) (*DecryptedCredential, error) {
res, err := dynamoSvc.Query(&dynamodb.QueryInput{
TableName: aws.String(Table),
ExpressionAttributeNames: map[string]*string{
"#N": aws.String("name"),
},
ExpressionAttributeValues: map[string]*dynamodb.AttributeValue{
":name": &dynamodb.AttributeValue{
S: aws.String(name),
},
},
KeyConditionExpression: aws.String("#N = :name"),
Limit: aws.Int64(1),
ConsistentRead: aws.Bool(true),
ScanIndexForward: aws.Bool(false), // descending order
})
if err != nil {
return nil, err
}
cred := new(Credential)
if len(res.Items) == 0 {
return nil, ErrSecretNotFound
}
err = Decode(res.Items[0], cred)
if err != nil {
return nil, err
}
return decryptCredential(cred)
}
// ListSecrets return a list of secrets
func ListSecrets() ([]*DecryptedCredential, error) {
res, err := dynamoSvc.Scan(&dynamodb.ScanInput{
TableName: aws.String(Table),
AttributesToGet: []*string{
aws.String("name"),
aws.String("version"),
aws.String("key"),
aws.String("contents"),
aws.String("hmac"),
aws.String("created_at"),
},
ConsistentRead: aws.Bool(true),
})
if err != nil {
return nil, err
}
var results []*DecryptedCredential
for _, item := range res.Items {
cred := new(Credential)
err = Decode(item, cred)
if err != nil {
return nil, err
}
dcred, err := decryptCredential(cred)
if err != nil {
return nil, err
}
results = append(results, dcred)
}
return results, nil
}
// PutSecret retrieve the secret from dynamodb
func PutSecret(alias, name, secret, version string) error {
kmsKey := DefaultKmsKey
if alias != "" {
kmsKey = alias
}
if version == "" {
version = "1"
}
dk, err := GenerateDataKey(kmsKey, 64)
if err != nil {
return err
}
dataKey := dk.Plaintext[:32]
hmacKey := dk.Plaintext[32:]
wrappedKey := dk.CiphertextBlob
ctext, err := Encrypt(dataKey, []byte(secret))
b64hmac := ComputeHmac256(ctext, hmacKey)
b64ctext := base64.StdEncoding.EncodeToString(ctext)
cred := &Credential{
Name: name,
Version: version,
Key: base64.StdEncoding.EncodeToString(wrappedKey),
Contents: b64ctext,
Hmac: b64hmac,
CreatedAt: time.Now().Unix(),
}
data, err := Encode(cred)
if err != nil {
return err
}
_, err = dynamoSvc.PutItem(&dynamodb.PutItemInput{
TableName: aws.String(Table),
Item: data,
})
return err
}
// DeleteSecret delete a secret
func DeleteSecret(name string) error {
res, err := dynamoSvc.Query(&dynamodb.QueryInput{
TableName: aws.String(Table),
ExpressionAttributeNames: map[string]*string{
"#N": aws.String("name"),
},
ExpressionAttributeValues: map[string]*dynamodb.AttributeValue{
":name": &dynamodb.AttributeValue{
S: aws.String(name),
},
},
KeyConditionExpression: aws.String("#N = :name"),
ConsistentRead: aws.Bool(true),
ScanIndexForward: aws.Bool(false), // descending order
})
if err != nil {
return err
}
for _, item := range res.Items {
cred := new(Credential)
err = Decode(item, cred)
if err != nil {
return err
}
fmt.Printf("deleting name=%s version=%s\n", cred.Name, cred.Version)
_, err = dynamoSvc.DeleteItem(&dynamodb.DeleteItemInput{
TableName: aws.String(Table),
Key: map[string]*dynamodb.AttributeValue{
"name": &dynamodb.AttributeValue{
S: aws.String(cred.Name),
},
"version": &dynamodb.AttributeValue{
S: aws.String(cred.Version),
},
},
})
if err != nil {
return err
}
}
return nil
}
func decryptCredential(cred *Credential) (*DecryptedCredential, error) {
wrappedKey, err := base64.StdEncoding.DecodeString(cred.Key)
if err != nil {
return nil, err
}
dk, err := DecryptDataKey(wrappedKey)
if err != nil {
return nil, err
}
dataKey := dk.Plaintext[:32]
hmacKey := dk.Plaintext[32:]
contents, err := base64.StdEncoding.DecodeString(cred.Contents)
if err != nil {
return nil, err
}
hexhmac := ComputeHmac256(contents, hmacKey)
if hexhmac != cred.Hmac {
return nil, ErrHmacValidationFailed
}
secret, err := Decrypt(dataKey, contents)
if err != nil {
return nil, err
}
plainText := string(secret)
return &DecryptedCredential{Credential: cred, Secret: plainText}, nil
}
func waitForTable() error {
timeout := make(chan bool, 1)
go func() {
time.Sleep(tableCreateTimeout)
timeout <- true
}()
ticker := time.NewTicker(1 * time.Second)
defer ticker.Stop()
for {
select {
case <-ticker.C:
// a read from ch has occurred
res, err := dynamoSvc.DescribeTable(&dynamodb.DescribeTableInput{
TableName: aws.String(Table),
})
if err != nil {
return err
}
if *res.Table.TableStatus == "ACTIVE" {
return nil
}
case <-timeout:
// polling for table status has taken more than the timeout
return ErrTimeout
}
}
}