/* * Minio Go Library for Amazon S3 Compatible Cloud Storage * (C) 2017 Minio, Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package credentials import ( "bufio" "encoding/json" "errors" "net/http" "net/url" "path" "time" ) // DefaultExpiryWindow - Default expiry window. // ExpiryWindow will allow the credentials to trigger refreshing // prior to the credentials actually expiring. This is beneficial // so race conditions with expiring credentials do not cause // request to fail unexpectedly due to ExpiredTokenException exceptions. const DefaultExpiryWindow = time.Second * 10 // 10 secs // A IAM retrieves credentials from the EC2 service, and keeps track if // those credentials are expired. type IAM struct { Expiry // Required http Client to use when connecting to IAM metadata service. Client *http.Client // Custom endpoint to fetch IAM role credentials. endpoint string } // redirectHeaders copies all headers when following a redirect URL. // This won't be needed anymore from go 1.8 (https://github.com/golang/go/issues/4800) func redirectHeaders(req *http.Request, via []*http.Request) error { if len(via) == 0 { return nil } for key, val := range via[0].Header { req.Header[key] = val } return nil } // IAM Roles for Amazon EC2 // http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html const ( defaultIAMRoleEndpoint = "http://169.254.169.254" defaultIAMSecurityCredsPath = "/latest/meta-data/iam/security-credentials" ) // NewIAM returns a pointer to a new Credentials object wrapping // the IAM. Takes a ConfigProvider to create a EC2Metadata client. // The ConfigProvider is satisfied by the session.Session type. func NewIAM(endpoint string) *Credentials { if endpoint == "" { endpoint = defaultIAMRoleEndpoint } p := &IAM{ Client: &http.Client{ Transport: http.DefaultTransport, CheckRedirect: redirectHeaders, }, endpoint: endpoint, } return New(p) } // Retrieve retrieves credentials from the EC2 service. // Error will be returned if the request fails, or unable to extract // the desired func (m *IAM) Retrieve() (Value, error) { roleCreds, err := getCredentials(m.Client, m.endpoint) if err != nil { return Value{}, err } // Expiry window is set to 10secs. m.SetExpiration(roleCreds.Expiration, DefaultExpiryWindow) return Value{ AccessKeyID: roleCreds.AccessKeyID, SecretAccessKey: roleCreds.SecretAccessKey, SessionToken: roleCreds.Token, SignerType: SignatureV4, }, nil } // A ec2RoleCredRespBody provides the shape for unmarshaling credential // request responses. type ec2RoleCredRespBody struct { // Success State Expiration time.Time AccessKeyID string SecretAccessKey string Token string // Error state Code string Message string // Unused params. LastUpdated time.Time Type string } // Get the final IAM role URL where the request will // be sent to fetch the rolling access credentials. // http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html func getIAMRoleURL(endpoint string) (*url.URL, error) { if endpoint == "" { endpoint = defaultIAMRoleEndpoint } u, err := url.Parse(endpoint) if err != nil { return nil, err } u.Path = defaultIAMSecurityCredsPath return u, nil } // listRoleNames lists of credential role names associated // with the current EC2 service. If there are no credentials, // or there is an error making or receiving the request. // http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html func listRoleNames(client *http.Client, u *url.URL) ([]string, error) { req, err := http.NewRequest("GET", u.String(), nil) if err != nil { return nil, err } resp, err := client.Do(req) if err != nil { return nil, err } defer resp.Body.Close() if resp.StatusCode != http.StatusOK { return nil, errors.New(resp.Status) } credsList := []string{} s := bufio.NewScanner(resp.Body) for s.Scan() { credsList = append(credsList, s.Text()) } if err := s.Err(); err != nil { return nil, err } return credsList, nil } // getCredentials - obtains the credentials from the IAM role name associated with // the current EC2 service. // // If the credentials cannot be found, or there is an error // reading the response an error will be returned. func getCredentials(client *http.Client, endpoint string) (ec2RoleCredRespBody, error) { // http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html u, err := getIAMRoleURL(endpoint) if err != nil { return ec2RoleCredRespBody{}, err } // http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html roleNames, err := listRoleNames(client, u) if err != nil { return ec2RoleCredRespBody{}, err } if len(roleNames) == 0 { return ec2RoleCredRespBody{}, errors.New("No IAM roles attached to this EC2 service") } // http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html // - An instance profile can contain only one IAM role. This limit cannot be increased. roleName := roleNames[0] // http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html // The following command retrieves the security credentials for an // IAM role named `s3access`. // // $ curl http://169.254.169.254/latest/meta-data/iam/security-credentials/s3access // u.Path = path.Join(u.Path, roleName) req, err := http.NewRequest("GET", u.String(), nil) if err != nil { return ec2RoleCredRespBody{}, err } resp, err := client.Do(req) if err != nil { return ec2RoleCredRespBody{}, err } defer resp.Body.Close() if resp.StatusCode != http.StatusOK { return ec2RoleCredRespBody{}, errors.New(resp.Status) } respCreds := ec2RoleCredRespBody{} if err := json.NewDecoder(resp.Body).Decode(&respCreds); err != nil { return ec2RoleCredRespBody{}, err } if respCreds.Code != "Success" { // If an error code was returned something failed requesting the role. return ec2RoleCredRespBody{}, errors.New(respCreds.Message) } return respCreds, nil }