Add STSClientGrants and STSWebIdentity credential provider (#1059)

Both provider implements a way to retrieve temporary
credentials from Minio STS service

- using client grants token (Only Minio)
- using web identity token (Both Minio and AWS)

These temporary credentials will be used to perform API
operations, to be used with applications which are never
using static credentials.

pkg/credentials/iam_aws.go

@@ -67,9 +67,7 @@ func getEndpoint(endpoint string) (string, bool) {
 	return defaultIAMRoleEndpoint, false
 }
 
-// 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.
+// NewIAM returns a pointer to a new Credentials object wrapping the IAM.
 func NewIAM(endpoint string) *Credentials {
 	p := &IAM{
 		Client: &http.Client{

pkg/credentials/sts_client_grants.go

@@ -0,0 +1,173 @@
+/*
+ * Minio Go Library for Amazon S3 Compatible Cloud Storage
+ * Copyright 2019 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 (
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/url"
+	"time"
+)
+
+// AssumedRoleUser - The identifiers for the temporary security credentials that
+// the operation returns. Please also see https://docs.aws.amazon.com/goto/WebAPI/sts-2011-06-15/AssumedRoleUser
+type AssumedRoleUser struct {
+	Arn           string
+	AssumedRoleID string `xml:"AssumeRoleId"`
+}
+
+// AssumeRoleWithClientGrantsResponse contains the result of successful AssumeRoleWithClientGrants request.
+type AssumeRoleWithClientGrantsResponse struct {
+	XMLName          xml.Name           `xml:"https://sts.amazonaws.com/doc/2011-06-15/ AssumeRoleWithClientGrantsResponse" json:"-"`
+	Result           ClientGrantsResult `xml:"AssumeRoleWithClientGrantsResult"`
+	ResponseMetadata struct {
+		RequestID string `xml:"RequestId,omitempty"`
+	} `xml:"ResponseMetadata,omitempty"`
+}
+
+// ClientGrantsResult - Contains the response to a successful AssumeRoleWithClientGrants
+// request, including temporary credentials that can be used to make Minio API requests.
+type ClientGrantsResult struct {
+	AssumedRoleUser AssumedRoleUser `xml:",omitempty"`
+	Audience        string          `xml:",omitempty"`
+	Credentials     struct {
+		AccessKey    string    `xml:"AccessKeyId" json:"accessKey,omitempty"`
+		SecretKey    string    `xml:"SecretAccessKey" json:"secretKey,omitempty"`
+		Expiration   time.Time `xml:"Expiration" json:"expiration,omitempty"`
+		SessionToken string    `xml:"SessionToken" json:"sessionToken,omitempty"`
+	} `xml:",omitempty"`
+	PackedPolicySize             int    `xml:",omitempty"`
+	Provider                     string `xml:",omitempty"`
+	SubjectFromClientGrantsToken string `xml:",omitempty"`
+}
+
+// ClientGrantsToken - client grants token with expiry.
+type ClientGrantsToken struct {
+	token  string
+	expiry int
+}
+
+// Token - access token returned after authenticating client grants.
+func (c *ClientGrantsToken) Token() string {
+	return c.token
+}
+
+// Expiry - expiry for the access token returned after authenticating
+// client grants.
+func (c *ClientGrantsToken) Expiry() string {
+	return fmt.Sprintf("%d", c.expiry)
+}
+
+// A STSClientGrants retrieves credentials from Minio service, and keeps track if
+// those credentials are expired.
+type STSClientGrants struct {
+	Expiry
+
+	// Required http Client to use when connecting to Minio STS service.
+	Client *http.Client
+
+	// Minio endpoint to fetch STS credentials.
+	stsEndpoint string
+
+	// getClientGrantsTokenExpiry function to retrieve tokens
+	// from IDP This function should return two values one is
+	// accessToken which is a self contained access token (JWT)
+	// and second return value is the expiry associated with
+	// this token. This is a customer provided function and
+	// is mandatory.
+	getClientGrantsTokenExpiry func() (*ClientGrantsToken, error)
+}
+
+// NewSTSClientGrants returns a pointer to a new
+// Credentials object wrapping the STSClientGrants.
+func NewSTSClientGrants(stsEndpoint string, getClientGrantsTokenExpiry func() (*ClientGrantsToken, error)) (*Credentials, error) {
+	if stsEndpoint == "" {
+		return nil, errors.New("STS endpoint cannot be empty")
+	}
+	if getClientGrantsTokenExpiry == nil {
+		return nil, errors.New("Client grants access token and expiry retrieval function should be defined")
+	}
+	return New(&STSClientGrants{
+		Client: &http.Client{
+			Transport: http.DefaultTransport,
+		},
+		stsEndpoint:                stsEndpoint,
+		getClientGrantsTokenExpiry: getClientGrantsTokenExpiry,
+	}), nil
+}
+
+func getClientGrantsCredentials(clnt *http.Client, endpoint string,
+	getClientGrantsTokenExpiry func() (*ClientGrantsToken, error)) (AssumeRoleWithClientGrantsResponse, error) {
+
+	accessToken, err := getClientGrantsTokenExpiry()
+	if err != nil {
+		return AssumeRoleWithClientGrantsResponse{}, err
+	}
+
+	v := url.Values{}
+	v.Set("Action", "AssumeRoleWithClientGrants")
+	v.Set("Token", accessToken.Token())
+	v.Set("DurationSeconds", accessToken.Expiry())
+	v.Set("Version", "2011-06-15")
+
+	u, err := url.Parse(endpoint)
+	if err != nil {
+		return AssumeRoleWithClientGrantsResponse{}, err
+	}
+	u.RawQuery = v.Encode()
+
+	req, err := http.NewRequest("POST", u.String(), nil)
+	if err != nil {
+		return AssumeRoleWithClientGrantsResponse{}, err
+	}
+	resp, err := clnt.Do(req)
+	if err != nil {
+		return AssumeRoleWithClientGrantsResponse{}, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return AssumeRoleWithClientGrantsResponse{}, errors.New(resp.Status)
+	}
+
+	a := AssumeRoleWithClientGrantsResponse{}
+	if err = xml.NewDecoder(resp.Body).Decode(&a); err != nil {
+		return AssumeRoleWithClientGrantsResponse{}, err
+	}
+	return a, nil
+}
+
+// Retrieve retrieves credentials from the Minio service.
+// Error will be returned if the request fails.
+func (m *STSClientGrants) Retrieve() (Value, error) {
+	a, err := getClientGrantsCredentials(m.Client, m.stsEndpoint, m.getClientGrantsTokenExpiry)
+	if err != nil {
+		return Value{}, err
+	}
+
+	// Expiry window is set to 10secs.
+	m.SetExpiration(a.Result.Credentials.Expiration, DefaultExpiryWindow)
+
+	return Value{
+		AccessKeyID:     a.Result.Credentials.AccessKey,
+		SecretAccessKey: a.Result.Credentials.SecretKey,
+		SessionToken:    a.Result.Credentials.SessionToken,
+		SignerType:      SignatureV4,
+	}, nil
+}

pkg/credentials/sts_web_identity.go

@@ -0,0 +1,169 @@
+/*
+ * Minio Go Library for Amazon S3 Compatible Cloud Storage
+ * Copyright 2019 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 (
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/url"
+	"time"
+)
+
+// AssumeRoleWithWebIdentityResponse contains the result of successful AssumeRoleWithWebIdentity request.
+type AssumeRoleWithWebIdentityResponse struct {
+	XMLName          xml.Name          `xml:"https://sts.amazonaws.com/doc/2011-06-15/ AssumeRoleWithWebIdentityResponse" json:"-"`
+	Result           WebIdentityResult `xml:"AssumeRoleWithWebIdentityResult"`
+	ResponseMetadata struct {
+		RequestID string `xml:"RequestId,omitempty"`
+	} `xml:"ResponseMetadata,omitempty"`
+}
+
+// WebIdentityResult - Contains the response to a successful AssumeRoleWithWebIdentity
+// request, including temporary credentials that can be used to make Minio API requests.
+type WebIdentityResult struct {
+	AssumedRoleUser AssumedRoleUser `xml:",omitempty"`
+	Audience        string          `xml:",omitempty"`
+	Credentials     struct {
+		AccessKey    string    `xml:"AccessKeyId" json:"accessKey,omitempty"`
+		SecretKey    string    `xml:"SecretAccessKey" json:"secretKey,omitempty"`
+		Expiration   time.Time `xml:"Expiration" json:"expiration,omitempty"`
+		SessionToken string    `xml:"SessionToken" json:"sessionToken,omitempty"`
+	} `xml:",omitempty"`
+	PackedPolicySize            int    `xml:",omitempty"`
+	Provider                    string `xml:",omitempty"`
+	SubjectFromWebIdentityToken string `xml:",omitempty"`
+}
+
+// WebIdentityToken - web identity token with expiry.
+type WebIdentityToken struct {
+	token  string
+	expiry int
+}
+
+// Token - access token returned after authenticating web identity.
+func (c *WebIdentityToken) Token() string {
+	return c.token
+}
+
+// Expiry - expiry for the access token returned after authenticating
+// web identity.
+func (c *WebIdentityToken) Expiry() string {
+	return fmt.Sprintf("%d", c.expiry)
+}
+
+// A STSWebIdentity retrieves credentials from Minio service, and keeps track if
+// those credentials are expired.
+type STSWebIdentity struct {
+	Expiry
+
+	// Required http Client to use when connecting to Minio STS service.
+	Client *http.Client
+
+	// Minio endpoint to fetch STS credentials.
+	stsEndpoint string
+
+	// getWebIDTokenExpiry function which returns ID tokens
+	// from IDP. This function should return two values one
+	// is ID token which is a self contained ID token (JWT)
+	// and second return value is the expiry associated with
+	// this token.
+	// This is a customer provided function and is mandatory.
+	getWebIDTokenExpiry func() (*WebIdentityToken, error)
+}
+
+// NewSTSWebIdentity returns a pointer to a new
+// Credentials object wrapping the STSWebIdentity.
+func NewSTSWebIdentity(stsEndpoint string, getWebIDTokenExpiry func() (*WebIdentityToken, error)) (*Credentials, error) {
+	if stsEndpoint == "" {
+		return nil, errors.New("STS endpoint cannot be empty")
+	}
+	if getWebIDTokenExpiry == nil {
+		return nil, errors.New("Web ID token and expiry retrieval function should be defined")
+	}
+	return New(&STSWebIdentity{
+		Client: &http.Client{
+			Transport: http.DefaultTransport,
+		},
+		stsEndpoint:         stsEndpoint,
+		getWebIDTokenExpiry: getWebIDTokenExpiry,
+	}), nil
+}
+
+func getWebIdentityCredentials(clnt *http.Client, endpoint string,
+	getWebIDTokenExpiry func() (*WebIdentityToken, error)) (AssumeRoleWithWebIdentityResponse, error) {
+	idToken, err := getWebIDTokenExpiry()
+	if err != nil {
+		return AssumeRoleWithWebIdentityResponse{}, err
+	}
+
+	v := url.Values{}
+	v.Set("Action", "AssumeRoleWithWebIdentity")
+	v.Set("WebIdentityToken", idToken.Token())
+	v.Set("DurationSeconds", idToken.Expiry())
+	v.Set("Version", "2011-06-15")
+
+	u, err := url.Parse(endpoint)
+	if err != nil {
+		return AssumeRoleWithWebIdentityResponse{}, err
+	}
+
+	u.RawQuery = v.Encode()
+
+	req, err := http.NewRequest("POST", u.String(), nil)
+	if err != nil {
+		return AssumeRoleWithWebIdentityResponse{}, err
+	}
+
+	resp, err := clnt.Do(req)
+	if err != nil {
+		return AssumeRoleWithWebIdentityResponse{}, err
+	}
+
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return AssumeRoleWithWebIdentityResponse{}, errors.New(resp.Status)
+	}
+
+	a := AssumeRoleWithWebIdentityResponse{}
+	if err = xml.NewDecoder(resp.Body).Decode(&a); err != nil {
+		return AssumeRoleWithWebIdentityResponse{}, err
+	}
+
+	return a, nil
+}
+
+// Retrieve retrieves credentials from the Minio service.
+// Error will be returned if the request fails.
+func (m *STSWebIdentity) Retrieve() (Value, error) {
+	a, err := getWebIdentityCredentials(m.Client, m.stsEndpoint, m.getWebIDTokenExpiry)
+	if err != nil {
+		return Value{}, err
+	}
+
+	// Expiry window is set to 10secs.
+	m.SetExpiration(a.Result.Credentials.Expiration, DefaultExpiryWindow)
+
+	return Value{
+		AccessKeyID:     a.Result.Credentials.AccessKey,
+		SecretAccessKey: a.Result.Credentials.SecretKey,
+		SessionToken:    a.Result.Credentials.SessionToken,
+		SignerType:      SignatureV4,
+	}, nil
+}