/*
 * Minio Cloud Storage, (C) 2015-2018 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 cmd

import (
	"bytes"
	"context"
	"crypto/subtle"
	"encoding/base64"
	"encoding/hex"
	"errors"
	"io"
	"io/ioutil"
	"net/http"
	"strings"

	jwtgo "github.com/dgrijalva/jwt-go"
	"github.com/minio/minio/cmd/logger"
	"github.com/minio/minio/pkg/auth"
	"github.com/minio/minio/pkg/hash"
	"github.com/minio/minio/pkg/iam/policy"
	"github.com/minio/minio/pkg/policy"
)

// Verify if request has JWT.
func isRequestJWT(r *http.Request) bool {
	return strings.HasPrefix(r.Header.Get("Authorization"), jwtAlgorithm)
}

// Verify if request has AWS Signature Version '4'.
func isRequestSignatureV4(r *http.Request) bool {
	return strings.HasPrefix(r.Header.Get("Authorization"), signV4Algorithm)
}

// Verify if request has AWS Signature Version '2'.
func isRequestSignatureV2(r *http.Request) bool {
	return (!strings.HasPrefix(r.Header.Get("Authorization"), signV4Algorithm) &&
		strings.HasPrefix(r.Header.Get("Authorization"), signV2Algorithm))
}

// Verify if request has AWS PreSign Version '4'.
func isRequestPresignedSignatureV4(r *http.Request) bool {
	_, ok := r.URL.Query()["X-Amz-Credential"]
	return ok
}

// Verify request has AWS PreSign Version '2'.
func isRequestPresignedSignatureV2(r *http.Request) bool {
	_, ok := r.URL.Query()["AWSAccessKeyId"]
	return ok
}

// Verify if request has AWS Post policy Signature Version '4'.
func isRequestPostPolicySignatureV4(r *http.Request) bool {
	return strings.Contains(r.Header.Get("Content-Type"), "multipart/form-data") &&
		r.Method == http.MethodPost
}

// Verify if the request has AWS Streaming Signature Version '4'. This is only valid for 'PUT' operation.
func isRequestSignStreamingV4(r *http.Request) bool {
	return r.Header.Get("x-amz-content-sha256") == streamingContentSHA256 &&
		r.Method == http.MethodPut
}

// Authorization type.
type authType int

// List of all supported auth types.
const (
	authTypeUnknown authType = iota
	authTypeAnonymous
	authTypePresigned
	authTypePresignedV2
	authTypePostPolicy
	authTypeStreamingSigned
	authTypeSigned
	authTypeSignedV2
	authTypeJWT
	authTypeSTS
)

// Get request authentication type.
func getRequestAuthType(r *http.Request) authType {
	if isRequestSignatureV2(r) {
		return authTypeSignedV2
	} else if isRequestPresignedSignatureV2(r) {
		return authTypePresignedV2
	} else if isRequestSignStreamingV4(r) {
		return authTypeStreamingSigned
	} else if isRequestSignatureV4(r) {
		return authTypeSigned
	} else if isRequestPresignedSignatureV4(r) {
		return authTypePresigned
	} else if isRequestJWT(r) {
		return authTypeJWT
	} else if isRequestPostPolicySignatureV4(r) {
		return authTypePostPolicy
	} else if _, ok := r.URL.Query()["Action"]; ok {
		return authTypeSTS
	} else if _, ok := r.Header["Authorization"]; !ok {
		return authTypeAnonymous
	}
	return authTypeUnknown
}

// checkAdminRequestAuthType checks whether the request is a valid signature V2 or V4 request.
// It does not accept presigned or JWT or anonymous requests.
func checkAdminRequestAuthType(ctx context.Context, r *http.Request, region string) APIErrorCode {
	s3Err := ErrAccessDenied
	if _, ok := r.Header["X-Amz-Content-Sha256"]; ok &&
		getRequestAuthType(r) == authTypeSigned && !skipContentSha256Cksum(r) {
		// We only support admin credentials to access admin APIs.

		var owner bool
		_, owner, s3Err = getReqAccessKeyV4(r, region)
		if s3Err != ErrNone {
			return s3Err
		}

		if !owner {
			return ErrAccessDenied
		}

		// we only support V4 (no presign) with auth body
		s3Err = isReqAuthenticated(ctx, r, region)
	}
	if s3Err != ErrNone {
		reqInfo := (&logger.ReqInfo{}).AppendTags("requestHeaders", dumpRequest(r))
		ctx := logger.SetReqInfo(ctx, reqInfo)
		logger.LogIf(ctx, errors.New(getAPIError(s3Err).Description))
	}
	return s3Err
}

// Fetch the security token set by the client.
func getSessionToken(r *http.Request) (token string) {
	token = r.Header.Get("X-Amz-Security-Token")
	if token != "" {
		return token
	}
	return r.URL.Query().Get("X-Amz-Security-Token")
}

// Fetch claims in the security token returned by the client, doesn't return
// errors - upon errors the returned claims map will be empty.
func mustGetClaimsFromToken(r *http.Request) map[string]interface{} {
	claims, _ := getClaimsFromToken(r)
	return claims
}

// Fetch claims in the security token returned by the client.
func getClaimsFromToken(r *http.Request) (map[string]interface{}, error) {
	claims := make(map[string]interface{})
	token := getSessionToken(r)
	if token == "" {
		return claims, nil
	}
	stsTokenCallback := func(jwtToken *jwtgo.Token) (interface{}, error) {
		// JWT token for x-amz-security-token is signed with admin
		// secret key, temporary credentials become invalid if
		// server admin credentials change. This is done to ensure
		// that clients cannot decode the token using the temp
		// secret keys and generate an entirely new claim by essentially
		// hijacking the policies. We need to make sure that this is
		// based an admin credential such that token cannot be decoded
		// on the client side and is treated like an opaque value.
		return []byte(globalServerConfig.GetCredential().SecretKey), nil
	}
	p := &jwtgo.Parser{
		ValidMethods: []string{
			jwtgo.SigningMethodHS256.Alg(),
			jwtgo.SigningMethodHS512.Alg(),
		},
	}
	jtoken, err := p.ParseWithClaims(token, jwtgo.MapClaims(claims), stsTokenCallback)
	if err != nil {
		return nil, err
	}
	if !jtoken.Valid {
		return nil, errAuthentication
	}
	v, ok := claims["accessKey"]
	if !ok {
		return nil, errInvalidAccessKeyID
	}
	if _, ok = v.(string); !ok {
		return nil, errInvalidAccessKeyID
	}
	return claims, nil
}

// Fetch claims in the security token returned by the client and validate the token.
func checkClaimsFromToken(r *http.Request, cred auth.Credentials) (map[string]interface{}, APIErrorCode) {
	token := getSessionToken(r)
	if token != "" && cred.AccessKey == "" {
		return nil, ErrNoAccessKey
	}
	if subtle.ConstantTimeCompare([]byte(token), []byte(cred.SessionToken)) != 1 {
		return nil, ErrInvalidToken
	}
	claims, err := getClaimsFromToken(r)
	if err != nil {
		return nil, toAPIErrorCode(context.Background(), err)
	}
	return claims, ErrNone
}

// Check request auth type verifies the incoming http request
// - validates the request signature
// - validates the policy action if anonymous tests bucket policies if any,
//   for authenticated requests validates IAM policies.
// returns APIErrorCode if any to be replied to the client.
func checkRequestAuthType(ctx context.Context, r *http.Request, action policy.Action, bucketName, objectName string) (s3Err APIErrorCode) {
	var cred auth.Credentials
	var owner bool
	switch getRequestAuthType(r) {
	case authTypeUnknown, authTypeStreamingSigned:
		return ErrAccessDenied
	case authTypePresignedV2, authTypeSignedV2:
		if s3Err = isReqAuthenticatedV2(r); s3Err != ErrNone {
			return s3Err
		}
		cred, owner, s3Err = getReqAccessKeyV2(r)
	case authTypeSigned, authTypePresigned:
		region := globalServerConfig.GetRegion()
		switch action {
		case policy.GetBucketLocationAction, policy.ListAllMyBucketsAction:
			region = ""
		}
		if s3Err = isReqAuthenticated(ctx, r, region); s3Err != ErrNone {
			return s3Err
		}
		cred, owner, s3Err = getReqAccessKeyV4(r, region)
	}
	if s3Err != ErrNone {
		return s3Err
	}

	claims, s3Err := checkClaimsFromToken(r, cred)
	if s3Err != ErrNone {
		return s3Err
	}

	// LocationConstraint is valid only for CreateBucketAction.
	var locationConstraint string
	if action == policy.CreateBucketAction {
		// To extract region from XML in request body, get copy of request body.
		payload, err := ioutil.ReadAll(io.LimitReader(r.Body, maxLocationConstraintSize))
		if err != nil {
			logger.LogIf(ctx, err)
			return ErrMalformedXML
		}

		// Populate payload to extract location constraint.
		r.Body = ioutil.NopCloser(bytes.NewReader(payload))

		var s3Error APIErrorCode
		locationConstraint, s3Error = parseLocationConstraint(r)
		if s3Error != ErrNone {
			return s3Error
		}

		// Populate payload again to handle it in HTTP handler.
		r.Body = ioutil.NopCloser(bytes.NewReader(payload))
	}

	if cred.AccessKey == "" {
		if globalPolicySys.IsAllowed(policy.Args{
			AccountName:     cred.AccessKey,
			Action:          action,
			BucketName:      bucketName,
			ConditionValues: getConditionValues(r, locationConstraint, ""),
			IsOwner:         false,
			ObjectName:      objectName,
		}) {
			return ErrNone
		}
		return ErrAccessDenied
	}

	if globalIAMSys.IsAllowed(iampolicy.Args{
		AccountName:     cred.AccessKey,
		Action:          iampolicy.Action(action),
		BucketName:      bucketName,
		ConditionValues: getConditionValues(r, "", cred.AccessKey),
		ObjectName:      objectName,
		IsOwner:         owner,
		Claims:          claims,
	}) {
		return ErrNone
	}
	return ErrAccessDenied
}

// Verify if request has valid AWS Signature Version '2'.
func isReqAuthenticatedV2(r *http.Request) (s3Error APIErrorCode) {
	if isRequestSignatureV2(r) {
		return doesSignV2Match(r)
	}
	return doesPresignV2SignatureMatch(r)
}

func reqSignatureV4Verify(r *http.Request, region string) (s3Error APIErrorCode) {
	sha256sum := getContentSha256Cksum(r)
	switch {
	case isRequestSignatureV4(r):
		return doesSignatureMatch(sha256sum, r, region)
	case isRequestPresignedSignatureV4(r):
		return doesPresignedSignatureMatch(sha256sum, r, region)
	default:
		return ErrAccessDenied
	}
}

// Verify if request has valid AWS Signature Version '4'.
func isReqAuthenticated(ctx context.Context, r *http.Request, region string) (s3Error APIErrorCode) {
	if errCode := reqSignatureV4Verify(r, region); errCode != ErrNone {
		return errCode
	}

	var (
		err                       error
		contentMD5, contentSHA256 []byte
	)
	// Extract 'Content-Md5' if present.
	if _, ok := r.Header["Content-Md5"]; ok {
		contentMD5, err = base64.StdEncoding.Strict().DecodeString(r.Header.Get("Content-Md5"))
		if err != nil || len(contentMD5) == 0 {
			return ErrInvalidDigest
		}
	}

	// Extract either 'X-Amz-Content-Sha256' header or 'X-Amz-Content-Sha256' query parameter (if V4 presigned)
	// Do not verify 'X-Amz-Content-Sha256' if skipSHA256.
	if skipSHA256 := skipContentSha256Cksum(r); !skipSHA256 && isRequestPresignedSignatureV4(r) {
		if sha256Sum, ok := r.URL.Query()["X-Amz-Content-Sha256"]; ok && len(sha256Sum) > 0 {
			contentSHA256, err = hex.DecodeString(sha256Sum[0])
			if err != nil {
				return ErrContentSHA256Mismatch
			}
		}
	} else if _, ok := r.Header["X-Amz-Content-Sha256"]; !skipSHA256 && ok {
		contentSHA256, err = hex.DecodeString(r.Header.Get("X-Amz-Content-Sha256"))
		if err != nil || len(contentSHA256) == 0 {
			return ErrContentSHA256Mismatch
		}
	}

	// Verify 'Content-Md5' and/or 'X-Amz-Content-Sha256' if present.
	// The verification happens implicit during reading.
	reader, err := hash.NewReader(r.Body, -1, hex.EncodeToString(contentMD5), hex.EncodeToString(contentSHA256), -1)
	if err != nil {
		return toAPIErrorCode(ctx, err)
	}
	r.Body = ioutil.NopCloser(reader)
	return ErrNone
}

// authHandler - handles all the incoming authorization headers and validates them if possible.
type authHandler struct {
	handler http.Handler
}

// setAuthHandler to validate authorization header for the incoming request.
func setAuthHandler(h http.Handler) http.Handler {
	return authHandler{h}
}

// List of all support S3 auth types.
var supportedS3AuthTypes = map[authType]struct{}{
	authTypeAnonymous:       {},
	authTypePresigned:       {},
	authTypePresignedV2:     {},
	authTypeSigned:          {},
	authTypeSignedV2:        {},
	authTypePostPolicy:      {},
	authTypeStreamingSigned: {},
}

// Validate if the authType is valid and supported.
func isSupportedS3AuthType(aType authType) bool {
	_, ok := supportedS3AuthTypes[aType]
	return ok
}

// handler for validating incoming authorization headers.
func (a authHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	aType := getRequestAuthType(r)
	if isSupportedS3AuthType(aType) {
		// Let top level caller validate for anonymous and known signed requests.
		a.handler.ServeHTTP(w, r)
		return
	} else if aType == authTypeJWT {
		// Validate Authorization header if its valid for JWT request.
		if _, _, authErr := webRequestAuthenticate(r); authErr != nil {
			w.WriteHeader(http.StatusUnauthorized)
			return
		}
		a.handler.ServeHTTP(w, r)
		return
	} else if aType == authTypeSTS {
		a.handler.ServeHTTP(w, r)
		return
	}
	writeErrorResponse(w, ErrSignatureVersionNotSupported, r.URL, guessIsBrowserReq(r))
}

// isPutAllowed - check if PUT operation is allowed on the resource, this
// call verifies bucket policies and IAM policies, supports multi user
// checks etc.
func isPutAllowed(atype authType, bucketName, objectName string, r *http.Request) (s3Err APIErrorCode) {
	var cred auth.Credentials
	var owner bool
	switch atype {
	case authTypeUnknown:
		return ErrAccessDenied
	case authTypeSignedV2, authTypePresignedV2:
		cred, owner, s3Err = getReqAccessKeyV2(r)
	case authTypeStreamingSigned, authTypePresigned, authTypeSigned:
		region := globalServerConfig.GetRegion()
		cred, owner, s3Err = getReqAccessKeyV4(r, region)
	}
	if s3Err != ErrNone {
		return s3Err
	}

	claims, s3Err := checkClaimsFromToken(r, cred)
	if s3Err != ErrNone {
		return s3Err
	}

	if cred.AccessKey == "" {
		if globalPolicySys.IsAllowed(policy.Args{
			AccountName:     cred.AccessKey,
			Action:          policy.PutObjectAction,
			BucketName:      bucketName,
			ConditionValues: getConditionValues(r, "", ""),
			IsOwner:         false,
			ObjectName:      objectName,
		}) {
			return ErrNone
		}
		return ErrAccessDenied
	}

	if globalIAMSys.IsAllowed(iampolicy.Args{
		AccountName:     cred.AccessKey,
		Action:          policy.PutObjectAction,
		BucketName:      bucketName,
		ConditionValues: getConditionValues(r, "", cred.AccessKey),
		ObjectName:      objectName,
		IsOwner:         owner,
		Claims:          claims,
	}) {
		return ErrNone
	}
	return ErrAccessDenied
}