// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package cmd

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"mime/multipart"
	"net/http"
	"net/textproto"
	"regexp"
	"strings"

	"github.com/minio/madmin-go/v2"
	"github.com/minio/minio/internal/auth"
	"github.com/minio/minio/internal/handlers"
	xhttp "github.com/minio/minio/internal/http"
	"github.com/minio/minio/internal/logger"
	xnet "github.com/minio/pkg/net"
)

const (
	copyDirective    = "COPY"
	replaceDirective = "REPLACE"
)

// Parses location constraint from the incoming reader.
func parseLocationConstraint(r *http.Request) (location string, s3Error APIErrorCode) {
	// If the request has no body with content-length set to 0,
	// we do not have to validate location constraint. Bucket will
	// be created at default region.
	locationConstraint := createBucketLocationConfiguration{}
	err := xmlDecoder(r.Body, &locationConstraint, r.ContentLength)
	if err != nil && r.ContentLength != 0 {
		logger.LogIf(GlobalContext, err)
		// Treat all other failures as XML parsing errors.
		return "", ErrMalformedXML
	} // else for both err as nil or io.EOF
	location = locationConstraint.Location
	if location == "" {
		location = globalSite.Region
	}
	if !isValidLocation(location) {
		return location, ErrInvalidRegion
	}

	return location, ErrNone
}

// Validates input location is same as configured region
// of MinIO server.
func isValidLocation(location string) bool {
	return globalSite.Region == "" || globalSite.Region == location
}

// Supported headers that needs to be extracted.
var supportedHeaders = []string{
	"content-type",
	"cache-control",
	"content-language",
	"content-encoding",
	"content-disposition",
	"x-amz-storage-class",
	xhttp.AmzStorageClass,
	xhttp.AmzObjectTagging,
	"expires",
	xhttp.AmzBucketReplicationStatus,
	// Add more supported headers here.
}

// isDirectiveValid - check if tagging-directive is valid.
func isDirectiveValid(v string) bool {
	// Check if set metadata-directive is valid.
	return isDirectiveCopy(v) || isDirectiveReplace(v)
}

// Check if the directive COPY is requested.
func isDirectiveCopy(value string) bool {
	// By default if directive is not set we
	// treat it as 'COPY' this function returns true.
	return value == copyDirective || value == ""
}

// Check if the directive REPLACE is requested.
func isDirectiveReplace(value string) bool {
	return value == replaceDirective
}

// userMetadataKeyPrefixes contains the prefixes of used-defined metadata keys.
// All values stored with a key starting with one of the following prefixes
// must be extracted from the header.
var userMetadataKeyPrefixes = []string{
	"x-amz-meta-",
	"x-minio-meta-",
}

// extractMetadata extracts metadata from HTTP header and HTTP queryString.
func extractMetadata(ctx context.Context, r *http.Request) (metadata map[string]string, err error) {
	query := r.Form
	header := r.Header
	metadata = make(map[string]string)
	// Extract all query values.
	err = extractMetadataFromMime(ctx, textproto.MIMEHeader(query), metadata)
	if err != nil {
		return nil, err
	}

	// Extract all header values.
	err = extractMetadataFromMime(ctx, textproto.MIMEHeader(header), metadata)
	if err != nil {
		return nil, err
	}

	// Set content-type to default value if it is not set.
	if _, ok := metadata[strings.ToLower(xhttp.ContentType)]; !ok {
		metadata[strings.ToLower(xhttp.ContentType)] = "binary/octet-stream"
	}

	// https://github.com/google/security-research/security/advisories/GHSA-76wf-9vgp-pj7w
	for k := range metadata {
		if equals(k, xhttp.AmzMetaUnencryptedContentLength, xhttp.AmzMetaUnencryptedContentMD5) {
			delete(metadata, k)
		}
	}

	if contentEncoding, ok := metadata[strings.ToLower(xhttp.ContentEncoding)]; ok {
		contentEncoding = trimAwsChunkedContentEncoding(contentEncoding)
		if contentEncoding != "" {
			// Make sure to trim and save the content-encoding
			// parameter for a streaming signature which is set
			// to a custom value for example: "aws-chunked,gzip".
			metadata[strings.ToLower(xhttp.ContentEncoding)] = contentEncoding
		} else {
			// Trimmed content encoding is empty when the header
			// value is set to "aws-chunked" only.

			// Make sure to delete the content-encoding parameter
			// for a streaming signature which is set to value
			// for example: "aws-chunked"
			delete(metadata, strings.ToLower(xhttp.ContentEncoding))
		}
	}

	// Success.
	return metadata, nil
}

// extractMetadata extracts metadata from map values.
func extractMetadataFromMime(ctx context.Context, v textproto.MIMEHeader, m map[string]string) error {
	if v == nil {
		logger.LogIf(ctx, errInvalidArgument)
		return errInvalidArgument
	}

	nv := make(textproto.MIMEHeader, len(v))
	for k, kv := range v {
		// Canonicalize all headers, to remove any duplicates.
		nv[http.CanonicalHeaderKey(k)] = kv
	}

	// Save all supported headers.
	for _, supportedHeader := range supportedHeaders {
		value, ok := nv[http.CanonicalHeaderKey(supportedHeader)]
		if ok {
			m[supportedHeader] = strings.Join(value, ",")
		}
	}

	for key := range v {
		for _, prefix := range userMetadataKeyPrefixes {
			if !strings.HasPrefix(strings.ToLower(key), strings.ToLower(prefix)) {
				continue
			}
			value, ok := nv[http.CanonicalHeaderKey(key)]
			if ok {
				m[key] = strings.Join(value, ",")
				break
			}
		}
	}
	return nil
}

// Returns access credentials in the request Authorization header.
func getReqAccessCred(r *http.Request, region string) (cred auth.Credentials) {
	cred, _, _ = getReqAccessKeyV4(r, region, serviceS3)
	if cred.AccessKey == "" {
		cred, _, _ = getReqAccessKeyV2(r)
	}
	return cred
}

// Extract request params to be sent with event notifiation.
func extractReqParams(r *http.Request) map[string]string {
	if r == nil {
		return nil
	}

	region := globalSite.Region
	cred := getReqAccessCred(r, region)

	principalID := cred.AccessKey
	if cred.ParentUser != "" {
		principalID = cred.ParentUser
	}

	// Success.
	m := map[string]string{
		"region":          region,
		"principalId":     principalID,
		"sourceIPAddress": handlers.GetSourceIP(r),
		// Add more fields here.
	}
	if rangeField := r.Header.Get(xhttp.Range); rangeField != "" {
		m["range"] = rangeField
	}

	if _, ok := r.Header[xhttp.MinIOSourceReplicationRequest]; ok {
		m[xhttp.MinIOSourceReplicationRequest] = ""
	}
	return m
}

// Extract response elements to be sent with event notifiation.
func extractRespElements(w http.ResponseWriter) map[string]string {
	if w == nil {
		return map[string]string{}
	}
	return map[string]string{
		"requestId":      w.Header().Get(xhttp.AmzRequestID),
		"nodeId":         w.Header().Get(xhttp.AmzRequestHostID),
		"content-length": w.Header().Get(xhttp.ContentLength),
		// Add more fields here.
	}
}

// Trims away `aws-chunked` from the content-encoding header if present.
// Streaming signature clients can have custom content-encoding such as
// `aws-chunked,gzip` here we need to only save `gzip`.
// For more refer http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-streaming.html
func trimAwsChunkedContentEncoding(contentEnc string) (trimmedContentEnc string) {
	if contentEnc == "" {
		return contentEnc
	}
	var newEncs []string
	for _, enc := range strings.Split(contentEnc, ",") {
		if enc != streamingContentEncoding {
			newEncs = append(newEncs, enc)
		}
	}
	return strings.Join(newEncs, ",")
}

// Validate form field size for s3 specification requirement.
func validateFormFieldSize(ctx context.Context, formValues http.Header) error {
	// Iterate over form values
	for k := range formValues {
		// Check if value's field exceeds S3 limit
		if int64(len(formValues.Get(k))) > maxFormFieldSize {
			logger.LogIf(ctx, errSizeUnexpected)
			return errSizeUnexpected
		}
	}

	// Success.
	return nil
}

// Extract form fields and file data from a HTTP POST Policy
func extractPostPolicyFormValues(ctx context.Context, form *multipart.Form) (filePart io.ReadCloser, fileName string, fileSize int64, formValues http.Header, err error) {
	// HTML Form values
	fileName = ""

	// Canonicalize the form values into http.Header.
	formValues = make(http.Header)
	for k, v := range form.Value {
		formValues[http.CanonicalHeaderKey(k)] = v
	}

	// Validate form values.
	if err = validateFormFieldSize(ctx, formValues); err != nil {
		return nil, "", 0, nil, err
	}

	// this means that filename="" was not specified for file key and Go has
	// an ugly way of handling this situation. Refer here
	// https://golang.org/src/mime/multipart/formdata.go#L61
	if len(form.File) == 0 {
		b := &bytes.Buffer{}
		for _, v := range formValues["File"] {
			b.WriteString(v)
		}
		fileSize = int64(b.Len())
		filePart = io.NopCloser(b)
		return filePart, fileName, fileSize, formValues, nil
	}

	// Iterator until we find a valid File field and break
	for k, v := range form.File {
		canonicalFormName := http.CanonicalHeaderKey(k)
		if canonicalFormName == "File" {
			if len(v) == 0 {
				logger.LogIf(ctx, errInvalidArgument)
				return nil, "", 0, nil, errInvalidArgument
			}
			// Fetch fileHeader which has the uploaded file information
			fileHeader := v[0]
			// Set filename
			fileName = fileHeader.Filename
			// Open the uploaded part
			filePart, err = fileHeader.Open()
			if err != nil {
				logger.LogIf(ctx, err)
				return nil, "", 0, nil, err
			}
			// Compute file size
			fileSize, err = filePart.(io.Seeker).Seek(0, 2)
			if err != nil {
				logger.LogIf(ctx, err)
				return nil, "", 0, nil, err
			}
			// Reset Seek to the beginning
			_, err = filePart.(io.Seeker).Seek(0, 0)
			if err != nil {
				logger.LogIf(ctx, err)
				return nil, "", 0, nil, err
			}
			// File found and ready for reading
			break
		}
	}
	return filePart, fileName, fileSize, formValues, nil
}

func collectAPIStats(api string, f http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		globalHTTPStats.currentS3Requests.Inc(api)
		defer globalHTTPStats.currentS3Requests.Dec(api)

		statsWriter := xhttp.NewResponseRecorder(w)

		f.ServeHTTP(statsWriter, r)

		globalHTTPStats.updateStats(api, r, statsWriter)
	}
}

// Returns "/bucketName/objectName" for path-style or virtual-host-style requests.
func getResource(path string, host string, domains []string) (string, error) {
	if len(domains) == 0 {
		return path, nil
	}

	// If virtual-host-style is enabled construct the "resource" properly.
	xhost, err := xnet.ParseHost(host)
	if err != nil {
		return "", err
	}

	for _, domain := range domains {
		if xhost.Name == minioReservedBucket+"."+domain {
			continue
		}
		if !strings.HasSuffix(xhost.Name, "."+domain) {
			continue
		}
		bucket := strings.TrimSuffix(xhost.Name, "."+domain)
		return SlashSeparator + pathJoin(bucket, path), nil
	}
	return path, nil
}

var regexVersion = regexp.MustCompile(`^/minio.*/(v\d+)/.*`)

func extractAPIVersion(r *http.Request) string {
	if matches := regexVersion.FindStringSubmatch(r.URL.Path); len(matches) > 1 {
		return matches[1]
	}
	return "unknown"
}

func methodNotAllowedHandler(api string) func(w http.ResponseWriter, r *http.Request) {
	return errorResponseHandler
}

// If none of the http routes match respond with appropriate errors
func errorResponseHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodOptions {
		return
	}
	desc := "Do not upgrade one server at a time - please follow the recommended guidelines mentioned here https://github.com/minio/minio#upgrading-minio for your environment"
	switch {
	case strings.HasPrefix(r.URL.Path, peerS3Prefix):
		writeErrorResponseString(r.Context(), w, APIError{
			Code:           "XMinioPeerS3VersionMismatch",
			Description:    desc,
			HTTPStatusCode: http.StatusUpgradeRequired,
		}, r.URL)
	case strings.HasPrefix(r.URL.Path, peerRESTPrefix):
		writeErrorResponseString(r.Context(), w, APIError{
			Code:           "XMinioPeerVersionMismatch",
			Description:    desc,
			HTTPStatusCode: http.StatusUpgradeRequired,
		}, r.URL)
	case strings.HasPrefix(r.URL.Path, storageRESTPrefix):
		writeErrorResponseString(r.Context(), w, APIError{
			Code:           "XMinioStorageVersionMismatch",
			Description:    desc,
			HTTPStatusCode: http.StatusUpgradeRequired,
		}, r.URL)
	case strings.HasPrefix(r.URL.Path, lockRESTPrefix):
		writeErrorResponseString(r.Context(), w, APIError{
			Code:           "XMinioLockVersionMismatch",
			Description:    desc,
			HTTPStatusCode: http.StatusUpgradeRequired,
		}, r.URL)
	case strings.HasPrefix(r.URL.Path, adminPathPrefix):
		var desc string
		version := extractAPIVersion(r)
		switch version {
		case "v1", madmin.AdminAPIVersionV2:
			desc = fmt.Sprintf("Server expects client requests with 'admin' API version '%s', found '%s', please upgrade the client to latest releases", madmin.AdminAPIVersion, version)
		case madmin.AdminAPIVersion:
			desc = fmt.Sprintf("This 'admin' API is not supported by server in '%s'", getMinioMode())
		default:
			desc = fmt.Sprintf("Unexpected client 'admin' API version found '%s', expected '%s', please downgrade the client to older releases", version, madmin.AdminAPIVersion)
		}
		writeErrorResponseJSON(r.Context(), w, APIError{
			Code:           "XMinioAdminVersionMismatch",
			Description:    desc,
			HTTPStatusCode: http.StatusUpgradeRequired,
		}, r.URL)
	default:
		writeErrorResponse(r.Context(), w, APIError{
			Code: "BadRequest",
			Description: fmt.Sprintf("An error occurred when parsing the HTTP request %s at '%s'",
				r.Method, r.URL.Path),
			HTTPStatusCode: http.StatusBadRequest,
		}, r.URL)
	}
}

// gets host name for current node
func getHostName(r *http.Request) (hostName string) {
	if globalIsDistErasure {
		hostName = globalLocalNodeName
	} else {
		hostName = r.Host
	}
	return
}

// Proxy any request to an endpoint.
func proxyRequest(ctx context.Context, w http.ResponseWriter, r *http.Request, ep ProxyEndpoint) (success bool) {
	success = true

	// Make sure we remove any existing headers before
	// proxying the request to another node.
	for k := range w.Header() {
		w.Header().Del(k)
	}

	f := handlers.NewForwarder(&handlers.Forwarder{
		PassHost:     true,
		RoundTripper: ep.Transport,
		ErrorHandler: func(w http.ResponseWriter, r *http.Request, err error) {
			success = false
			if err != nil && !errors.Is(err, context.Canceled) {
				logger.LogIf(GlobalContext, err)
			}
		},
	})

	r.URL.Scheme = "http"
	if globalIsTLS {
		r.URL.Scheme = "https"
	}

	r.URL.Host = ep.Host
	f.ServeHTTP(w, r)
	return
}
