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package storage
// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License. See License.txt in the project root for license information.
import (
"errors"
"fmt"
"net/url"
"strings"
"time"
)
// OverrideHeaders defines overridable response heaedrs in
// a request using a SAS URI.
// See https://docs.microsoft.com/en-us/rest/api/storageservices/constructing-a-service-sas
type OverrideHeaders struct {
CacheControl string
ContentDisposition string
ContentEncoding string
ContentLanguage string
ContentType string
}
// BlobSASOptions are options to construct a blob SAS
// URI.
// See https://docs.microsoft.com/en-us/rest/api/storageservices/constructing-a-service-sas
type BlobSASOptions struct {
BlobServiceSASPermissions
OverrideHeaders
SASOptions
}
// BlobServiceSASPermissions includes the available permissions for
// blob service SAS URI.
type BlobServiceSASPermissions struct {
Read bool
Add bool
Create bool
Write bool
Delete bool
}
func (p BlobServiceSASPermissions) buildString() string {
permissions := ""
if p.Read {
permissions += "r"
}
if p.Add {
permissions += "a"
}
if p.Create {
permissions += "c"
}
if p.Write {
permissions += "w"
}
if p.Delete {
permissions += "d"
}
return permissions
}
// GetSASURI creates an URL to the blob which contains the Shared
// Access Signature with the specified options.
//
// See https://docs.microsoft.com/en-us/rest/api/storageservices/constructing-a-service-sas
func (b *Blob) GetSASURI(options BlobSASOptions) (string, error) {
uri := b.GetURL()
signedResource := "b"
canonicalizedResource, err := b.Container.bsc.client.buildCanonicalizedResource(uri, b.Container.bsc.auth, true)
if err != nil {
return "", err
}
permissions := options.BlobServiceSASPermissions.buildString()
return b.Container.bsc.client.blobAndFileSASURI(options.SASOptions, uri, permissions, canonicalizedResource, signedResource, options.OverrideHeaders)
}
func (c *Client) blobAndFileSASURI(options SASOptions, uri, permissions, canonicalizedResource, signedResource string, headers OverrideHeaders) (string, error) {
start := ""
if options.Start != (time.Time{}) {
start = options.Start.UTC().Format(time.RFC3339)
}
expiry := options.Expiry.UTC().Format(time.RFC3339)
// We need to replace + with %2b first to avoid being treated as a space (which is correct for query strings, but not the path component).
canonicalizedResource = strings.Replace(canonicalizedResource, "+", "%2b", -1)
canonicalizedResource, err := url.QueryUnescape(canonicalizedResource)
if err != nil {
return "", err
}
protocols := ""
if options.UseHTTPS {
protocols = "https"
}
stringToSign, err := blobSASStringToSign(permissions, start, expiry, canonicalizedResource, options.Identifier, options.IP, protocols, c.apiVersion, signedResource, "", headers)
if err != nil {
return "", err
}
sig := c.computeHmac256(stringToSign)
sasParams := url.Values{
"sv": {c.apiVersion},
"se": {expiry},
"sr": {signedResource},
"sp": {permissions},
"sig": {sig},
}
if start != "" {
sasParams.Add("st", start)
}
if c.apiVersion >= "2015-04-05" {
if protocols != "" {
sasParams.Add("spr", protocols)
}
if options.IP != "" {
sasParams.Add("sip", options.IP)
}
}
// Add override response hedaers
addQueryParameter(sasParams, "rscc", headers.CacheControl)
addQueryParameter(sasParams, "rscd", headers.ContentDisposition)
addQueryParameter(sasParams, "rsce", headers.ContentEncoding)
addQueryParameter(sasParams, "rscl", headers.ContentLanguage)
addQueryParameter(sasParams, "rsct", headers.ContentType)
sasURL, err := url.Parse(uri)
if err != nil {
return "", err
}
sasURL.RawQuery = sasParams.Encode()
return sasURL.String(), nil
}
func blobSASStringToSign(signedPermissions, signedStart, signedExpiry, canonicalizedResource, signedIdentifier, signedIP, protocols, signedVersion, signedResource, signedSnapshotTime string, headers OverrideHeaders) (string, error) {
rscc := headers.CacheControl
rscd := headers.ContentDisposition
rsce := headers.ContentEncoding
rscl := headers.ContentLanguage
rsct := headers.ContentType
if signedVersion >= "2015-02-21" {
canonicalizedResource = "/blob" + canonicalizedResource
}
// https://docs.microsoft.com/en-us/rest/api/storageservices/constructing-a-service-sas
if signedVersion >= "2018-11-09" {
return fmt.Sprintf("%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s", signedPermissions, signedStart, signedExpiry, canonicalizedResource, signedIdentifier, signedIP, protocols, signedVersion, signedResource, signedSnapshotTime, rscc, rscd, rsce, rscl, rsct), nil
}
// https://msdn.microsoft.com/en-us/library/azure/dn140255.aspx#Anchor_12
if signedVersion >= "2015-04-05" {
return fmt.Sprintf("%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s", signedPermissions, signedStart, signedExpiry, canonicalizedResource, signedIdentifier, signedIP, protocols, signedVersion, rscc, rscd, rsce, rscl, rsct), nil
}
// reference: http://msdn.microsoft.com/en-us/library/azure/dn140255.aspx
if signedVersion >= "2013-08-15" {
return fmt.Sprintf("%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s", signedPermissions, signedStart, signedExpiry, canonicalizedResource, signedIdentifier, signedVersion, rscc, rscd, rsce, rscl, rsct), nil
}
return "", errors.New("storage: not implemented SAS for versions earlier than 2013-08-15")
}
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