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// Package storage provides clients for Microsoft Azure Storage Services.
package storage
import (
"bytes"
"fmt"
"net/url"
"sort"
"strings"
)
// See: https://docs.microsoft.com/rest/api/storageservices/fileservices/authentication-for-the-azure-storage-services
type authentication string
const (
sharedKey authentication = "sharedKey"
sharedKeyForTable authentication = "sharedKeyTable"
sharedKeyLite authentication = "sharedKeyLite"
sharedKeyLiteForTable authentication = "sharedKeyLiteTable"
// headers
headerAuthorization = "Authorization"
headerContentLength = "Content-Length"
headerDate = "Date"
headerXmsDate = "x-ms-date"
headerXmsVersion = "x-ms-version"
headerContentEncoding = "Content-Encoding"
headerContentLanguage = "Content-Language"
headerContentType = "Content-Type"
headerContentMD5 = "Content-MD5"
headerIfModifiedSince = "If-Modified-Since"
headerIfMatch = "If-Match"
headerIfNoneMatch = "If-None-Match"
headerIfUnmodifiedSince = "If-Unmodified-Since"
headerRange = "Range"
)
func (c *Client) addAuthorizationHeader(verb, url string, headers map[string]string, auth authentication) (map[string]string, error) {
authHeader, err := c.getSharedKey(verb, url, headers, auth)
if err != nil {
return nil, err
}
headers[headerAuthorization] = authHeader
return headers, nil
}
func (c *Client) getSharedKey(verb, url string, headers map[string]string, auth authentication) (string, error) {
canRes, err := c.buildCanonicalizedResource(url, auth)
if err != nil {
return "", err
}
canString, err := buildCanonicalizedString(verb, headers, canRes, auth)
if err != nil {
return "", err
}
return c.createAuthorizationHeader(canString, auth), nil
}
func (c *Client) buildCanonicalizedResource(uri string, auth authentication) (string, error) {
errMsg := "buildCanonicalizedResource error: %s"
u, err := url.Parse(uri)
if err != nil {
return "", fmt.Errorf(errMsg, err.Error())
}
cr := bytes.NewBufferString("/")
cr.WriteString(c.getCanonicalizedAccountName())
if len(u.Path) > 0 {
// Any portion of the CanonicalizedResource string that is derived from
// the resource's URI should be encoded exactly as it is in the URI.
// -- https://msdn.microsoft.com/en-gb/library/azure/dd179428.aspx
cr.WriteString(u.EscapedPath())
}
params, err := url.ParseQuery(u.RawQuery)
if err != nil {
return "", fmt.Errorf(errMsg, err.Error())
}
// See https://github.com/Azure/azure-storage-net/blob/master/Lib/Common/Core/Util/AuthenticationUtility.cs#L277
if auth == sharedKey {
if len(params) > 0 {
cr.WriteString("\n")
keys := []string{}
for key := range params {
keys = append(keys, key)
}
sort.Strings(keys)
completeParams := []string{}
for _, key := range keys {
if len(params[key]) > 1 {
sort.Strings(params[key])
}
completeParams = append(completeParams, fmt.Sprintf("%s:%s", key, strings.Join(params[key], ",")))
}
cr.WriteString(strings.Join(completeParams, "\n"))
}
} else {
// search for "comp" parameter, if exists then add it to canonicalizedresource
if v, ok := params["comp"]; ok {
cr.WriteString("?comp=" + v[0])
}
}
return string(cr.Bytes()), nil
}
func (c *Client) getCanonicalizedAccountName() string {
// since we may be trying to access a secondary storage account, we need to
// remove the -secondary part of the storage name
return strings.TrimSuffix(c.accountName, "-secondary")
}
func buildCanonicalizedString(verb string, headers map[string]string, canonicalizedResource string, auth authentication) (string, error) {
contentLength := headers[headerContentLength]
if contentLength == "0" {
contentLength = ""
}
date := headers[headerDate]
if v, ok := headers[headerXmsDate]; ok {
if auth == sharedKey || auth == sharedKeyLite {
date = ""
} else {
date = v
}
}
var canString string
switch auth {
case sharedKey:
canString = strings.Join([]string{
verb,
headers[headerContentEncoding],
headers[headerContentLanguage],
contentLength,
headers[headerContentMD5],
headers[headerContentType],
date,
headers[headerIfModifiedSince],
headers[headerIfMatch],
headers[headerIfNoneMatch],
headers[headerIfUnmodifiedSince],
headers[headerRange],
buildCanonicalizedHeader(headers),
canonicalizedResource,
}, "\n")
case sharedKeyForTable:
canString = strings.Join([]string{
verb,
headers[headerContentMD5],
headers[headerContentType],
date,
canonicalizedResource,
}, "\n")
case sharedKeyLite:
canString = strings.Join([]string{
verb,
headers[headerContentMD5],
headers[headerContentType],
date,
buildCanonicalizedHeader(headers),
canonicalizedResource,
}, "\n")
case sharedKeyLiteForTable:
canString = strings.Join([]string{
date,
canonicalizedResource,
}, "\n")
default:
return "", fmt.Errorf("%s authentication is not supported yet", auth)
}
return canString, nil
}
func buildCanonicalizedHeader(headers map[string]string) string {
cm := make(map[string]string)
for k, v := range headers {
headerName := strings.TrimSpace(strings.ToLower(k))
if strings.HasPrefix(headerName, "x-ms-") {
cm[headerName] = v
}
}
if len(cm) == 0 {
return ""
}
keys := []string{}
for key := range cm {
keys = append(keys, key)
}
sort.Strings(keys)
ch := bytes.NewBufferString("")
for _, key := range keys {
ch.WriteString(key)
ch.WriteRune(':')
ch.WriteString(cm[key])
ch.WriteRune('\n')
}
return strings.TrimSuffix(string(ch.Bytes()), "\n")
}
func (c *Client) createAuthorizationHeader(canonicalizedString string, auth authentication) string {
signature := c.computeHmac256(canonicalizedString)
var key string
switch auth {
case sharedKey, sharedKeyForTable:
key = "SharedKey"
case sharedKeyLite, sharedKeyLiteForTable:
key = "SharedKeyLite"
}
return fmt.Sprintf("%s %s:%s", key, c.getCanonicalizedAccountName(), signature)
}
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