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service.go
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service.go
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//go:build go1.18
// +build go1.18
// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.
package sas
import (
"bytes"
"fmt"
"strings"
"time"
"github.com/Azure/azure-sdk-for-go/sdk/storage/azblob/internal/exported"
)
// BlobSignatureValues is used to generate a Shared Access Signature (SAS) for an Azure Storage container or blob.
// For more information, see https://docs.microsoft.com/rest/api/storageservices/constructing-a-service-sas
type BlobSignatureValues struct {
Version string `param:"sv"` // If not specified, this defaults to Version
Protocol Protocol `param:"spr"` // See the Protocol* constants
StartTime time.Time `param:"st"` // Not specified if IsZero
ExpiryTime time.Time `param:"se"` // Not specified if IsZero
SnapshotTime time.Time
Permissions string `param:"sp"` // Create by initializing a ContainerSASPermissions or BlobSASPermissions and then call String()
IPRange IPRange `param:"sip"`
Identifier string `param:"si"`
ContainerName string
BlobName string // Use "" to create a Container SAS
Directory string // Not nil for a directory SAS (ie sr=d)
CacheControl string // rscc
ContentDisposition string // rscd
ContentEncoding string // rsce
ContentLanguage string // rscl
ContentType string // rsct
BlobVersion string // sr=bv
PreauthorizedAgentObjectId string
AgentObjectId string
CorrelationId string
}
func getDirectoryDepth(path string) string {
if path == "" {
return ""
}
return fmt.Sprint(strings.Count(path, "/") + 1)
}
// SignWithSharedKey uses an account's SharedKeyCredential to sign this signature values to produce the proper SAS query parameters.
func (v BlobSignatureValues) SignWithSharedKey(sharedKeyCredential *SharedKeyCredential) (QueryParameters, error) {
if sharedKeyCredential == nil {
return QueryParameters{}, fmt.Errorf("cannot sign SAS query without Shared Key Credential")
}
//Make sure the permission characters are in the correct order
perms, err := parseBlobPermissions(v.Permissions)
if err != nil {
return QueryParameters{}, err
}
v.Permissions = perms.String()
resource := "c"
if !v.SnapshotTime.IsZero() {
resource = "bs"
} else if v.BlobVersion != "" {
resource = "bv"
} else if v.Directory != "" {
resource = "d"
v.BlobName = ""
} else if v.BlobName == "" {
// do nothing
} else {
resource = "b"
}
if v.Version == "" {
v.Version = Version
}
startTime, expiryTime, snapshotTime := formatTimesForSigning(v.StartTime, v.ExpiryTime, v.SnapshotTime)
signedIdentifier := v.Identifier
// String to sign: http://msdn.microsoft.com/en-us/library/azure/dn140255.aspx
stringToSign := strings.Join([]string{
v.Permissions,
startTime,
expiryTime,
getCanonicalName(sharedKeyCredential.AccountName(), v.ContainerName, v.BlobName, v.Directory),
signedIdentifier,
v.IPRange.String(),
string(v.Protocol),
v.Version,
resource,
snapshotTime, // signed timestamp
v.CacheControl, // rscc
v.ContentDisposition, // rscd
v.ContentEncoding, // rsce
v.ContentLanguage, // rscl
v.ContentType}, // rsct
"\n")
signature, err := exported.ComputeHMACSHA256(sharedKeyCredential, stringToSign)
if err != nil {
return QueryParameters{}, err
}
p := QueryParameters{
// Common SAS parameters
version: v.Version,
protocol: v.Protocol,
startTime: v.StartTime,
expiryTime: v.ExpiryTime,
permissions: v.Permissions,
ipRange: v.IPRange,
// Container/Blob-specific SAS parameters
resource: resource,
identifier: v.Identifier,
cacheControl: v.CacheControl,
contentDisposition: v.ContentDisposition,
contentEncoding: v.ContentEncoding,
contentLanguage: v.ContentLanguage,
contentType: v.ContentType,
snapshotTime: v.SnapshotTime,
signedDirectoryDepth: getDirectoryDepth(v.Directory),
preauthorizedAgentObjectID: v.PreauthorizedAgentObjectId,
agentObjectID: v.AgentObjectId,
correlationID: v.CorrelationId,
// Calculated SAS signature
signature: signature,
}
return p, nil
}
// SignWithUserDelegation uses an account's UserDelegationCredential to sign this signature values to produce the proper SAS query parameters.
func (v BlobSignatureValues) SignWithUserDelegation(userDelegationCredential *UserDelegationCredential) (QueryParameters, error) {
if userDelegationCredential == nil {
return QueryParameters{}, fmt.Errorf("cannot sign SAS query without User Delegation Key")
}
//Make sure the permission characters are in the correct order
perms, err := parseBlobPermissions(v.Permissions)
if err != nil {
return QueryParameters{}, err
}
v.Permissions = perms.String()
resource := "c"
if !v.SnapshotTime.IsZero() {
resource = "bs"
} else if v.BlobVersion != "" {
resource = "bv"
} else if v.Directory != "" {
resource = "d"
v.BlobName = ""
} else if v.BlobName == "" {
// do nothing
} else {
resource = "b"
}
if v.Version == "" {
v.Version = Version
}
startTime, expiryTime, snapshotTime := formatTimesForSigning(v.StartTime, v.ExpiryTime, v.SnapshotTime)
udk := exported.GetUDKParams(userDelegationCredential)
udkStart, udkExpiry, _ := formatTimesForSigning(*udk.SignedStart, *udk.SignedExpiry, time.Time{})
//I don't like this answer to combining the functions
//But because signedIdentifier and the user delegation key strings share a place, this is an _OK_ way to do it.
signedIdentifier := strings.Join([]string{
*udk.SignedOID,
*udk.SignedTID,
udkStart,
udkExpiry,
*udk.SignedService,
*udk.SignedVersion,
v.PreauthorizedAgentObjectId,
v.AgentObjectId,
v.CorrelationId,
}, "\n")
// String to sign: http://msdn.microsoft.com/en-us/library/azure/dn140255.aspx
stringToSign := strings.Join([]string{
v.Permissions,
startTime,
expiryTime,
getCanonicalName(exported.GetAccountName(userDelegationCredential), v.ContainerName, v.BlobName, v.Directory),
signedIdentifier,
v.IPRange.String(),
string(v.Protocol),
v.Version,
resource,
snapshotTime, // signed timestamp
v.CacheControl, // rscc
v.ContentDisposition, // rscd
v.ContentEncoding, // rsce
v.ContentLanguage, // rscl
v.ContentType}, // rsct
"\n")
signature, err := exported.ComputeUDCHMACSHA256(userDelegationCredential, stringToSign)
if err != nil {
return QueryParameters{}, err
}
p := QueryParameters{
// Common SAS parameters
version: v.Version,
protocol: v.Protocol,
startTime: v.StartTime,
expiryTime: v.ExpiryTime,
permissions: v.Permissions,
ipRange: v.IPRange,
// Container/Blob-specific SAS parameters
resource: resource,
identifier: v.Identifier,
cacheControl: v.CacheControl,
contentDisposition: v.ContentDisposition,
contentEncoding: v.ContentEncoding,
contentLanguage: v.ContentLanguage,
contentType: v.ContentType,
snapshotTime: v.SnapshotTime,
signedDirectoryDepth: getDirectoryDepth(v.Directory),
preauthorizedAgentObjectID: v.PreauthorizedAgentObjectId,
agentObjectID: v.AgentObjectId,
correlationID: v.CorrelationId,
// Calculated SAS signature
signature: signature,
}
//User delegation SAS specific parameters
p.signedOID = *udk.SignedOID
p.signedTID = *udk.SignedTID
p.signedStart = *udk.SignedStart
p.signedExpiry = *udk.SignedExpiry
p.signedService = *udk.SignedService
p.signedVersion = *udk.SignedVersion
return p, nil
}
// getCanonicalName computes the canonical name for a container or blob resource for SAS signing.
func getCanonicalName(account string, containerName string, blobName string, directoryName string) string {
// Container: "/blob/account/containername"
// Blob: "/blob/account/containername/blobname"
elements := []string{"/blob/", account, "/", containerName}
if blobName != "" {
elements = append(elements, "/", strings.Replace(blobName, "\\", "/", -1))
} else if directoryName != "" {
elements = append(elements, "/", directoryName)
}
return strings.Join(elements, "")
}
// ContainerPermissions type simplifies creating the permissions string for an Azure Storage container SAS.
// Initialize an instance of this type and then call its String method to set BlobSASSignatureValues's Permissions field.
// All permissions descriptions can be found here: https://docs.microsoft.com/en-us/rest/api/storageservices/create-service-sas#permissions-for-a-directory-container-or-blob
type ContainerPermissions struct {
Read, Add, Create, Write, Delete, DeletePreviousVersion, List, Tag bool
Execute, ModifyOwnership, ModifyPermissions bool // Hierarchical Namespace only
}
// String produces the SAS permissions string for an Azure Storage container.
// Call this method to set BlobSASSignatureValues's Permissions field.
func (p *ContainerPermissions) String() string {
var b bytes.Buffer
if p.Read {
b.WriteRune('r')
}
if p.Add {
b.WriteRune('a')
}
if p.Create {
b.WriteRune('c')
}
if p.Write {
b.WriteRune('w')
}
if p.Delete {
b.WriteRune('d')
}
if p.DeletePreviousVersion {
b.WriteRune('x')
}
if p.List {
b.WriteRune('l')
}
if p.Tag {
b.WriteRune('t')
}
if p.Execute {
b.WriteRune('e')
}
if p.ModifyOwnership {
b.WriteRune('o')
}
if p.ModifyPermissions {
b.WriteRune('p')
}
return b.String()
}
// Parse initializes the ContainerSASPermissions' fields from a string.
/*func parseContainerPermissions(s string) (ContainerPermissions, error) {
p := ContainerPermissions{} // Clear the flags
for _, r := range s {
switch r {
case 'r':
p.Read = true
case 'a':
p.Add = true
case 'c':
p.Create = true
case 'w':
p.Write = true
case 'd':
p.Delete = true
case 'x':
p.DeletePreviousVersion = true
case 'l':
p.List = true
case 't':
p.Tag = true
case 'e':
p.Execute = true
case 'o':
p.ModifyOwnership = true
case 'p':
p.ModifyPermissions = true
default:
return ContainerPermissions{}, fmt.Errorf("invalid permission: '%v'", r)
}
}
return p, nil
}*/
// BlobPermissions type simplifies creating the permissions string for an Azure Storage blob SAS.
// Initialize an instance of this type and then call its String method to set BlobSASSignatureValues's Permissions field.
type BlobPermissions struct {
Read, Add, Create, Write, Delete, DeletePreviousVersion, Tag, List, Move, Execute, Ownership, Permissions bool
}
// String produces the SAS permissions string for an Azure Storage blob.
// Call this method to set BlobSignatureValues's Permissions field.
func (p *BlobPermissions) String() string {
var b bytes.Buffer
if p.Read {
b.WriteRune('r')
}
if p.Add {
b.WriteRune('a')
}
if p.Create {
b.WriteRune('c')
}
if p.Write {
b.WriteRune('w')
}
if p.Delete {
b.WriteRune('d')
}
if p.DeletePreviousVersion {
b.WriteRune('x')
}
if p.Tag {
b.WriteRune('t')
}
if p.List {
b.WriteRune('l')
}
if p.Move {
b.WriteRune('m')
}
if p.Execute {
b.WriteRune('e')
}
if p.Ownership {
b.WriteRune('o')
}
if p.Permissions {
b.WriteRune('p')
}
return b.String()
}
// Parse initializes the BlobSASPermissions's fields from a string.
func parseBlobPermissions(s string) (BlobPermissions, error) {
p := BlobPermissions{} // Clear the flags
for _, r := range s {
switch r {
case 'r':
p.Read = true
case 'a':
p.Add = true
case 'c':
p.Create = true
case 'w':
p.Write = true
case 'd':
p.Delete = true
case 'x':
p.DeletePreviousVersion = true
case 't':
p.Tag = true
case 'l':
p.List = true
case 'm':
p.Move = true
case 'e':
p.Execute = true
case 'o':
p.Ownership = true
case 'p':
p.Permissions = true
default:
return BlobPermissions{}, fmt.Errorf("invalid permission: '%v'", r)
}
}
return p, nil
}