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package azblob
import (
"bytes"
"fmt"
"strings"
"time"
)
// BlobSASSignatureValues is used to generate a Shared Access Signature (SAS) for an Azure Storage container or blob.
type BlobSASSignatureValues struct {
Version string `param:"sv"` // If not specified, this defaults to SASVersion
Protocol SASProtocol `param:"spr"` // See the SASProtocol* constants
StartTime time.Time `param:"st"` // Not specified if IsZero
ExpiryTime time.Time `param:"se"` // Not specified if IsZero
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
CacheControl string // rscc
ContentDisposition string // rscd
ContentEncoding string // rsce
ContentLanguage string // rscl
ContentType string // rsct
}
// NewSASQueryParameters uses an account's shared key credential to sign this signature values to produce
// the proper SAS query parameters.
func (v BlobSASSignatureValues) NewSASQueryParameters(sharedKeyCredential *SharedKeyCredential) SASQueryParameters {
if sharedKeyCredential == nil {
panic("sharedKeyCredential can't be nil")
}
resource := "c"
if v.BlobName == "" {
// Make sure the permission characters are in the correct order
perms := &ContainerSASPermissions{}
if err := perms.Parse(v.Permissions); err != nil {
panic(err)
}
v.Permissions = perms.String()
} else {
resource = "b"
// Make sure the permission characters are in the correct order
perms := &BlobSASPermissions{}
if err := perms.Parse(v.Permissions); err != nil {
panic(err)
}
v.Permissions = perms.String()
}
if v.Version == "" {
v.Version = SASVersion
}
startTime, expiryTime := FormatTimesForSASSigning(v.StartTime, v.ExpiryTime)
// 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.Identifier,
v.IPRange.String(),
string(v.Protocol),
v.Version,
v.CacheControl, // rscc
v.ContentDisposition, // rscd
v.ContentEncoding, // rsce
v.ContentLanguage, // rscl
v.ContentType}, // rsct
"\n")
signature := sharedKeyCredential.ComputeHMACSHA256(stringToSign)
p := SASQueryParameters{
// 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,
// Calculated SAS signature
signature: signature,
}
return p
}
// getCanonicalName computes the canonical name for a container or blob resource for SAS signing.
func getCanonicalName(account string, containerName string, blobName 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))
}
return strings.Join(elements, "")
}
// The ContainerSASPermissions 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.
type ContainerSASPermissions struct {
Read, Add, Create, Write, Delete, List bool
}
// String produces the SAS permissions string for an Azure Storage container.
// Call this method to set BlobSASSignatureValues's Permissions field.
func (p ContainerSASPermissions) 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.List {
b.WriteRune('l')
}
return b.String()
}
// Parse initializes the ContainerSASPermissions's fields from a string.
func (p *ContainerSASPermissions) Parse(s string) error {
*p = ContainerSASPermissions{} // 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 'l':
p.List = true
default:
return fmt.Errorf("Invalid permission: '%v'", r)
}
}
return nil
}
// The BlobSASPermissions 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 BlobSASPermissions struct{ Read, Add, Create, Write, Delete bool }
// String produces the SAS permissions string for an Azure Storage blob.
// Call this method to set BlobSASSignatureValues's Permissions field.
func (p BlobSASPermissions) 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')
}
return b.String()
}
// Parse initializes the BlobSASPermissions's fields from a string.
func (p *BlobSASPermissions) Parse(s string) error {
*p = BlobSASPermissions{} // 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
default:
return fmt.Errorf("Invalid permission: '%v'", r)
}
}
return nil
}
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