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sspi.go
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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build windows
package sspi
import (
"fmt"
"syscall"
"time"
"unsafe"
)
// TODO: add documentation
type PackageInfo struct {
Capabilities uint32
Version uint16
RPCID uint16
MaxToken uint32
Name string
Comment string
}
func QueryPackageInfo(pkgname string) (*PackageInfo, error) {
name, err := syscall.UTF16PtrFromString(pkgname)
if err != nil {
return nil, err
}
var pi *SecPkgInfo
ret := QuerySecurityPackageInfo(name, &pi)
if ret != SEC_E_OK {
return nil, ret
}
defer FreeContextBuffer((*byte)(unsafe.Pointer(pi)))
return &PackageInfo{
Capabilities: pi.Capabilities,
Version: pi.Version,
RPCID: pi.RPCID,
MaxToken: pi.MaxToken,
Name: syscall.UTF16ToString((*[2 << 12]uint16)(unsafe.Pointer(pi.Name))[:]),
Comment: syscall.UTF16ToString((*[2 << 12]uint16)(unsafe.Pointer(pi.Comment))[:]),
}, nil
}
type Credentials struct {
Handle CredHandle
expiry syscall.Filetime
}
// AcquireCredentials calls the windows AcquireCredentialsHandle function and
// returns Credentials containing a security handle that can be used for
// InitializeSecurityContext or AcceptSecurityContext operations.
// As a special case, passing an empty string as the principal parameter will
// pass a null string to the underlying function.
func AcquireCredentials(principal string, pkgname string, creduse uint32, authdata *byte) (*Credentials, error) {
var principalName *uint16
if principal != "" {
var err error
principalName, err = syscall.UTF16PtrFromString(principal)
if err != nil {
return nil, err
}
}
name, err := syscall.UTF16PtrFromString(pkgname)
if err != nil {
return nil, err
}
var c Credentials
ret := AcquireCredentialsHandle(principalName, name, creduse, nil, authdata, 0, 0, &c.Handle, &c.expiry)
if ret != SEC_E_OK {
return nil, ret
}
return &c, nil
}
func (c *Credentials) Release() error {
if c == nil {
return nil
}
ret := FreeCredentialsHandle(&c.Handle)
if ret != SEC_E_OK {
return ret
}
return nil
}
func (c *Credentials) Expiry() time.Time {
return time.Unix(0, c.expiry.Nanoseconds())
}
// TODO: add functions to display and manage RequestedFlags and EstablishedFlags fields.
// TODO: maybe get rid of RequestedFlags and EstablishedFlags fields, and replace them with input parameter for New...Context and return value of Update (instead of current bool parameter).
type updateFunc func(c *Context, targname *uint16, h, newh *CtxtHandle, out, in *SecBufferDesc) syscall.Errno
type Context struct {
Cred *Credentials
Handle *CtxtHandle
handle CtxtHandle
updFn updateFunc
expiry syscall.Filetime
RequestedFlags uint32
EstablishedFlags uint32
}
func NewClientContext(cred *Credentials, flags uint32) *Context {
return &Context{
Cred: cred,
updFn: initialize,
RequestedFlags: flags,
}
}
func NewServerContext(cred *Credentials, flags uint32) *Context {
return &Context{
Cred: cred,
updFn: accept,
RequestedFlags: flags,
}
}
func initialize(c *Context, targname *uint16, h, newh *CtxtHandle, out, in *SecBufferDesc) syscall.Errno {
return InitializeSecurityContext(&c.Cred.Handle, h, targname, c.RequestedFlags,
0, SECURITY_NATIVE_DREP, in, 0, newh, out, &c.EstablishedFlags, &c.expiry)
}
func accept(c *Context, targname *uint16, h, newh *CtxtHandle, out, in *SecBufferDesc) syscall.Errno {
return AcceptSecurityContext(&c.Cred.Handle, h, in, c.RequestedFlags,
SECURITY_NATIVE_DREP, newh, out, &c.EstablishedFlags, &c.expiry)
}
func (c *Context) Update(targname *uint16, out, in *SecBufferDesc) syscall.Errno {
h := c.Handle
if c.Handle == nil {
c.Handle = &c.handle
}
return c.updFn(c, targname, h, c.Handle, out, in)
}
func (c *Context) Release() error {
if c == nil {
return nil
}
ret := DeleteSecurityContext(c.Handle)
if ret != SEC_E_OK {
return ret
}
return nil
}
func (c *Context) Expiry() time.Time {
return time.Unix(0, c.expiry.Nanoseconds())
}
// TODO: add comment to function doco that this "impersonation" is applied to current OS thread.
func (c *Context) ImpersonateUser() error {
ret := ImpersonateSecurityContext(c.Handle)
if ret != SEC_E_OK {
return ret
}
return nil
}
func (c *Context) RevertToSelf() error {
ret := RevertSecurityContext(c.Handle)
if ret != SEC_E_OK {
return ret
}
return nil
}
// Sizes queries the context for the sizes used in per-message functions.
// It returns the maximum token size used in authentication exchanges, the
// maximum signature size, the preferred integral size of messages, the
// size of any security trailer, and any error.
func (c *Context) Sizes() (uint32, uint32, uint32, uint32, error) {
var s _SecPkgContext_Sizes
ret := QueryContextAttributes(c.Handle, _SECPKG_ATTR_SIZES, (*byte)(unsafe.Pointer(&s)))
if ret != SEC_E_OK {
return 0, 0, 0, 0, ret
}
return s.MaxToken, s.MaxSignature, s.BlockSize, s.SecurityTrailer, nil
}
// VerifyFlags determines if all flags used to construct the context
// were honored (see NewClientContext). It should be called after c.Update.
func (c *Context) VerifyFlags() error {
return c.VerifySelectiveFlags(c.RequestedFlags)
}
// VerifySelectiveFlags determines if the given flags were honored (see NewClientContext).
// It should be called after c.Update.
func (c *Context) VerifySelectiveFlags(flags uint32) error {
if valid, missing, extra := verifySelectiveFlags(flags, c.RequestedFlags); !valid {
return fmt.Errorf("sspi: invalid flags check: desired=%b requested=%b missing=%b extra=%b", flags, c.RequestedFlags, missing, extra)
}
if valid, missing, extra := verifySelectiveFlags(flags, c.EstablishedFlags); !valid {
return fmt.Errorf("sspi: invalid flags: desired=%b established=%b missing=%b extra=%b", flags, c.EstablishedFlags, missing, extra)
}
return nil
}
// verifySelectiveFlags determines if all bits requested in flags are set in establishedFlags.
// missing represents the bits set in flags that are not set in establishedFlags.
// extra represents the bits set in establishedFlags that are not set in flags.
// valid is true and missing is zero when establishedFlags has all of the requested flags.
func verifySelectiveFlags(flags, establishedFlags uint32) (valid bool, missing, extra uint32) {
missing = flags&establishedFlags ^ flags
extra = flags | establishedFlags ^ flags
valid = missing == 0
return valid, missing, extra
}
// NewSecBufferDesc returns an initialized SecBufferDesc describing the
// provided SecBuffer.
func NewSecBufferDesc(b []SecBuffer) *SecBufferDesc {
return &SecBufferDesc{
Version: SECBUFFER_VERSION,
BuffersCount: uint32(len(b)),
Buffers: &b[0],
}
}