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// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package piv
import (
"errors"
"fmt"
)
type scErr struct {
// rc holds the return code for a given call.
rc int64
}
func (e *scErr) Error() string {
if msg, ok := pcscErrMsgs[e.rc]; ok {
return msg
}
return fmt.Sprintf("unknown pcsc return code 0x%08x", e.rc)
}
// AuthErr is an error indicating an authentication error occurred (wrong PIN or blocked).
type AuthErr struct {
// Retries is the number of retries remaining if this error resulted from a retriable
// authentication attempt. If the authentication method is blocked or does not support
// retries, this will be 0.
Retries int
}
func (v AuthErr) Error() string {
r := "retries"
if v.Retries == 1 {
r = "retry"
}
return fmt.Sprintf("verification failed (%d %s remaining)", v.Retries, r)
}
// ErrNotFound is returned when the requested object on the smart card is not found.
var ErrNotFound = errors.New("data object or application not found")
// apduErr is an error interacting with the PIV application on the smart card.
// This error may wrap more accessible errors, like ErrNotFound or an instance
// of AuthErr, so callers are encouraged to use errors.Is and errors.As for
// these common cases.
type apduErr struct {
sw1 byte
sw2 byte
}
// Status returns the Status Word returned by the card command.
func (a *apduErr) Status() uint16 {
return uint16(a.sw1)<<8 | uint16(a.sw2)
}
func (a *apduErr) Error() string {
var msg string
if u := a.Unwrap(); u != nil {
msg = u.Error()
}
switch a.Status() {
// 0x6300 is "verification failed", represented as AuthErr{0}
// 0x63Cn is "verification failed" with retry, represented as AuthErr{n}
case 0x6882:
msg = "secure messaging not supported"
case 0x6982:
msg = "security status not satisfied"
case 0x6983:
// This will also be AuthErr{0} but we override the message here
// so that it's clear that the reason is a block rather than a simple
// failed authentication verification.
msg = "authentication method blocked"
case 0x6987:
msg = "expected secure messaging data objects are missing"
case 0x6988:
msg = "secure messaging data objects are incorrect"
case 0x6a80:
msg = "incorrect parameter in command data field"
case 0x6a81:
msg = "function not supported"
// 0x6a82 is "data object or application not found" aka ErrNotFound
case 0x6a84:
msg = "not enough memory"
case 0x6a86:
msg = "incorrect parameter in P1 or P2"
case 0x6a88:
msg = "referenced data or reference data not found"
}
if msg != "" {
msg = ": " + msg
}
return fmt.Sprintf("smart card error %04x%s", a.Status(), msg)
}
// Unwrap retrieves an accessible error type, if able.
func (a *apduErr) Unwrap() error {
st := a.Status()
switch {
case st == 0x6a82:
return ErrNotFound
case st == 0x6300:
return AuthErr{0}
case st == 0x6983:
return AuthErr{0}
case st&0xfff0 == 0x63c0:
return AuthErr{int(st & 0xf)}
case st&0xfff0 == 0x6300:
// Older YubiKeys sometimes return sw1=0x63 and sw2=0x0N to indicate the
// number of retries. This isn't spec compliant, but support it anyway.
//
// https://github.com/go-piv/piv-go/issues/60
return AuthErr{int(st & 0xf)}
}
return nil
}
type apdu struct {
instruction byte
param1 byte
param2 byte
data []byte
}
func (t *scTx) Transmit(d apdu) ([]byte, error) {
data := d.data
var resp []byte
const maxAPDUDataSize = 0xff
for len(data) > maxAPDUDataSize {
req := make([]byte, 5+maxAPDUDataSize)
req[0] = 0x10 // ISO/IEC 7816-4 5.1.1
req[1] = d.instruction
req[2] = d.param1
req[3] = d.param2
req[4] = 0xff
copy(req[5:], data[:maxAPDUDataSize])
data = data[maxAPDUDataSize:]
_, r, err := t.transmit(req)
if err != nil {
return nil, fmt.Errorf("transmitting initial chunk %w", err)
}
resp = append(resp, r...)
}
req := make([]byte, 5+len(data))
req[1] = d.instruction
req[2] = d.param1
req[3] = d.param2
req[4] = byte(len(data))
copy(req[5:], data)
hasMore, r, err := t.transmit(req)
if err != nil {
return nil, err
}
resp = append(resp, r...)
for hasMore {
req := make([]byte, 5)
req[1] = insGetResponseAPDU
var r []byte
hasMore, r, err = t.transmit(req)
if err != nil {
return nil, fmt.Errorf("reading further response: %w", err)
}
resp = append(resp, r...)
}
return resp, nil
}
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