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// Copyright (c) 2019, Google Inc.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
package subprocess
import (
"encoding/hex"
"encoding/json"
"fmt"
"strconv"
)
// The following structures reflect the JSON of ACVP HMAC tests. See
// https://pages.nist.gov/ACVP/draft-fussell-acvp-mac.html#name-test-vectors
type hmacTestVectorSet struct {
Groups []hmacTestGroup `json:"testGroups"`
}
type hmacTestGroup struct {
ID uint64 `json:"tgId"`
Type string `json:"testType"`
MsgBits int `json:"msgLen"`
KeyBits int `json:"keyLen"` // maximum possible value is 524288
MACBits int `json:"macLen"` // maximum possible value is 512
Tests []struct {
ID uint64 `json:"tcId"`
KeyHex string `json:"key"`
MsgHex string `json:"msg"`
} `json:"tests"`
}
type hmacTestGroupResponse struct {
ID uint64 `json:"tgId"`
Tests []hmacTestResponse `json:"tests"`
}
type hmacTestResponse struct {
ID uint64 `json:"tcId"`
MACHex string `json:"mac,omitempty"`
}
// hmacPrimitive implements an ACVP algorithm by making requests to the
// subprocess to HMAC strings with the given key.
type hmacPrimitive struct {
// algo is the ACVP name for this algorithm and also the command name
// given to the subprocess to HMAC with this hash function.
algo string
mdLen int // mdLen is the number of bytes of output that the underlying hash produces.
}
// hmac uses the subprocess to compute HMAC and returns the result.
func (h *hmacPrimitive) hmac(msg []byte, key []byte, outBits int, m Transactable) []byte {
if outBits%8 != 0 {
panic("fractional-byte output length requested: " + strconv.Itoa(outBits))
}
outBytes := outBits / 8
result, err := m.Transact(h.algo, 1, msg, key)
if err != nil {
panic("HMAC operation failed: " + err.Error())
}
if l := len(result[0]); l < outBytes {
panic(fmt.Sprintf("HMAC result too short: %d bytes but wanted %d", l, outBytes))
}
return result[0][:outBytes]
}
func (h *hmacPrimitive) Process(vectorSet []byte, m Transactable) (interface{}, error) {
var parsed hmacTestVectorSet
if err := json.Unmarshal(vectorSet, &parsed); err != nil {
return nil, err
}
var ret []hmacTestGroupResponse
// See
// https://pages.nist.gov/ACVP/draft-fussell-acvp-mac.html#name-test-vectors
// for details about the tests.
for _, group := range parsed.Groups {
response := hmacTestGroupResponse{
ID: group.ID,
}
if group.MACBits > h.mdLen*8 {
return nil, fmt.Errorf("test group %d specifies MAC length should be %d, but maximum possible length is %d", group.ID, group.MACBits, h.mdLen*8)
}
for _, test := range group.Tests {
if len(test.MsgHex)*4 != group.MsgBits {
return nil, fmt.Errorf("test case %d/%d contains hex message of length %d but specifies a bit length of %d", group.ID, test.ID, len(test.MsgHex), group.MsgBits)
}
msg, err := hex.DecodeString(test.MsgHex)
if err != nil {
return nil, fmt.Errorf("failed to decode hex in test case %d/%d: %s", group.ID, test.ID, err)
}
if len(test.KeyHex)*4 != group.KeyBits {
return nil, fmt.Errorf("test case %d/%d contains hex key of length %d but specifies a bit length of %d", group.ID, test.ID, len(test.KeyHex), group.KeyBits)
}
key, err := hex.DecodeString(test.KeyHex)
if err != nil {
return nil, fmt.Errorf("failed to decode key in test case %d/%d: %s", group.ID, test.ID, err)
}
// https://pages.nist.gov/ACVP/draft-fussell-acvp-mac.html#name-test-vectors
response.Tests = append(response.Tests, hmacTestResponse{
ID: test.ID,
MACHex: hex.EncodeToString(h.hmac(msg, key, group.MACBits, m)),
})
}
ret = append(ret, response)
}
return ret, nil
}