Kyle Isom
115f23a3ea
Vendor dependencies and expose control program binaries via nix build. Uses nixpkgs-unstable for Go 1.26 support. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
117 lines
4.2 KiB
Go
117 lines
4.2 KiB
Go
// Copyright (c) 2018, Google LLC All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package tpm2
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import (
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"crypto"
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"crypto/hmac"
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"encoding/binary"
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"hash"
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)
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// KDFa implements TPM 2.0's default key derivation function, as defined in
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// section 11.4.9.2 of the TPM revision 2 specification part 1.
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// See: https://trustedcomputinggroup.org/resource/tpm-library-specification/
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// The key & label parameters must not be zero length.
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// The label parameter is a non-null-terminated string.
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// The contextU & contextV parameters are optional.
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// Deprecated: Use KDFaHash.
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func KDFa(hashAlg Algorithm, key []byte, label string, contextU, contextV []byte, bits int) ([]byte, error) {
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h, err := hashAlg.Hash()
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if err != nil {
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return nil, err
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}
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return KDFaHash(h, key, label, contextU, contextV, bits), nil
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}
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// KDFe implements TPM 2.0's ECDH key derivation function, as defined in
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// section 11.4.9.3 of the TPM revision 2 specification part 1.
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// See: https://trustedcomputinggroup.org/resource/tpm-library-specification/
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// The z parameter is the x coordinate of one party's private ECC key multiplied
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// by the other party's public ECC point.
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// The use parameter is a non-null-terminated string.
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// The partyUInfo and partyVInfo are the x coordinates of the initiator's and
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// Deprecated: Use KDFeHash.
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func KDFe(hashAlg Algorithm, z []byte, use string, partyUInfo, partyVInfo []byte, bits int) ([]byte, error) {
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h, err := hashAlg.Hash()
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if err != nil {
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return nil, err
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}
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return KDFeHash(h, z, use, partyUInfo, partyVInfo, bits), nil
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}
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// KDFaHash implements TPM 2.0's default key derivation function, as defined in
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// section 11.4.9.2 of the TPM revision 2 specification part 1.
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// See: https://trustedcomputinggroup.org/resource/tpm-library-specification/
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// The key & label parameters must not be zero length.
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// The label parameter is a non-null-terminated string.
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// The contextU & contextV parameters are optional.
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func KDFaHash(h crypto.Hash, key []byte, label string, contextU, contextV []byte, bits int) []byte {
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mac := hmac.New(h.New, key)
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out := kdf(mac, bits, func() {
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mac.Write([]byte(label))
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mac.Write([]byte{0}) // Terminating null character for C-string.
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mac.Write(contextU)
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mac.Write(contextV)
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binary.Write(mac, binary.BigEndian, uint32(bits))
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})
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return out
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}
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// KDFeHash implements TPM 2.0's ECDH key derivation function, as defined in
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// section 11.4.9.3 of the TPM revision 2 specification part 1.
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// See: https://trustedcomputinggroup.org/resource/tpm-library-specification/
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// The z parameter is the x coordinate of one party's private ECC key multiplied
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// by the other party's public ECC point.
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// The use parameter is a non-null-terminated string.
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// The partyUInfo and partyVInfo are the x coordinates of the initiator's and
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// the responder's ECC points, respectively.
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func KDFeHash(h crypto.Hash, z []byte, use string, partyUInfo, partyVInfo []byte, bits int) []byte {
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hash := h.New()
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out := kdf(hash, bits, func() {
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hash.Write(z)
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hash.Write([]byte(use))
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hash.Write([]byte{0}) // Terminating null character for C-string.
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hash.Write(partyUInfo)
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hash.Write(partyVInfo)
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})
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return out
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}
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func kdf(h hash.Hash, bits int, update func()) []byte {
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bytes := (bits + 7) / 8
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out := []byte{}
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for counter := 1; len(out) < bytes; counter++ {
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h.Reset()
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binary.Write(h, binary.BigEndian, uint32(counter))
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update()
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out = h.Sum(out)
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}
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// out's length is a multiple of hash size, so there will be excess
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// bytes if bytes isn't a multiple of hash size.
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out = out[:bytes]
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// As mentioned in the KDFa and KDFe specs mentioned above,
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// the unused bits of the most significant octet are masked off.
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if maskBits := uint8(bits % 8); maskBits > 0 {
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out[0] &= (1 << maskBits) - 1
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}
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return out
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}
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