github.com/kubiko/snapd@v0.0.0-20201013125620-d4f3094d9ddf/asserts/digest.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2015 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package asserts
    21  
    22  import (
    23  	"crypto"
    24  	"encoding/base64"
    25  	"fmt"
    26  )
    27  
    28  // EncodeDigest encodes the digest from hash algorithm to be put in an assertion header.
    29  func EncodeDigest(hash crypto.Hash, hashDigest []byte) (string, error) {
    30  	algo := ""
    31  	switch hash {
    32  	case crypto.SHA512:
    33  		algo = "sha512"
    34  	case crypto.SHA3_384:
    35  		algo = "sha3-384"
    36  	default:
    37  		return "", fmt.Errorf("unsupported hash")
    38  	}
    39  	if len(hashDigest) != hash.Size() {
    40  		return "", fmt.Errorf("hash digest by %s should be %d bytes", algo, hash.Size())
    41  	}
    42  	return base64.RawURLEncoding.EncodeToString(hashDigest), nil
    43  }