github.com/minio/console@v1.4.1/pkg/auth/utils/utils.go (about)

     1  // This file is part of MinIO Console Server
     2  // Copyright (c) 2021 MinIO, Inc.
     3  //
     4  // This program is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Affero General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // This program is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    12  // GNU Affero General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Affero General Public License
    15  // along with this program.  If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package utils
    18  
    19  import (
    20  	"crypto/hmac"
    21  	"crypto/rand"
    22  	"crypto/sha256"
    23  	"encoding/base64"
    24  	"io"
    25  	"strings"
    26  )
    27  
    28  // Do not use:
    29  // https://stackoverflow.com/questions/22892120/how-to-generate-a-random-string-of-a-fixed-length-in-go
    30  // It relies on math/rand and therefore not on a cryptographically secure RNG => It must not be used
    31  // for access/secret keys.
    32  
    33  // The alphabet of random character string. Each character must be unique.
    34  //
    35  // The RandomCharString implementation requires that: 256 / len(letters) is a natural numbers.
    36  // For example: 256 / 64 = 4. However, 5 > 256/62 > 4 and therefore we must not use a alphabet
    37  // of 62 characters.
    38  // The reason is that if 256 / len(letters) is not a natural number then certain characters become
    39  // more likely then others.
    40  const letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ012345"
    41  
    42  func RandomCharString(n int) string {
    43  	random := make([]byte, n)
    44  	if _, err := io.ReadFull(rand.Reader, random); err != nil {
    45  		panic(err) // Can only happen if we would run out of entropy.
    46  	}
    47  
    48  	var s strings.Builder
    49  	for _, v := range random {
    50  		j := v % byte(len(letters))
    51  		s.WriteByte(letters[j])
    52  	}
    53  	return s.String()
    54  }
    55  
    56  func ComputeHmac256(message string, key []byte) string {
    57  	h := hmac.New(sha256.New, key)
    58  	h.Write([]byte(message))
    59  	return base64.StdEncoding.EncodeToString(h.Sum(nil))
    60  }