github.com/iDigitalFlame/xmt@v0.5.4/util/crypt/crypt.go (about)

     1  //go:build crypt
     2  // +build crypt
     3  
     4  // Copyright (C) 2020 - 2023 iDigitalFlame
     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 as published by
     8  // the Free Software Foundation, either version 3 of the License, or
     9  // any later version.
    10  //
    11  // This program is distributed in the hope that it will be useful,
    12  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    13  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    14  // GNU General Public License for more details.
    15  //
    16  // You should have received a copy of the GNU General Public License
    17  // along with this program.  If not, see <https://www.gnu.org/licenses/>.
    18  //
    19  
    20  // Package crypt is a builtin package that provides compile-time encoded string
    21  // values to be decoded and used when first starting up.
    22  //
    23  // This package should only be used with the "crypt" tag, which is auto compiled
    24  // during build.
    25  package crypt
    26  
    27  import (
    28  	"encoding/base64"
    29  	"os"
    30  
    31  	"github.com/iDigitalFlame/xmt/data/crypto/subtle"
    32  	"github.com/iDigitalFlame/xmt/util/xerr"
    33  )
    34  
    35  const cryptMax = 0xFF
    36  
    37  var (
    38  	key     string
    39  	values  [cryptMax]string
    40  	payload string
    41  )
    42  
    43  func init() {
    44  	if len(payload) == 0 || len(key) == 0 {
    45  		if xerr.ExtendedInfo {
    46  			panic("crypt: no data supplied during build")
    47  		}
    48  		os.Exit(2)
    49  	}
    50  	var (
    51  		b      = make([]byte, base64.URLEncoding.DecodedLen(len(payload)))
    52  		v, err = base64.URLEncoding.Decode(b, []byte(payload))
    53  	)
    54  	if err != nil || len(b) == 0 || v == 0 {
    55  		if xerr.ExtendedInfo {
    56  			panic("crypt: cannot read supplied data")
    57  		}
    58  		os.Exit(2)
    59  	}
    60  	var (
    61  		k = make([]byte, base64.URLEncoding.DecodedLen(len(key)))
    62  		c int
    63  	)
    64  	if c, err = base64.URLEncoding.Decode(k, []byte(key)); err != nil || len(k) == 0 || c == 0 {
    65  		if xerr.ExtendedInfo {
    66  			panic("crypt: empty or invalid crypt encoded data")
    67  		}
    68  		os.Exit(2)
    69  	}
    70  	subtle.XorOp(b[:v], k[:c])
    71  	for s, e, n := 0, 0, 0; e < v && n < cryptMax; e++ {
    72  		if b[e] != 0 {
    73  			continue
    74  		}
    75  		if e-s > 0 {
    76  			values[n] = string(b[s:e])
    77  		}
    78  		s, n = e+1, n+1
    79  	}
    80  	key, payload = "", ""
    81  }
    82  
    83  // Get returns the crypt value at the provided string index.
    84  func Get(i uint8) string {
    85  	return values[i]
    86  }