Merge pull request #27 from creachadair/librify
Separate OTP generation into a library
This commit is contained in:
Pierre Carrier
GitHub
commit
61ada0495b
@ -3,4 +3,7 @@ language: go
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go:
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- 1.7
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- 1.8
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- 1.9
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- 1.9
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- "1.10"
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- 1.11
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- 1.12
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79
gauth.go
79
gauth.go
@ -4,72 +4,20 @@ import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"crypto/hmac"
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"crypto/sha1"
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"crypto/sha256"
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"encoding/base32"
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"encoding/csv"
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"fmt"
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"io/ioutil"
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"log"
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"math/big"
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"os/user"
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"path"
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"strings"
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"syscall"
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"time"
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"github.com/pcarrier/gauth/gauth"
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"golang.org/x/crypto/ssh/terminal"
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)
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func TimeStamp() (int64, int) {
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time := time.Now().Unix()
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return time / 30, int(time % 30)
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}
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func normalizeSecret(sec string) string {
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noPadding := strings.ToUpper(strings.Replace(sec, " ", "", -1))
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padLength := 8 - (len(noPadding) % 8)
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if padLength < 8 {
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return noPadding + strings.Repeat("=", padLength)
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}
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return noPadding
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}
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func AuthCode(sec string, ts int64) (string, error) {
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key, err := base32.StdEncoding.DecodeString(sec)
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if err != nil {
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return "", err
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}
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enc := hmac.New(sha1.New, key)
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msg := make([]byte, 8, 8)
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msg[0] = (byte)(ts >> (7 * 8) & 0xff)
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msg[1] = (byte)(ts >> (6 * 8) & 0xff)
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msg[2] = (byte)(ts >> (5 * 8) & 0xff)
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msg[3] = (byte)(ts >> (4 * 8) & 0xff)
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msg[4] = (byte)(ts >> (3 * 8) & 0xff)
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msg[5] = (byte)(ts >> (2 * 8) & 0xff)
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msg[6] = (byte)(ts >> (1 * 8) & 0xff)
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msg[7] = (byte)(ts >> (0 * 8) & 0xff)
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if _, err := enc.Write(msg); err != nil {
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return "", err
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}
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hash := enc.Sum(nil)
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offset := hash[19] & 0x0f
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trunc := hash[offset : offset+4]
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trunc[0] &= 0x7F
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res := new(big.Int).Mod(new(big.Int).SetBytes(trunc), big.NewInt(1000000))
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return fmt.Sprintf("%06d", res), nil
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}
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func authCodeOrDie(sec string, ts int64) string {
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str, e := AuthCode(sec, ts)
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if e != nil {
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log.Fatal(e)
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}
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return str
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}
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func main() {
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user, e := user.Current()
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if e != nil {
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@ -83,7 +31,7 @@ func main() {
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}
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// Support for 'openssl enc -aes-128-cbc -md sha256 -pass pass:'
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if bytes.Compare(cfgContent[:8], []byte{0x53, 0x61, 0x6c, 0x74, 0x65, 0x64, 0x5f, 0x5f}) == 0 {
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if bytes.HasPrefix(cfgContent, []byte("Salted__")) {
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fmt.Printf("Encryption password: ")
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passwd, e := terminal.ReadPassword(int(syscall.Stdin))
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fmt.Printf("\n")
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@ -122,7 +70,7 @@ func main() {
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log.Fatal(e)
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}
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currentTS, progress := TimeStamp()
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currentTS, progress := gauth.IndexNow()
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prevTS := currentTS - 1
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nextTS := currentTS + 1
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@ -150,3 +98,24 @@ func main() {
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func leftPad(s string, padStr string, pLen int) string {
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return strings.Repeat(padStr, pLen) + s
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}
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// normalizeSecret cleans up whitespace and adds any missing padding to sec to
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// use it as an OTP seed.
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func normalizeSecret(sec string) string {
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noPadding := strings.ToUpper(strings.Replace(sec, " ", "", -1))
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padLength := 8 - (len(noPadding) % 8)
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if padLength < 8 {
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return noPadding + strings.Repeat("=", padLength)
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}
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return noPadding
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}
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// authCodeOrDie returns a code for the specified parameters, or aborts if an
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// error occurred while generating the code.
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func authCodeOrDie(sec string, ts int64) string {
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str, e := gauth.Code(sec, ts)
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if e != nil {
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log.Fatal(e)
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}
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return str
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}
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48
gauth/gauth.go
Normal file
48
gauth/gauth.go
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@ -0,0 +1,48 @@
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// Package gauth implements the time-based OTP generation scheme used by Google
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// Authenticator.
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package gauth
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import (
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"crypto/hmac"
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"crypto/sha1"
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"encoding/base32"
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"fmt"
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"math/big"
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"time"
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)
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// IndexNow returns the current 30-second time slice index, and the number of
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// seconds remaining until it ends.
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func IndexNow() (int64, int) {
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time := time.Now().Unix()
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return time / 30, int(time % 30)
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}
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// Code returns the OTP code for the given secret at the specified time slice
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// index. It will report an error if the secret is not valid Base32 or if HMAC
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// generation fails.
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func Code(sec string, ts int64) (string, error) {
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key, err := base32.StdEncoding.DecodeString(sec)
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if err != nil {
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return "", err
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}
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enc := hmac.New(sha1.New, key)
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msg := make([]byte, 8)
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msg[0] = (byte)(ts >> (7 * 8) & 0xff)
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msg[1] = (byte)(ts >> (6 * 8) & 0xff)
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msg[2] = (byte)(ts >> (5 * 8) & 0xff)
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msg[3] = (byte)(ts >> (4 * 8) & 0xff)
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msg[4] = (byte)(ts >> (3 * 8) & 0xff)
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msg[5] = (byte)(ts >> (2 * 8) & 0xff)
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msg[6] = (byte)(ts >> (1 * 8) & 0xff)
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msg[7] = (byte)(ts >> (0 * 8) & 0xff)
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if _, err := enc.Write(msg); err != nil {
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return "", err
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}
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hash := enc.Sum(nil)
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offset := hash[19] & 0x0f
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trunc := hash[offset : offset+4]
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trunc[0] &= 0x7F
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res := new(big.Int).Mod(new(big.Int).SetBytes(trunc), big.NewInt(1000000))
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return fmt.Sprintf("%06d", res), nil
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}
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30
gauth/gauth_test.go
Normal file
30
gauth/gauth_test.go
Normal file
@ -0,0 +1,30 @@
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package gauth_test
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import (
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"testing"
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"github.com/pcarrier/gauth/gauth"
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)
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func TestCode(t *testing.T) {
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tests := []struct {
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secret string
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index int64
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want string
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fail bool
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}{
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// Manually verified with the Google authenticator app.
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{"ABCDEFGH", 51790421, "305441", false},
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// Invalid Base32 input for the secret.
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{"blargh!", 123, "", true},
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}
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for _, test := range tests {
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got, err := gauth.Code(test.secret, test.index)
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if err != nil && !test.fail {
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t.Errorf("Code(%q, %d): unexpected error: %v", test.secret, test.index, err)
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} else if got != test.want {
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t.Errorf("Code(%q, %d): got %q, want %q", test.secret, test.index, got, test.want)
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}
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}
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}
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8
go.mod
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8
go.mod
Normal file
@ -0,0 +1,8 @@
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module github.com/pcarrier/gauth
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go 1.12
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require (
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golang.org/x/crypto v0.0.0-20190530122614-20be4c3c3ed5
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golang.org/x/sys v0.0.0-20190531175056-4c3a928424d2 // indirect
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)
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10
go.sum
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10
go.sum
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@ -0,0 +1,10 @@
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golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
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golang.org/x/crypto v0.0.0-20190530122614-20be4c3c3ed5 h1:8dUaAV7K4uHsF56JQWkprecIQKdPHtR9jCHF5nB8uzc=
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golang.org/x/crypto v0.0.0-20190530122614-20be4c3c3ed5/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
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golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
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golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a h1:1BGLXjeY4akVXGgbC9HugT3Jv3hCI0z56oJR5vAMgBU=
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golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
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golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
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golang.org/x/sys v0.0.0-20190531175056-4c3a928424d2 h1:T5DasATyLQfmbTpfEXx/IOL9vfjzW6up+ZDkmHvIf2s=
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golang.org/x/sys v0.0.0-20190531175056-4c3a928424d2/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
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golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
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