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DecodeHash fixes #24

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DecodeHash fixes #24

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ef1a6e0
Fail DecodeHash on trailing parameter junk
scop Nov 13, 2023
587f314
Fail DecodeHash on \r or \n in base64 data
scop Nov 13, 2023
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36 changes: 27 additions & 9 deletions argon2id.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,11 +7,13 @@
package argon2id

import (
"bytes"
"crypto/rand"
"crypto/subtle"
"encoding/base64"
"errors"
"fmt"
"io/ioutil"
"runtime"
"strings"

Expand Down Expand Up @@ -148,17 +150,16 @@ func generateRandomBytes(n uint32) ([]byte, error) {
// DecodeHash expects a hash created from this package, and parses it to return the params used to
// create it, as well as the salt and key (password hash).
func DecodeHash(hash string) (params *Params, salt, key []byte, err error) {
vals := strings.Split(hash, "$")
if len(vals) != 6 {
return nil, nil, nil, ErrInvalidHash
}

if vals[1] != "argon2id" {
r := strings.NewReader(hash)

_, err = fmt.Fscanf(r, "$argon2id$")
if err != nil {
return nil, nil, nil, ErrIncompatibleVariant
}

var version int
_, err = fmt.Sscanf(vals[2], "v=%d", &version)
_, err = fmt.Fscanf(r, "v=%d$", &version)
if err != nil {
return nil, nil, nil, err
}
Expand All @@ -167,18 +168,35 @@ func DecodeHash(hash string) (params *Params, salt, key []byte, err error) {
}

params = &Params{}
_, err = fmt.Sscanf(vals[3], "m=%d,t=%d,p=%d", &params.Memory, &params.Iterations, &params.Parallelism)
_, err = fmt.Fscanf(r, "m=%d,t=%d,p=%d$", &params.Memory, &params.Iterations, &params.Parallelism)
if err != nil {
return nil, nil, nil, err
}

rest, err := ioutil.ReadAll(r)
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ioutil is deprecated, could use io.ReadAll if we can assume Go 1.16+. The only info in the package I could locate about the supported version is 1.12 in go.mod.

if err != nil {
return nil, nil, nil, err
}
if bytes.ContainsAny(rest, "\r\n") { // base64 decoder ignores these
return nil, nil, nil, ErrInvalidHash
}

var i int
if i = bytes.IndexByte(rest, '$'); i == -1 {
return nil, nil, nil, ErrInvalidHash
}

b64Enc := base64.RawStdEncoding.Strict()

salt, err = base64.RawStdEncoding.Strict().DecodeString(vals[4])
salt = make([]byte, b64Enc.DecodedLen(i))
_, err = b64Enc.Decode(salt, rest[:i])
if err != nil {
return nil, nil, nil, err
}
params.SaltLength = uint32(len(salt))

key, err = base64.RawStdEncoding.Strict().DecodeString(vals[5])
key = make([]byte, b64Enc.DecodedLen(len(rest)-i-1))
_, err = b64Enc.Decode(key, rest[i+1:])
if err != nil {
return nil, nil, nil, err
}
Expand Down
25 changes: 22 additions & 3 deletions argon2id_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,8 @@ func TestComparePasswordAndHash(t *testing.T) {
}
}

const bugHash = "$argon2id$v=19$m=65536,t=1,p=2$UDk0zEuIzbt0x3bwkf8Bgw$ihSfHWUJpTgDvNWiojrgcN4E0pJdUVmqCEdRZesx9tE"

func TestDecodeHash(t *testing.T) {
hash, err := CreateHash("pa$$word", DefaultParams)
if err != nil {
Expand All @@ -69,6 +71,24 @@ func TestDecodeHash(t *testing.T) {
if *params != *DefaultParams {
t.Fatalf("expected %#v got %#v", *DefaultParams, *params)
}

for _, c := range []string{"v", "m", "t", "p"} {
re := regexp.MustCompile("([$,])(" + c + "=[^$,]+)")
_, _, _, err = DecodeHash(re.ReplaceAllString(bugHash, "$1JUNK+$2"))
if err == nil {
t.Fatalf("leading %s key junk should fail decode", c)
}
_, _, _, err = DecodeHash(re.ReplaceAllString(bugHash, "$1$2+JUNK"))
if err == nil {
t.Fatalf("trailing %s value junk should fail decode", c)
}
}

i := strings.LastIndex(bugHash, "$")
_, _, _, err = DecodeHash(bugHash[:i] + "\r$\n" + bugHash[i+1:])
if err == nil {
t.Fatalf(`\r and \n in base64 data should fail decode`)
}
}

func TestCheckHash(t *testing.T) {
Expand All @@ -90,8 +110,7 @@ func TestCheckHash(t *testing.T) {
}

func TestStrictDecoding(t *testing.T) {
// "bug" valid hash: $argon2id$v=19$m=65536,t=1,p=2$UDk0zEuIzbt0x3bwkf8Bgw$ihSfHWUJpTgDvNWiojrgcN4E0pJdUVmqCEdRZesx9tE
ok, _, err := CheckHash("bug", "$argon2id$v=19$m=65536,t=1,p=2$UDk0zEuIzbt0x3bwkf8Bgw$ihSfHWUJpTgDvNWiojrgcN4E0pJdUVmqCEdRZesx9tE")
ok, _, err := CheckHash("bug", bugHash)
if err != nil {
t.Fatal(err)
}
Expand All @@ -100,7 +119,7 @@ func TestStrictDecoding(t *testing.T) {
}

// changed one last character of the hash
ok, _, err = CheckHash("bug", "$argon2id$v=19$m=65536,t=1,p=2$UDk0zEuIzbt0x3bwkf8Bgw$ihSfHWUJpTgDvNWiojrgcN4E0pJdUVmqCEdRZesx9tF")
ok, _, err = CheckHash("bug", bugHash[:len(bugHash)-1]+"F")
if err == nil {
t.Fatal("Hash validation should fail")
}
Expand Down