Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Store hashed token in DB #707

Draft
wants to merge 1 commit into
base: master
Choose a base branch
from
Draft

Store hashed token in DB #707

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
64 changes: 64 additions & 0 deletions auth/token.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,13 @@

import (
"crypto/rand"
"crypto/sha256"
"encoding/hex"
"errors"
"fmt"
"io"
"math/big"
"strings"
)

var (
Expand All @@ -24,6 +30,64 @@
return int(res.Int64())
}

// Convert a Token to its hashed representation.
func HashToken(s string, salt []byte) (string, error) {
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Any reason not using bcrypt like we do for hashing passwords?

Copy link
Member Author

@eternal-flame-AD eternal-flame-AD Oct 23, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

It's too expensive and poses a DoS concern.

Tokens are guaranteed to be pseudorandom and have enough entropy, so many of the mitigations by KDFs like bcrypt is not required. The attacker will need to enumerate every possible key to find the result which is usually not true for user-chosen passwords.

Theoretically you can do a bloom filter with a salt or something ... but it is too much effort for the unlikely scenario this original reported attack will have sufficient preconditions to be exploited and not enough preconditions such that the attacker gain no additional practical advantage that they do not already automatically have.

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

It's too expensive and poses a DoS concern.

we could use a low strength / iteration count. The big benefit I see we have a prefix we can check if the token is already hashed $2a$ and the salt is already built in. Less code we have to write.

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I don't think we need to salt at all after a second thought. See #707 (comment). We need constant time lookup ourselves. Using any individualized salting (built-in to bcrypt or custom rolled) make this impossible.

saltHex := fmt.Sprintf("%x", salt)
sha := sha256.New()
_, err := sha.Write(salt)
if err != nil {
return "", err
}
_, err = sha.Write([]byte(s))
if err != nil {
return "", err
}
hashed := fmt.Sprintf("%x", sha.Sum(nil))
return fmt.Sprintf("%s$%s", saltHex, hashed), nil
}

// CompareToken compares a token with a hashed representation, optionally upgrading the hash if necessary.
func CompareToken(s string, hashed string) (bool, *string, error) {

Check failure on line 50 in auth/token.go

View workflow job for this annotation

GitHub Actions / gotify 

File is not `gofumpt`-ed with `-extra` (gofumpt)

Check failure on line 50 in auth/token.go

View workflow job for this annotation

GitHub Actions / gotify 

File is not `gofumpt`-ed with `-extra` (gofumpt)
if len(s) != randomTokenLength+1 /* prefix */ {
return false, nil, errors.New("invalid token length")
}

split := strings.SplitN(hashed, "$", 2)

// determine if we need to upgrade the hash
if len(split) == 1 {
match := s == hashed
if match {
var salt [16]byte
_, err := io.ReadFull(randReader, salt[:])
if err != nil {
return false, nil, err
}
hashed, err := HashToken(s, salt[:])
if err != nil {
return false, nil, err
}
return true, &hashed, nil
} else {
return false, nil, nil
}
}

if len(split) == 2 {
salt, err := hex.DecodeString(split[0])
if err != nil {
return false, nil, err
}
inputHashed, err := HashToken(s, salt)
if err != nil {
return false, nil, err
}
return inputHashed == hashed, nil, nil
}

return false, nil, errors.New("invalid hash format")
}

// GenerateNotExistingToken receives a token generation func and a func to check whether the token exists, returns a unique token.
func GenerateNotExistingToken(generateToken func() string, tokenExists func(token string) bool) string {
for {
Expand Down
40 changes: 40 additions & 0 deletions auth/token_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,46 @@ func TestTokenHavePrefix(t *testing.T) {
}
}

func TestHashTokenStable(t *testing.T) {
salt1 := []byte("salt")
salt2 := []byte("pepper")
seen := make(map[string]bool)
for _, plain := range []string{"", "a", "b", "c", "a\x00", "a\n"} {
hash1, err := HashToken(plain, salt1)
assert.NoError(t, err)
hash1Again, err := HashToken(plain, salt1)
assert.NoError(t, err)
assert.Equal(t, hash1, hash1Again)
hash2, err := HashToken(plain, salt2)
assert.NoError(t, err)
hash2Again, err := HashToken(plain, salt2)
assert.NoError(t, err)
assert.Equal(t, hash2, hash2Again)

assert.NotEqual(t, hash1, hash2)
assert.False(t, seen[hash1])
assert.False(t, seen[hash2])
seen[hash1] = true
seen[hash2] = true
}
}

func TestCompareToken(t *testing.T) {
salt := []byte("salt")
tokenPlain := GenerateApplicationToken()
hashed, err := HashToken(tokenPlain, salt)
assert.NoError(t, err)
cmpPlain, upgPlain, err := CompareToken(tokenPlain, tokenPlain)
assert.NoError(t, err)
assert.True(t, cmpPlain)
assert.NotEmpty(t, *upgPlain)

cmpHashed, upgHashed, err := CompareToken(tokenPlain, hashed)
assert.NoError(t, err)
assert.True(t, cmpHashed)
assert.Nil(t, upgHashed)
}

func TestGenerateNotExistingToken(t *testing.T) {
count := 5
token := GenerateNotExistingToken(func() string {
Expand Down
Loading