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chore: fix 30% startup time hit from userpassword #12769

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Merged
merged 1 commit into from
Mar 27, 2024
Merged

chore: fix 30% startup time hit from userpassword #12769

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17 changes: 14 additions & 3 deletions coderd/userpassword/userpassword.go
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,8 @@ import (
"golang.org/x/crypto/pbkdf2"
"golang.org/x/exp/slices"
"golang.org/x/xerrors"

"github.com/coder/coder/v2/coderd/util/lazy"
)

var (
Expand All @@ -38,8 +40,15 @@ var (
defaultSaltSize = 16

// The simulated hash is used when trying to simulate password checks for
// users that don't exist.
simulatedHash, _ = Hash("hunter2")
// users that don't exist. It's meant to preserve the timing of the hash
// comparison.
simulatedHash = lazy.New(func() string {
h, err := Hash("hunter2")
if err != nil {
panic(err)
}
return h
})
)

// Make password hashing much faster in tests.
Expand All @@ -65,7 +74,9 @@ func init() {
func Compare(hashed string, password string) (bool, error) {
// If the hased password provided is empty, simulate comparing a real hash.
if hashed == "" {
hashed = simulatedHash
// TODO: this seems ripe for creating a vulnerability where
// hunter2 can log into any account.
hashed = simulatedHash.Load()
}

if len(hashed) < hashLength {
Expand Down
28 changes: 28 additions & 0 deletions coderd/util/lazy/value.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,28 @@
// Package lazy provides a lazy value implementation.
// It's useful especially in global variable initialization to avoid
// slowing down the program startup time.
package lazy

import (
"sync"
"sync/atomic"
)

type Value[T any] struct {
once sync.Once
fn func() T
cached atomic.Pointer[T]
}

func (v *Value[T]) Load() T {
v.once.Do(func() {
vv := v.fn()
v.cached.Store(&vv)
})
return *v.cached.Load()
}

// New creates a new lazy value with the given load function.
func New[T any](fn func() T) *Value[T] {
return &Value[T]{fn: fn}
}
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