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package restserver
import (
"crypto/subtle"
"fmt"
"sync"
"time"
"github.com/go-ldap/ldap/v3"
"github.com/minio/sha256-simd"
)
type Ldap struct {
// Addr is the LDAP server URL.
// Passed to ldap.DialURL.
//
// The following schemas are supported: ldap://, ldaps://, ldapi://, and cldap://.
Addr string
// Uid is the LDAP attribute that maps to the username that users use to sign in.
Uid string
// Base where to search for users.
Base string
// Mutex for cache.
mtx sync.Mutex
// A cache for verified users to prevent repeatedly verifying the same auth credentials.
cache map[string]cacheEntry
}
func NewLdap(addr, uid, base string) *Ldap {
return &Ldap{
Addr: addr,
Uid: uid,
Base: base,
mtx: sync.Mutex{},
cache: make(map[string]cacheEntry),
}
}
func (l *Ldap) validateRemote(user, password string) (bool, error) {
// Connect to LDAP server
conn, err := ldap.DialURL(l.Addr)
if err != nil {
return false, fmt.Errorf("failed to connect to LDAP server: %w", err)
}
defer func(conn *ldap.Conn) {
_ = conn.Close()
}(conn)
// Search for user
searchReq := ldap.NewSearchRequest(
l.Base,
ldap.ScopeWholeSubtree,
ldap.NeverDerefAliases,
0,
0,
false,
fmt.Sprintf("(%s=%s)", l.Uid, user),
[]string{"dn"},
nil,
)
sr, err := conn.Search(searchReq)
if err != nil {
return false, fmt.Errorf("LDAP search failed: %w", err)
}
if len(sr.Entries) != 1 {
return false, fmt.Errorf("expected exactly one LDAP entry for '%s', got %d", user, len(sr.Entries))
}
userDN := sr.Entries[0].DN
// Bind to user
err = conn.Bind(userDN, password)
return err == nil, nil
}
func (l *Ldap) Validate(user, password string) (bool, error) {
hash := sha256.New()
// hash.Write can never fail
_, _ = hash.Write([]byte(user))
_, _ = hash.Write([]byte(":"))
_, _ = hash.Write([]byte(password))
l.mtx.Lock()
entry, cacheExists := l.cache[user]
l.mtx.Unlock()
if cacheExists && subtle.ConstantTimeCompare(entry.verifier, hash.Sum(nil)) == 1 {
l.mtx.Lock()
// extend cache entry
l.cache[user] = cacheEntry{
verifier: entry.verifier,
expiry: time.Now().Add(PasswordCacheDuration),
}
l.mtx.Unlock()
return true, nil
}
isValid, err := l.validateRemote(user, password)
if err != nil {
return false, err
}
if !isValid {
return false, nil
}
l.mtx.Lock()
l.cache[user] = cacheEntry{
verifier: hash.Sum(nil),
expiry: time.Now().Add(PasswordCacheDuration),
}
l.mtx.Unlock()
return true, nil
}
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