VAULT-13614 Support SCRAM-SHA-256 encrypted passwords for PostgreSQL (#19616)

plugins/database/postgresql/scram/scram.go

@@ -0,0 +1,86 @@
+package scram
+
+//
+// @see https://github.com/postgres/postgres/blob/c30f54ad732ca5c8762bb68bbe0f51de9137dd72/src/interfaces/libpq/fe-auth.c#L1167-L1285
+// @see https://github.com/postgres/postgres/blob/e6bdfd9700ebfc7df811c97c2fc46d7e94e329a2/src/interfaces/libpq/fe-auth-scram.c#L868-L905
+// @see https://github.com/postgres/postgres/blob/c30f54ad732ca5c8762bb68bbe0f51de9137dd72/src/port/pg_strong_random.c#L66-L96
+// @see https://github.com/postgres/postgres/blob/e6bdfd9700ebfc7df811c97c2fc46d7e94e329a2/src/common/scram-common.c#L160-L274
+// @see https://github.com/postgres/postgres/blob/e6bdfd9700ebfc7df811c97c2fc46d7e94e329a2/src/common/scram-common.c#L27-L85
+
+// Implementation from https://github.com/supercaracal/scram-sha-256/blob/d3c05cd927770a11c6e12de3e3a99c3446a1f78d/main.go
+import (
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/pbkdf2"
+)
+
+const (
+	// @see https://github.com/postgres/postgres/blob/e6bdfd9700ebfc7df811c97c2fc46d7e94e329a2/src/include/common/scram-common.h#L36-L41
+	saltSize = 16
+
+	// @see https://github.com/postgres/postgres/blob/c30f54ad732ca5c8762bb68bbe0f51de9137dd72/src/include/common/sha2.h#L22
+	digestLen = 32
+
+	// @see https://github.com/postgres/postgres/blob/e6bdfd9700ebfc7df811c97c2fc46d7e94e329a2/src/include/common/scram-common.h#L43-L47
+	iterationCnt = 4096
+)
+
+var (
+	clientRawKey = []byte("Client Key")
+	serverRawKey = []byte("Server Key")
+)
+
+func genSalt(size int) ([]byte, error) {
+	salt := make([]byte, size)
+	if _, err := io.ReadFull(rand.Reader, salt); err != nil {
+		return nil, err
+	}
+	return salt, nil
+}
+
+func encodeB64(src []byte) (dst []byte) {
+	dst = make([]byte, base64.StdEncoding.EncodedLen(len(src)))
+	base64.StdEncoding.Encode(dst, src)
+	return
+}
+
+func getHMACSum(key, msg []byte) []byte {
+	h := hmac.New(sha256.New, key)
+	_, _ = h.Write(msg)
+	return h.Sum(nil)
+}
+
+func getSHA256Sum(key []byte) []byte {
+	h := sha256.New()
+	_, _ = h.Write(key)
+	return h.Sum(nil)
+}
+
+func hashPassword(rawPassword, salt []byte, iter, keyLen int) string {
+	digestKey := pbkdf2.Key(rawPassword, salt, iter, keyLen, sha256.New)
+	clientKey := getHMACSum(digestKey, clientRawKey)
+	storedKey := getSHA256Sum(clientKey)
+	serverKey := getHMACSum(digestKey, serverRawKey)
+
+	return fmt.Sprintf("SCRAM-SHA-256$%d:%s$%s:%s",
+		iter,
+		string(encodeB64(salt)),
+		string(encodeB64(storedKey)),
+		string(encodeB64(serverKey)),
+	)
+}
+
+func Hash(password string) (string, error) {
+	salt, err := genSalt(saltSize)
+	if err != nil {
+		return "", err
+	}
+
+	hashedPassword := hashPassword([]byte(password), salt, iterationCnt, digestLen)
+	return hashedPassword, nil
+}