snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

credentials/alts/internal/conn/common.go

@@ -0,0 +1,80 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package conn
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+)
+
+const (
+	// GcmTagSize is the GCM tag size is the difference in length between
+	// plaintext and ciphertext. From crypto/cipher/gcm.go in Go crypto
+	// library.
+	GcmTagSize = 16
+)
+
+// ErrAuth occurs on authentication failure.
+var ErrAuth = errors.New("message authentication failed")
+
+// SliceForAppend takes a slice and a requested number of bytes. It returns a
+// slice with the contents of the given slice followed by that many bytes and a
+// second slice that aliases into it and contains only the extra bytes. If the
+// original slice has sufficient capacity then no allocation is performed.
+func SliceForAppend(in []byte, n int) (head, tail []byte) {
+	if total := len(in) + n; cap(in) >= total {
+		head = in[:total]
+	} else {
+		head = make([]byte, total)
+		copy(head, in)
+	}
+	tail = head[len(in):]
+	return head, tail
+}
+
+// ParseFramedMsg parse the provided buffer and returns a frame of the format
+// msgLength+msg and any remaining bytes in that buffer.
+func ParseFramedMsg(b []byte, maxLen uint32) ([]byte, []byte, error) {
+	// If the size field is not complete, return the provided buffer as
+	// remaining buffer.
+	length, sufficientBytes := parseMessageLength(b)
+	if !sufficientBytes {
+		return nil, b, nil
+	}
+	if length > maxLen {
+		return nil, nil, fmt.Errorf("received the frame length %d larger than the limit %d", length, maxLen)
+	}
+	if len(b) < int(length)+4 { // account for the first 4 msg length bytes.
+		// Frame is not complete yet.
+		return nil, b, nil
+	}
+	return b[:MsgLenFieldSize+length], b[MsgLenFieldSize+length:], nil
+}
+
+// parseMessageLength returns the message length based on frame header. It also
+// returns a boolean indicating if the buffer contains sufficient bytes to parse
+// the length header. If there are insufficient bytes, (0, false) is returned.
+func parseMessageLength(b []byte) (uint32, bool) {
+	if len(b) < MsgLenFieldSize {
+		return 0, false
+	}
+	msgLenField := b[:MsgLenFieldSize]
+	return binary.LittleEndian.Uint32(msgLenField), true
+}