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Made-with: Cursor

server/vendor/github.com/pion/srtp/v2/srtp.go

@@ -0,0 +1,109 @@
+// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
+// SPDX-License-Identifier: MIT
+
+// Package srtp implements Secure Real-time Transport Protocol
+package srtp
+
+import (
+	"fmt"
+
+	"github.com/pion/rtp"
+)
+
+func (c *Context) decryptRTP(dst, ciphertext []byte, header *rtp.Header, headerLen int) ([]byte, error) {
+	authTagLen, err := c.cipher.AuthTagRTPLen()
+	if err != nil {
+		return nil, err
+	}
+	aeadAuthTagLen, err := c.cipher.AEADAuthTagLen()
+	if err != nil {
+		return nil, err
+	}
+	mkiLen := len(c.sendMKI)
+
+	// Verify that encrypted packet is long enough
+	if len(ciphertext) < (headerLen + aeadAuthTagLen + mkiLen + authTagLen) {
+		return nil, fmt.Errorf("%w: %d", errTooShortRTP, len(ciphertext))
+	}
+
+	s := c.getSRTPSSRCState(header.SSRC)
+
+	roc, diff, _ := s.nextRolloverCount(header.SequenceNumber)
+	markAsValid, ok := s.replayDetector.Check(
+		(uint64(roc) << 16) | uint64(header.SequenceNumber),
+	)
+	if !ok {
+		return nil, &duplicatedError{
+			Proto: "srtp", SSRC: header.SSRC, Index: uint32(header.SequenceNumber),
+		}
+	}
+
+	cipher := c.cipher
+	if len(c.mkis) > 0 {
+		// Find cipher for MKI
+		actualMKI := c.cipher.getMKI(ciphertext, true)
+		cipher, ok = c.mkis[string(actualMKI)]
+		if !ok {
+			return nil, ErrMKINotFound
+		}
+	}
+
+	dst = growBufferSize(dst, len(ciphertext)-authTagLen-len(c.sendMKI))
+
+	dst, err = cipher.decryptRTP(dst, ciphertext, header, headerLen, roc)
+	if err != nil {
+		return nil, err
+	}
+
+	markAsValid()
+	s.updateRolloverCount(header.SequenceNumber, diff)
+	return dst, nil
+}
+
+// DecryptRTP decrypts a RTP packet with an encrypted payload
+func (c *Context) DecryptRTP(dst, encrypted []byte, header *rtp.Header) ([]byte, error) {
+	if header == nil {
+		header = &rtp.Header{}
+	}
+
+	headerLen, err := header.Unmarshal(encrypted)
+	if err != nil {
+		return nil, err
+	}
+
+	return c.decryptRTP(dst, encrypted, header, headerLen)
+}
+
+// EncryptRTP marshals and encrypts an RTP packet, writing to the dst buffer provided.
+// If the dst buffer does not have the capacity to hold `len(plaintext) + 10` bytes, a new one will be allocated and returned.
+// If a rtp.Header is provided, it will be Unmarshaled using the plaintext.
+func (c *Context) EncryptRTP(dst []byte, plaintext []byte, header *rtp.Header) ([]byte, error) {
+	if header == nil {
+		header = &rtp.Header{}
+	}
+
+	headerLen, err := header.Unmarshal(plaintext)
+	if err != nil {
+		return nil, err
+	}
+
+	return c.encryptRTP(dst, header, plaintext[headerLen:])
+}
+
+// encryptRTP marshals and encrypts an RTP packet, writing to the dst buffer provided.
+// If the dst buffer does not have the capacity, a new one will be allocated and returned.
+// Similar to above but faster because it can avoid unmarshaling the header and marshaling the payload.
+func (c *Context) encryptRTP(dst []byte, header *rtp.Header, payload []byte) (ciphertext []byte, err error) {
+	s := c.getSRTPSSRCState(header.SSRC)
+	roc, diff, ovf := s.nextRolloverCount(header.SequenceNumber)
+	if ovf {
+		// ... when 2^48 SRTP packets or 2^31 SRTCP packets have been secured with the same key
+		// (whichever occurs before), the key management MUST be called to provide new master key(s)
+		// (previously stored and used keys MUST NOT be used again), or the session MUST be terminated.
+		// https://www.rfc-editor.org/rfc/rfc3711#section-9.2
+		return nil, errExceededMaxPackets
+	}
+	s.updateRolloverCount(header.SequenceNumber, diff)
+
+	return c.cipher.encryptRTP(dst, header, payload, roc)
+}