79 lines
2.4 KiB
Go
79 lines
2.4 KiB
Go
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package ws
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import (
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"bufio"
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"bytes"
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"crypto/sha1"
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"encoding/base64"
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"fmt"
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"math/rand"
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)
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const (
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// RFC6455: The value of this header field MUST be a nonce consisting of a
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// randomly selected 16-byte value that has been base64-encoded (see
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// Section 4 of [RFC4648]). The nonce MUST be selected randomly for each
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// connection.
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nonceKeySize = 16
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nonceSize = 24 // base64.StdEncoding.EncodedLen(nonceKeySize)
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// RFC6455: The value of this header field is constructed by concatenating
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// /key/, defined above in step 4 in Section 4.2.2, with the string
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// "258EAFA5- E914-47DA-95CA-C5AB0DC85B11", taking the SHA-1 hash of this
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// concatenated value to obtain a 20-byte value and base64- encoding (see
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// Section 4 of [RFC4648]) this 20-byte hash.
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acceptSize = 28 // base64.StdEncoding.EncodedLen(sha1.Size)
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)
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// initNonce fills given slice with random base64-encoded nonce bytes.
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func initNonce(dst []byte) {
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// NOTE: bts does not escape.
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bts := make([]byte, nonceKeySize)
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if _, err := rand.Read(bts); err != nil {
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panic(fmt.Sprintf("rand read error: %s", err))
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}
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base64.StdEncoding.Encode(dst, bts)
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}
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// checkAcceptFromNonce reports whether given accept bytes are valid for given
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// nonce bytes.
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func checkAcceptFromNonce(accept, nonce []byte) bool {
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if len(accept) != acceptSize {
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return false
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}
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// NOTE: expect does not escape.
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expect := make([]byte, acceptSize)
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initAcceptFromNonce(expect, nonce)
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return bytes.Equal(expect, accept)
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}
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// initAcceptFromNonce fills given slice with accept bytes generated from given
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// nonce bytes. Given buffer should be exactly acceptSize bytes.
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func initAcceptFromNonce(accept, nonce []byte) {
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const magic = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
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if len(accept) != acceptSize {
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panic("accept buffer is invalid")
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}
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if len(nonce) != nonceSize {
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panic("nonce is invalid")
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}
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p := make([]byte, nonceSize+len(magic))
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copy(p[:nonceSize], nonce)
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copy(p[nonceSize:], magic)
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sum := sha1.Sum(p)
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base64.StdEncoding.Encode(accept, sum[:])
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}
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func writeAccept(bw *bufio.Writer, nonce []byte) (int, error) {
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accept := make([]byte, acceptSize)
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initAcceptFromNonce(accept, nonce)
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// NOTE: write accept bytes as a string to prevent heap allocation –
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// WriteString() copy given string into its inner buffer, unlike Write()
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// which may write p directly to the underlying io.Writer – which in turn
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// will lead to p escape.
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return bw.WriteString(btsToString(accept))
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}
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