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/*
* Copyright (C) 2020 Square, Inc.
*
* 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 okhttp3.internal.ws
import java.io.IOException
import okhttp3.Headers
import okhttp3.internal.delimiterOffset
import okhttp3.internal.trimSubstring
/**
* Models the contents of a `Sec-WebSocket-Extensions` response header. OkHttp honors one extension
* `permessage-deflate` and four parameters, `client_max_window_bits`, `client_no_context_takeover`,
* `server_max_window_bits`, and `server_no_context_takeover`.
*
* Typically this will look like one of the following:
*
* ```
* Sec-WebSocket-Extensions: permessage-deflate
* Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits="15"
* Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits=15
* Sec-WebSocket-Extensions: permessage-deflate; client_no_context_takeover
* Sec-WebSocket-Extensions: permessage-deflate; server_max_window_bits="15"
* Sec-WebSocket-Extensions: permessage-deflate; server_max_window_bits=15
* Sec-WebSocket-Extensions: permessage-deflate; server_no_context_takeover
* Sec-WebSocket-Extensions: permessage-deflate; server_no_context_takeover;
* client_no_context_takeover
* Sec-WebSocket-Extensions: permessage-deflate; server_max_window_bits="15";
* client_max_window_bits="15"; server_no_context_takeover; client_no_context_takeover
* ```
*
* If any other extension or parameter is specified, then [unknownValues] will be true. Such
* responses should be refused as their web socket extensions will not be understood.
*
* Note that [java.util.zip.Deflater] is hardcoded to use 15 bits (32 KiB) for
* `client_max_window_bits` and [java.util.zip.Inflater] is hardcoded to use 15 bits (32 KiB) for
* `server_max_window_bits`. This harms our ability to support these parameters:
*
* * If `client_max_window_bits` is less than 15, OkHttp must close the web socket with code 1010.
* Otherwise it would compress values in a way that servers could not decompress.
* * If `server_max_window_bits` is less than 15, OkHttp will waste memory on an oversized buffer.
*
* See [RFC 7692, 7.1][rfc_7692] for details on negotiation process.
*
* [rfc_7692]: https://tools.ietf.org/html/rfc7692#section-7.1
*/
data class WebSocketExtensions(
/** True if the agreed upon extensions includes the permessage-deflate extension. */
@JvmField val perMessageDeflate: Boolean = false,
/** Should be a value in [8..15]. Only 15 is acceptable by OkHttp as Java APIs are limited. */
@JvmField val clientMaxWindowBits: Int? = null,
/** True if the agreed upon extension parameters includes "client_no_context_takeover". */
@JvmField val clientNoContextTakeover: Boolean = false,
/** Should be a value in [8..15]. Any value in that range is acceptable by OkHttp. */
@JvmField val serverMaxWindowBits: Int? = null,
/** True if the agreed upon extension parameters includes "server_no_context_takeover". */
@JvmField val serverNoContextTakeover: Boolean = false,
/**
* True if the agreed upon extensions or parameters contained values unrecognized by OkHttp.
* Typically this indicates that the client will need to close the web socket with code 1010.
*/
@JvmField val unknownValues: Boolean = false
) {
fun noContextTakeover(clientOriginated: Boolean): Boolean {
if (clientOriginated) {
return clientNoContextTakeover // Client is deflating.
} else {
return serverNoContextTakeover // Server is deflating.
}
}
companion object {
private const val HEADER_WEB_SOCKET_EXTENSION = "Sec-WebSocket-Extensions"
@Throws(IOException::class)
fun parse(responseHeaders: Headers): WebSocketExtensions {
// Note that this code does case-insensitive comparisons, even though the spec doesn't specify
// whether extension tokens and parameters are case-insensitive or not.
var compressionEnabled = false
var clientMaxWindowBits: Int? = null
var clientNoContextTakeover = false
var serverMaxWindowBits: Int? = null
var serverNoContextTakeover = false
var unexpectedValues = false
// Parse each header.
for (i in 0 until responseHeaders.size) {
if (!responseHeaders.name(i).equals(HEADER_WEB_SOCKET_EXTENSION, ignoreCase = true)) {
continue // Not a header we're interested in.
}
val header = responseHeaders.value(i)
// Parse each extension.
var pos = 0
while (pos < header.length) {
val extensionEnd = header.delimiterOffset(',', pos)
val extensionTokenEnd = header.delimiterOffset(';', pos, extensionEnd)
val extensionToken = header.trimSubstring(pos, extensionTokenEnd)
pos = extensionTokenEnd + 1
when {
extensionToken.equals("permessage-deflate", ignoreCase = true) -> {
if (compressionEnabled) unexpectedValues = true // Repeated extension!
compressionEnabled = true
// Parse each permessage-deflate parameter.
while (pos < extensionEnd) {
val parameterEnd = header.delimiterOffset(';', pos, extensionEnd)
val equals = header.delimiterOffset('=', pos, parameterEnd)
val name = header.trimSubstring(pos, equals)
val value = if (equals < parameterEnd) {
header.trimSubstring(equals + 1, parameterEnd).removeSurrounding("\"")
} else {
null
}
pos = parameterEnd + 1
when {
name.equals("client_max_window_bits", ignoreCase = true) -> {
if (clientMaxWindowBits != null) unexpectedValues = true // Repeated parameter!
clientMaxWindowBits = value?.toIntOrNull()
if (clientMaxWindowBits == null) unexpectedValues = true // Not an int!
}
name.equals("client_no_context_takeover", ignoreCase = true) -> {
if (clientNoContextTakeover) unexpectedValues = true // Repeated parameter!
if (value != null) unexpectedValues = true // Unexpected value!
clientNoContextTakeover = true
}
name.equals("server_max_window_bits", ignoreCase = true) -> {
if (serverMaxWindowBits != null) unexpectedValues = true // Repeated parameter!
serverMaxWindowBits = value?.toIntOrNull()
if (serverMaxWindowBits == null) unexpectedValues = true // Not an int!
}
name.equals("server_no_context_takeover", ignoreCase = true) -> {
if (serverNoContextTakeover) unexpectedValues = true // Repeated parameter!
if (value != null) unexpectedValues = true // Unexpected value!
serverNoContextTakeover = true
}
else -> {
unexpectedValues = true // Unexpected parameter.
}
}
}
}
else -> {
unexpectedValues = true // Unexpected extension.
}
}
}
}
return WebSocketExtensions(
perMessageDeflate = compressionEnabled,
clientMaxWindowBits = clientMaxWindowBits,
clientNoContextTakeover = clientNoContextTakeover,
serverMaxWindowBits = serverMaxWindowBits,
serverNoContextTakeover = serverNoContextTakeover,
unknownValues = unexpectedValues
)
}
}
}
