diff options
Diffstat (limited to 'telephony/common')
| -rw-r--r-- | telephony/common/com/android/internal/telephony/SipMessageParsingUtils.java | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/telephony/common/com/android/internal/telephony/SipMessageParsingUtils.java b/telephony/common/com/android/internal/telephony/SipMessageParsingUtils.java new file mode 100644 index 000000000000..c7e7cd5ec64e --- /dev/null +++ b/telephony/common/com/android/internal/telephony/SipMessageParsingUtils.java @@ -0,0 +1,238 @@ +/* + * Copyright (C) 2020 The Android Open Source Project + * + * 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 com.android.internal.telephony; + +import android.net.Uri; +import android.util.Log; +import android.util.Pair; + +import java.util.ArrayList; +import java.util.Arrays; +import java.util.Collections; +import java.util.List; + +/** + * Utility methods for parsing parts of {@link android.telephony.ims.SipMessage}s. + * See RFC 3261 for more information. + * @hide + */ +// Note: This is lightweight in order to avoid a full SIP stack import in frameworks/base. +public class SipMessageParsingUtils { + private static final String TAG = "SipMessageParsingUtils"; + // "Method" in request-line + // Request-Line = Method SP Request-URI SP SIP-Version CRLF + private static final String[] SIP_REQUEST_METHODS = new String[] {"INVITE", "ACK", "OPTIONS", + "BYE", "CANCEL", "REGISTER", "PRACK", "SUBSCRIBE", "NOTIFY", "PUBLISH", "INFO", "REFER", + "MESSAGE", "UPDATE"}; + + // SIP Version 2.0 (corresponding to RCS 3261), set in "SIP-Version" of Status-Line and + // Request-Line + // + // Request-Line = Method SP Request-URI SP SIP-Version CRLF + // Status-Line = SIP-Version SP Status-Code SP Reason-Phrase CRLF + private static final String SIP_VERSION_2 = "SIP/2.0"; + + // headers are formatted Key:Value + private static final String HEADER_KEY_VALUE_SEPARATOR = ":"; + // Multiple of the same header can be concatenated and put into one header Key:Value pair, for + // example "v: XX1;branch=YY1,XX2;branch=YY2". This needs to be treated as two "v:" headers. + private static final String SUBHEADER_VALUE_SEPARATOR = ","; + + // SIP header parameters have the format ";paramName=paramValue" + private static final String PARAM_SEPARATOR = ";"; + // parameters are formatted paramName=ParamValue + private static final String PARAM_KEY_VALUE_SEPARATOR = "="; + + // The via branch parameter definition + private static final String BRANCH_PARAM_KEY = "branch"; + + // via header key + private static final String VIA_SIP_HEADER_KEY = "via"; + // compact form of the via header key + private static final String VIA_SIP_HEADER_KEY_COMPACT = "v"; + + /** + * @return true if the SIP message start line is considered a request (based on known request + * methods). + */ + public static boolean isSipRequest(String startLine) { + String[] splitLine = splitStartLineAndVerify(startLine); + if (splitLine == null) return false; + return verifySipRequest(splitLine); + } + + /** + * Return the via branch parameter, which is used to identify the transaction ID (request and + * response pair) in a SIP transaction. + * @param headerString The string containing the headers of the SIP message. + */ + public static String getTransactionId(String headerString) { + // search for Via: or v: parameter, we only care about the first one. + List<Pair<String, String>> headers = parseHeaders(headerString, true, + VIA_SIP_HEADER_KEY, VIA_SIP_HEADER_KEY_COMPACT); + for (Pair<String, String> header : headers) { + // Headers can also be concatenated together using a "," between each header value. + // format becomes v: XX1;branch=YY1,XX2;branch=YY2. Need to extract only the first ID's + // branch param YY1. + String[] subHeaders = header.second.split(SUBHEADER_VALUE_SEPARATOR); + for (String subHeader : subHeaders) { + // Search for ;branch=z9hG4bKXXXXXX and return parameter value + String[] params = subHeader.split(PARAM_SEPARATOR); + if (params.length < 2) { + // This param doesn't include a branch param, move to next param. + Log.w(TAG, "getTransactionId: via detected without branch param:" + + subHeader); + continue; + } + // by spec, each param can only appear once in a header. + for (String param : params) { + String[] pair = param.split(PARAM_KEY_VALUE_SEPARATOR); + if (pair.length < 2) { + // ignore info before the first parameter + continue; + } + if (pair.length > 2) { + Log.w(TAG, + "getTransactionId: unexpected parameter" + Arrays.toString(pair)); + } + // Trim whitespace in parameter + pair[0] = pair[0].trim(); + pair[1] = pair[1].trim(); + if (BRANCH_PARAM_KEY.equalsIgnoreCase(pair[0])) { + // There can be multiple "Via" headers in the SIP message, however we want + // to return the first once found, as this corresponds with the transaction + // that is relevant here. + return pair[1]; + } + } + } + } + return null; + } + + private static String[] splitStartLineAndVerify(String startLine) { + String[] splitLine = startLine.split(" "); + if (isStartLineMalformed(splitLine)) return null; + return splitLine; + } + + private static boolean isStartLineMalformed(String[] startLine) { + if (startLine == null || startLine.length == 0) { + return true; + } + // start lines contain three segments separated by spaces (SP): + // Request-Line = Method SP Request-URI SP SIP-Version CRLF + // Status-Line = SIP-Version SP Status-Code SP Reason-Phrase CRLF + return (startLine.length != 3); + } + + private static boolean verifySipRequest(String[] request) { + // Request-Line = Method SP Request-URI SP SIP-Version CRLF + boolean verified = request[2].contains(SIP_VERSION_2); + verified &= (Uri.parse(request[1]).getScheme() != null); + verified &= Arrays.stream(SIP_REQUEST_METHODS).anyMatch(s -> request[0].contains(s)); + return verified; + } + + private static boolean verifySipResponse(String[] response) { + // Status-Line = SIP-Version SP Status-Code SP Reason-Phrase CRLF + boolean verified = response[0].contains(SIP_VERSION_2); + int statusCode = Integer.parseInt(response[1]); + verified &= (statusCode >= 100 && statusCode < 700); + return verified; + } + + /** + * Parse a String representation of the Header portion of the SIP Message and re-structure it + * into a List of key->value pairs representing each header in the order that they appeared in + * the message. + * + * @param headerString The raw string containing all headers + * @param stopAtFirstMatch Return early when the first match is found from matching header keys. + * @param matchingHeaderKeys An optional list of Strings containing header keys that should be + * returned if they exist. If none exist, all keys will be returned. + * (This is internally an equalsIgnoreMatch comparison). + * @return the matched header keys and values. + */ + private static List<Pair<String, String>> parseHeaders(String headerString, + boolean stopAtFirstMatch, String... matchingHeaderKeys) { + // Ensure there is no leading whitespace + headerString = removeLeadingWhitespace(headerString); + + List<Pair<String, String>> result = new ArrayList<>(); + // Split the string line-by-line. + String[] headerLines = headerString.split("\\r?\\n"); + if (headerLines.length == 0) { + return Collections.emptyList(); + } + + String headerKey = null; + StringBuilder headerValueSegment = new StringBuilder(); + // loop through each line, either parsing a "key: value" pair or appending values that span + // multiple lines. + for (String line : headerLines) { + // This line is a continuation of the last line if it starts with whitespace or tab + if (line.startsWith("\t") || line.startsWith(" ")) { + headerValueSegment.append(removeLeadingWhitespace(line)); + continue; + } + // This line is the start of a new key, If headerKey/value is already populated from a + // previous key/value pair, add it to list of parsed header pairs. + if (headerKey != null) { + final String key = headerKey; + if (matchingHeaderKeys == null || matchingHeaderKeys.length == 0 + || Arrays.stream(matchingHeaderKeys).anyMatch( + (s) -> s.equalsIgnoreCase(key))) { + result.add(new Pair<>(key, headerValueSegment.toString())); + if (stopAtFirstMatch) { + return result; + } + } + headerKey = null; + headerValueSegment = new StringBuilder(); + } + + // Format is "Key:Value", ignore any ":" after the first. + String[] pair = line.split(HEADER_KEY_VALUE_SEPARATOR, 2); + if (pair.length < 2) { + // malformed line, skip + Log.w(TAG, "parseHeaders - received malformed line: " + line); + continue; + } + + headerKey = pair[0].trim(); + for (int i = 1; i < pair.length; i++) { + headerValueSegment.append(removeLeadingWhitespace(pair[i])); + } + } + // Pick up the last pending header being parsed, if it exists. + if (headerKey != null) { + final String key = headerKey; + if (matchingHeaderKeys == null || matchingHeaderKeys.length == 0 + || Arrays.stream(matchingHeaderKeys).anyMatch( + (s) -> s.equalsIgnoreCase(key))) { + result.add(new Pair<>(key, headerValueSegment.toString())); + } + } + + return result; + } + + private static String removeLeadingWhitespace(String line) { + return line.replaceFirst("^\\s*", ""); + } +} |