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1 files changed, 507 insertions, 0 deletions

diff --git a/src/de/measite/minidns/DNSMessage.java b/src/de/measite/minidns/DNSMessage.java
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+++ b/src/de/measite/minidns/DNSMessage.java
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+package de.measite.minidns;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.Arrays;
+
+/**
+ * A DNS message as defined by rfc1035. The message consists of a header and
+ * 4 sections: question, answer, nameserver and addition resource record
+ * section.
+ * A message can either be parsed ({@see #parse(byte[])}) or serialized
+ * ({@see #toArray()}).
+ */
+public class DNSMessage {
+
+    /**
+     * Possible DNS reply codes.
+     */
+    public static enum RESPONSE_CODE {
+        NO_ERROR(0), FORMAT_ERR(1), SERVER_FAIL(2), NX_DOMAIN(3),
+        NO_IMP(4), REFUSED(5), YXDOMAIN(6), YXRRSET(7),
+        NXRRSET(8), NOT_AUTH(9),NOT_ZONE(10);
+
+        /**
+         * Reverse lookup table for response codes.
+         */
+        private final static RESPONSE_CODE INVERSE_LUT[] = new RESPONSE_CODE[]{
+            NO_ERROR, FORMAT_ERR, SERVER_FAIL, NX_DOMAIN, NO_IMP,
+            REFUSED, YXDOMAIN, YXRRSET, NXRRSET, NOT_AUTH, NOT_ZONE,
+            null, null, null, null, null
+        };
+
+        /**
+         * The response code value.
+         */
+        private final byte value;
+
+        /**
+         * Create a new response code.
+         * @param value The response code value.
+         */
+        private RESPONSE_CODE(int value) {
+            this.value = (byte)value;
+        }
+
+        /**
+         * Retrieve the byte value of the response code.
+         * @return
+         */
+        public byte getValue() {
+            return (byte) value;
+        }
+
+        /**
+         * Retrieve the response code for a byte value.
+         * @param value The byte value.
+         * @return The symbolic response code or null.
+         * @throws IllegalArgumentException if the value is not in the range of
+         *         0..15.
+         */
+        public static RESPONSE_CODE getResponseCode(int value) {
+            if (value < 0 || value > 15) {
+                throw new IllegalArgumentException();
+            }
+            return INVERSE_LUT[value];
+        }
+
+    };
+
+    /**
+     * Symbolic DNS Opcode values.
+     */
+    public static enum OPCODE {
+        QUERY(0),
+        INVERSE_QUERY(1),
+        STATUS(2),
+        NOTIFY(4),
+        UPDATE(5);
+
+        /**
+         * Lookup table for for obcode reolution.
+         */
+        private final static OPCODE INVERSE_LUT[] = new OPCODE[]{
+            QUERY, INVERSE_QUERY, STATUS, null, NOTIFY, UPDATE, null,
+            null, null, null, null, null, null, null, null
+        };
+
+        /**
+         * The value of this opcode.
+         */
+        private final byte value;
+
+        /**
+         * Create a new opcode for a given byte value.
+         * @param value The byte value of the opcode.
+         */
+        private OPCODE(int value) {
+            this.value = (byte)value;
+        }
+
+        /**
+         * Retrieve the byte value of this opcode.
+         * @return The byte value of this opcode.
+         */
+        public byte getValue() {
+            return value;
+        }
+
+        /**
+         * Retrieve the symbolic name of an opcode byte.
+         * @param value The byte value of the opcode.
+         * @return The symbolic opcode or null.
+         * @throws IllegalArgumentException If the byte value is not in the
+         *         range 0..15.
+         */
+        public static OPCODE getOpcode(int value) {
+            if (value < 0 || value > 15) {
+                throw new IllegalArgumentException();
+            }
+            return INVERSE_LUT[value];
+        }
+
+    };
+
+    /**
+     * The DNS message id.
+     */
+    protected int id;
+
+    /**
+     * The DNS message opcode.
+     */
+    protected OPCODE opcode;
+
+    /**
+     * The response code of this dns message.
+     */
+    protected RESPONSE_CODE responseCode;
+
+    /**
+     * True if this is a query.
+     */
+    protected boolean query;
+
+    /**
+     * True if this is a authorative response.
+     */
+    protected boolean authoritativeAnswer;
+
+    /**
+     * True on truncate, tcp should be used.
+     */
+    protected boolean truncated;
+
+    /**
+     * True if the server should recurse.
+     */
+    protected boolean recursionDesired;
+
+    /**
+     * True if recursion is possible.
+     */
+    protected boolean recursionAvailable;
+
+    /**
+     * True if the server regarded the response as authentic.
+     */
+    protected boolean authenticData;
+
+    /**
+     * True if the server should not check the replies.
+     */
+    protected boolean checkDisabled;
+
+    /**
+     * The question section content.
+     */
+    protected Question questions[];
+
+    /**
+     * The answers section content.
+     */
+    protected Record answers[];
+
+    /**
+     * The nameserver records.
+     */
+    protected Record nameserverRecords[];
+
+    /**
+     * Additional resousrce records.
+     */
+    protected Record additionalResourceRecords[];
+
+    /**
+     * Retrieve the current DNS message id.
+     * @return The current DNS message id.
+     */
+    public int getId() {
+        return id;
+    }
+
+    /**
+     * Set the current DNS message id.
+     * @param id The new DNS message id.
+     */
+    public void setId(int id) {
+        this.id = id & 0xffff;
+    }
+
+    /**
+     * Retrieve the query type (true or false;
+     * @return True if this DNS message is a query.
+     */
+    public boolean isQuery() {
+        return query;
+    }
+
+    /**
+     * Set the query status of this message.
+     * @param query The new query status.
+     */
+    public void setQuery(boolean query) {
+        this.query = query;
+    }
+
+    /**
+     * True if the DNS message is an authoritative answer.
+     * @return True if this an authoritative DNS message.
+     */
+    public boolean isAuthoritativeAnswer() {
+        return authoritativeAnswer;
+    }
+
+    /**
+     * Set the authoritative answer flag.
+     * @param authoritativeAnswer Tge new authoritative answer value.
+     */
+    public void setAuthoritativeAnswer(boolean authoritativeAnswer) {
+        this.authoritativeAnswer = authoritativeAnswer;
+    }
+
+    /**
+     * Retrieve the truncation status of this message. True means that the
+     * client should try a tcp lookup.
+     * @return True if this message was truncated.
+     */
+    public boolean isTruncated() {
+        return truncated;
+    }
+
+    /**
+     * Set the truncation bit on this DNS message.
+     * @param truncated The new truncated bit status.
+     */
+    public void setTruncated(boolean truncated) {
+        this.truncated = truncated;
+    }
+
+    /**
+     * Check if this message preferes recursion.
+     * @return True if recursion is desired.
+     */
+    public boolean isRecursionDesired() {
+        return recursionDesired;
+    }
+
+    /**
+     * Set the recursion desired flag on this message.
+     * @param recursionDesired The new recusrion setting.
+     */
+    public void setRecursionDesired(boolean recursionDesired) {
+        this.recursionDesired = recursionDesired;
+    }
+
+    /**
+     * Retrieve the recursion available flag of this DNS message.
+     * @return The recursion available flag of this message.
+     */
+    public boolean isRecursionAvailable() {
+        return recursionAvailable;
+    }
+
+    /**
+     * Set the recursion available flog from this DNS message.
+     * @param recursionAvailable The new recursion available status.
+     */
+    public void setRecursionAvailable(boolean recursionAvailable) {
+        this.recursionAvailable = recursionAvailable;
+    }
+
+    /**
+     * Retrieve the authentic data flag of this message.
+     * @return The authentic data flag.
+     */
+    public boolean isAuthenticData() {
+        return authenticData;
+    }
+
+    /**
+     * Set the authentic data flag on this DNS message.
+     * @param authenticData The new authentic data flag value.
+     */
+    public void setAuthenticData(boolean authenticData) {
+        this.authenticData = authenticData;
+    }
+
+    /**
+     * Check if checks are disabled.
+     * @return The status of the CheckDisabled flag.
+     */
+    public boolean isCheckDisabled() {
+        return checkDisabled;
+    }
+
+    /**
+     * Change the check status of this packet.
+     * @param checkDisabled
+     */
+    public void setCheckDisabled(boolean checkDisabled) {
+        this.checkDisabled = checkDisabled;
+    }
+
+    /**
+     * Generate a binary dns packet out of this message.
+     * @return byte[] the binary representation.
+     * @throws IOException Should never happen.
+     */
+    public byte[] toArray() throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream(512);
+        DataOutputStream dos = new DataOutputStream(baos);
+        int header = 0;
+        if (query) {
+            header += 1 << 15;
+        }
+        if (opcode != null) {
+            header += opcode.getValue() << 11;
+        }
+        if (authoritativeAnswer) {
+            header += 1 << 10;
+        }
+        if (truncated) {
+            header += 1 << 9;
+        }
+        if (recursionDesired) {
+            header += 1 << 8;
+        }
+        if (recursionAvailable) {
+            header += 1 << 7;
+        }
+        if (authenticData) {
+            header += 1 << 5;
+        }
+        if (checkDisabled) {
+            header += 1 << 4;
+        }
+        if (responseCode != null) {
+            header += responseCode.getValue();
+        }
+        dos.writeShort((short)id);
+        dos.writeShort((short)header);
+        if (questions == null) {
+            dos.writeShort(0);
+        } else {
+            dos.writeShort((short)questions.length);
+        }
+        if (answers == null) {
+            dos.writeShort(0);
+        } else {
+            dos.writeShort((short)answers.length);
+        }
+        if (nameserverRecords == null) {
+            dos.writeShort(0);
+        } else {
+            dos.writeShort((short)nameserverRecords.length);
+        }
+        if (additionalResourceRecords == null) {
+            dos.writeShort(0);
+        } else {
+            dos.writeShort((short)additionalResourceRecords.length);
+        }
+        for (Question question: questions) {
+            dos.write(question.toByteArray());
+        }
+        dos.flush();
+        return baos.toByteArray();
+    }
+
+    /**
+     * Build a DNS Message based on a binary DNS message.
+     * @param data The DNS message data.
+     * @return Parsed DNSMessage message.
+     * @throws IOException On read errors.
+     */
+    public static DNSMessage parse(byte data[]) throws IOException {
+        ByteArrayInputStream bis = new ByteArrayInputStream(data);
+        DataInputStream dis = new DataInputStream(bis);
+        DNSMessage message = new DNSMessage();
+        message.id = dis.readUnsignedShort();
+        int header = dis.readUnsignedShort();
+        message.query = ((header >> 15) & 1) == 0;
+        message.opcode = OPCODE.getOpcode((header >> 11) & 0xf);
+        message.authoritativeAnswer = ((header >> 10) & 1) == 1;
+        message.truncated = ((header >> 9) & 1) == 1;
+        message.recursionDesired = ((header >> 8) & 1) == 1;
+        message.recursionAvailable = ((header >> 7) & 1) == 1;
+        message.authenticData = ((header >> 5) & 1) == 1;
+        message.checkDisabled = ((header >> 4) & 1) == 1;
+        message.responseCode = RESPONSE_CODE.getResponseCode(header & 0xf);
+        int questionCount = dis.readUnsignedShort();
+        int answerCount = dis.readUnsignedShort();
+        int nameserverCount = dis.readUnsignedShort();
+        int additionalResourceRecordCount = dis.readUnsignedShort();
+        message.questions = new Question[questionCount];
+        while (questionCount-- > 0) {
+            Question q = new Question();
+            q.parse(dis, data);
+            message.questions[questionCount] = q;
+        }
+        message.answers = new Record[answerCount];
+        while (answerCount-- > 0) {
+            Record rr = new Record();
+            rr.parse(dis, data);
+            message.answers[answerCount] = rr;
+        }
+        message.nameserverRecords = new Record[nameserverCount];
+        while (nameserverCount-- > 0) {
+            Record rr = new Record();
+            rr.parse(dis, data);
+            message.nameserverRecords[nameserverCount] = rr;
+        }
+        message.additionalResourceRecords =
+                                    new Record[additionalResourceRecordCount];
+        while (additionalResourceRecordCount-- > 0) {
+            Record rr = new Record();
+            rr.parse(dis, data);
+            message.additionalResourceRecords[additionalResourceRecordCount] =
+                    rr;
+        }
+        return message;
+    }
+
+    /**
+     * Set the question part of this message.
+     * @param questions The questions.
+     */
+    public void setQuestions(Question ... questions) {
+        this.questions = questions;
+    }
+
+    /**
+     * Retrieve the opcode of this message.
+     * @return The opcode of this message.
+     */
+    public OPCODE getOpcode() {
+        return opcode;
+    }
+
+    /**
+     * Retrieve the response code of this message.
+     * @return The response code.
+     */
+    public RESPONSE_CODE getResponseCode() {
+        return responseCode;
+    }
+
+    /**
+     * Retrieve the question section of this message.
+     * @return The DNS question section.
+     */
+    public Question[] getQuestions() {
+        return questions;
+    }
+
+    /**
+     * Retrieve the answer records of this DNS message.
+     * @return The answer section of this DNS message.
+     */
+    public Record[] getAnswers() {
+        return answers;
+    }
+
+    /**
+     * Retrieve the nameserver records of this DNS message.
+     * @return The nameserver section of this DNS message.
+     */
+    public Record[] getNameserverRecords() {
+        return nameserverRecords;
+    }
+
+    /**
+     * Retrieve the additional resource records attached to this DNS message.
+     * @return The additional resource record section of this DNS message.
+     */
+    public Record[] getAdditionalResourceRecords() {
+        return additionalResourceRecords;
+    }
+
+    public String toString() {
+        return "-- DNSMessage " + id + " --\n" +
+               Arrays.toString(answers);
+    }
+
+}