protected void prepareNewKeys()

in sshd-core/src/main/java/org/apache/sshd/common/session/helpers/AbstractSession.java [1912:2014]
87 lines of code
10 McCabe index (conditional complexity)

    protected void prepareNewKeys() throws Exception {
        byte[] k = kex.getK();
        byte[] h = kex.getH();
        Digest hash = kex.getHash();

        boolean debugEnabled = log.isDebugEnabled();
        if (sessionId == null) {
            sessionId = h.clone();
            if (debugEnabled) {
                log.debug("prepareNewKeys({}) session ID={}", this, BufferUtils.toHex(':', sessionId));
            }
        }

        Buffer buffer = new ByteArrayBuffer();
        buffer.putBytes(k);
        buffer.putRawBytes(h);
        buffer.putByte((byte) 0x41);
        buffer.putRawBytes(sessionId);

        int pos = buffer.available();
        byte[] buf = buffer.array();
        hash.update(buf, 0, pos);

        byte[] iv_c2s = hash.digest();
        int j = pos - sessionId.length - 1;

        buf[j]++;
        hash.update(buf, 0, pos);
        byte[] iv_s2c = hash.digest();

        buf[j]++;
        hash.update(buf, 0, pos);
        byte[] e_c2s = hash.digest();

        buf[j]++;
        hash.update(buf, 0, pos);
        byte[] e_s2c = hash.digest();

        buf[j]++;
        hash.update(buf, 0, pos);
        byte[] mac_c2s = hash.digest();

        buf[j]++;
        hash.update(buf, 0, pos);
        byte[] mac_s2c = hash.digest();

        boolean serverSession = isServerSession();
        String value = getNegotiatedKexParameter(KexProposalOption.S2CENC);
        Cipher s2ccipher = ValidateUtils.checkNotNull(
                NamedFactory.create(getCipherFactories(), value), "Unknown s2c cipher: %s", value);
        e_s2c = resizeKey(e_s2c, s2ccipher.getKdfSize(), hash, k, h);

        Mac s2cmac;
        if (s2ccipher.getAuthenticationTagSize() == 0) {
            value = getNegotiatedKexParameter(KexProposalOption.S2CMAC);
            s2cmac = NamedFactory.create(getMacFactories(), value);
            if (s2cmac == null) {
                throw new SshException(SshConstants.SSH2_DISCONNECT_MAC_ERROR, "Unknown s2c MAC: " + value);
            }
            mac_s2c = resizeKey(mac_s2c, s2cmac.getBlockSize(), hash, k, h);
            s2cmac.init(mac_s2c);
        } else {
            s2cmac = null;
        }

        value = getNegotiatedKexParameter(KexProposalOption.S2CCOMP);
        Compression s2ccomp = NamedFactory.create(getCompressionFactories(), value);
        if (s2ccomp == null) {
            throw new SshException(SshConstants.SSH2_DISCONNECT_COMPRESSION_ERROR, "Unknown s2c compression: " + value);
        }

        value = getNegotiatedKexParameter(KexProposalOption.C2SENC);
        Cipher c2scipher = ValidateUtils.checkNotNull(
                NamedFactory.create(getCipherFactories(), value), "Unknown c2s cipher: %s", value);
        e_c2s = resizeKey(e_c2s, c2scipher.getKdfSize(), hash, k, h);

        Mac c2smac;
        if (c2scipher.getAuthenticationTagSize() == 0) {
            value = getNegotiatedKexParameter(KexProposalOption.C2SMAC);
            c2smac = NamedFactory.create(getMacFactories(), value);
            if (c2smac == null) {
                throw new SshException(SshConstants.SSH2_DISCONNECT_MAC_ERROR, "Unknown c2s MAC: " + value);
            }
            mac_c2s = resizeKey(mac_c2s, c2smac.getBlockSize(), hash, k, h);
            c2smac.init(mac_c2s);
        } else {
            c2smac = null;
        }

        value = getNegotiatedKexParameter(KexProposalOption.C2SCOMP);
        Compression c2scomp = NamedFactory.create(getCompressionFactories(), value);
        if (c2scomp == null) {
            throw new SshException(SshConstants.SSH2_DISCONNECT_COMPRESSION_ERROR, "Unknown c2s compression: " + value);
        }

        if (serverSession) {
            outSettings = new MessageCodingSettings(s2ccipher, s2cmac, s2ccomp, Cipher.Mode.Encrypt, e_s2c, iv_s2c);
            inSettings = new MessageCodingSettings(c2scipher, c2smac, c2scomp, Cipher.Mode.Decrypt, e_c2s, iv_c2s);
        } else {
            outSettings = new MessageCodingSettings(c2scipher, c2smac, c2scomp, Cipher.Mode.Encrypt, e_c2s, iv_c2s);
            inSettings = new MessageCodingSettings(s2ccipher, s2cmac, s2ccomp, Cipher.Mode.Decrypt, e_s2c, iv_s2c);
        }
    }