Content security Policy (CSP) handled from Plugin

Hello! I solved it working directly with the internal.properties file where the content-security-policies are defined.

Using some environment variables and system properties, I managed to find the <TeamCity_Data> directory, and inside the "config" folder where the internal.properties should be.

System.env: "TEAMCITY_DATA_PATH";
System.property: "teamcity.data.path";

When running the Teamcity instance on windows, installed as a services, the System.env: "TEAMCITY_DATA_PATH" wasn't asigned, so I figured it out reading the agent.home.dir first, going back to his parent to get the TeamCity_Server directory, and then going inside "conf" folder, and reading the "teamcity-startup.properties" which have the teamcity_data path in there.

System.property: "agent.home.dir";

new File(this.getSystemProperties().get(PluginConstants.AGENT_HOME_DIR)).getParent()

I'm leaving my approach below:

String pathSeparator = PluginConstants.SLASH;
String teamcityDataPath = teamcityContext.getDataPath();
if ( OSValidator.isWindows() ){
    pathSeparator = PluginConstants.BACK_SLASH;
    teamcityDataPath = teamcityDataPath.replace(PluginConstants.C_BACK_SLASH_COLON_DOUBLE_BACK_SLASH, PluginConstants.C_COLON_BACK_SLASH);
}
StringBuilder internalPropertiesFilePath = new StringBuilder();
internalPropertiesFilePath.append(teamcityDataPath);
internalPropertiesFilePath.append(pathSeparator);
internalPropertiesFilePath.append(PluginConstants.CONFIG);
internalPropertiesFilePath.append(pathSeparator);
internalPropertiesFilePath.append(pathSeparator);
internalPropertiesFilePath.append(PluginConstants.INTERNAL_PROPERTIES_FILE);
File internalPropertiesFile = new File(internalPropertiesFilePath.toString());
try {
    internalPropertiesFile.createNewFile();
    boolean lineEdited = false;
    StringBuffer stringBuffer = new StringBuffer();
    Scanner reader = new Scanner(internalPropertiesFile);
    while (reader.hasNextLine()) {
        String line = reader.nextLine();
        String firstChar = !line.isBlank() ? Character.toString(line.trim().charAt(0)) : "";
        if ( !firstChar.equals("#") && line.contains(PluginConstants.CONTENT_POLICY_PROPERTY)
                && line.contains(PluginConstants.IMG_SRC_POLICY)
                && line.contains(PluginConstants.SOOS_IMAGES_PRODUCTION_CDN)) {
            reader.close();
            return;
        } else if ( !firstChar.equals("#") && line.contains(PluginConstants.CONTENT_POLICY_PROPERTY)
                && line.contains(PluginConstants.IMG_SRC_POLICY) ) {
            int index = line.indexOf("blob: ");
            line = line.substring(0, index + 6).concat(PluginConstants.SOOS_IMAGES_PRODUCTION_CDN).concat(" ").concat(line.substring(index + 6));
            lineEdited = true;
        }
        stringBuffer.append(line.concat(System.lineSeparator()));
    }
    reader.close();
    if ( !lineEdited ) {
        BufferedWriter writer = new BufferedWriter(new FileWriter(internalPropertiesFile,true));
        StringBuilder fileText = new StringBuilder();
        fileText.append(PluginConstants.CONTENT_POLICY_PROPERTY);
        fileText.append(PluginConstants.EQUAL);
        fileText.append(PluginConstants.IMG_SRC_POLICY);
        fileText.append(PluginConstants.SOOS_IMAGES_PRODUCTION_CDN);
        writer.newLine();
        writer.write(fileText.toString());
        writer.close();
        return;
    }
    BufferedWriter writer = new BufferedWriter(new FileWriter(internalPropertiesFile));
    writer.write(stringBuffer.toString());
    writer.close();
} catch (IOException e) {
    LOG.severe("Failed to write to internal.properties file: ".concat(e.getMessage()));
}

Hope this information can help you! I didn't find another approach on this.