Calculate the MD5 hash of an attachment in ServiceNow (Scope & global)

calculateAttachmentMD5Hash.js

var recordTable = 'incident';
var idOfRecord = '755d52b137b0b30090b68cf6c3990e6f';
var grAttachment = getAttachmentRecord(recordTable, idOfRecord, 'example text doc.txt', true);
if (grAttachment !== false) {
	var attachmentStream = new GlideSysAttachment().getContentStream(
		grAttachment.getValue('sys_id')
	);
	var gDigest = new GlideDigest();
	var base64MD5 = gDigest.getMD5Base64FromInputStream(attachmentStream); //Scope only
	gs.info(base64MD5);
}

/**
 * Get the GlideRecord object for an attachment on a given record.
 * @param {string} recordTable - The table name for the record that has the attachment. Example: "incident".
 * @param {string} idOfRecord - The sys_id of the record that has the attachment.
 * @param {string} [nameOfFile] - The name of the attachment file to retrieve.
 * @param {boolean} [exactMatch] - Whether to look for an exact match on the file-name provided. If false (or unspecified), a "starts with..." query will be done.
 * This param only applies if a valid file name is provided.
 * @returns {GlideRecord|boolean} - The GlideRecord for the related sys_attachment record.
 */
function getAttachmentRecord(recordTable, idOfRecord, nameOfFile, exactMatch) {
	var grAttachment = new GlideRecord('sys_attachment');
	
	grAttachment.addQuery('table_name', recordTable);
	grAttachment.addQuery('table_sys_id', idOfRecord);
	
	if (nameOfFile && exactMatch) {
		//If the file name is provided, and exactMatch is true
		grAttachment.addQuery('file_name', nameOfFile);
	} else if (nameOfFile) {
		//If the file name is provided, but exactMatch is not, or is false
		grAttachment.addQuery('file_name', 'STARTSWITH', nameOfFile);
	}
	
	//If multiple attachments match, get newest one
	grAttachment.orderByDesc('sys_created_on');
	grAttachment.setLimit(1); //Be more efficient
	grAttachment.query();
	
	if (grAttachment.next()) {
		return grAttachment;
	}
	
	gs.debug('Attachment for record on table ' +
		recordTable + ' with sys_id ' + idOfRecord +
		' not found with the specified arguments.');
	
	return false; //If attachment is not found, return false
}