Bx Esapi

bx-esapi: OWASP ESAPI Security Module

Installation

install-bx-module bx-esapi
# CommandBox
box install bx-esapi

Encoding BIFs

Available encodeFor() Contexts

CSS, DN, HTML, HTMLAttribute, JavaScript, LDAP, SQL, URL, XML, XMLAttribute, XPath

Output Encoding (XSS Prevention)

<!-- HTML body -->
<bx:output>
    <h2>#encodeForHTML( user.displayName )#</h2>
    <p>#encodeForHTML( user.bio )#</p>
</bx:output>

<!-- HTML attribute -->
<bx:output>
    <a href="#encodeForHTMLAttribute( user.profileUrl )#">Profile</a>
    <img src="/img/avatar.png" alt="#encodeForHTMLAttribute( user.displayName )#" />
</bx:output>

<!-- Inline JavaScript -->
<bx:output>
    <script>
        var username = "#encodeForJavaScript( user.username )#";
        var userId   = #encodeForJavaScript( user.id )#;
    </script>
</bx:output>

<!-- URL parameters -->
<bx:output>
    <a href="/search?q=#encodeForURL( form.searchTerm )#">Search</a>
</bx:output>

Generic encodeFor()

// Using the generic BIF
safeHtml    = encodeFor( "HTML", user.comment )
safeJs      = encodeFor( "JavaScript", user.name )
safeUrl     = encodeFor( "URL", queryParam )
safeAttr    = encodeFor( "HTMLAttribute", user.title )

Decoding BIFs

// Decode from specific contexts
decoded = decodeFromHTML( "&lt;script&gt;" )          // Returns: <script>
decoded = decodeFromURL( "hello%20world" )             // Returns: hello world
decoded = decodeFromBase64( encodedString )
decoded = decodeFrom( "HTML", "&lt;p&gt;content&lt;/p&gt;" )

Canonicalization

Canonicalization normalizes encoded input before encoding. Useful to detect double-encoded attacks:

// With canonicalize=true: first decodes, then re-encodes
// With canonicalize=false (default): encode as-is
safe = encodeForHTML( userInput, true )

HTML Sanitization with AntiSamy

// Sanitize HTML with AntiSamy (built-in safelists)
// Removes dangerous tags while allowing safe formatting
clean = htmlSanitize( userHtmlInput )

// Use specific AntiSamy policy
clean = htmlSanitize( userHtmlInput, "antisamy-slashdot" )
// Policies: antisamy (default), antisamy-slashdot, antisamy-ebay, antisamy-myspace, antisamy-anythinggoes

Common Encoding Patterns

// Form output — always encode when displaying user data
function renderUserProfile( user ) {
    return "
        <div class='profile'>
            <h1>#encodeForHTML( user.name )#</h1>
            <p class='bio'>#encodeForHTML( user.bio )#</p>
            <a href='#encodeForHTMLAttribute( user.website )#'>
                #encodeForHTML( user.websiteLabel )#
            </a>
        </div>
    "
}

// URL building
function buildSearchUrl( term, category ) {
    return "/search?q=#encodeForURL( term )#&category=#encodeForURL( category )#"
}

Common Pitfalls

• ❌ Never use encodeForHTML() inside JavaScript — use encodeForJavaScript() instead
• ❌ Never use encodeForHTML() inside HTML attribute values — use encodeForHTMLAttribute()
• ✅ Always encode user-supplied data at output time in the context where it's used
• ✅ Use htmlSanitize() (AntiSamy) when you want to allow SOME HTML but not arbitrary markup
• ❌ encodeForSQL() should not replace parameterized queries — use queryExecute() with proper params instead
• ✅ Use canonicalize=true when processing input that may have been double-encoded