src/houdini_html_e.c



#include <assert.h>
#include <stdio.h>
#include <string.h>

#include "houdini.h"

/**
 * According to the OWASP rules:
 *
 * & --> &amp;
 * < --> &lt;
 * > --> &gt;
 * " --> &quot;
 * ' --> &#x27;     &apos; is not recommended
 * / --> &#x2F;     forward slash is included as it helps end an HTML entity
 *
 */
static const char HTML_ESCAPE_TABLE[] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 1, 0, 0, 0, 2, 3, 0, 0, 0, 0, 0, 0, 0, 4,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 6, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};

static const char *HTML_ESCAPES[] = {
    "",
    "&quot;",
    "&amp;",
    "&#39;",
    "&#47;",
    "&lt;",
    "&gt;"
};

int
houdini_escape_html0(cmark_strbuf *ob, const uint8_t *src, size_t size, int secure)
{
    size_t  i = 0, org, esc = 0;

    while (i < size) {
        org = i;
        while (i < size && (esc = HTML_ESCAPE_TABLE[src[i]]) == 0)
            i++;

        if (i > org)
            cmark_strbuf_put(ob, src + org, i - org);

        /* escaping */
        if (unlikely(i >= size))
            break;

        /* The forward slash is only escaped in secure mode */
        if ((src[i] == '/' || src[i] == '\'') && !secure) {
            cmark_strbuf_putc(ob, src[i]);
        } else {
            cmark_strbuf_puts(ob, HTML_ESCAPES[esc]);
        }

        i++;
    }

    return 1;
}

int
houdini_escape_html(cmark_strbuf *ob, const uint8_t *src, size_t size)
{
    return houdini_escape_html0(ob, src, size, 1);
}