datauri.c

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/*
 * Copyright (C) 2026 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */
 
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
FILE_SECBOOT ( PERMITTED );
 
#include <string.h>
#include <strings.h>
#include <errno.h>
#include <ipxe/base64.h>
#include <ipxe/blob.h>
#include <ipxe/open.h>
#include <ipxe/datauri.h>
 
/** @file
 *
 * Data URIs
 *
 * The "data" URI scheme is defined in RFC 2397.  In the interest of
 * reducing code size, we support only a practical subset of the
 * specification.  Media types will be ignored (and must not contain a
 * literal comma character).  Base64 encoding is supported.
 *
 * URI encoding will already have been stripped by the URI parser.
 * Special characters may therefore be used in the URI string
 * (e.g. "hello%20world").  However, URI-encoded NUL bytes (%00) will
 * not work as expected, since they will be interpreted as terminating
 * the URI string.  If NUL bytes are required, then Base64 encoding
 * must be used instead.
 */
 
/**
 * Parse data URI
 *
 * @v uri               Data URI
 * @v buf               Buffer to fill in
 * @ret len             Length of data, or negative error
 *
 * The buffer length must be at least the size reported by
 * datauri_max_len().
 */
int datauri_parse ( struct uri *uri, void *buf ) {
        static const char b64marker[7] = ";base64";
        const char *comma;
        const char *encoded;
        size_t prefix_len;
        int len;
        int rc;
 
        /* Sanity check */
        if ( ! uri->opaque ) {
                DBGC ( uri, "DATA %p has no opaque part\n", uri );
                return -EINVAL;
        }
 
        /* Locate encoded string */
        comma = strchr ( uri->opaque, ',' );
        if ( ! comma ) {
                DBGC ( uri, "DATA %p has no comma separator\n", uri );
                return -EINVAL;
        }
        prefix_len = ( comma - uri->opaque );
        encoded = ( comma + 1 );
        len = strlen ( encoded );
 
        /* Decode string */
        if ( ( prefix_len >= sizeof ( b64marker ) ) &&
             ( strncasecmp ( ( comma - sizeof ( b64marker ) ), b64marker,
                             sizeof ( b64marker ) ) == 0 ) ) {
 
                /* Decode Base64 string */
                len = base64_decode ( encoded, buf, len );
                if ( len < 0 ) {
                        rc = len;
                        DBGC ( uri, "DATA %p could not decode Base64: %s\n",
                               uri, strerror ( rc ) );
                        return rc;
                }
 
        } else {
 
                /* Copy raw string */
                strcpy ( buf, encoded );
        }
 
        DBGC ( uri, "DATA %p decoded \"%s\":\n", uri, uri->opaque );
        DBGC_HDA ( uri, 0, buf, len );
        return len;
}
 
/**
 * Open data URI
 *
 * @v xfer              Data transfer interface
 * @v uri               URI
 * @ret rc              Return status code
 */
static int datauri_open ( struct interface *xfer, struct uri *uri ) {
        void *data;
        int len;
        int rc;
 
        /* Allocate space for parsed data */
        data = malloc ( datauri_max_len ( uri ) );
        if ( ! data ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
 
        /* Parse data */
        len = datauri_parse ( uri, data );
        if ( len < 0 )  {
                rc = len;
                goto err_parse;
        }
 
        /* Open downloadable blob */
        if ( ( rc = blob_open ( xfer, data, len ) ) != 0 )
                goto err_open;
 
 err_open:
 err_parse:
        free ( data );
 err_alloc:
        return rc;
}
 
/** Data URI opener */
struct uri_opener data_uri_opener __uri_opener = {
        .scheme = "data",
        .open = datauri_open,
};