pem.c

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/*
 * Copyright (C) 2016 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 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 );

#include <stdlib.h>
#include <errno.h>
#include <assert.h>
#include <ipxe/asn1.h>
#include <ipxe/base64.h>
#include <ipxe/uaccess.h>
#include <ipxe/image.h>
#include <ipxe/pem.h>

/** @file
 *
 * PEM-encoded ASN.1 data
 *
 */

/**
 * Locate next line
 *
 * @v data              PEM data
 * @v len               Length of PEM data
 * @v offset            Starting offset
 * @ret next            Offset to next line
 */
static size_t pem_next ( userptr_t data, size_t len, size_t offset ) {
        off_t eol;

        /* Find and skip next newline character, if any */
        eol = memchr_user ( data, offset, '\n', ( len - offset ) );
        if ( eol < 0 )
                return len;
        return ( eol + 1 );
}

/**
 * Locate boundary marker line
 *
 * @v data              PEM data
 * @v len               Length of PEM data
 * @v offset            Starting offset
 * @v marker            Boundary marker
 * @ret offset          Offset to boundary marker line, or negative error
 */
static int pem_marker ( userptr_t data, size_t len, size_t offset,
                        const char *marker ) {
        char buf[ strlen ( marker ) ];

        /* Sanity check */
        assert ( offset <= len );

        /* Scan for marker at start of line */
        while ( offset < len ) {

                /* Check for marker */
                if ( ( len - offset ) < sizeof ( buf ) )
                        break;
                copy_from_user ( buf, data, offset, sizeof ( buf ) );
                if ( memcmp ( buf, marker, sizeof ( buf ) ) == 0 )
                        return offset;

                /* Move to next line */
                offset = pem_next ( data, len, offset );
                assert ( offset <= len );
        }

        return -ENOENT;
}

/**
 * Extract ASN.1 object from PEM data
 *
 * @v data              PEM data
 * @v len               Length of PEM data
 * @v offset            Offset within data
 * @v cursor            ASN.1 cursor to fill in
 * @ret next            Offset to next object, or negative error
 *
 * The caller is responsible for eventually calling free() on the
 * allocated ASN.1 cursor.
 */
int pem_asn1 ( userptr_t data, size_t len, size_t offset,
               struct asn1_cursor **cursor ) {
        size_t encoded_len;
        size_t decoded_max_len;
        char *encoded;
        void *decoded;
        int decoded_len;
        int begin;
        int end;
        int rc;

        /* Locate and skip BEGIN marker */
        begin = pem_marker ( data, len, offset, PEM_BEGIN );
        if ( begin < 0 ) {
                rc = begin;
                DBGC ( data, "PEM [%#zx,%#zx) missing BEGIN marker: %s\n",
                       offset, len, strerror ( rc ) );
                goto err_begin;
        }
        begin = pem_next ( data, len, begin );

        /* Locate and skip END marker */
        end = pem_marker ( data, len, begin, PEM_END );
        if ( end < 0 ) {
                rc = end;
                DBGC ( data, "PEM [%#zx,%#zx) missing END marker: %s\n",
                       offset, len, strerror ( rc ) );
                goto err_end;
        }
        encoded_len = ( end - begin );
        end = pem_next ( data, len, end );

        /* Extract Base64-encoded data */
        encoded = malloc ( encoded_len + 1 /* NUL */ );
        if ( ! encoded ) {
                rc = -ENOMEM;
                goto err_alloc_encoded;
        }
        copy_from_user ( encoded, data, begin, encoded_len );
        encoded[encoded_len] = '\0';

        /* Allocate cursor and data buffer */
        decoded_max_len = base64_decoded_max_len ( encoded );
        *cursor = malloc ( sizeof ( **cursor ) + decoded_max_len );
        if ( ! *cursor ) {
                rc = -ENOMEM;
                goto err_alloc_cursor;
        }
        decoded = ( ( ( void * ) *cursor ) + sizeof ( **cursor ) );

        /* Decode Base64-encoded data */
        decoded_len = base64_decode ( encoded, decoded, decoded_max_len );
        if ( decoded_len < 0 ) {
                rc = decoded_len;
                DBGC ( data, "PEM could not decode: %s\n", strerror ( rc ) );
                goto err_decode;
        }
        (*cursor)->data = decoded;
        (*cursor)->len = decoded_len;
        assert ( (*cursor)->len <= decoded_max_len );

        /* Free Base64-encoded data */
        free ( encoded );

        /* Update offset and skip any unencapsulated trailer */
        offset = end;
        if ( pem_marker ( data, len, offset, PEM_BEGIN ) < 0 )
                offset = len;

        return offset;

 err_decode:
        free ( *cursor );
        *cursor = NULL;
 err_alloc_cursor:
        free ( encoded );
 err_alloc_encoded:
 err_end:
 err_begin:
        return rc;
}

/**
 * Probe PEM image
 *
 * @v image             PEM image
 * @ret rc              Return status code
 */
static int pem_image_probe ( struct image *image ) {
        int offset;
        int rc;

        /* Check that image contains a BEGIN marker */
        if ( ( offset = pem_marker ( image->data, image->len, 0,
                                     PEM_BEGIN ) ) < 0 ) {
                rc = offset;
                DBGC ( image, "PEM %s has no BEGIN marker: %s\n",
                       image->name, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Extract ASN.1 object from image
 *
 * @v image             PEM image
 * @v offset            Offset within image
 * @v cursor            ASN.1 cursor to fill in
 * @ret next            Offset to next image, or negative error
 *
 * The caller is responsible for eventually calling free() on the
 * allocated ASN.1 cursor.
 */
static int pem_image_asn1 ( struct image *image, size_t offset,
                            struct asn1_cursor **cursor ) {
        int next;
        int rc;

        /* Extract ASN.1 object */
        if ( ( next = pem_asn1 ( image->data, image->len, offset,
                                 cursor ) ) < 0 ) {
                rc = next;
                DBGC ( image, "PEM %s could not extract ASN.1: %s\n",
                       image->name, strerror ( rc ) );
                return rc;
        }

        return next;
}

/** PEM image type */
struct image_type pem_image_type __image_type ( PROBE_NORMAL ) = {
        .name = "PEM",
        .probe = pem_image_probe,
        .asn1 = pem_image_asn1,
};