path: root/camel/camel-multipart-signed.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- 
 * camel-multipart.c : Abstract class for a multipart 
 *
 * Authors: Michael Zucchi <notzed@ximian.com>
 *
 * Copyright 2002 Ximian, Inc. (www.ximian.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#ifdef HAVE_ALLOCA_H
#include <alloca.h>
#endif

#include <stdio.h>

#include <string.h>
#include <unistd.h>
#include <time.h>

#include <errno.h>

#include "camel-mime-part.h"
#include "camel-mime-message.h"
#include "camel-mime-parser.h"
#include "camel-stream-mem.h"
#include "camel-multipart-signed.h"
#include "camel-mime-part.h"
#include "camel-exception.h"
#include "md5-utils.h"

#include "camel-stream-filter.h"
#include "camel-seekable-substream.h"
#include "camel-mime-filter-crlf.h"
#include "camel-mime-filter-canon.h"

#define d(x) /*(printf("%s(%d): ", __FILE__, __LINE__),(x))
           #include <stdio.h>;*/

static void signed_add_part (CamelMultipart *multipart, CamelMimePart *part);
static void signed_add_part_at (CamelMultipart *multipart, CamelMimePart *part, guint index);
static void signed_remove_part (CamelMultipart *multipart, CamelMimePart *part);
static CamelMimePart *signed_remove_part_at (CamelMultipart *multipart, guint index);
static CamelMimePart *signed_get_part (CamelMultipart *multipart, guint index);
static guint signed_get_number (CamelMultipart *multipart);

static ssize_t write_to_stream (CamelDataWrapper *data_wrapper, CamelStream *stream);
static void set_mime_type_field (CamelDataWrapper *data_wrapper, CamelContentType *mime_type);
static int construct_from_stream (CamelDataWrapper *data_wrapper, CamelStream *stream);
static int signed_construct_from_parser (CamelMultipart *multipart, struct _CamelMimeParser *mp);

static CamelMultipartClass *parent_class = NULL;

/* Returns the class for a CamelMultipartSigned */
#define CMP_CLASS(so) CAMEL_MULTIPART_SIGNED_CLASS (CAMEL_OBJECT_GET_CLASS(so))

/* Returns the class for a CamelDataWrapper */
#define CDW_CLASS(so) CAMEL_DATA_WRAPPER_CLASS (CAMEL_OBJECT_GET_CLASS(so))

static void
camel_multipart_signed_class_init (CamelMultipartSignedClass *camel_multipart_signed_class)
{
    CamelDataWrapperClass *camel_data_wrapper_class = CAMEL_DATA_WRAPPER_CLASS(camel_multipart_signed_class);
    CamelMultipartClass *mpclass = (CamelMultipartClass *)camel_multipart_signed_class;

    parent_class = (CamelMultipartClass *)camel_multipart_get_type();

    /* virtual method overload */
    camel_data_wrapper_class->construct_from_stream = construct_from_stream;
    camel_data_wrapper_class->write_to_stream = write_to_stream;
    camel_data_wrapper_class->decode_to_stream = write_to_stream;
    camel_data_wrapper_class->set_mime_type_field = set_mime_type_field;

    mpclass->add_part = signed_add_part;
    mpclass->add_part_at = signed_add_part_at;
    mpclass->remove_part = signed_remove_part;
    mpclass->remove_part_at = signed_remove_part_at;
    mpclass->get_part = signed_get_part;
    mpclass->get_number = signed_get_number;
    mpclass->construct_from_parser = signed_construct_from_parser;

/*
    mpclass->get_boundary = signed_get_boundary;
    mpclass->set_boundary = signed_set_boundary;
*/
}

static void
camel_multipart_signed_init (gpointer object, gpointer klass)
{
    CamelMultipartSigned *multipart = (CamelMultipartSigned *)object;

    camel_data_wrapper_set_mime_type(CAMEL_DATA_WRAPPER(multipart), "multipart/signed");
    multipart->start1 = -1;
}

static void
camel_multipart_signed_finalize (CamelObject *object)
{
    CamelMultipartSigned *mps = (CamelMultipartSigned *)object;

    g_free(mps->protocol);
    g_free(mps->micalg);
    if (mps->signature)
        camel_object_unref((CamelObject *)mps->signature);
    if (mps->content)
        camel_object_unref((CamelObject *)mps->content);
    if (mps->contentraw)
        camel_object_unref((CamelObject *)mps->contentraw);
}

CamelType
camel_multipart_signed_get_type (void)
{
    static CamelType camel_multipart_signed_type = CAMEL_INVALID_TYPE;

    if (camel_multipart_signed_type == CAMEL_INVALID_TYPE) {
        camel_multipart_signed_type = camel_type_register (camel_multipart_get_type (), "CamelMultipartSigned",
                                   sizeof (CamelMultipartSigned),
                                   sizeof (CamelMultipartSignedClass),
                                   (CamelObjectClassInitFunc) camel_multipart_signed_class_init,
                                   NULL,
                                   (CamelObjectInitFunc) camel_multipart_signed_init,
                                   (CamelObjectFinalizeFunc) camel_multipart_signed_finalize);
    }

    return camel_multipart_signed_type;
}

/**
 * camel_multipart_signed_new:
 *
 * Create a new CamelMultipartSigned object.
 *
 * A MultipartSigned should be used to store and create parts of
 * type "multipart/signed".  This is because multipart/signed is
 * entirely broken-by-design (tm) and uses completely
 * different semantics to other mutlipart types.  It must be treated
 * as opaque data by any transport.  See rfc 3156 for details.
 *
 * There are 3 ways to create the part:
 * Use construct_from_stream.  If this is used, then you must
 * set the mime_type appropriately to match the data uses, so
 * that the multiple parts my be extracted.
 *
 * Use construct_from_parser.  The parser MUST be in the CAMEL_MIME_PARSER_STATE_HEADER
 * state, and the current content_type MUST be "multipart/signed" with
 * the appropriate boundary and it SHOULD include the appropriate protocol
 * and hash specifiers.
 *
 * Use sign_part.  A signature part will automatically be created
 * and the whole part may be written using write_to_stream to
 * create a 'transport-safe' version (as safe as can be expected with
 * such a broken specification).
 *
 * Return value: a new CamelMultipartSigned
 **/
CamelMultipartSigned *
camel_multipart_signed_new (void)
{
    CamelMultipartSigned *multipart;

    multipart = (CamelMultipartSigned *)camel_object_new(CAMEL_MULTIPART_SIGNED_TYPE);

    return multipart;
}

/* find the next boundary @bound from @start, return the start of the actual data
   @end points to the end of the data BEFORE the boundary */
static char *parse_boundary(char *start, const char *bound, char **end)
{
    char *data, *begin;

    begin = strstr(start, bound);
    if (begin == NULL)
        return NULL;

    data = begin+strlen(bound);
    if (begin > start && begin[-1] == '\n')
        begin--;
    if (begin > start && begin[-1] == '\r')
        begin--;
    if (data[0] == '\r')
        data++;
    if (data[0] == '\n')
        data++;

    *end = begin;
    return data;
}

/* yeah yuck.
   Well, we could probably use the normal mime parser, but then it would change our
   headers.
   This is good enough ... till its not! */
static int
parse_content(CamelMultipartSigned *mps)
{
    CamelMultipart *mp = (CamelMultipart *)mps;
    char *start, *end, *start2, *end2, *last, *post;
    CamelStreamMem *mem;
    char *bound;
    const char *boundary;

    boundary = camel_multipart_get_boundary(mp);
    if (boundary == NULL) {
        g_warning("Trying to get multipart/signed content without setting boundary first");
        return -1;
    }

    /* turn it into a string, and 'fix' it up */
    /* this is extremely dodgey but should work! */
    mem = (CamelStreamMem *)((CamelDataWrapper *)mps)->stream;
    if (mem == NULL) {
        g_warning("Trying to parse multipart/signed without constructing first");
        return -1;
    }

    camel_stream_write((CamelStream *)mem, "", 1);
    g_byte_array_set_size(mem->buffer, mem->buffer->len-1);
    last = mem->buffer->data + mem->buffer->len;

    bound = alloca(strlen(boundary)+5);
    sprintf(bound, "--%s", boundary);

    start = parse_boundary(mem->buffer->data, bound, &end);
    if (start == NULL || start[0] == 0)
        return -1;

    if (end > (char *)mem->buffer->data) {
        char *tmp = g_strndup(mem->buffer->data, start-(char *)mem->buffer->data-1);
        camel_multipart_set_preface(mp, tmp);
        g_free(tmp);
    }

    start2 = parse_boundary(start, bound, &end);
    if (start2 == NULL || start2[0] == 0)
        return -1;

    sprintf(bound, "--%s--", boundary);
    post = parse_boundary(start2, bound, &end2);
    if (post == NULL)
        return -1;

    if (post[0])
        camel_multipart_set_postface(mp, post);

    mps->start1 = start-(char *)mem->buffer->data;
    mps->end1 = end-(char *)mem->buffer->data;
    mps->start2 = start2-(char *)mem->buffer->data;
    mps->end2 = end2-(char *)mem->buffer->data;

    return 0;
}

/* we snoop the mime type to get boundary and hash info */
static void
set_mime_type_field(CamelDataWrapper *data_wrapper, CamelContentType *mime_type)
{
    CamelMultipartSigned *mps = (CamelMultipartSigned *)data_wrapper;

    ((CamelDataWrapperClass *)parent_class)->set_mime_type_field(data_wrapper, mime_type);
    if (mime_type) {
        const char *micalg, *protocol;

        protocol = camel_content_type_param(mime_type, "protocol");
        g_free(mps->protocol);
        mps->protocol = g_strdup(protocol);

        micalg = camel_content_type_param(mime_type, "micalg");
        g_free(mps->micalg);
        mps->micalg = g_strdup(micalg);
    }
}

static void
signed_add_part(CamelMultipart *multipart, CamelMimePart *part)
{
    g_warning("Cannot add parts to a signed part using add_part");
}

static void
signed_add_part_at(CamelMultipart *multipart, CamelMimePart *part, guint index)
{
    g_warning("Cannot add parts to a signed part using add_part_at");
}

static void
signed_remove_part(CamelMultipart *multipart, CamelMimePart *part)
{
    g_warning("Cannot remove parts from a signed part using remove_part");
}

static CamelMimePart *
signed_remove_part_at (CamelMultipart *multipart, guint index)
{
    g_warning("Cannot remove parts from a signed part using remove_part");
    return NULL;
}

static CamelMimePart *
signed_get_part(CamelMultipart *multipart, guint index)
{
    CamelMultipartSigned *mps = (CamelMultipartSigned *)multipart;
    CamelDataWrapper *dw = (CamelDataWrapper *)multipart;
    CamelStream *stream;

    switch (index) {
    case CAMEL_MULTIPART_SIGNED_CONTENT:
        if (mps->content)
            return mps->content;
        if (mps->contentraw) {
            stream = mps->contentraw;
            camel_object_ref((CamelObject *)stream);
        } else if (mps->start1 == -1
               && parse_content(mps) == -1
               && (stream = ((CamelDataWrapper *)mps)->stream) == NULL) {
            g_warning("Trying to get content on an invalid multipart/signed");
            return NULL;
        } else if (dw->stream == NULL) {
            return NULL;
        } else if (mps->start1 == -1) {
            stream = dw->stream;
            camel_object_ref(stream);
        } else {
            stream = camel_seekable_substream_new((CamelSeekableStream *)dw->stream, mps->start1, mps->end1);
        }
        camel_stream_reset(stream);
        mps->content = camel_mime_part_new();
        camel_data_wrapper_construct_from_stream((CamelDataWrapper *)mps->content, stream);
        camel_object_unref(stream);
        return mps->content;
    case CAMEL_MULTIPART_SIGNED_SIGNATURE:
        if (mps->signature)
            return mps->signature;
        if (mps->start1 == -1
            && parse_content(mps) == -1) {
            g_warning("Trying to get signature on invalid multipart/signed");
            return NULL;
        } else if (dw->stream == NULL) {
            return NULL;
        }
        stream = camel_seekable_substream_new((CamelSeekableStream *)dw->stream, mps->start2, mps->end2);
        camel_stream_reset(stream);
        mps->signature = camel_mime_part_new();
        camel_data_wrapper_construct_from_stream((CamelDataWrapper *)mps->signature, stream);
        camel_object_unref((CamelObject *)stream);
        return mps->signature;
    default:
        g_warning("trying to get object out of bounds for multipart");
    }

    return NULL;
}

static guint
signed_get_number(CamelMultipart *multipart)
{
    CamelDataWrapper *dw = (CamelDataWrapper *)multipart;
    CamelMultipartSigned *mps = (CamelMultipartSigned *)multipart;

    /* check what we have, so we return something reasonable */

    if ((mps->content || mps->contentraw) && mps->signature)
        return 2;

    if (mps->start1 == -1 && parse_content(mps) == -1) {
        if (dw->stream == NULL)
            return 0;
        else
            return 1;
    } else {
        return 2;
    }
}

static void
set_stream(CamelMultipartSigned *mps, CamelStream *mem)
{
    CamelDataWrapper *dw = (CamelDataWrapper *)mps;

    if (dw->stream)
        camel_object_unref((CamelObject *)dw->stream);
    dw->stream = (CamelStream *)mem;

    mps->start1 = -1;
    if (mps->content) {
        camel_object_unref((CamelObject *)mps->content);
        mps->content = NULL;
    }
    if (mps->contentraw) {
        camel_object_unref((CamelObject *)mps->contentraw);
        mps->contentraw = NULL;
    }
    if (mps->signature) {
        camel_object_unref((CamelObject *)mps->signature);
        mps->signature = NULL;
    }
}

static int
construct_from_stream(CamelDataWrapper *data_wrapper, CamelStream *stream)
{
    CamelMultipartSigned *mps = (CamelMultipartSigned *)data_wrapper;
    CamelStream *mem = camel_stream_mem_new();

    if (camel_stream_write_to_stream(stream, mem) == -1)
        return -1;

    set_stream(mps, mem);

    return 0;
}

static int
signed_construct_from_parser(CamelMultipart *multipart, struct _CamelMimeParser *mp)
{
    int err;
    CamelContentType *content_type;
    CamelMultipartSigned *mps = (CamelMultipartSigned *)multipart;
    char *buf;
    size_t len;
    CamelStream *mem;

    /* we *must not* be in multipart state, otherwise the mime parser will
       parse the headers which is a no no @#$@# stupid multipart/signed spec */
    g_assert(camel_mime_parser_state(mp) == CAMEL_MIME_PARSER_STATE_HEADER);

    /* All we do is copy it to a memstream */
    content_type = camel_mime_parser_content_type(mp);
    camel_multipart_set_boundary(multipart, camel_content_type_param(content_type, "boundary"));

    mem = camel_stream_mem_new();
    while (camel_mime_parser_step(mp, &buf, &len) != CAMEL_MIME_PARSER_STATE_BODY_END)
        camel_stream_write(mem, buf, len);

    set_stream(mps, mem);

    err = camel_mime_parser_errno(mp);
    if (err != 0) {
        errno = err;
        return -1;
    } else
        return 0;
}

static ssize_t
write_to_stream (CamelDataWrapper *data_wrapper, CamelStream *stream)
{
    CamelMultipartSigned *mps = (CamelMultipartSigned *)data_wrapper;
    CamelMultipart *mp = (CamelMultipart *)mps;
    const char *boundary;
    ssize_t total = 0;
    ssize_t count;
    
    /* we have 3 basic cases:
       1. constructed, we write out the data wrapper stream we got
       2. signed content, we create and write out a new stream
       3. invalid
    */

    /* 1 */
    /* FIXME: locking? */
    if (data_wrapper->stream) {
        camel_stream_reset(data_wrapper->stream);
        return camel_stream_write_to_stream(data_wrapper->stream, stream);
    }

    /* 3 */
    if (mps->signature == NULL || mps->contentraw == NULL)
        return -1;

    /* 2 */
    boundary = camel_multipart_get_boundary(mp);
    if (mp->preface) {
        count = camel_stream_write_string(stream, mp->preface);
        if (count == -1)
            return -1;
        total += count;
    }

    /* first boundary */
    count = camel_stream_printf(stream, "\n--%s\n", boundary);
    if (count == -1)
        return -1;
    total += count;

    /* output content part */
    camel_stream_reset(mps->contentraw);
    count = camel_stream_write_to_stream(mps->contentraw, stream);
    if (count == -1)
        return -1;
    total += count;
    
    /* boundary */
    count = camel_stream_printf(stream, "\n--%s\n", boundary);
    if (count == -1)
        return -1;
    total += count;

    /* signature */
    count = camel_data_wrapper_write_to_stream((CamelDataWrapper *)mps->signature, stream);
    if (count == -1)
        return -1;
    total += count;

    /* write the terminating boudary delimiter */
    count = camel_stream_printf(stream, "\n--%s--\n", boundary);
    if (count == -1)
        return -1;
    total += count;

    /* and finally the postface */
    if (mp->postface) {
        count = camel_stream_write_string(stream, mp->postface);
        if (count == -1)
            return -1;
        total += count;
    }

    return total;   
}

/* See rfc3156, section 2 and others */
/* We do this simply: Anything not base64 must be qp
   This is so that we can safely translate any occurance of "From "
   into the quoted-printable escaped version safely. */
static void
prepare_sign(CamelMimePart *mime_part)
{
    CamelDataWrapper *wrapper;
    CamelTransferEncoding encoding;
    int parts, i;
    
    wrapper = camel_medium_get_content_object (CAMEL_MEDIUM (mime_part));
    if (!wrapper)
        return;
    
    if (CAMEL_IS_MULTIPART (wrapper)) {
        parts = camel_multipart_get_number((CamelMultipart *)wrapper);
        for (i = 0; i < parts; i++)
            prepare_sign(camel_multipart_get_part((CamelMultipart *)wrapper, i));
    } else if (CAMEL_IS_MIME_MESSAGE (wrapper)) {
        prepare_sign((CamelMimePart *)wrapper);
    } else {
        encoding = camel_mime_part_get_encoding(mime_part);

        if (encoding != CAMEL_TRANSFER_ENCODING_BASE64
            && encoding != CAMEL_TRANSFER_ENCODING_QUOTEDPRINTABLE) {
            camel_mime_part_set_encoding(mime_part, CAMEL_TRANSFER_ENCODING_QUOTEDPRINTABLE);
        }
    }
}

/**
 * camel_multipart_signed_sign:
 * @mps: 
 * @context: The CipherContext to use for signing.
 * @content: CamelMimePart content you wish to sign/transport.
 * @userid: The id of the signing key to use.
 * @hash: The algorithm to use.
 * @ex: 
 * 
 * Sign the part @content, and attach it as the first part
 * (CAMEL_MULTIPART_SIGNED_CONTENT) of the multipart @mps.  A
 * signature object will be created and setup as the second part
 * (CAMEL_MULTIPART_SIGNED_SIGNATURE) of the object.  Once a part has
 * been successfully signed the mutlipart is ready for transmission.
 *
 * This method should be used to create multipart/signed objects
 * which are properly canoncalised before signing, etc.
 * 
 * Return value: -1 on error, setting @ex appropriately.  On error
 * neither the content or signature parts will be setup.
 **/
int
camel_multipart_signed_sign(CamelMultipartSigned *mps, CamelCipherContext *context, CamelMimePart *content, const char *userid, CamelCipherHash hash, CamelException *ex)
{
    CamelMimeFilter *canon_filter;
    CamelStream *sigstream, *mem;
    CamelStreamFilter *filter;
    CamelContentType *mime_type;
    CamelMimePart *signature;
    CamelDataWrapper *dw;
    char *type;

    /* this needs to be set */
    g_return_val_if_fail(context->sign_protocol != NULL, -1);

    prepare_sign(content);

    mem = camel_stream_mem_new();
    filter = camel_stream_filter_new_with_stream(mem);
    
    /* Note: see rfc2015 or rfc3156, section 5 */
    canon_filter = camel_mime_filter_canon_new(CAMEL_MIME_FILTER_CANON_STRIP|CAMEL_MIME_FILTER_CANON_CRLF|CAMEL_MIME_FILTER_CANON_FROM);
    camel_stream_filter_add(filter, (CamelMimeFilter *)canon_filter);
    camel_object_unref((CamelObject *)canon_filter);

    camel_data_wrapper_write_to_stream((CamelDataWrapper *)content, (CamelStream *)filter);
    camel_stream_flush((CamelStream *)filter);
    camel_object_unref((CamelObject *)filter);
    camel_stream_reset(mem);

#if 0
    printf("-- Signing:\n");
    fwrite(((CamelStreamMem *)mem)->buffer->data, ((CamelStreamMem *)mem)->buffer->len, 1, stdout);
    printf("-- end\n");
#endif

    sigstream = camel_stream_mem_new();

    if (camel_cipher_sign(context, userid, hash, mem, sigstream, ex) == -1) {
        camel_object_unref((CamelObject *)mem);
        camel_object_unref((CamelObject *)sigstream);
        return -1;
    }

    /* create the signature wrapper object */
    signature = camel_mime_part_new();
    dw = camel_data_wrapper_new();
    type = alloca(strlen(context->sign_protocol) + 32);
    sprintf(type, "%s; name=signature.asc", context->sign_protocol);
    camel_data_wrapper_set_mime_type(dw, type);
    camel_stream_reset(sigstream);
    camel_data_wrapper_construct_from_stream(dw, sigstream);
    camel_object_unref((CamelObject *)sigstream);
    camel_medium_set_content_object((CamelMedium *)signature, dw);
    camel_object_unref((CamelObject *)dw);
    camel_mime_part_set_description(signature, _("This is a digitally signed message part"));

    /* setup our mime type and boundary */
    mime_type = camel_content_type_new("multipart", "signed");
    camel_content_type_set_param(mime_type, "micalg", camel_cipher_hash_to_id(context, hash));
    camel_content_type_set_param(mime_type, "protocol", context->sign_protocol);
    camel_data_wrapper_set_mime_type_field(CAMEL_DATA_WRAPPER (mps), mime_type);
    camel_content_type_unref(mime_type);
    camel_multipart_set_boundary((CamelMultipart *)mps, NULL);

    /* just keep the whole raw content.  We dont *really* need to do this because
       we know how we just proccessed it, but, well, better to be safe than sorry */
    mps->signature = signature;
    mps->contentraw = mem;
    camel_stream_reset(mem);

    /* clear the data-wrapper stream - tells write_to_stream to use the right object */
    if (((CamelDataWrapper *)mps)->stream) {
        camel_object_unref((CamelObject *) ((CamelDataWrapper *)mps)->stream);
        ((CamelDataWrapper *)mps)->stream = NULL;
    }

    return 0;
}

/**
 * camel_multipart_signed_verify:
 * @mps: 
 * @context: 
 * @ex: 
 * 
 * Verify a signed object.  This may be used to verify newly signed
 * objects as well as those created from external streams or parsers.
 * 
 * Return value: A validity value, or NULL on error, setting @ex
 * appropriately.
 **/
CamelCipherValidity *
camel_multipart_signed_verify(CamelMultipartSigned *mps, CamelCipherContext *context, CamelException *ex)
{
    CamelCipherValidity *valid;
    CamelMimePart *sigpart;
    CamelStream *sigstream, *constream;

    /* we need to be able to verify stuff we just signed as well as stuff we loaded from a stream/parser */

    if (mps->contentraw) {
        constream = mps->contentraw;
        camel_object_ref((CamelObject *)constream);
    } else {
        CamelStream *sub;
        CamelMimeFilter *canon_filter;

        if (mps->start1 == -1 && parse_content(mps) == -1) {
            camel_exception_setv(ex, CAMEL_EXCEPTION_SYSTEM, _("parse error"));
            return NULL;
        }

        /* first, prepare our parts */
        sub = camel_seekable_substream_new((CamelSeekableStream *)((CamelDataWrapper *)mps)->stream, mps->start1, mps->end1);
        constream = (CamelStream *)camel_stream_filter_new_with_stream(sub);
        camel_object_unref((CamelObject *)sub);
        
        /* Note: see rfc2015 or rfc3156, section 5 */
        canon_filter = camel_mime_filter_canon_new (CAMEL_MIME_FILTER_CANON_CRLF);
        camel_stream_filter_add((CamelStreamFilter *)constream, (CamelMimeFilter *)canon_filter);
        camel_object_unref((CamelObject *)canon_filter);
    }

    /* we do this as a normal mime part so we can have it handle transfer encoding etc */
    sigstream = camel_stream_mem_new();
    sigpart = camel_multipart_get_part((CamelMultipart *)mps, CAMEL_MULTIPART_SIGNED_SIGNATURE);
    camel_data_wrapper_write_to_stream((CamelDataWrapper *)sigpart, sigstream);
    camel_stream_reset(sigstream);

    /* do the magic, the caller must supply the right context for this kind of object */
    valid = camel_cipher_verify(context, camel_cipher_id_to_hash(context, mps->micalg), constream, sigstream, ex);

#if 0
    {
        CamelStream *sout = camel_stream_fs_new_with_fd(dup(0));

        camel_stream_printf(sout, "-- Verifying:\n");
        camel_stream_reset(constream);
        camel_stream_write_to_stream(constream, sout);
        camel_stream_printf(sout, "-- end\n");
        camel_object_unref((CamelObject *)sout);
    }
#endif

    camel_object_unref((CamelObject *)constream);
    camel_object_unref((CamelObject *)sigstream);

    return valid;
}