pEpEngine/src/internal_format.c

/**
 * @file    internal_format.c
 * @brief   internal format (FIXME: derived from filename)
 * @license GNU General Public License 3.0 - see LICENSE.txt
 */

#include "platform.h"

#include "pEp_internal.h"
#include "internal_format.h"

/**
 * <!-- _internal_message_type -->
 * @brief Definition of internal message format
 * @see https://dev.pep.foundation/Engine/ElevatedAttachments#internal-message-format
 * 
 * @par Key material
 * Key material is encoded with 0 ‘K’ subtype 0 followed by the binary representation of the .value of the attachment for transports.
 * 
 * @par p≡p Sync
 * A p≡p Sync message is encoded with 0 ‘S’ subtype 0 followed by the binary representation of the .value of the attachment.
 * 
 * @par p≡p Distribution
 * A p≡p Distribution message is encoded with 0 ‘D’ subtype 0 followed by the binary representation of the .value of the attachment.
 * 
 * @par Authentication material
 * Key material is encoded with 0 ‘A’ subtype 0 followed by the binary representation of the .value of the attachment.
 * 
 */
static struct _internal_message_type {
    char type;
    char subtype;
    const char *mime_type;
} message_type[] = {
    // Keys
    { 'K',  0, "application/keys" },

    // OpenPGP
    { 'K',  2, "application/pgp-keys" },

    // x.509
    { 'K',  3, "application/pkcs10" },
    { 'K',  4, "application/pkix-cert" },
    { 'K',  5, "application/pkix-crl" },
    { 'K',  6, "application/pkcs7-mime" },
    { 'K',  7, "application/x-x509-ca-cert" },
    { 'K',  8, "application/x-x509-user-cert" },
    { 'K',  9, "application/x-pkcs7-crl" },
    { 'K', 10, "application/x-pem-file" },
    { 'K', 11, "application/x-pkcs12" },
    { 'K', 12, "application/x-pkcs7-certificates" },
    { 'K', 13, "application/x-pkcs7-certreqresp" },

    // Sync
    { 'S', 0, "application/pEp.sync" },

    // Distribution
    { 'D', 0, "application/pEp.distribution" },
    { 'D', 0, "application/pEp.keyreset" },

    // Authentication
    { 'A', 0, "application/auth" },
    { 'A', 1, "application/signature" },

    // OpenPGP
    { 'A', 2, "application/pgp-signature" },

    // x.509
    { 'A', 3, "application/pkcs7-signature" },
    { 'A', 3, "application/x-pkcs7-signature" },
    
    // end marker
    { 0, 0, NULL }
};

DYNAMIC_API PEP_STATUS encode_internal(
        const char *value,
        size_t size,
        const char *mime_type,
        char **code,
        size_t *code_size
    )
{
    assert(value && size && mime_type && code && code_size);
    if (!(value && size && mime_type && code && code_size))
        return PEP_ILLEGAL_VALUE;

    *code = NULL;
    *code_size = 0;

    char type = 0;
    char subtype;

    struct _internal_message_type *mt;
    for (mt = message_type; mt->type; ++mt) {
        if (strcasecmp(mime_type, mt->mime_type) == 0) {
            type = mt->type;
            subtype = mt->subtype;
            break;
        }
    }

    // unsupported MIME type
    if (!type)
        return PEP_STATUS_OK;

    // those are more BSOBs than BLOBS, so we copy
    char *result = malloc(size + 4);
    assert(result);
    if (!result)
        return PEP_OUT_OF_MEMORY;

    result[0] = 0;
    result[1] = type;
    result[2] = subtype;
    result[3] = 0;

    memcpy(result + 4, value, size);
    
    *code = result;
    *code_size = size + 4;

    return PEP_STATUS_OK;
}

DYNAMIC_API PEP_STATUS decode_internal(
        const char *code,
        size_t code_size,
        char **value,
        size_t *size,
        char **mime_type
    )
{
    assert(value && size && mime_type && code && !code[0] && code_size);
    if (!(value && size && mime_type && code && !code[0] && code_size))
        return PEP_ILLEGAL_VALUE;

    *value = NULL;
    *size = 0;
    *mime_type = NULL;

    // elevated attachments have at least 5 bytes
    assert(code_size > 4);
    if (code_size < 5)
        return PEP_ILLEGAL_VALUE;

    assert(!code[0]);
    char type = code[1];
    char subtype = code[2];
    // char reserved = code[3];

    char *_mime_type = NULL;

    struct _internal_message_type *mt;
    for (mt = message_type; mt->type; ++mt) {
        if (type == mt->type && subtype == mt->subtype) {
            assert(mt->mime_type);
            _mime_type = strdup(mt->mime_type);
            assert(_mime_type);
            if (!_mime_type)
                return PEP_OUT_OF_MEMORY;

            break;
        }
    }

    if (!_mime_type)
        return PEP_ILLEGAL_VALUE;

    char *result = malloc(code_size - 4);
    assert(result);
    if (!result) {
        free(_mime_type);
        return PEP_OUT_OF_MEMORY;
    }

    memcpy(result, code + 4, code_size - 4);

    *value = result;
    *size = code_size - 4;
    *mime_type = _mime_type;

    return PEP_STATUS_OK;
}