nop_encrypt.c

Shows the basic framework for building an encryptor as a plug in library.

/*-
 * Public Domain 2014-present MongoDB, Inc.
 * Public Domain 2008-2014 WiredTiger, Inc.
 *
 * This is free and unencumbered software released into the public domain.
 *
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 *
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */
 
#include <errno.h>
#include <stdlib.h>
#include <string.h>
 
#include <wiredtiger.h>
#include <wiredtiger_ext.h>
 
/* Local encryptor structure. */
typedef struct {
    WT_ENCRYPTOR encryptor; /* Must come first */
 
    WT_EXTENSION_API *wt_api; /* Extension API */
 
    unsigned long nop_calls; /* Count of calls */
 
} NOP_ENCRYPTOR;
/*
 * nop_error --
 *     Display an error from this module in a standard way.
 */
static int
nop_error(NOP_ENCRYPTOR *encryptor, WT_SESSION *session, int err, const char *msg)
{
    WT_EXTENSION_API *wt_api;
 
    wt_api = encryptor->wt_api;
    (void)wt_api->err_printf(
      wt_api, session, "nop encryption: %s: %s", msg, wt_api->strerror(wt_api, NULL, err));
    return (err);
}
 
/*
 * nop_encrypt --
 *     A simple encryption example that passes data through unchanged.
 */
static int
nop_encrypt(WT_ENCRYPTOR *encryptor, WT_SESSION *session, uint8_t *src, size_t src_len,
  uint8_t *dst, size_t dst_len, size_t *result_lenp)
{
    NOP_ENCRYPTOR *nop_encryptor = (NOP_ENCRYPTOR *)encryptor;
 
    (void)session; /* Unused parameters */
 
    ++nop_encryptor->nop_calls; /* Call count */
 
    if (dst_len < src_len)
        return (nop_error(nop_encryptor, session, ENOMEM, "encrypt buffer not big enough"));
 
    memcpy(dst, src, src_len);
    *result_lenp = src_len;
 
    return (0);
}
/*
 * nop_decrypt --
 *     A simple decryption example that passes data through unchanged.
 */
static int
nop_decrypt(WT_ENCRYPTOR *encryptor, WT_SESSION *session, uint8_t *src, size_t src_len,
  uint8_t *dst, size_t dst_len, size_t *result_lenp)
{
    NOP_ENCRYPTOR *nop_encryptor = (NOP_ENCRYPTOR *)encryptor;
 
    (void)session; /* Unused parameters */
    (void)src_len;
 
    ++nop_encryptor->nop_calls; /* Call count */
 
    /*
     * The destination length is the number of unencrypted bytes we're expected to return.
     */
    memcpy(dst, src, dst_len);
    *result_lenp = dst_len;
    return (0);
}
/*
 * nop_sizing --
 *     A simple sizing example that tells wiredtiger that the encrypted buffer is always the same as
 *     the source buffer.
 */
static int
nop_sizing(WT_ENCRYPTOR *encryptor, WT_SESSION *session, size_t *expansion_constantp)
{
    NOP_ENCRYPTOR *nop_encryptor = (NOP_ENCRYPTOR *)encryptor;
 
    (void)session; /* Unused parameters */
 
    ++nop_encryptor->nop_calls; /* Call count */
 
    *expansion_constantp = 0;
    return (0);
}
/*
 * nop_customize --
 *     The customize function creates a customized encryptor.
 */
static int
nop_customize(WT_ENCRYPTOR *encryptor, WT_SESSION *session, WT_CONFIG_ARG *encrypt_config,
  WT_ENCRYPTOR **customp)
{
    /*
     * This is how keys are set: the extension is first loaded, and then for every distinct key used
     * a copy is made by calling the customize method. The original uncustomized WT_ENCRYPTOR is
     * ordinarily never used to encrypt or decrypt anything.
     *
     * The copy, with the key installed into it, should be returned to the caller via the customp
     * argument. If the customize method succeeds but sets *customp to NULL, the original encryptor
     * is used for that key.
     *
     * The customize method need not be provided, but in that case key configuration is not
     * performed, the original encryptor is used for all encryption, and it must have some other
     * means to get the key or keys it should use.
     */
 
    const NOP_ENCRYPTOR *orig;
    NOP_ENCRYPTOR *new;
    WT_CONFIG_ITEM keyid, secretkey;
    WT_EXTENSION_API *wt_api;
    int ret;
 
    orig = (const NOP_ENCRYPTOR *)encryptor;
    wt_api = orig->wt_api;
 
    /* Allocate and initialize the new encryptor. */
    if ((new = calloc(1, sizeof(*new))) == NULL)
        return (errno);
    *new = *orig;
 
    /* Get the keyid, if any. */
    ret = wt_api->config_get(wt_api, session, encrypt_config, "keyid", &keyid);
    if (ret != 0)
        keyid.len = 0;
 
    /* Get the explicit secret key, if any. */
    ret = wt_api->config_get(wt_api, session, encrypt_config, "secretkey", &secretkey);
    if (ret != 0)
        secretkey.len = 0;
 
    /* Providing both a keyid and a secretkey is an error. */
    if (keyid.len != 0 && secretkey.len != 0) {
        ret = nop_error(
          new, NULL, EINVAL, "nop_customize: keys specified with both keyid= and secretkey=");
        goto err;
    }
 
    /*
     * Providing neither is also normally an error. Allow it here for the benefit of the test suite.
     */
    if (keyid.len == 0 && secretkey.len == 0)
        (void)keyid; /* do nothing */
 
    if (keyid.len != 0)
        /*
         * Here one would contact a key manager to get the key, then install it.
         */
        (void)keyid.str; /* do nothing; add code here */
 
    if (secretkey.len != 0)
        /*
         * Here one would install the explicit secret key, probably after base64- or hex-decoding
         * it. If it's a passphrase rather than a key, one might hash it first. Other
         * transformations might be needed or wanted as well.
         */
        (void)secretkey.str; /* do nothing; add code here */
 
    /* Return the new encryptor. */
    *customp = (WT_ENCRYPTOR *)new;
    return (0);
 
err:
    free(new);
    return (ret);
}
/*
 * nop_terminate --
 *     WiredTiger no-op encryption termination.
 */
static int
nop_terminate(WT_ENCRYPTOR *encryptor, WT_SESSION *session)
{
    NOP_ENCRYPTOR *nop_encryptor = (NOP_ENCRYPTOR *)encryptor;
 
    (void)session; /* Unused parameters */
 
    ++nop_encryptor->nop_calls; /* Call count */
 
    /* Free the allocated memory. */
    free(encryptor);
 
    return (0);
}
/*
 * wiredtiger_extension_init --
 *     A simple shared library encryption example.
 */
int
wiredtiger_extension_init(WT_CONNECTION *connection, WT_CONFIG_ARG *config)
{
    NOP_ENCRYPTOR *nop_encryptor;
    int ret;
 
    (void)config; /* Unused parameters */
 
    if ((nop_encryptor = calloc(1, sizeof(NOP_ENCRYPTOR))) == NULL)
        return (errno);
 
    /*
     * Allocate a local encryptor structure, with a WT_ENCRYPTOR structure as the first field,
     * allowing us to treat references to either type of structure as a reference to the other type.
     *
     * Heap memory (not static), because it can support multiple databases.
     */
    nop_encryptor->encryptor.encrypt = nop_encrypt;
    nop_encryptor->encryptor.decrypt = nop_decrypt;
    nop_encryptor->encryptor.sizing = nop_sizing;
    nop_encryptor->encryptor.customize = nop_customize;
    nop_encryptor->encryptor.terminate = nop_terminate;
 
    nop_encryptor->wt_api = connection->get_extension_api(connection);
 
    /* Load the encryptor */
    if ((ret = connection->add_encryptor(connection, "nop", (WT_ENCRYPTOR *)nop_encryptor, NULL)) ==
      0)
        return (0);
 
    free(nop_encryptor);
    return (ret);
}