Version 10.0.2
sodium_encrypt.c

An encryptor using the libsodium cryptography 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.
*/
/*
* Encryption extension using libsodium for cryptography.
*
* Note: we recommend that all applications relying on encryption for security audit their
* application and storage toolchain code, including this implementation and the underlying
* cryptographic libraries.
*
* The only threat model this extension is intended to protect against is: your database was on your
* laptop, and your laptop was stolen while the database was at rest (shut down).
*
* Because the key is necessarily kept in memory while the database is running, it is important to
* make sure it does not get written to disk by OS mechanisms; for example, core dumps and kernel
* crash dumps should be disabled, and swapping should be either disabled or set up to be encrypted.
* Also note that a still-running database on a laptop that is suspended is not at rest.
*
* This code does not, for the moment, support any form of external key server or key management
* service. Keys must be configured with "secretkey=" at database open time, and not with "keyid=".
* This is workable, but less than optimal. To add support for your favorite key service, copy this
* file, edit where indicated below, and install as your own custom extension. (See the other
* encryption examples for further information about how to do this.)
*
* The secretkey= configured at database open time is expected to be a 256-bit chacha20 key, printed
* as hex (with no leading 0x), thus 64 characters long. If you want to use a passphrase instead,
* use the recommended tools in libsodium to generate a key from a passphrase and pass the results
* as the secretkey= configuration.
*/
#include <errno.h>
#include <wiredtiger.h>
#include <wiredtiger_ext.h>
#include <sodium.h>
/*
* Lengths of the pieces involved: the secret key, the non-secret but unique nonce, and the
* cryptographic checksum added as part of the encryption.
*/
#define CHECK_LEN crypto_aead_xchacha20poly1305_ietf_ABYTES
#define KEY_LEN crypto_aead_xchacha20poly1305_ietf_KEYBYTES
#define NONCE_LEN crypto_aead_xchacha20poly1305_ietf_NPUBBYTES
/*
* We write a header on each block that records the expected format version and the cryptographic
* construction used. This is incorporated into the block's cryptographic checksum and thus
* protected from interference. The header is 4 bytes long to keep the following data aligned, but
* we only use two of them. Currently we only support the one construction, but that could
* conceivably change and in any event it's a good idea to make persistent formats extensible.
*/
#define HEADER_BYTE_FORMATVERSION 0
#define HEADER_BYTE_CONSTRUCTION 1
#define HEADER_BYTE_ZERO_0 2
#define HEADER_BYTE_ZERO_1 3
#define HEADER_LEN 4
/* Constants for the on-disk (output) format. */
#define ONDISK_CIPHER_XCHACHA20POLY1305 1
#define ONDISK_VERSION_CURRENT 1
/*
* Each output block contains, in order:
* - the header
* - the nonce
* - the cryptographic output (ciphertext and checksum)
* The header and nonce are not secret but are covered by the checksum.
*/
#define HEADER_LOCATION 0
#define NONCE_LOCATION HEADER_LEN
#define CIPHERTEXT_LOCATION (HEADER_LEN + NONCE_LEN)
/*
* Data for this extension. Note that the secret key has to be kept in memory for use.
*/
typedef struct {
WT_ENCRYPTOR encryptor; /* Must come first */
WT_EXTENSION_API *wt_api; /* Extension API */
uint8_t *secretkey; /* Secret key. (bytes) */
} SODIUM_ENCRYPTOR;
/*
* sodium_error --
* Display an error from this module in a standard way.
*/
static int
sodium_error(SODIUM_ENCRYPTOR *encryptor, WT_SESSION *session, int err, const char *msg)
{
wt_api = encryptor->wt_api;
(void)wt_api->err_printf(
wt_api, session, "sodium encryption: %s: %s", msg, wt_api->strerror(wt_api, NULL, err));
return (err);
}
/*
* create_nonce --
* Generate a random nonce.
*/
static void
create_nonce(uint8_t *dst, size_t len)
{
/*
* It would be tidier to use incrementing nonces, but currently doing so would require sharing
* the current nonce between all threads and then doing global locking to use it, which is
* probably not going to work out that well. There isn't a convenient way to store per-thread
* extension state.
*/
randombytes_buf(dst, len);
}
/*
* sodium_encrypt --
* Encrypt using libsodium.
*
* Note that the encryption does not require that the input be padded to any particular alignment.
*/
static int
sodium_encrypt(WT_ENCRYPTOR *encryptor, WT_SESSION *session, uint8_t *cleartext, size_t clear_len,
uint8_t *ciphertext, size_t cipher_maxlen, size_t *result_lenp)
{
SODIUM_ENCRYPTOR *sodium_encryptor = (SODIUM_ENCRYPTOR *)encryptor;
unsigned long long cipher_len;
int ret;
(void)session; /* Unused */
/* Make sure it is big enough. */
if (cipher_maxlen < HEADER_LEN + NONCE_LEN + clear_len + CHECK_LEN)
return (sodium_error(sodium_encryptor, session, ENOMEM, "encrypt buffer not big enough"));
/* Write the header. */
ciphertext[HEADER_LOCATION + HEADER_BYTE_FORMATVERSION] = ONDISK_VERSION_CURRENT;
ciphertext[HEADER_LOCATION + HEADER_BYTE_CONSTRUCTION] = ONDISK_CIPHER_XCHACHA20POLY1305;
ciphertext[HEADER_LOCATION + HEADER_BYTE_ZERO_0] = 0;
ciphertext[HEADER_LOCATION + HEADER_BYTE_ZERO_1] = 0;
/* Make a nonce. */
create_nonce(&ciphertext[NONCE_LOCATION], NONCE_LEN);
/* Encrypt and checksum into the ciphertext part of the output. */
ret = crypto_aead_xchacha20poly1305_ietf_encrypt(&ciphertext[CIPHERTEXT_LOCATION], &cipher_len,
cleartext, clear_len, &ciphertext[HEADER_LOCATION], HEADER_LEN, NULL,
&ciphertext[NONCE_LOCATION], sodium_encryptor->secretkey);
if (ret < 0)
return (sodium_error(sodium_encryptor, session, WT_ERROR, "encryption failed"));
*result_lenp = HEADER_LEN + NONCE_LEN + cipher_len;
return (0);
}
/*
* sodium_decrypt --
* Decrypt using libsodium.
*/
static int
sodium_decrypt(WT_ENCRYPTOR *encryptor, WT_SESSION *session, uint8_t *ciphertext, size_t cipher_len,
uint8_t *cleartext, size_t clear_maxlen, size_t *result_lenp)
{
SODIUM_ENCRYPTOR *sodium_encryptor = (SODIUM_ENCRYPTOR *)encryptor;
size_t cipher_check_only_len;
unsigned long long clear_len;
int ret;
/* Make sure it is big enough. */
if (HEADER_LEN + NONCE_LEN + clear_maxlen + CHECK_LEN < cipher_len)
return (sodium_error(sodium_encryptor, session, ENOMEM, "decrypt buffer not big enough"));
/* This is the length of just the ciphertext/checksum part. */
cipher_check_only_len = cipher_len - HEADER_LEN - NONCE_LEN;
/* Decrypt and verify the checksum. */
ret = crypto_aead_xchacha20poly1305_ietf_decrypt(cleartext, &clear_len, NULL,
&ciphertext[CIPHERTEXT_LOCATION], cipher_check_only_len, &ciphertext[HEADER_LOCATION],
HEADER_LEN, &ciphertext[NONCE_LOCATION], sodium_encryptor->secretkey);
if (ret < 0)
return (sodium_error(sodium_encryptor, session, WT_ERROR, "decryption failed"));
*result_lenp = clear_len;
return (0);
}
/*
* sodium_sizing --
* Report how much extra space we need in the output buffer.
*/
static int
sodium_sizing(WT_ENCRYPTOR *encryptor, WT_SESSION *session, size_t *expansion_constantp)
{
/*
* Note that the interface assumes the expansion is always a constant; for the construction
* we're using that's true, but for one based on a block cipher it might need to be rounded up
* to allow for the ciphertext part of the output always being an integer multiple of the cipher
* block size.
*/
(void)encryptor; /* Unused parameters */
(void)session; /* Unused parameters */
/* Expand by the header, the nonce, and the checksum. */
*expansion_constantp = HEADER_LEN + NONCE_LEN + CHECK_LEN;
return (0);
}
/*
* sodium_customize --
* The customize function creates a customized encryptor.
*/
static int
sodium_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
* never used to encrypt or decrypt anything.
*/
const SODIUM_ENCRYPTOR *orig;
SODIUM_ENCRYPTOR *new;
WT_CONFIG_ITEM keyid, secretkey;
size_t keylen;
int ret;
orig = (const SODIUM_ENCRYPTOR *)encryptor;
wt_api = orig->wt_api;
/* Allocate and initialize the new encryptor. */
if ((new = calloc(1, sizeof(*new))) == NULL)
return (errno);
*new = *orig;
new->secretkey = NULL;
/* 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 = sodium_error(
new, NULL, EINVAL, "sodium_customize: keys specified with both keyid= and secretkey=");
goto err;
}
/* Providing neither is also an error. */
if (keyid.len == 0 && secretkey.len == 0) {
ret = sodium_error(
new, NULL, EINVAL, "sodium_customize: no key given with either keyid= or secretkey=");
goto err;
}
/* Use sodium_malloc, which takes assorted precautions for working with secrets. */
new->secretkey = sodium_malloc(KEY_LEN);
if (new->secretkey == NULL) {
ret = errno;
goto err;
}
/*
* We don't support any key lookup services. Yet. To add support for your own, change the code
* here to fetch the key associated with the configured keyid string, and put it in ->secretkey.
* If the keyid is invalid, print an error and goto err. Note that there's no need to remember
* the keyid once the key is installed.
*/
if (keyid.len != 0) {
ret = sodium_error(new, NULL, EINVAL, "sodium_customize: keyids not supported yet");
goto err;
}
/*
* Load the key specified with secretkey=. This should be passed as a 64-character hex string
* (with no leading 0x). It is not a passphrase; passphrases should be converted to keys using
* appropriate tools (e.g. those provided by libsodium).
*/
if (secretkey.len != 0) {
/* Explicit keys are passed as hex strings of the proper length. */
ret = sodium_hex2bin(
new->secretkey, KEY_LEN, secretkey.str, secretkey.len, NULL, &keylen, NULL);
if (ret < 0) {
ret = sodium_error(new, NULL, EINVAL, "sodium_customize: secret key not hex");
goto err;
}
if (keylen != KEY_LEN) {
ret = sodium_error(new, NULL, EINVAL, "sodium_customize: wrong secret key length");
goto err;
}
}
*customp = (WT_ENCRYPTOR *)new;
return (0);
err:
sodium_free(new->secretkey);
free(new);
return (ret);
}
/*
* sodium_terminate --
* Shut down the extension and avoid leaking memory.
*/
static int
sodium_terminate(WT_ENCRYPTOR *encryptor, WT_SESSION *session)
{
SODIUM_ENCRYPTOR *sodium_encryptor = (SODIUM_ENCRYPTOR *)encryptor;
(void)session; /* Unused parameters */
/* Free the allocated memory. */
sodium_free(sodium_encryptor->secretkey);
free(sodium_encryptor);
return (0);
}
/*
* sodium_configure --
* Configure the extension.
*
* This is for static config, not where keys are loaded, so nothing happens.
*/
static int
sodium_configure(SODIUM_ENCRYPTOR *sodium_encryptor, WT_CONFIG_ARG *config)
{
WT_EXTENSION_API *wt_api; /* Extension API */
wt_api = sodium_encryptor->wt_api;
(void)config;
(void)wt_api;
return (0);
}
/*
* wiredtiger_extension_init --
* Called to load and initialize the extension.
*/
int
{
SODIUM_ENCRYPTOR *sodium_encryptor;
int ret;
if ((sodium_encryptor = calloc(1, sizeof(SODIUM_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.
*/
sodium_encryptor->encryptor.encrypt = sodium_encrypt;
sodium_encryptor->encryptor.decrypt = sodium_decrypt;
sodium_encryptor->encryptor.sizing = sodium_sizing;
sodium_encryptor->encryptor.customize = sodium_customize;
sodium_encryptor->encryptor.terminate = sodium_terminate;
sodium_encryptor->wt_api = connection->get_extension_api(connection);
/* Initialize the crypto library. */
if (sodium_init() < 0)
return (WT_ERROR);
/* Configure the extension. */
if ((ret = sodium_configure(sodium_encryptor, config)) != 0) {
free(sodium_encryptor);
return (ret);
}
/* Attach the extension. */
if ((ret = connection->add_encryptor(
connection, "sodium", (WT_ENCRYPTOR *)sodium_encryptor, NULL)) != 0) {
free(sodium_encryptor);
return (ret);
}
return (0);
}
WT_EXTENSION_API
Table of WiredTiger extension methods.
Definition: wiredtiger_ext.h:94
WT_CONFIG_ARG
struct WT_CONFIG_ARG WT_CONFIG_ARG
Definition: wiredtiger.in:3820
WT_CONNECTION::get_extension_api
WT_EXTENSION_API * get_extension_api(WT_CONNECTION *wt_conn)
Return a reference to the WiredTiger extension functions.
WT_CONFIG_ITEM::str
const char * str
The value of a configuration string.
Definition: wiredtiger.in:3476
WT_EXTENSION_API::strerror
const char *(* strerror)(WT_EXTENSION_API *, WT_SESSION *session, int error)
Return information about an error as a string.
Definition: wiredtiger_ext.h:136
WT_ENCRYPTOR
The interface implemented by applications to provide custom encryption.
Definition: wiredtiger.in:4174
WT_EXTENSION_API::config_get
int(* config_get)(WT_EXTENSION_API *wt_api, WT_SESSION *session, WT_CONFIG_ARG *config, const char *key, WT_CONFIG_ITEM *value)
Return the value of a configuration key.
Definition: wiredtiger_ext.h:220
wiredtiger_extension_init
int wiredtiger_extension_init(WT_CONNECTION *connection, WT_CONFIG_ARG *config)
Entry point to an extension, called when the extension is loaded.
WT_CONNECTION
A connection to a WiredTiger database.
Definition: wiredtiger.in:1964
WT_CONNECTION::add_encryptor
int add_encryptor(WT_CONNECTION *connection, const char *name, WT_ENCRYPTOR *encryptor, const char *config)
Add an encryption function.
WT_CONFIG_ITEM::len
size_t len
The number of bytes in the value referenced by str.
Definition: wiredtiger.in:3479
WT_EXTENSION_API::err_printf
int(* err_printf)(WT_EXTENSION_API *wt_api, WT_SESSION *session, const char *fmt,...)
Insert an error message into the WiredTiger error stream.
Definition: wiredtiger_ext.h:112
WT_ERROR
#define WT_ERROR
Non-specific WiredTiger error.
Definition: wiredtiger.in:3747
WT_SESSION
All data operations are performed in the context of a WT_SESSION.
Definition: wiredtiger.in:753
WT_CONFIG_ITEM
The configuration information returned by the WiredTiger configuration parsing functions in the WT_EX...
Definition: wiredtiger.in:3465