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RIOT/sys/net/credman/credman.c
Marian Buschsieweke a00fb233dc
sys/net/credman: fix insecure memory wiping
2022-09-20 17:44:24 +02:00

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/*
* Copyright (C) 2019 HAW Hamburg
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup net_credman
* @{
*
* @file
* @brief (D)TLS Credentials management module implementation
*
* @author Aiman Ismail <muhammadaimanbin.ismail@haw-hamburg.de>
*/
#include "kernel_defines.h"
#include "mutex.h"
#include "net/credman.h"
#include "string_utils.h"
#include <assert.h>
#include <string.h>
#include <inttypes.h>
#define ENABLE_DEBUG 0
#include "debug.h"
static mutex_t _mutex = MUTEX_INIT;
#if IS_USED(MODULE_CREDMAN_LOAD)
#include "tiny-asn1.h"
/* Context-specific tag in DER encoding
* (see section 8.1.2.2 of ITU-T X.690 https://www.itu.int/rec/T-REC-X.690-200811-S) */
#define ASN1_CONTEXT_TAG(v) (0xA0 | (v & 0x1F))
/* ASN.1 representation of ecPublicKey - OID 1.2.840.10045.2.1
* (see https://oidref.com/1.2.840.10045.2.1) */
static const uint8_t ecPublicKey[] = { 0x2A, 0x86, 0x48, 0xCE, 0x3D, 0x02, 0x01 };
static int _parse_ecc_point(const asn1_tree *key, const void **x, const void **y);
#endif /* MODULE_CREDMAN_LOAD */
static credman_credential_t credentials[CONFIG_CREDMAN_MAX_CREDENTIALS];
static unsigned used = 0;
static int _find_credential_pos(credman_tag_t tag, credman_type_t type,
credman_credential_t **empty);
int credman_add(const credman_credential_t *credential)
{
credman_credential_t *entry = NULL;
assert(credential);
mutex_lock(&_mutex);
int pos = -1;
int ret = CREDMAN_ERROR;
if ((credential->type == CREDMAN_TYPE_EMPTY) ||
(credential->tag == CREDMAN_TAG_EMPTY)) {
DEBUG("credman: invalid credential type/tag\n");
ret = CREDMAN_INVALID;
goto end;
}
switch (credential->type) {
case CREDMAN_TYPE_PSK:
if ((credential->params.psk.key.s == NULL) ||
(credential->params.psk.key.len == 0)) {
DEBUG("credman: invalid PSK parameters\n");
ret = CREDMAN_INVALID;
goto end;
}
break;
case CREDMAN_TYPE_ECDSA:
if ((credential->params.ecdsa.private_key == NULL) ||
(credential->params.ecdsa.public_key.x == NULL) ||
(credential->params.ecdsa.public_key.y == NULL)) {
DEBUG("credman: invalid ECDSA parameters\n");
ret = CREDMAN_INVALID;
goto end;
}
break;
default:
ret = CREDMAN_TYPE_UNKNOWN;
goto end;
}
pos = _find_credential_pos(credential->tag, credential->type, &entry);
if (pos >= 0) {
DEBUG("credman: credential with tag %d and type %d already exist\n",
credential->tag, credential->type);
ret = CREDMAN_EXIST;
}
else if (entry == NULL) {
DEBUG("credman: no space for new credential\n");
ret = CREDMAN_NO_SPACE;
}
else {
*entry = *credential;
used++;
ret = CREDMAN_OK;
}
end:
mutex_unlock(&_mutex);
return ret;
}
#if IS_USED(MODULE_CREDMAN_LOAD)
int credman_load_public_key(const void *buf, size_t buf_len, ecdsa_public_key_t *out)
{
asn1_tree objects[CONFIG_CREDMAN_MAX_ASN1_OBJ];
asn1_tree pub_key;
assert(buf);
assert(out);
int obj_count = der_object_count((uint8_t *)buf, buf_len);
if (obj_count <= 0) {
DEBUG("credman: could not calculate the number of elements within the key\n");
return CREDMAN_INVALID;
}
if (obj_count > CONFIG_CREDMAN_MAX_ASN1_OBJ) {
DEBUG("credman: not enough ASN.1 objects to decode key.\n");
DEBUG("credman: current max is %d, and we need %d\n",
CONFIG_CREDMAN_MAX_ASN1_OBJ, obj_count);
return CREDMAN_INVALID;
}
int32_t res = der_decode((uint8_t *)buf, buf_len, &pub_key, objects, obj_count);
if (res < 0) {
DEBUG("credman: could not parse the key (%" PRId32 ")\n", res);
return CREDMAN_INVALID;
}
/*
* From https://tools.ietf.org/html/rfc5280#section-4.1
*
* SubjectPublicKeyInfo ::= SEQUENCE {
* algorithm AlgorithmIdentifier,
* subjectPublicKey BIT STRING }
*
* AlgorithmIdentifier ::= SEQUENCE {
* algorithm OBJECT IDENTIFIER,
* parameters ANY DEFINED BY algorithm OPTIONAL }
*/
/* the outer container is a 'SubjectPublicKeyInfo', which should be a SEQUENCE */
if (pub_key.type != ASN1_TYPE_SEQUENCE) {
DEBUG("credman: the public key information should be contained in an ASN.1 SEQUENCE\n");
return CREDMAN_INVALID;
}
asn1_tree *algorithm_id = pub_key.child;
asn1_tree *algorithm = algorithm_id->child;
/* for now only ECDSA is supported by credman */
/* the algorithm should be Elliptic Curve Public Key (OID 1.2.840.10045.2.1) */
if (sizeof(ecPublicKey) != algorithm->length) {
DEBUG("credman: wrong OID length for algorithm\n");
return CREDMAN_INVALID;
}
if (memcmp(ecPublicKey, algorithm->data, sizeof(ecPublicKey)) != 0) {
DEBUG("credman: wrong OID for algorithm. Expected 1.2.840.10045.2.1\n");
return CREDMAN_INVALID;
}
return _parse_ecc_point(algorithm_id->next, &out->x, &out->y);
}
int credman_load_private_key(const void *buf, size_t buf_len, credman_credential_t *cred)
{
asn1_tree objects[CONFIG_CREDMAN_MAX_ASN1_OBJ];
asn1_tree priv_key;
assert(buf);
assert(cred);
int obj_count = der_object_count((uint8_t *)buf, buf_len);
if (obj_count <= 0) {
DEBUG("credman: could not calculate the number of elements within the key\n");
return CREDMAN_INVALID;
}
if (obj_count > CONFIG_CREDMAN_MAX_ASN1_OBJ) {
DEBUG("credman: not enough ASN.1 objects to decode key.\n");
DEBUG("credman: current max is %d, and we need %d\n",
CONFIG_CREDMAN_MAX_ASN1_OBJ, obj_count);
return CREDMAN_INVALID;
}
if (der_decode((uint8_t *)buf, buf_len, &priv_key, objects, obj_count) < 0) {
DEBUG("credman: could not parse the key\n");
return CREDMAN_INVALID;
}
/*
* From https://tools.ietf.org/html/rfc5958#section-2
*
* OneAsymmetricKey ::= SEQUENCE {
* version Version,
* privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
* privateKey PrivateKey,
* attributes [0] Attributes OPTIONAL,
* ...,
* [[2: publicKey [1] PublicKey OPTIONAL ]],
* ...
* }
*
* PrivateKeyAlgorithmIdentifier ::= AlgorithmIdentifier
* { PUBLIC-KEY,
* { PrivateKeyAlgorithms } }
*
* AlgorithmIdentifier ::= SEQUENCE {
* algorithm OBJECT IDENTIFIER,
* parameters ANY DEFINED BY algorithm OPTIONAL }
*
* PrivateKey ::= OCTET STRING
* -- Content varies based on type of key. The
* -- algorithm identifier dictates the format of
* -- the key.
*/
/* the outer container is a 'OneAsymmetricKey', which should be a SEQUENCE */
if (priv_key.type != ASN1_TYPE_SEQUENCE) {
DEBUG("credman: the private key information should be contained in an ASN.1 SEQUENCE\n");
return CREDMAN_INVALID;
}
/* point to version */
asn1_tree *node = priv_key.child;
if (!node || node->type != ASN1_TYPE_INTEGER) {
DEBUG("credman: invalid private key version\n");
return CREDMAN_INVALID;
}
/* point to privateKeyAlgorithm */
node = node->next;
if (!node || node->type != ASN1_TYPE_SEQUENCE || !node->length) {
DEBUG("credman: invalid private key algorithm identifier\n");
return CREDMAN_INVALID;
}
/* for now only ECDSA is supported by credman */
/* the algorithm should be Elliptic Curve Public Key (OID 1.2.840.10045.2.1) */
asn1_tree *algorithm = node->child;
if (sizeof(ecPublicKey) != algorithm->length) {
DEBUG("credman: wrong private key algorithm, only ecPublicKey is supported\n");
return CREDMAN_INVALID;
}
if (memcmp(ecPublicKey, algorithm->data, sizeof(ecPublicKey)) != 0) {
DEBUG("credman: wrong OID for algorithm. Expected 1.2.840.10045.2.1\n");
return CREDMAN_INVALID;
}
/* point to privateKey */
node = node->next;
if (!node || node->type != ASN1_TYPE_OCTET_STRING || !node->data || !node->length) {
DEBUG("credman: no private key found\n");
return CREDMAN_INVALID;
}
return credman_load_private_ecc_key(node->data, node->length, cred);
}
int credman_load_private_ecc_key(const void *buf, size_t buf_len, credman_credential_t *cred)
{
asn1_tree objects[CONFIG_CREDMAN_MAX_ASN1_OBJ];
asn1_tree priv_key;
assert(buf);
assert(cred);
int obj_count = der_object_count((uint8_t *)buf, buf_len);
if (obj_count <= 0) {
DEBUG("credman: could not calculate the number of elements within the key\n");
return CREDMAN_INVALID;
}
if (obj_count > CONFIG_CREDMAN_MAX_ASN1_OBJ) {
DEBUG("credman: not enough ASN.1 objects to decode key.\n");
DEBUG("credman: current max is %d, and we need %d\n",
CONFIG_CREDMAN_MAX_ASN1_OBJ, obj_count);
return CREDMAN_INVALID;
}
if (der_decode((uint8_t *)buf, buf_len, &priv_key, objects, obj_count) < 0) {
DEBUG("credman: could not parse the key\n");
return CREDMAN_INVALID;
}
/*
* From https://tools.ietf.org/html/rfc5915#section-3
*
* ECPrivateKey ::= SEQUENCE {
* version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
* privateKey OCTET STRING,
* parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
* publicKey [1] BIT STRING OPTIONAL
* }
*/
/* point to version, it SHALL be 1 */
asn1_tree *node = priv_key.child;
if (!node || node->type != ASN1_TYPE_INTEGER || node->data[0] != 0x01) {
DEBUG("credman: invalid private key version\n");
return CREDMAN_INVALID;
}
/* point to privateKey */
node = node->next;
if (!node || node->type != ASN1_TYPE_OCTET_STRING || !node->data || !node->length) {
DEBUG("credman: invalid private key\n");
return CREDMAN_INVALID;
}
cred->type = CREDMAN_TYPE_ECDSA;
cred->params.ecdsa.public_key.x = NULL;
cred->params.ecdsa.public_key.y = NULL;
cred->params.ecdsa.private_key = node->data;
/* try to find a publicKey by tag */
while (node && node->type != ASN1_CONTEXT_TAG(1)) {
node = node->next;
}
if (!node) {
return CREDMAN_OK;
}
return _parse_ecc_point(node->child, &cred->params.ecdsa.public_key.x,
&cred->params.ecdsa.public_key.y);
}
static int _parse_ecc_point(const asn1_tree *key, const void **x, const void **y)
{
if (!key || key->type != ASN1_TYPE_BIT_STRING) {
DEBUG("credman: the key should be an ASN.1 BIT STRING\n");
return CREDMAN_INVALID;
}
if (!key->length) {
DEBUG("credman: the key is missing\n");
return CREDMAN_INVALID;
}
/* SEC 1: Elliptic Curve Cryptography - Section 2.3.4 (https://www.secg.org/sec1-v2.pdf) */
/* check for uncompressed key format */
if (key->data[1] != 0x04) {
DEBUG("credman: only uncompressed format is supported\n");
return CREDMAN_INVALID;
}
size_t coords_len = (key->length - 2) / 2;
const uint8_t *_x = &key->data[2]; /* skip format specifier and unused bits */
const uint8_t *_y = &_x[coords_len];
*x = _x;
*y = _y;
return CREDMAN_OK;
}
#endif /* MODULE_CREDMAN_LOAD */
int credman_get(credman_credential_t *credential, credman_tag_t tag,
credman_type_t type)
{
assert(credential);
mutex_lock(&_mutex);
int ret = CREDMAN_ERROR;
int pos = _find_credential_pos(tag, type, NULL);
if (pos < 0) {
DEBUG("credman: credential with tag %d and type %d not found\n",
tag, type);
ret = CREDMAN_NOT_FOUND;
}
else {
memcpy(credential, &credentials[pos], sizeof(credman_credential_t));
ret = CREDMAN_OK;
}
mutex_unlock(&_mutex);
return ret;
}
void credman_delete(credman_tag_t tag, credman_type_t type)
{
mutex_lock(&_mutex);
int pos = _find_credential_pos(tag, type, NULL);
if (pos >= 0) {
explicit_bzero(&credentials[pos], sizeof(credman_credential_t));
used--;
}
mutex_unlock(&_mutex);
}
int credman_get_used_count(void)
{
return used;
}
static int _find_credential_pos(credman_tag_t tag, credman_type_t type,
credman_credential_t **empty)
{
for (unsigned i = 0; i < CONFIG_CREDMAN_MAX_CREDENTIALS; i++) {
credman_credential_t *c = &credentials[i];
if ((c->tag == tag) && (c->type == type)) {
return i;
}
/* only check until empty position found */
if ((empty) && (*empty == NULL) &&
(c->tag == CREDMAN_TAG_EMPTY) && (c->type == CREDMAN_TYPE_EMPTY)) {
*empty = c;
}
}
return -1;
}
#ifdef TEST_SUITES
void credman_reset(void)
{
mutex_lock(&_mutex);
memset(credentials, 0,
sizeof(credman_credential_t) * CONFIG_CREDMAN_MAX_CREDENTIALS);
used = 0;
mutex_unlock(&_mutex);
}
#endif /* TEST_SUITES */
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