eng_keystore.cpp revision bef8083783df4b06972f33b468eccf941e335864 
1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
16 * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY
17 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
18 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
19 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
20 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 *
24 */
25
26#include <keystore.h>
27
28#include <utils/UniquePtr.h>
29
30#include <sys/socket.h>
31#include <stdarg.h>
32#include <string.h>
33#include <unistd.h>
34
35#include <openssl/objects.h>
36#include <openssl/engine.h>
37#include <openssl/evp.h>
38
39#define LOG_NDEBUG 0
40#define LOG_TAG "OpenSSL-keystore"
41#include <cutils/log.h>
42
43#include <keystore_client.h>
44
45
46#define DYNAMIC_ENGINE
47#define KEYSTORE_ENGINE_ID   "keystore"
48#define KEYSTORE_ENGINE_NAME "Android keystore engine"
49
50/**
51 * Many OpenSSL APIs take ownership of an argument on success but don't free the argument
52 * on failure. This means we need to tell our scoped pointers when we've transferred ownership,
53 * without triggering a warning by not using the result of release().
54 */
55#define OWNERSHIP_TRANSFERRED(obj) \
56    typeof (obj.release()) _dummy __attribute__((unused)) = obj.release()
57
58struct ENGINE_Delete {
59    void operator()(ENGINE* p) const {
60        ENGINE_free(p);
61    }
62};
63typedef UniquePtr<ENGINE, ENGINE_Delete> Unique_ENGINE;
64
65struct EVP_PKEY_Delete {
66    void operator()(EVP_PKEY* p) const {
67        EVP_PKEY_free(p);
68    }
69};
70typedef UniquePtr<EVP_PKEY, EVP_PKEY_Delete> Unique_EVP_PKEY;
71
72struct RSA_Delete {
73    void operator()(RSA* p) const {
74        RSA_free(p);
75    }
76};
77typedef UniquePtr<RSA, RSA_Delete> Unique_RSA;
78
79
80/*
81 * RSA ex_data index for keystore's key handle.
82 */
83static int rsa_key_handle;
84
85/*
86 * Only initialize the rsa_key_handle once.
87 */
88static pthread_once_t rsa_key_handle_control = PTHREAD_ONCE_INIT;
89
90
91/**
92 * Makes sure the ex_data for the keyhandle is initially set to NULL.
93 */
94int keyhandle_new(void*, void*, CRYPTO_EX_DATA* ad, int idx, long, void*) {
95    return CRYPTO_set_ex_data(ad, idx, NULL);
96}
97
98/**
99 * Frees a previously allocated keyhandle stored in ex_data.
100 */
101void keyhandle_free(void *, void *ptr, CRYPTO_EX_DATA*, int, long, void*) {
102    char* keyhandle = reinterpret_cast<char*>(ptr);
103    if (keyhandle != NULL) {
104        free(keyhandle);
105    }
106}
107
108/**
109 * Duplicates a keyhandle stored in ex_data in case we copy a key.
110 */
111int keyhandle_dup(CRYPTO_EX_DATA* to, CRYPTO_EX_DATA*, void *ptrRef, int idx, long, void *) {
112    // This appears to be a bug in OpenSSL.
113    void** ptr = reinterpret_cast<void**>(ptrRef);
114    char* keyhandle = reinterpret_cast<char*>(*ptr);
115    if (keyhandle != NULL) {
116        char* keyhandle_copy = strdup(keyhandle);
117        *ptr = keyhandle_copy;
118
119        // Call this in case OpenSSL is fixed in the future.
120        (void) CRYPTO_set_ex_data(to, idx, keyhandle_copy);
121    }
122    return 1;
123}
124
125int keystore_rsa_priv_enc(int flen, const unsigned char* from, unsigned char* to, RSA* rsa,
126        int padding) {
127    ALOGV("keystore_rsa_sign(%d, %p, %p, %p, %d)", flen, from, to, rsa, padding);
128
129    int num = RSA_size(rsa);
130    UniquePtr<uint8_t> padded(new uint8_t[num]);
131    if (padded.get() == NULL) {
132        ALOGE("could not allocate padded signature");
133        return 0;
134    }
135
136    switch (padding) {
137    case RSA_PKCS1_PADDING:
138        if (!RSA_padding_add_PKCS1_type_1(padded.get(), num, from, flen)) {
139            return 0;
140        }
141        break;
142    case RSA_X931_PADDING:
143        if (!RSA_padding_add_X931(padded.get(), num, from, flen)) {
144            return 0;
145        }
146        break;
147    case RSA_NO_PADDING:
148        if (!RSA_padding_add_none(padded.get(), num, from, flen)) {
149            return 0;
150        }
151        break;
152    default:
153        ALOGE("Unknown padding type: %d", padding);
154        return 0;
155    }
156
157    uint8_t* key_id = reinterpret_cast<uint8_t*>(RSA_get_ex_data(rsa, rsa_key_handle));
158    if (key_id == NULL) {
159        ALOGE("key had no key_id!");
160        return 0;
161    }
162
163    Keystore_Reply reply;
164    if (keystore_cmd(CommandCodes[SIGN], &reply, 2, strlen(reinterpret_cast<const char*>(key_id)),
165            key_id, static_cast<size_t>(num), reinterpret_cast<const uint8_t*>(padded.get()))
166            != NO_ERROR) {
167        ALOGE("There was an error during rsa_mod_exp");
168        return 0;
169    }
170
171    const size_t replyLen = reply.length();
172    if (replyLen <= 0) {
173        ALOGW("No valid signature returned");
174        return 0;
175    }
176
177    memcpy(to, reply.get(), replyLen);
178
179    ALOGV("rsa=%p keystore_rsa_sign => returning %p len %llu", rsa, to,
180            (unsigned long long) replyLen);
181    return static_cast<int>(replyLen);
182}
183
184static RSA_METHOD keystore_rsa_meth = {
185        KEYSTORE_ENGINE_NAME,
186        NULL, /* rsa_pub_enc */
187        NULL, /* rsa_pub_dec (verification) */
188        keystore_rsa_priv_enc, /* rsa_priv_enc (signing) */
189        NULL, /* rsa_priv_dec */
190        NULL, /* rsa_mod_exp */
191        NULL, /* bn_mod_exp */
192        NULL, /* init */
193        NULL, /* finish */
194        RSA_FLAG_EXT_PKEY | RSA_FLAG_NO_BLINDING, /* flags */
195        NULL, /* app_data */
196        NULL, /* rsa_sign */
197        NULL, /* rsa_verify */
198        NULL, /* rsa_keygen */
199};
200
201static int register_rsa_methods() {
202    const RSA_METHOD* rsa_meth = RSA_PKCS1_SSLeay();
203
204    keystore_rsa_meth.rsa_pub_enc = rsa_meth->rsa_pub_enc;
205    keystore_rsa_meth.rsa_pub_dec = rsa_meth->rsa_pub_dec;
206    keystore_rsa_meth.rsa_priv_dec = rsa_meth->rsa_priv_dec;
207    keystore_rsa_meth.rsa_mod_exp = rsa_meth->rsa_mod_exp;
208    keystore_rsa_meth.bn_mod_exp = rsa_meth->bn_mod_exp;
209
210    return 1;
211}
212
213static EVP_PKEY* keystore_loadkey(ENGINE* e, const char* key_id, UI_METHOD *ui_method,
214        void *callback_data) {
215    ALOGV("keystore_loadkey(%p, \"%s\", %p, %p)", e, key_id, ui_method, callback_data);
216
217    Keystore_Reply reply;
218    if (keystore_cmd(CommandCodes[GET_PUBKEY], &reply, 1, strlen(key_id), key_id) != NO_ERROR) {
219        ALOGV("Cannot get public key for %s", key_id);
220        return NULL;
221    }
222
223    const unsigned char* tmp = reinterpret_cast<const unsigned char*>(reply.get());
224    Unique_EVP_PKEY pkey(d2i_PUBKEY(NULL, &tmp, reply.length()));
225    if (pkey.get() == NULL) {
226        ALOGW("Cannot convert pubkey");
227        return NULL;
228    }
229
230    switch (EVP_PKEY_type(pkey->type)) {
231    case EVP_PKEY_RSA: {
232        Unique_RSA rsa(EVP_PKEY_get1_RSA(pkey.get()));
233        if (!RSA_set_ex_data(rsa.get(), rsa_key_handle, reinterpret_cast<void*>(strdup(key_id)))) {
234            ALOGW("Could not set ex_data for loaded RSA key");
235            return NULL;
236        }
237
238        RSA_set_method(rsa.get(), &keystore_rsa_meth);
239        RSA_blinding_off(rsa.get());
240
241        /*
242         * This should probably be an OpenSSL API, but EVP_PKEY_free calls
243         * ENGINE_finish(), so we need to call ENGINE_init() here.
244         */
245        ENGINE_init(e);
246        rsa->engine = e;
247        rsa->flags |= RSA_FLAG_EXT_PKEY;
248
249        break;
250    }
251    default:
252        ALOGE("Unsupported key type %d", EVP_PKEY_type(pkey->type));
253        return NULL;
254    }
255
256    return pkey.release();
257}
258
259static const ENGINE_CMD_DEFN keystore_cmd_defns[] = {
260    {0, NULL, NULL, 0}
261};
262
263/**
264 * Called to initialize RSA's ex_data for the key_id handle. This should
265 * only be called when protected by a lock.
266 */
267static void init_rsa_key_handle() {
268    rsa_key_handle = RSA_get_ex_new_index(0, NULL, keyhandle_new, keyhandle_dup,
269            keyhandle_free);
270}
271
272static int keystore_engine_setup(ENGINE* e) {
273    ALOGV("keystore_engine_setup");
274
275    if (!ENGINE_set_id(e, KEYSTORE_ENGINE_ID)
276            || !ENGINE_set_name(e, KEYSTORE_ENGINE_NAME)
277            || !ENGINE_set_load_privkey_function(e, keystore_loadkey)
278            || !ENGINE_set_load_pubkey_function(e, keystore_loadkey)
279            || !ENGINE_set_cmd_defns(e, keystore_cmd_defns)) {
280        ALOGE("Could not set up keystore engine");
281        return 0;
282    }
283
284    if (!ENGINE_set_RSA(e, &keystore_rsa_meth)
285            || !register_rsa_methods()) {
286        ALOGE("Could not set up keystore RSA methods");
287        return 0;
288    }
289
290    /* We need a handle in the RSA keys as well for keygen if it's not already initialized. */
291    pthread_once(&rsa_key_handle_control, init_rsa_key_handle);
292    if (rsa_key_handle < 0) {
293        ALOGE("Could not set up RSA ex_data index");
294        return 0;
295    }
296
297    return 1;
298}
299
300ENGINE* ENGINE_keystore() {
301    ALOGV("ENGINE_keystore");
302
303    Unique_ENGINE engine(ENGINE_new());
304    if (engine.get() == NULL) {
305        return NULL;
306    }
307
308    if (!keystore_engine_setup(engine.get())) {
309        return NULL;
310    }
311
312    return engine.release();
313}
314
315static int keystore_bind_fn(ENGINE *e, const char *id) {
316    ALOGV("keystore_bind_fn");
317
318    if (!id) {
319        return 0;
320    }
321
322    if (strcmp(id, KEYSTORE_ENGINE_ID)) {
323        return 0;
324    }
325
326    if (!keystore_engine_setup(e)) {
327        return 0;
328    }
329
330    return 1;
331}
332
333extern "C" {
334#undef OPENSSL_EXPORT
335#define OPENSSL_EXPORT extern __attribute__ ((visibility ("default")))
336
337IMPLEMENT_DYNAMIC_CHECK_FN()
338IMPLEMENT_DYNAMIC_BIND_FN(keystore_bind_fn)
339};
340