eng_keystore.cpp revision 70e3a86abd2c412d602a018967c01c177eb6cf4e 
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 <UniquePtr.h>
29
30#include <sys/socket.h>
31#include <stdarg.h>
32#include <string.h>
33
34#include <openssl/objects.h>
35#include <openssl/engine.h>
36#include <openssl/evp.h>
37
38#define LOG_NDEBUG 0
39#define LOG_TAG "OpenSSL-keystore"
40#include <cutils/log.h>
41
42#include <keystore_client.h>
43
44
45#define DYNAMIC_ENGINE
46#define KEYSTORE_ENGINE_ID   "keystore"
47#define KEYSTORE_ENGINE_NAME "Android keystore engine"
48
49/**
50 * Many OpenSSL APIs take ownership of an argument on success but don't free the argument
51 * on failure. This means we need to tell our scoped pointers when we've transferred ownership,
52 * without triggering a warning by not using the result of release().
53 */
54#define OWNERSHIP_TRANSFERRED(obj) \
55    typeof (obj.release()) _dummy __attribute__((unused)) = obj.release()
56
57struct ENGINE_Delete {
58    void operator()(ENGINE* p) const {
59        ENGINE_free(p);
60    }
61};
62typedef UniquePtr<ENGINE, ENGINE_Delete> Unique_ENGINE;
63
64struct EVP_PKEY_Delete {
65    void operator()(EVP_PKEY* p) const {
66        EVP_PKEY_free(p);
67    }
68};
69typedef UniquePtr<EVP_PKEY, EVP_PKEY_Delete> Unique_EVP_PKEY;
70
71struct RSA_Delete {
72    void operator()(RSA* p) const {
73        RSA_free(p);
74    }
75};
76typedef UniquePtr<RSA, RSA_Delete> Unique_RSA;
77
78
79/*
80 * RSA ex_data index for keystore's key handle.
81 */
82static int rsa_key_handle;
83
84
85/**
86 * Execute a keystore command. The number of arguments should be passed in
87 * "numArgs" and be preceeded by the length as a size_t.
88 *
89 * If a reply is expected, the "reply" field must be of size
90 * KEYSTORE_MESSAGE_SIZE.
91 *
92 * Example for numArgs == 2:
93 *   keystore_cmd(cmd, reply, 2, size_t, char*, size_t, char*);
94 *
95 * The return value will be the length of the reply stored in "reply."
96 * If an error occurs, the return value will be -1.
97 */
98
99/**
100 * Makes sure the ex_data for the keyhandle is initially set to NULL.
101 */
102int keyhandle_new(void*, void*, CRYPTO_EX_DATA* ad, int idx, long, void*) {
103    return CRYPTO_set_ex_data(ad, idx, NULL);
104}
105
106/**
107 * Frees a previously allocated keyhandle stored in ex_data.
108 */
109void keyhandle_free(void *, void *ptr, CRYPTO_EX_DATA*, int, long, void*) {
110    char* keyhandle = reinterpret_cast<char*>(ptr);
111    if (keyhandle != NULL) {
112        free(keyhandle);
113    }
114}
115
116/**
117 * Duplicates a keyhandle stored in ex_data in case we copy a key.
118 */
119int keyhandle_dup(CRYPTO_EX_DATA* to, CRYPTO_EX_DATA*, void *ptrRef, int idx, long, void *) {
120    // This appears to be a bug in OpenSSL.
121    void** ptr = reinterpret_cast<void**>(ptrRef);
122    char* keyhandle = reinterpret_cast<char*>(*ptr);
123    if (keyhandle != NULL) {
124        char* keyhandle_copy = strdup(keyhandle);
125        *ptr = keyhandle_copy;
126
127        // Call this in case OpenSSL is fixed in the future.
128        (void) CRYPTO_set_ex_data(to, idx, keyhandle_copy);
129    }
130    return 1;
131}
132
133int keystore_rsa_priv_enc(int flen, const unsigned char* from, unsigned char* to, RSA* rsa,
134        int padding) {
135    ALOGV("keystore_rsa_sign(%d, %p, %p, %p, %d)", flen, from, to, rsa, padding);
136
137    int num = RSA_size(rsa);
138    UniquePtr<uint8_t> padded(new uint8_t[num]);
139    if (padded.get() == NULL) {
140        ALOGE("could not allocate padded signature");
141        return 0;
142    }
143
144    switch (padding) {
145    case RSA_PKCS1_PADDING:
146        if (!RSA_padding_add_PKCS1_type_1(padded.get(), num, from, flen)) {
147            return 0;
148        }
149        break;
150    case RSA_X931_PADDING:
151        if (!RSA_padding_add_X931(padded.get(), num, from, flen)) {
152            return 0;
153        }
154        break;
155    case RSA_NO_PADDING:
156        if (!RSA_padding_add_none(padded.get(), num, from, flen)) {
157            return 0;
158        }
159        break;
160    default:
161        ALOGE("Unknown padding type: %d", padding);
162        return 0;
163    }
164
165    uint8_t* key_id = reinterpret_cast<uint8_t*>(RSA_get_ex_data(rsa, rsa_key_handle));
166    if (key_id == NULL) {
167        ALOGE("key had no key_id!");
168        return 0;
169    }
170
171    Keystore_Reply reply;
172    if (keystore_cmd(CommandCodes[SIGN], &reply, 2, strlen(reinterpret_cast<const char*>(key_id)),
173            key_id, static_cast<size_t>(num), reinterpret_cast<const uint8_t*>(padded.get()))
174            != NO_ERROR) {
175        ALOGE("There was an error during rsa_mod_exp");
176        return 0;
177    }
178
179    const size_t replyLen = reply.length();
180    if (replyLen <= 0) {
181        ALOGW("No valid signature returned");
182        return 0;
183    }
184
185    memcpy(to, reply.get(), replyLen);
186
187    ALOGV("rsa=%p keystore_rsa_sign => returning %p len %llu", rsa, to,
188            (unsigned long long) replyLen);
189    return static_cast<int>(replyLen);
190}
191
192static RSA_METHOD keystore_rsa_meth = {
193        KEYSTORE_ENGINE_NAME,
194        NULL, /* rsa_pub_enc */
195        NULL, /* rsa_pub_dec (verification) */
196        keystore_rsa_priv_enc, /* rsa_priv_enc (signing) */
197        NULL, /* rsa_priv_dec */
198        NULL, /* rsa_mod_exp */
199        NULL, /* bn_mod_exp */
200        NULL, /* init */
201        NULL, /* finish */
202        RSA_FLAG_EXT_PKEY | RSA_FLAG_NO_BLINDING, /* flags */
203        NULL, /* app_data */
204        NULL, /* rsa_sign */
205        NULL, /* rsa_verify */
206        NULL, /* rsa_keygen */
207};
208
209static int register_rsa_methods() {
210    const RSA_METHOD* rsa_meth = RSA_PKCS1_SSLeay();
211
212    keystore_rsa_meth.rsa_pub_enc = rsa_meth->rsa_pub_enc;
213    keystore_rsa_meth.rsa_pub_dec = rsa_meth->rsa_pub_dec;
214    keystore_rsa_meth.rsa_priv_dec = rsa_meth->rsa_priv_dec;
215    keystore_rsa_meth.rsa_mod_exp = rsa_meth->rsa_mod_exp;
216    keystore_rsa_meth.bn_mod_exp = rsa_meth->bn_mod_exp;
217
218    return 1;
219}
220
221static EVP_PKEY* keystore_loadkey(ENGINE* e, const char* key_id, UI_METHOD *ui_method,
222        void *callback_data) {
223    ALOGV("keystore_loadkey(%p, \"%s\", %p, %p)", e, key_id, ui_method, callback_data);
224
225    Keystore_Reply reply;
226    if (keystore_cmd(CommandCodes[GET_PUBKEY], &reply, 1, strlen(key_id), key_id) != NO_ERROR) {
227        ALOGV("Cannot get public key for %s", key_id);
228        return NULL;
229    }
230
231    const unsigned char* tmp = reinterpret_cast<const unsigned char*>(reply.get());
232    Unique_EVP_PKEY pkey(d2i_PUBKEY(NULL, &tmp, reply.length()));
233    if (pkey.get() == NULL) {
234        ALOGW("Cannot convert pubkey");
235        return NULL;
236    }
237
238    switch (EVP_PKEY_type(pkey->type)) {
239    case EVP_PKEY_RSA: {
240        Unique_RSA rsa(EVP_PKEY_get1_RSA(pkey.get()));
241        if (!RSA_set_ex_data(rsa.get(), rsa_key_handle, reinterpret_cast<void*>(strdup(key_id)))) {
242            ALOGW("Could not set ex_data for loaded RSA key");
243            return NULL;
244        }
245
246        RSA_set_method(rsa.get(), &keystore_rsa_meth);
247        RSA_blinding_off(rsa.get());
248
249        /*
250         * This should probably be an OpenSSL API, but EVP_PKEY_free calls
251         * ENGINE_finish(), so we need to call ENGINE_init() here.
252         */
253        ENGINE_init(e);
254        rsa->engine = e;
255        rsa->flags |= RSA_FLAG_EXT_PKEY;
256
257        break;
258    }
259    default:
260        ALOGE("Unsupported key type %d", EVP_PKEY_type(pkey->type));
261        return NULL;
262    }
263
264    return pkey.release();
265}
266
267static const ENGINE_CMD_DEFN keystore_cmd_defns[] = {
268    {0, NULL, NULL, 0}
269};
270
271static int keystore_engine_setup(ENGINE* e) {
272    ALOGV("keystore_engine_setup");
273
274    if (!ENGINE_set_id(e, KEYSTORE_ENGINE_ID)
275            || !ENGINE_set_name(e, KEYSTORE_ENGINE_NAME)
276            || !ENGINE_set_load_privkey_function(e, keystore_loadkey)
277            || !ENGINE_set_load_pubkey_function(e, keystore_loadkey)
278            || !ENGINE_set_cmd_defns(e, keystore_cmd_defns)) {
279        ALOGE("Could not set up keystore engine");
280        return 0;
281    }
282
283    if (!ENGINE_set_RSA(e, &keystore_rsa_meth)
284            || !register_rsa_methods()) {
285        ALOGE("Could not set up keystore RSA methods");
286        return 0;
287    }
288
289    /* We need a handle in the RSA keys as well for keygen. */
290    rsa_key_handle = RSA_get_ex_new_index(0, NULL, keyhandle_new, keyhandle_dup, keyhandle_free);
291    if (rsa_key_handle < 0) {
292        ALOGE("Could not set up RSA ex_data index");
293        return 0;
294    }
295
296    return 1;
297}
298
299ENGINE* ENGINE_keystore() {
300    ALOGV("ENGINE_keystore");
301
302    Unique_ENGINE engine(ENGINE_new());
303    if (engine.get() == NULL) {
304        return NULL;
305    }
306
307    if (!keystore_engine_setup(engine.get())) {
308        return NULL;
309    }
310
311    return engine.release();
312}
313
314static int keystore_bind_fn(ENGINE *e, const char *id) {
315    ALOGV("keystore_bind_fn");
316
317    if (!id) {
318        return 0;
319    }
320
321    if (strcmp(id, KEYSTORE_ENGINE_ID)) {
322        return 0;
323    }
324
325    if (!keystore_engine_setup(e)) {
326        return 0;
327    }
328
329    return 1;
330}
331
332extern "C" {
333#undef OPENSSL_EXPORT
334#define OPENSSL_EXPORT extern __attribute__ ((visibility ("default")))
335
336IMPLEMENT_DYNAMIC_CHECK_FN()
337IMPLEMENT_DYNAMIC_BIND_FN(keystore_bind_fn)
338};
339