xref: /openbmc/qemu/backends/tpm/tpm_passthrough.c (revision ced29396)
1 /*
2  *  passthrough TPM driver
3  *
4  *  Copyright (c) 2010 - 2013 IBM Corporation
5  *  Authors:
6  *    Stefan Berger <stefanb@us.ibm.com>
7  *
8  *  Copyright (C) 2011 IAIK, Graz University of Technology
9  *    Author: Andreas Niederl
10  *
11  * This library is free software; you can redistribute it and/or
12  * modify it under the terms of the GNU Lesser General Public
13  * License as published by the Free Software Foundation; either
14  * version 2.1 of the License, or (at your option) any later version.
15  *
16  * This library is distributed in the hope that it will be useful,
17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
19  * Lesser General Public License for more details.
20  *
21  * You should have received a copy of the GNU Lesser General Public
22  * License along with this library; if not, see <http://www.gnu.org/licenses/>
23  */
24 
25 #include "qemu/osdep.h"
26 #include "qemu/error-report.h"
27 #include "qemu/module.h"
28 #include "qemu/sockets.h"
29 #include "sysemu/tpm_backend.h"
30 #include "sysemu/tpm_util.h"
31 #include "tpm_int.h"
32 #include "qapi/clone-visitor.h"
33 #include "qapi/qapi-visit-tpm.h"
34 #include "trace.h"
35 #include "qom/object.h"
36 
37 #define TYPE_TPM_PASSTHROUGH "tpm-passthrough"
38 OBJECT_DECLARE_SIMPLE_TYPE(TPMPassthruState, TPM_PASSTHROUGH)
39 
40 /* data structures */
41 struct TPMPassthruState {
42     TPMBackend parent;
43 
44     TPMPassthroughOptions *options;
45     const char *tpm_dev;
46     int tpm_fd;
47     bool tpm_executing;
48     bool tpm_op_canceled;
49     int cancel_fd;
50 
51     TPMVersion tpm_version;
52     size_t tpm_buffersize;
53 };
54 
55 
56 #define TPM_PASSTHROUGH_DEFAULT_DEVICE "/dev/tpm0"
57 
58 /* functions */
59 
60 static void tpm_passthrough_cancel_cmd(TPMBackend *tb);
61 
tpm_passthrough_unix_read(int fd,uint8_t * buf,uint32_t len)62 static int tpm_passthrough_unix_read(int fd, uint8_t *buf, uint32_t len)
63 {
64     int ret;
65  reread:
66     ret = read(fd, buf, len);
67     if (ret < 0) {
68         if (errno != EINTR && errno != EAGAIN) {
69             return -1;
70         }
71         goto reread;
72     }
73     return ret;
74 }
75 
tpm_passthrough_unix_tx_bufs(TPMPassthruState * tpm_pt,const uint8_t * in,uint32_t in_len,uint8_t * out,uint32_t out_len,bool * selftest_done,Error ** errp)76 static void tpm_passthrough_unix_tx_bufs(TPMPassthruState *tpm_pt,
77                                          const uint8_t *in, uint32_t in_len,
78                                          uint8_t *out, uint32_t out_len,
79                                          bool *selftest_done, Error **errp)
80 {
81     ssize_t ret;
82     bool is_selftest;
83 
84     /* FIXME: protect shared variables or use other sync mechanism */
85     tpm_pt->tpm_op_canceled = false;
86     tpm_pt->tpm_executing = true;
87     *selftest_done = false;
88 
89     is_selftest = tpm_util_is_selftest(in, in_len);
90 
91     ret = qemu_write_full(tpm_pt->tpm_fd, in, in_len);
92     if (ret != in_len) {
93         if (!tpm_pt->tpm_op_canceled || errno != ECANCELED) {
94             error_setg_errno(errp, errno, "tpm_passthrough: error while "
95                              "transmitting data to TPM");
96         }
97         goto err_exit;
98     }
99 
100     tpm_pt->tpm_executing = false;
101 
102     ret = tpm_passthrough_unix_read(tpm_pt->tpm_fd, out, out_len);
103     if (ret < 0) {
104         if (!tpm_pt->tpm_op_canceled || errno != ECANCELED) {
105             error_setg_errno(errp, errno, "tpm_passthrough: error while "
106                              "reading data from TPM");
107         }
108     } else if (ret < sizeof(struct tpm_resp_hdr) ||
109                tpm_cmd_get_size(out) != ret) {
110         ret = -1;
111         error_setg_errno(errp, errno, "tpm_passthrough: received invalid "
112                      "response packet from TPM");
113     }
114 
115     if (is_selftest && (ret >= sizeof(struct tpm_resp_hdr))) {
116         *selftest_done = tpm_cmd_get_errcode(out) == 0;
117     }
118 
119 err_exit:
120     if (ret < 0) {
121         tpm_util_write_fatal_error_response(out, out_len);
122     }
123 
124     tpm_pt->tpm_executing = false;
125 }
126 
tpm_passthrough_handle_request(TPMBackend * tb,TPMBackendCmd * cmd,Error ** errp)127 static void tpm_passthrough_handle_request(TPMBackend *tb, TPMBackendCmd *cmd,
128                                            Error **errp)
129 {
130     TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
131 
132     trace_tpm_passthrough_handle_request(cmd);
133 
134     tpm_passthrough_unix_tx_bufs(tpm_pt, cmd->in, cmd->in_len,
135                                  cmd->out, cmd->out_len, &cmd->selftest_done,
136                                  errp);
137 }
138 
tpm_passthrough_reset(TPMBackend * tb)139 static void tpm_passthrough_reset(TPMBackend *tb)
140 {
141     trace_tpm_passthrough_reset();
142 
143     tpm_passthrough_cancel_cmd(tb);
144 }
145 
tpm_passthrough_get_tpm_established_flag(TPMBackend * tb)146 static bool tpm_passthrough_get_tpm_established_flag(TPMBackend *tb)
147 {
148     return false;
149 }
150 
tpm_passthrough_reset_tpm_established_flag(TPMBackend * tb,uint8_t locty)151 static int tpm_passthrough_reset_tpm_established_flag(TPMBackend *tb,
152                                                       uint8_t locty)
153 {
154     /* only a TPM 2.0 will support this */
155     return 0;
156 }
157 
tpm_passthrough_cancel_cmd(TPMBackend * tb)158 static void tpm_passthrough_cancel_cmd(TPMBackend *tb)
159 {
160     TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
161     int n;
162 
163     /*
164      * As of Linux 3.7 the tpm_tis driver does not properly cancel
165      * commands on all TPM manufacturers' TPMs.
166      * Only cancel if we're busy so we don't cancel someone else's
167      * command, e.g., a command executed on the host.
168      */
169     if (tpm_pt->tpm_executing) {
170         if (tpm_pt->cancel_fd >= 0) {
171             tpm_pt->tpm_op_canceled = true;
172             n = write(tpm_pt->cancel_fd, "-", 1);
173             if (n != 1) {
174                 error_report("Canceling TPM command failed: %s",
175                              strerror(errno));
176             }
177         } else {
178             error_report("Cannot cancel TPM command due to missing "
179                          "TPM sysfs cancel entry");
180         }
181     }
182 }
183 
tpm_passthrough_get_tpm_version(TPMBackend * tb)184 static TPMVersion tpm_passthrough_get_tpm_version(TPMBackend *tb)
185 {
186     TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
187 
188     return tpm_pt->tpm_version;
189 }
190 
tpm_passthrough_get_buffer_size(TPMBackend * tb)191 static size_t tpm_passthrough_get_buffer_size(TPMBackend *tb)
192 {
193     TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
194     int ret;
195 
196     ret = tpm_util_get_buffer_size(tpm_pt->tpm_fd, tpm_pt->tpm_version,
197                                    &tpm_pt->tpm_buffersize);
198     if (ret < 0) {
199         tpm_pt->tpm_buffersize = 4096;
200     }
201     return tpm_pt->tpm_buffersize;
202 }
203 
204 /*
205  * Unless path or file descriptor set has been provided by user,
206  * determine the sysfs cancel file following kernel documentation
207  * in Documentation/ABI/stable/sysfs-class-tpm.
208  * From /dev/tpm0 create /sys/class/tpm/tpm0/device/cancel
209  * before 4.0: /sys/class/misc/tpm0/device/cancel
210  */
tpm_passthrough_open_sysfs_cancel(TPMPassthruState * tpm_pt)211 static int tpm_passthrough_open_sysfs_cancel(TPMPassthruState *tpm_pt)
212 {
213     int fd = -1;
214     char *dev;
215     char path[PATH_MAX];
216 
217     if (tpm_pt->options->cancel_path) {
218         fd = qemu_open_old(tpm_pt->options->cancel_path, O_WRONLY);
219         if (fd < 0) {
220             error_report("tpm_passthrough: Could not open TPM cancel path: %s",
221                          strerror(errno));
222         }
223         return fd;
224     }
225 
226     dev = strrchr(tpm_pt->tpm_dev, '/');
227     if (!dev) {
228         error_report("tpm_passthrough: Bad TPM device path %s",
229                      tpm_pt->tpm_dev);
230         return -1;
231     }
232 
233     dev++;
234     if (snprintf(path, sizeof(path), "/sys/class/tpm/%s/device/cancel",
235                  dev) < sizeof(path)) {
236         fd = qemu_open_old(path, O_WRONLY);
237         if (fd < 0) {
238             if (snprintf(path, sizeof(path), "/sys/class/misc/%s/device/cancel",
239                          dev) < sizeof(path)) {
240                 fd = qemu_open_old(path, O_WRONLY);
241             }
242         }
243     }
244 
245     if (fd < 0) {
246         error_report("tpm_passthrough: Could not guess TPM cancel path");
247     } else {
248         tpm_pt->options->cancel_path = g_strdup(path);
249     }
250 
251     return fd;
252 }
253 
254 static int
tpm_passthrough_handle_device_opts(TPMPassthruState * tpm_pt,QemuOpts * opts)255 tpm_passthrough_handle_device_opts(TPMPassthruState *tpm_pt, QemuOpts *opts)
256 {
257     const char *value;
258 
259     value = qemu_opt_get(opts, "cancel-path");
260     if (value) {
261         tpm_pt->options->cancel_path = g_strdup(value);
262     }
263 
264     value = qemu_opt_get(opts, "path");
265     if (value) {
266         tpm_pt->options->path = g_strdup(value);
267     }
268 
269     tpm_pt->tpm_dev = value ? value : TPM_PASSTHROUGH_DEFAULT_DEVICE;
270     tpm_pt->tpm_fd = qemu_open_old(tpm_pt->tpm_dev, O_RDWR);
271     if (tpm_pt->tpm_fd < 0) {
272         error_report("Cannot access TPM device using '%s': %s",
273                      tpm_pt->tpm_dev, strerror(errno));
274         return -1;
275     }
276 
277     if (tpm_util_test_tpmdev(tpm_pt->tpm_fd, &tpm_pt->tpm_version)) {
278         error_report("'%s' is not a TPM device.",
279                      tpm_pt->tpm_dev);
280         return -1;
281     }
282 
283     tpm_pt->cancel_fd = tpm_passthrough_open_sysfs_cancel(tpm_pt);
284     if (tpm_pt->cancel_fd < 0) {
285         return -1;
286     }
287 
288     return 0;
289 }
290 
tpm_passthrough_create(QemuOpts * opts)291 static TPMBackend *tpm_passthrough_create(QemuOpts *opts)
292 {
293     Object *obj = object_new(TYPE_TPM_PASSTHROUGH);
294 
295     if (tpm_passthrough_handle_device_opts(TPM_PASSTHROUGH(obj), opts)) {
296         object_unref(obj);
297         return NULL;
298     }
299 
300     return TPM_BACKEND(obj);
301 }
302 
tpm_passthrough_startup_tpm(TPMBackend * tb,size_t buffersize)303 static int tpm_passthrough_startup_tpm(TPMBackend *tb, size_t buffersize)
304 {
305     TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
306 
307     if (buffersize && buffersize < tpm_pt->tpm_buffersize) {
308         error_report("Requested buffer size of %zu is smaller than host TPM's "
309                      "fixed buffer size of %zu",
310                      buffersize, tpm_pt->tpm_buffersize);
311         return -1;
312     }
313 
314     return 0;
315 }
316 
tpm_passthrough_get_tpm_options(TPMBackend * tb)317 static TpmTypeOptions *tpm_passthrough_get_tpm_options(TPMBackend *tb)
318 {
319     TpmTypeOptions *options = g_new0(TpmTypeOptions, 1);
320 
321     options->type = TPM_TYPE_PASSTHROUGH;
322     options->u.passthrough.data = QAPI_CLONE(TPMPassthroughOptions,
323                                              TPM_PASSTHROUGH(tb)->options);
324 
325     return options;
326 }
327 
328 static const QemuOptDesc tpm_passthrough_cmdline_opts[] = {
329     TPM_STANDARD_CMDLINE_OPTS,
330     {
331         .name = "cancel-path",
332         .type = QEMU_OPT_STRING,
333         .help = "Sysfs file entry for canceling TPM commands",
334     },
335     {
336         .name = "path",
337         .type = QEMU_OPT_STRING,
338         .help = "Path to TPM device on the host",
339     },
340     { /* end of list */ },
341 };
342 
tpm_passthrough_inst_init(Object * obj)343 static void tpm_passthrough_inst_init(Object *obj)
344 {
345     TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(obj);
346 
347     tpm_pt->options = g_new0(TPMPassthroughOptions, 1);
348     tpm_pt->tpm_fd = -1;
349     tpm_pt->cancel_fd = -1;
350 }
351 
tpm_passthrough_inst_finalize(Object * obj)352 static void tpm_passthrough_inst_finalize(Object *obj)
353 {
354     TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(obj);
355 
356     tpm_passthrough_cancel_cmd(TPM_BACKEND(obj));
357 
358     if (tpm_pt->tpm_fd >= 0) {
359         qemu_close(tpm_pt->tpm_fd);
360     }
361     if (tpm_pt->cancel_fd >= 0) {
362         qemu_close(tpm_pt->cancel_fd);
363     }
364     qapi_free_TPMPassthroughOptions(tpm_pt->options);
365 }
366 
tpm_passthrough_class_init(ObjectClass * klass,void * data)367 static void tpm_passthrough_class_init(ObjectClass *klass, void *data)
368 {
369     TPMBackendClass *tbc = TPM_BACKEND_CLASS(klass);
370 
371     tbc->type = TPM_TYPE_PASSTHROUGH;
372     tbc->opts = tpm_passthrough_cmdline_opts;
373     tbc->desc = "Passthrough TPM backend driver";
374     tbc->create = tpm_passthrough_create;
375     tbc->startup_tpm = tpm_passthrough_startup_tpm;
376     tbc->reset = tpm_passthrough_reset;
377     tbc->cancel_cmd = tpm_passthrough_cancel_cmd;
378     tbc->get_tpm_established_flag = tpm_passthrough_get_tpm_established_flag;
379     tbc->reset_tpm_established_flag =
380         tpm_passthrough_reset_tpm_established_flag;
381     tbc->get_tpm_version = tpm_passthrough_get_tpm_version;
382     tbc->get_buffer_size = tpm_passthrough_get_buffer_size;
383     tbc->get_tpm_options = tpm_passthrough_get_tpm_options;
384     tbc->handle_request = tpm_passthrough_handle_request;
385 }
386 
387 static const TypeInfo tpm_passthrough_info = {
388     .name = TYPE_TPM_PASSTHROUGH,
389     .parent = TYPE_TPM_BACKEND,
390     .instance_size = sizeof(TPMPassthruState),
391     .class_init = tpm_passthrough_class_init,
392     .instance_init = tpm_passthrough_inst_init,
393     .instance_finalize = tpm_passthrough_inst_finalize,
394 };
395 
tpm_passthrough_register(void)396 static void tpm_passthrough_register(void)
397 {
398     type_register_static(&tpm_passthrough_info);
399 }
400 
401 type_init(tpm_passthrough_register)
402