Annotation of src/usr.bin/ssh/ssh-sk-helper.c, Revision 1.10
1.10 ! djm 1: /* $OpenBSD: ssh-sk-helper.c,v 1.9 2020/01/25 23:13:09 djm Exp $ */
1.1 djm 2: /*
3: * Copyright (c) 2019 Google LLC
4: *
5: * Permission to use, copy, modify, and distribute this software for any
6: * purpose with or without fee is hereby granted, provided that the above
7: * copyright notice and this permission notice appear in all copies.
8: *
9: * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10: * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11: * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12: * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13: * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14: * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15: * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16: */
17:
18: /*
19: * This is a tiny program used to isolate the address space used for
20: * security key middleware signing operations from ssh-agent. It is similar
1.4 djm 21: * to ssh-pkcs11-helper.c but considerably simpler as the operations for
22: * security keys are stateless.
1.1 djm 23: *
1.4 djm 24: * Please crank SSH_SK_HELPER_VERSION in sshkey.h for any incompatible
25: * protocol changes.
1.1 djm 26: */
27:
1.4 djm 28: #include <limits.h>
1.1 djm 29: #include <stdarg.h>
30: #include <stdio.h>
31: #include <stdlib.h>
32: #include <string.h>
33: #include <unistd.h>
34: #include <errno.h>
35:
36: #include "xmalloc.h"
37: #include "log.h"
38: #include "sshkey.h"
39: #include "authfd.h"
40: #include "misc.h"
41: #include "sshbuf.h"
42: #include "msg.h"
43: #include "uidswap.h"
44: #include "sshkey.h"
45: #include "ssherr.h"
46: #include "ssh-sk.h"
47:
48: extern char *__progname;
49:
1.6 djm 50: static struct sshbuf *reply_error(int r, char *fmt, ...)
51: __attribute__((__format__ (printf, 2, 3)));
52:
53: static struct sshbuf *
54: reply_error(int r, char *fmt, ...)
55: {
56: char *msg;
57: va_list ap;
58: struct sshbuf *resp;
59:
60: va_start(ap, fmt);
61: xvasprintf(&msg, fmt, ap);
62: va_end(ap);
1.9 djm 63: debug("%s: %s", __progname, msg);
1.6 djm 64: free(msg);
65:
66: if (r >= 0)
67: fatal("%s: invalid error code %d", __func__, r);
68:
69: if ((resp = sshbuf_new()) == NULL)
70: fatal("%s: sshbuf_new failed", __progname);
71: if (sshbuf_put_u32(resp, SSH_SK_HELPER_ERROR) != 0 ||
72: sshbuf_put_u32(resp, (u_int)-r) != 0)
73: fatal("%s: buffer error", __progname);
74: return resp;
75: }
76:
1.7 djm 77: /* If the specified string is zero length, then free it and replace with NULL */
78: static void
79: null_empty(char **s)
80: {
81: if (s == NULL || *s == NULL || **s != '\0')
82: return;
83:
84: free(*s);
85: *s = NULL;
86: }
87:
1.4 djm 88: static struct sshbuf *
89: process_sign(struct sshbuf *req)
1.1 djm 90: {
1.4 djm 91: int r = SSH_ERR_INTERNAL_ERROR;
92: struct sshbuf *resp, *kbuf;
1.10 ! djm 93: struct sshkey *key = NULL;
1.1 djm 94: uint32_t compat;
95: const u_char *message;
1.10 ! djm 96: u_char *sig = NULL;
! 97: size_t msglen, siglen = 0;
! 98: char *provider = NULL, *pin = NULL;
1.4 djm 99:
100: if ((r = sshbuf_froms(req, &kbuf)) != 0 ||
101: (r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
102: (r = sshbuf_get_string_direct(req, &message, &msglen)) != 0 ||
103: (r = sshbuf_get_cstring(req, NULL, NULL)) != 0 || /* alg */
1.6 djm 104: (r = sshbuf_get_u32(req, &compat)) != 0 ||
105: (r = sshbuf_get_cstring(req, &pin, NULL)) != 0)
1.4 djm 106: fatal("%s: buffer error: %s", __progname, ssh_err(r));
107: if (sshbuf_len(req) != 0)
108: fatal("%s: trailing data in request", __progname);
109:
110: if ((r = sshkey_private_deserialize(kbuf, &key)) != 0)
111: fatal("Unable to parse private key: %s", ssh_err(r));
112: if (!sshkey_is_sk(key))
113: fatal("Unsupported key type %s", sshkey_ssh_name(key));
114:
115: debug("%s: ready to sign with key %s, provider %s: "
116: "msg len %zu, compat 0x%lx", __progname, sshkey_type(key),
117: provider, msglen, (u_long)compat);
118:
1.7 djm 119: null_empty(&pin);
1.6 djm 120:
1.4 djm 121: if ((r = sshsk_sign(provider, key, &sig, &siglen,
1.6 djm 122: message, msglen, compat, pin)) != 0) {
123: resp = reply_error(r, "Signing failed: %s", ssh_err(r));
124: goto out;
125: }
1.4 djm 126:
127: if ((resp = sshbuf_new()) == NULL)
128: fatal("%s: sshbuf_new failed", __progname);
129:
1.6 djm 130: if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_SIGN)) != 0 ||
131: (r = sshbuf_put_string(resp, sig, siglen)) != 0)
1.4 djm 132: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.6 djm 133: out:
1.10 ! djm 134: sshkey_free(key);
1.4 djm 135: sshbuf_free(kbuf);
136: free(provider);
1.10 ! djm 137: if (sig != NULL)
! 138: freezero(sig, siglen);
1.6 djm 139: if (pin != NULL)
140: freezero(pin, strlen(pin));
1.4 djm 141: return resp;
142: }
143:
144: static struct sshbuf *
145: process_enroll(struct sshbuf *req)
146: {
147: int r;
148: u_int type;
1.7 djm 149: char *provider, *application, *pin, *device, *userid;
1.4 djm 150: uint8_t flags;
151: struct sshbuf *challenge, *attest, *kbuf, *resp;
152: struct sshkey *key;
153:
1.6 djm 154: if ((attest = sshbuf_new()) == NULL ||
1.4 djm 155: (kbuf = sshbuf_new()) == NULL)
156: fatal("%s: sshbuf_new failed", __progname);
157:
158: if ((r = sshbuf_get_u32(req, &type)) != 0 ||
159: (r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
1.7 djm 160: (r = sshbuf_get_cstring(req, &device, NULL)) != 0 ||
1.4 djm 161: (r = sshbuf_get_cstring(req, &application, NULL)) != 0 ||
1.7 djm 162: (r = sshbuf_get_cstring(req, &userid, NULL)) != 0 ||
1.4 djm 163: (r = sshbuf_get_u8(req, &flags)) != 0 ||
1.6 djm 164: (r = sshbuf_get_cstring(req, &pin, NULL)) != 0 ||
1.4 djm 165: (r = sshbuf_froms(req, &challenge)) != 0)
166: fatal("%s: buffer error: %s", __progname, ssh_err(r));
167: if (sshbuf_len(req) != 0)
168: fatal("%s: trailing data in request", __progname);
169:
170: if (type > INT_MAX)
171: fatal("%s: bad type %u", __progname, type);
172: if (sshbuf_len(challenge) == 0) {
173: sshbuf_free(challenge);
174: challenge = NULL;
175: }
1.7 djm 176: null_empty(&device);
177: null_empty(&userid);
178: null_empty(&pin);
1.4 djm 179:
1.7 djm 180: if ((r = sshsk_enroll((int)type, provider, device, application, userid,
181: flags, pin, challenge, &key, attest)) != 0) {
1.6 djm 182: resp = reply_error(r, "Enrollment failed: %s", ssh_err(r));
183: goto out;
184: }
1.4 djm 185:
1.6 djm 186: if ((resp = sshbuf_new()) == NULL)
187: fatal("%s: sshbuf_new failed", __progname);
1.4 djm 188: if ((r = sshkey_private_serialize(key, kbuf)) != 0)
189: fatal("%s: serialize private key: %s", __progname, ssh_err(r));
1.6 djm 190: if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_ENROLL)) != 0 ||
191: (r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
1.4 djm 192: (r = sshbuf_put_stringb(resp, attest)) != 0)
193: fatal("%s: buffer error: %s", __progname, ssh_err(r));
194:
1.6 djm 195: out:
1.4 djm 196: sshkey_free(key);
197: sshbuf_free(kbuf);
198: sshbuf_free(attest);
199: sshbuf_free(challenge);
200: free(provider);
201: free(application);
1.6 djm 202: if (pin != NULL)
203: freezero(pin, strlen(pin));
1.4 djm 204:
205: return resp;
206: }
207:
1.5 djm 208: static struct sshbuf *
209: process_load_resident(struct sshbuf *req)
210: {
211: int r;
1.7 djm 212: char *provider, *pin, *device;
1.5 djm 213: struct sshbuf *kbuf, *resp;
214: struct sshkey **keys = NULL;
215: size_t nkeys = 0, i;
216:
1.6 djm 217: if ((kbuf = sshbuf_new()) == NULL)
1.5 djm 218: fatal("%s: sshbuf_new failed", __progname);
219:
220: if ((r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
1.7 djm 221: (r = sshbuf_get_cstring(req, &device, NULL)) != 0 ||
1.5 djm 222: (r = sshbuf_get_cstring(req, &pin, NULL)) != 0)
223: fatal("%s: buffer error: %s", __progname, ssh_err(r));
224: if (sshbuf_len(req) != 0)
225: fatal("%s: trailing data in request", __progname);
226:
1.7 djm 227: null_empty(&device);
228: null_empty(&pin);
1.6 djm 229:
1.7 djm 230: if ((r = sshsk_load_resident(provider, device, pin,
231: &keys, &nkeys)) != 0) {
1.6 djm 232: resp = reply_error(r, " sshsk_load_resident failed: %s",
233: ssh_err(r));
234: goto out;
235: }
236:
237: if ((resp = sshbuf_new()) == NULL)
238: fatal("%s: sshbuf_new failed", __progname);
239:
240: if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_LOAD_RESIDENT)) != 0)
241: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.5 djm 242:
243: for (i = 0; i < nkeys; i++) {
244: debug("%s: key %zu %s %s", __func__, i,
245: sshkey_type(keys[i]), keys[i]->sk_application);
246: sshbuf_reset(kbuf);
247: if ((r = sshkey_private_serialize(keys[i], kbuf)) != 0)
248: fatal("%s: serialize private key: %s",
249: __progname, ssh_err(r));
250: if ((r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
251: (r = sshbuf_put_cstring(resp, "")) != 0) /* comment */
252: fatal("%s: buffer error: %s", __progname, ssh_err(r));
253: }
254:
1.6 djm 255: out:
1.5 djm 256: for (i = 0; i < nkeys; i++)
257: sshkey_free(keys[i]);
258: free(keys);
259: sshbuf_free(kbuf);
260: free(provider);
1.6 djm 261: if (pin != NULL)
262: freezero(pin, strlen(pin));
1.5 djm 263: return resp;
264: }
265:
1.4 djm 266: int
267: main(int argc, char **argv)
268: {
269: SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
270: LogLevel log_level = SYSLOG_LEVEL_ERROR;
271: struct sshbuf *req, *resp;
1.8 djm 272: int in, out, ch, r, vflag = 0;
273: u_int rtype, ll = 0;
274: uint8_t version, log_stderr = 0;
1.1 djm 275:
276: sanitise_stdfd();
277: log_init(__progname, log_level, log_facility, log_stderr);
278:
279: while ((ch = getopt(argc, argv, "v")) != -1) {
280: switch (ch) {
281: case 'v':
1.8 djm 282: vflag = 1;
1.1 djm 283: if (log_level == SYSLOG_LEVEL_ERROR)
284: log_level = SYSLOG_LEVEL_DEBUG1;
285: else if (log_level < SYSLOG_LEVEL_DEBUG3)
286: log_level++;
287: break;
288: default:
289: fprintf(stderr, "usage: %s [-v]\n", __progname);
290: exit(1);
291: }
292: }
1.8 djm 293: log_init(__progname, log_level, log_facility, vflag);
1.1 djm 294:
295: /*
296: * Rearrange our file descriptors a little; we don't trust the
297: * providers not to fiddle with stdin/out.
298: */
299: closefrom(STDERR_FILENO + 1);
300: if ((in = dup(STDIN_FILENO)) == -1 || (out = dup(STDOUT_FILENO)) == -1)
301: fatal("%s: dup: %s", __progname, strerror(errno));
302: close(STDIN_FILENO);
303: close(STDOUT_FILENO);
304: sanitise_stdfd(); /* resets to /dev/null */
305:
1.4 djm 306: if ((req = sshbuf_new()) == NULL)
1.1 djm 307: fatal("%s: sshbuf_new failed", __progname);
308: if (ssh_msg_recv(in, req) < 0)
309: fatal("ssh_msg_recv failed");
310: close(in);
311: debug("%s: received message len %zu", __progname, sshbuf_len(req));
312:
313: if ((r = sshbuf_get_u8(req, &version)) != 0)
314: fatal("%s: buffer error: %s", __progname, ssh_err(r));
315: if (version != SSH_SK_HELPER_VERSION) {
316: fatal("unsupported version: received %d, expected %d",
317: version, SSH_SK_HELPER_VERSION);
318: }
319:
1.8 djm 320: if ((r = sshbuf_get_u32(req, &rtype)) != 0 ||
321: (r = sshbuf_get_u8(req, &log_stderr)) != 0 ||
322: (r = sshbuf_get_u32(req, &ll)) != 0)
1.1 djm 323: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.8 djm 324:
325: if (!vflag && log_level_name((LogLevel)ll) != NULL)
326: log_init(__progname, (LogLevel)ll, log_facility, log_stderr);
1.1 djm 327:
1.4 djm 328: switch (rtype) {
329: case SSH_SK_HELPER_SIGN:
330: resp = process_sign(req);
331: break;
332: case SSH_SK_HELPER_ENROLL:
333: resp = process_enroll(req);
1.5 djm 334: break;
335: case SSH_SK_HELPER_LOAD_RESIDENT:
336: resp = process_load_resident(req);
1.4 djm 337: break;
338: default:
339: fatal("%s: unsupported request type %u", __progname, rtype);
340: }
341: sshbuf_free(req);
342: debug("%s: reply len %zu", __progname, sshbuf_len(resp));
1.1 djm 343:
344: if (ssh_msg_send(out, SSH_SK_HELPER_VERSION, resp) == -1)
345: fatal("ssh_msg_send failed");
1.4 djm 346: sshbuf_free(resp);
1.1 djm 347: close(out);
348:
349: return (0);
350: }