Annotation of src/usr.bin/ssh/ssh-sk-helper.c, Revision 1.8
1.8 ! djm 1: /* $OpenBSD: ssh-sk-helper.c,v 1.7 2020/01/06 02:00:46 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);
63: error("%s: %s", __progname, msg);
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;
1.1 djm 93: struct sshkey *key;
94: uint32_t compat;
95: const u_char *message;
1.4 djm 96: u_char *sig;
1.1 djm 97: size_t msglen, siglen;
1.6 djm 98: char *provider, *pin;
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:
1.4 djm 134: sshbuf_free(kbuf);
135: free(provider);
1.6 djm 136: if (pin != NULL)
137: freezero(pin, strlen(pin));
1.4 djm 138: return resp;
139: }
140:
141: static struct sshbuf *
142: process_enroll(struct sshbuf *req)
143: {
144: int r;
145: u_int type;
1.7 djm 146: char *provider, *application, *pin, *device, *userid;
1.4 djm 147: uint8_t flags;
148: struct sshbuf *challenge, *attest, *kbuf, *resp;
149: struct sshkey *key;
150:
1.6 djm 151: if ((attest = sshbuf_new()) == NULL ||
1.4 djm 152: (kbuf = sshbuf_new()) == NULL)
153: fatal("%s: sshbuf_new failed", __progname);
154:
155: if ((r = sshbuf_get_u32(req, &type)) != 0 ||
156: (r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
1.7 djm 157: (r = sshbuf_get_cstring(req, &device, NULL)) != 0 ||
1.4 djm 158: (r = sshbuf_get_cstring(req, &application, NULL)) != 0 ||
1.7 djm 159: (r = sshbuf_get_cstring(req, &userid, NULL)) != 0 ||
1.4 djm 160: (r = sshbuf_get_u8(req, &flags)) != 0 ||
1.6 djm 161: (r = sshbuf_get_cstring(req, &pin, NULL)) != 0 ||
1.4 djm 162: (r = sshbuf_froms(req, &challenge)) != 0)
163: fatal("%s: buffer error: %s", __progname, ssh_err(r));
164: if (sshbuf_len(req) != 0)
165: fatal("%s: trailing data in request", __progname);
166:
167: if (type > INT_MAX)
168: fatal("%s: bad type %u", __progname, type);
169: if (sshbuf_len(challenge) == 0) {
170: sshbuf_free(challenge);
171: challenge = NULL;
172: }
1.7 djm 173: null_empty(&device);
174: null_empty(&userid);
175: null_empty(&pin);
1.4 djm 176:
1.7 djm 177: if ((r = sshsk_enroll((int)type, provider, device, application, userid,
178: flags, pin, challenge, &key, attest)) != 0) {
1.6 djm 179: resp = reply_error(r, "Enrollment failed: %s", ssh_err(r));
180: goto out;
181: }
1.4 djm 182:
1.6 djm 183: if ((resp = sshbuf_new()) == NULL)
184: fatal("%s: sshbuf_new failed", __progname);
1.4 djm 185: if ((r = sshkey_private_serialize(key, kbuf)) != 0)
186: fatal("%s: serialize private key: %s", __progname, ssh_err(r));
1.6 djm 187: if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_ENROLL)) != 0 ||
188: (r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
1.4 djm 189: (r = sshbuf_put_stringb(resp, attest)) != 0)
190: fatal("%s: buffer error: %s", __progname, ssh_err(r));
191:
1.6 djm 192: out:
1.4 djm 193: sshkey_free(key);
194: sshbuf_free(kbuf);
195: sshbuf_free(attest);
196: sshbuf_free(challenge);
197: free(provider);
198: free(application);
1.6 djm 199: if (pin != NULL)
200: freezero(pin, strlen(pin));
1.4 djm 201:
202: return resp;
203: }
204:
1.5 djm 205: static struct sshbuf *
206: process_load_resident(struct sshbuf *req)
207: {
208: int r;
1.7 djm 209: char *provider, *pin, *device;
1.5 djm 210: struct sshbuf *kbuf, *resp;
211: struct sshkey **keys = NULL;
212: size_t nkeys = 0, i;
213:
1.6 djm 214: if ((kbuf = sshbuf_new()) == NULL)
1.5 djm 215: fatal("%s: sshbuf_new failed", __progname);
216:
217: if ((r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
1.7 djm 218: (r = sshbuf_get_cstring(req, &device, NULL)) != 0 ||
1.5 djm 219: (r = sshbuf_get_cstring(req, &pin, NULL)) != 0)
220: fatal("%s: buffer error: %s", __progname, ssh_err(r));
221: if (sshbuf_len(req) != 0)
222: fatal("%s: trailing data in request", __progname);
223:
1.7 djm 224: null_empty(&device);
225: null_empty(&pin);
1.6 djm 226:
1.7 djm 227: if ((r = sshsk_load_resident(provider, device, pin,
228: &keys, &nkeys)) != 0) {
1.6 djm 229: resp = reply_error(r, " sshsk_load_resident failed: %s",
230: ssh_err(r));
231: goto out;
232: }
233:
234: if ((resp = sshbuf_new()) == NULL)
235: fatal("%s: sshbuf_new failed", __progname);
236:
237: if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_LOAD_RESIDENT)) != 0)
238: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.5 djm 239:
240: for (i = 0; i < nkeys; i++) {
241: debug("%s: key %zu %s %s", __func__, i,
242: sshkey_type(keys[i]), keys[i]->sk_application);
243: sshbuf_reset(kbuf);
244: if ((r = sshkey_private_serialize(keys[i], kbuf)) != 0)
245: fatal("%s: serialize private key: %s",
246: __progname, ssh_err(r));
247: if ((r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
248: (r = sshbuf_put_cstring(resp, "")) != 0) /* comment */
249: fatal("%s: buffer error: %s", __progname, ssh_err(r));
250: }
251:
1.6 djm 252: out:
1.5 djm 253: for (i = 0; i < nkeys; i++)
254: sshkey_free(keys[i]);
255: free(keys);
256: sshbuf_free(kbuf);
257: free(provider);
1.6 djm 258: if (pin != NULL)
259: freezero(pin, strlen(pin));
1.5 djm 260: return resp;
261: }
262:
1.4 djm 263: int
264: main(int argc, char **argv)
265: {
266: SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
267: LogLevel log_level = SYSLOG_LEVEL_ERROR;
268: struct sshbuf *req, *resp;
1.8 ! djm 269: int in, out, ch, r, vflag = 0;
! 270: u_int rtype, ll = 0;
! 271: uint8_t version, log_stderr = 0;
1.1 djm 272:
273: sanitise_stdfd();
274: log_init(__progname, log_level, log_facility, log_stderr);
275:
276: while ((ch = getopt(argc, argv, "v")) != -1) {
277: switch (ch) {
278: case 'v':
1.8 ! djm 279: vflag = 1;
1.1 djm 280: if (log_level == SYSLOG_LEVEL_ERROR)
281: log_level = SYSLOG_LEVEL_DEBUG1;
282: else if (log_level < SYSLOG_LEVEL_DEBUG3)
283: log_level++;
284: break;
285: default:
286: fprintf(stderr, "usage: %s [-v]\n", __progname);
287: exit(1);
288: }
289: }
1.8 ! djm 290: log_init(__progname, log_level, log_facility, vflag);
1.1 djm 291:
292: /*
293: * Rearrange our file descriptors a little; we don't trust the
294: * providers not to fiddle with stdin/out.
295: */
296: closefrom(STDERR_FILENO + 1);
297: if ((in = dup(STDIN_FILENO)) == -1 || (out = dup(STDOUT_FILENO)) == -1)
298: fatal("%s: dup: %s", __progname, strerror(errno));
299: close(STDIN_FILENO);
300: close(STDOUT_FILENO);
301: sanitise_stdfd(); /* resets to /dev/null */
302:
1.4 djm 303: if ((req = sshbuf_new()) == NULL)
1.1 djm 304: fatal("%s: sshbuf_new failed", __progname);
305: if (ssh_msg_recv(in, req) < 0)
306: fatal("ssh_msg_recv failed");
307: close(in);
308: debug("%s: received message len %zu", __progname, sshbuf_len(req));
309:
310: if ((r = sshbuf_get_u8(req, &version)) != 0)
311: fatal("%s: buffer error: %s", __progname, ssh_err(r));
312: if (version != SSH_SK_HELPER_VERSION) {
313: fatal("unsupported version: received %d, expected %d",
314: version, SSH_SK_HELPER_VERSION);
315: }
316:
1.8 ! djm 317: if ((r = sshbuf_get_u32(req, &rtype)) != 0 ||
! 318: (r = sshbuf_get_u8(req, &log_stderr)) != 0 ||
! 319: (r = sshbuf_get_u32(req, &ll)) != 0)
1.1 djm 320: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.8 ! djm 321:
! 322: if (!vflag && log_level_name((LogLevel)ll) != NULL)
! 323: log_init(__progname, (LogLevel)ll, log_facility, log_stderr);
1.1 djm 324:
1.4 djm 325: switch (rtype) {
326: case SSH_SK_HELPER_SIGN:
327: resp = process_sign(req);
328: break;
329: case SSH_SK_HELPER_ENROLL:
330: resp = process_enroll(req);
1.5 djm 331: break;
332: case SSH_SK_HELPER_LOAD_RESIDENT:
333: resp = process_load_resident(req);
1.4 djm 334: break;
335: default:
336: fatal("%s: unsupported request type %u", __progname, rtype);
337: }
338: sshbuf_free(req);
339: debug("%s: reply len %zu", __progname, sshbuf_len(resp));
1.1 djm 340:
341: if (ssh_msg_send(out, SSH_SK_HELPER_VERSION, resp) == -1)
342: fatal("ssh_msg_send failed");
1.4 djm 343: sshbuf_free(resp);
1.1 djm 344: close(out);
345:
346: return (0);
347: }
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