Annotation of src/usr.bin/ssh/ssh-sk-helper.c, Revision 1.13
1.13 ! dtucker 1: /* $OpenBSD: ssh-sk-helper.c,v 1.12 2021/10/28 02:54:18 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)
1.11 djm 67: fatal_f("invalid error code %d", r);
1.6 djm 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)
1.11 djm 106: fatal_r(r, "%s: parse", __progname);
1.4 djm 107: if (sshbuf_len(req) != 0)
108: fatal("%s: trailing data in request", __progname);
109:
110: if ((r = sshkey_private_deserialize(kbuf, &key)) != 0)
1.11 djm 111: fatal_r(r, "%s: Unable to parse private key", __progname);
112: if (!sshkey_is_sk(key)) {
113: fatal("%s: Unsupported key type %s",
114: __progname, sshkey_ssh_name(key));
115: }
1.4 djm 116:
1.11 djm 117: debug_f("ready to sign with key %s, provider %s: "
118: "msg len %zu, compat 0x%lx", sshkey_type(key),
1.4 djm 119: provider, msglen, (u_long)compat);
120:
1.7 djm 121: null_empty(&pin);
1.6 djm 122:
1.4 djm 123: if ((r = sshsk_sign(provider, key, &sig, &siglen,
1.6 djm 124: message, msglen, compat, pin)) != 0) {
125: resp = reply_error(r, "Signing failed: %s", ssh_err(r));
126: goto out;
127: }
1.4 djm 128:
129: if ((resp = sshbuf_new()) == NULL)
130: fatal("%s: sshbuf_new failed", __progname);
131:
1.6 djm 132: if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_SIGN)) != 0 ||
133: (r = sshbuf_put_string(resp, sig, siglen)) != 0)
1.11 djm 134: fatal_r(r, "%s: compose", __progname);
1.6 djm 135: out:
1.10 djm 136: sshkey_free(key);
1.4 djm 137: sshbuf_free(kbuf);
138: free(provider);
1.10 djm 139: if (sig != NULL)
140: freezero(sig, siglen);
1.6 djm 141: if (pin != NULL)
142: freezero(pin, strlen(pin));
1.4 djm 143: return resp;
144: }
145:
146: static struct sshbuf *
147: process_enroll(struct sshbuf *req)
148: {
149: int r;
150: u_int type;
1.7 djm 151: char *provider, *application, *pin, *device, *userid;
1.4 djm 152: uint8_t flags;
153: struct sshbuf *challenge, *attest, *kbuf, *resp;
154: struct sshkey *key;
155:
1.6 djm 156: if ((attest = sshbuf_new()) == NULL ||
1.4 djm 157: (kbuf = sshbuf_new()) == NULL)
158: fatal("%s: sshbuf_new failed", __progname);
159:
160: if ((r = sshbuf_get_u32(req, &type)) != 0 ||
161: (r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
1.7 djm 162: (r = sshbuf_get_cstring(req, &device, NULL)) != 0 ||
1.4 djm 163: (r = sshbuf_get_cstring(req, &application, NULL)) != 0 ||
1.7 djm 164: (r = sshbuf_get_cstring(req, &userid, NULL)) != 0 ||
1.4 djm 165: (r = sshbuf_get_u8(req, &flags)) != 0 ||
1.6 djm 166: (r = sshbuf_get_cstring(req, &pin, NULL)) != 0 ||
1.4 djm 167: (r = sshbuf_froms(req, &challenge)) != 0)
1.11 djm 168: fatal_r(r, "%s: parse", __progname);
1.4 djm 169: if (sshbuf_len(req) != 0)
170: fatal("%s: trailing data in request", __progname);
171:
172: if (type > INT_MAX)
173: fatal("%s: bad type %u", __progname, type);
174: if (sshbuf_len(challenge) == 0) {
175: sshbuf_free(challenge);
176: challenge = NULL;
177: }
1.7 djm 178: null_empty(&device);
179: null_empty(&userid);
180: null_empty(&pin);
1.4 djm 181:
1.7 djm 182: if ((r = sshsk_enroll((int)type, provider, device, application, userid,
183: flags, pin, challenge, &key, attest)) != 0) {
1.6 djm 184: resp = reply_error(r, "Enrollment failed: %s", ssh_err(r));
185: goto out;
186: }
1.4 djm 187:
1.6 djm 188: if ((resp = sshbuf_new()) == NULL)
189: fatal("%s: sshbuf_new failed", __progname);
1.4 djm 190: if ((r = sshkey_private_serialize(key, kbuf)) != 0)
1.11 djm 191: fatal_r(r, "%s: encode key", __progname);
1.6 djm 192: if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_ENROLL)) != 0 ||
193: (r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
1.4 djm 194: (r = sshbuf_put_stringb(resp, attest)) != 0)
1.11 djm 195: fatal_r(r, "%s: compose", __progname);
1.4 djm 196:
1.6 djm 197: out:
1.4 djm 198: sshkey_free(key);
199: sshbuf_free(kbuf);
200: sshbuf_free(attest);
201: sshbuf_free(challenge);
202: free(provider);
203: free(application);
1.6 djm 204: if (pin != NULL)
205: freezero(pin, strlen(pin));
1.4 djm 206:
207: return resp;
208: }
209:
1.5 djm 210: static struct sshbuf *
211: process_load_resident(struct sshbuf *req)
212: {
213: int r;
1.7 djm 214: char *provider, *pin, *device;
1.5 djm 215: struct sshbuf *kbuf, *resp;
1.12 djm 216: struct sshsk_resident_key **srks = NULL;
217: size_t nsrks = 0, i;
218: u_int flags;
1.5 djm 219:
1.6 djm 220: if ((kbuf = sshbuf_new()) == NULL)
1.5 djm 221: fatal("%s: sshbuf_new failed", __progname);
222:
223: if ((r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
1.7 djm 224: (r = sshbuf_get_cstring(req, &device, NULL)) != 0 ||
1.12 djm 225: (r = sshbuf_get_cstring(req, &pin, NULL)) != 0 ||
226: (r = sshbuf_get_u32(req, &flags)) != 0)
1.11 djm 227: fatal_r(r, "%s: parse", __progname);
1.5 djm 228: if (sshbuf_len(req) != 0)
229: fatal("%s: trailing data in request", __progname);
230:
1.7 djm 231: null_empty(&device);
232: null_empty(&pin);
1.6 djm 233:
1.12 djm 234: if ((r = sshsk_load_resident(provider, device, pin, flags,
235: &srks, &nsrks)) != 0) {
236: resp = reply_error(r, "sshsk_load_resident failed: %s",
1.6 djm 237: ssh_err(r));
238: goto out;
239: }
240:
241: if ((resp = sshbuf_new()) == NULL)
242: fatal("%s: sshbuf_new failed", __progname);
243:
244: if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_LOAD_RESIDENT)) != 0)
1.11 djm 245: fatal_r(r, "%s: compose", __progname);
1.5 djm 246:
1.12 djm 247: for (i = 0; i < nsrks; i++) {
248: debug_f("key %zu %s %s uidlen %zu", i,
249: sshkey_type(srks[i]->key), srks[i]->key->sk_application,
250: srks[i]->user_id_len);
1.5 djm 251: sshbuf_reset(kbuf);
1.12 djm 252: if ((r = sshkey_private_serialize(srks[i]->key, kbuf)) != 0)
1.11 djm 253: fatal_r(r, "%s: encode key", __progname);
1.5 djm 254: if ((r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
1.12 djm 255: (r = sshbuf_put_cstring(resp, "")) != 0 || /* comment */
256: (r = sshbuf_put_string(resp, srks[i]->user_id,
257: srks[i]->user_id_len)) != 0)
1.11 djm 258: fatal_r(r, "%s: compose key", __progname);
1.5 djm 259: }
260:
1.6 djm 261: out:
1.12 djm 262: sshsk_free_resident_keys(srks, nsrks);
1.5 djm 263: sshbuf_free(kbuf);
264: free(provider);
1.13 ! dtucker 265: free(device);
1.6 djm 266: if (pin != NULL)
267: freezero(pin, strlen(pin));
1.5 djm 268: return resp;
269: }
270:
1.4 djm 271: int
272: main(int argc, char **argv)
273: {
274: SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
275: LogLevel log_level = SYSLOG_LEVEL_ERROR;
276: struct sshbuf *req, *resp;
1.8 djm 277: int in, out, ch, r, vflag = 0;
278: u_int rtype, ll = 0;
279: uint8_t version, log_stderr = 0;
1.1 djm 280:
281: sanitise_stdfd();
282: log_init(__progname, log_level, log_facility, log_stderr);
283:
284: while ((ch = getopt(argc, argv, "v")) != -1) {
285: switch (ch) {
286: case 'v':
1.8 djm 287: vflag = 1;
1.1 djm 288: if (log_level == SYSLOG_LEVEL_ERROR)
289: log_level = SYSLOG_LEVEL_DEBUG1;
290: else if (log_level < SYSLOG_LEVEL_DEBUG3)
291: log_level++;
292: break;
293: default:
294: fprintf(stderr, "usage: %s [-v]\n", __progname);
295: exit(1);
296: }
297: }
1.8 djm 298: log_init(__progname, log_level, log_facility, vflag);
1.1 djm 299:
300: /*
301: * Rearrange our file descriptors a little; we don't trust the
302: * providers not to fiddle with stdin/out.
303: */
304: closefrom(STDERR_FILENO + 1);
305: if ((in = dup(STDIN_FILENO)) == -1 || (out = dup(STDOUT_FILENO)) == -1)
306: fatal("%s: dup: %s", __progname, strerror(errno));
307: close(STDIN_FILENO);
308: close(STDOUT_FILENO);
309: sanitise_stdfd(); /* resets to /dev/null */
310:
1.4 djm 311: if ((req = sshbuf_new()) == NULL)
1.1 djm 312: fatal("%s: sshbuf_new failed", __progname);
313: if (ssh_msg_recv(in, req) < 0)
314: fatal("ssh_msg_recv failed");
315: close(in);
1.11 djm 316: debug_f("received message len %zu", sshbuf_len(req));
1.1 djm 317:
318: if ((r = sshbuf_get_u8(req, &version)) != 0)
1.11 djm 319: fatal_r(r, "%s: parse version", __progname);
1.1 djm 320: if (version != SSH_SK_HELPER_VERSION) {
321: fatal("unsupported version: received %d, expected %d",
322: version, SSH_SK_HELPER_VERSION);
323: }
324:
1.8 djm 325: if ((r = sshbuf_get_u32(req, &rtype)) != 0 ||
326: (r = sshbuf_get_u8(req, &log_stderr)) != 0 ||
327: (r = sshbuf_get_u32(req, &ll)) != 0)
1.11 djm 328: fatal_r(r, "%s: parse", __progname);
1.8 djm 329:
330: if (!vflag && log_level_name((LogLevel)ll) != NULL)
331: log_init(__progname, (LogLevel)ll, log_facility, log_stderr);
1.1 djm 332:
1.4 djm 333: switch (rtype) {
334: case SSH_SK_HELPER_SIGN:
335: resp = process_sign(req);
336: break;
337: case SSH_SK_HELPER_ENROLL:
338: resp = process_enroll(req);
1.5 djm 339: break;
340: case SSH_SK_HELPER_LOAD_RESIDENT:
341: resp = process_load_resident(req);
1.4 djm 342: break;
343: default:
344: fatal("%s: unsupported request type %u", __progname, rtype);
345: }
346: sshbuf_free(req);
1.11 djm 347: debug_f("reply len %zu", sshbuf_len(resp));
1.1 djm 348:
349: if (ssh_msg_send(out, SSH_SK_HELPER_VERSION, resp) == -1)
350: fatal("ssh_msg_send failed");
1.4 djm 351: sshbuf_free(resp);
1.1 djm 352: close(out);
353:
354: return (0);
355: }
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