Annotation of src/usr.bin/ssh/ssh-sk-helper.c, Revision 1.11
1.11 ! djm 1: /* $OpenBSD: ssh-sk-helper.c,v 1.10 2020/05/26 01:59:46 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);
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;
216: struct sshkey **keys = NULL;
217: size_t nkeys = 0, i;
218:
1.6 djm 219: if ((kbuf = sshbuf_new()) == NULL)
1.5 djm 220: fatal("%s: sshbuf_new failed", __progname);
221:
222: if ((r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
1.7 djm 223: (r = sshbuf_get_cstring(req, &device, NULL)) != 0 ||
1.5 djm 224: (r = sshbuf_get_cstring(req, &pin, NULL)) != 0)
1.11 ! djm 225: fatal_r(r, "%s: parse", __progname);
1.5 djm 226: if (sshbuf_len(req) != 0)
227: fatal("%s: trailing data in request", __progname);
228:
1.7 djm 229: null_empty(&device);
230: null_empty(&pin);
1.6 djm 231:
1.7 djm 232: if ((r = sshsk_load_resident(provider, device, pin,
233: &keys, &nkeys)) != 0) {
1.6 djm 234: resp = reply_error(r, " sshsk_load_resident failed: %s",
235: ssh_err(r));
236: goto out;
237: }
238:
239: if ((resp = sshbuf_new()) == NULL)
240: fatal("%s: sshbuf_new failed", __progname);
241:
242: if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_LOAD_RESIDENT)) != 0)
1.11 ! djm 243: fatal_r(r, "%s: compose", __progname);
1.5 djm 244:
245: for (i = 0; i < nkeys; i++) {
1.11 ! djm 246: debug_f("key %zu %s %s", i, sshkey_type(keys[i]),
! 247: keys[i]->sk_application);
1.5 djm 248: sshbuf_reset(kbuf);
249: if ((r = sshkey_private_serialize(keys[i], kbuf)) != 0)
1.11 ! djm 250: fatal_r(r, "%s: encode key", __progname);
1.5 djm 251: if ((r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
252: (r = sshbuf_put_cstring(resp, "")) != 0) /* comment */
1.11 ! djm 253: fatal_r(r, "%s: compose key", __progname);
1.5 djm 254: }
255:
1.6 djm 256: out:
1.5 djm 257: for (i = 0; i < nkeys; i++)
258: sshkey_free(keys[i]);
259: free(keys);
260: sshbuf_free(kbuf);
261: free(provider);
1.6 djm 262: if (pin != NULL)
263: freezero(pin, strlen(pin));
1.5 djm 264: return resp;
265: }
266:
1.4 djm 267: int
268: main(int argc, char **argv)
269: {
270: SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
271: LogLevel log_level = SYSLOG_LEVEL_ERROR;
272: struct sshbuf *req, *resp;
1.8 djm 273: int in, out, ch, r, vflag = 0;
274: u_int rtype, ll = 0;
275: uint8_t version, log_stderr = 0;
1.1 djm 276:
277: sanitise_stdfd();
278: log_init(__progname, log_level, log_facility, log_stderr);
279:
280: while ((ch = getopt(argc, argv, "v")) != -1) {
281: switch (ch) {
282: case 'v':
1.8 djm 283: vflag = 1;
1.1 djm 284: if (log_level == SYSLOG_LEVEL_ERROR)
285: log_level = SYSLOG_LEVEL_DEBUG1;
286: else if (log_level < SYSLOG_LEVEL_DEBUG3)
287: log_level++;
288: break;
289: default:
290: fprintf(stderr, "usage: %s [-v]\n", __progname);
291: exit(1);
292: }
293: }
1.8 djm 294: log_init(__progname, log_level, log_facility, vflag);
1.1 djm 295:
296: /*
297: * Rearrange our file descriptors a little; we don't trust the
298: * providers not to fiddle with stdin/out.
299: */
300: closefrom(STDERR_FILENO + 1);
301: if ((in = dup(STDIN_FILENO)) == -1 || (out = dup(STDOUT_FILENO)) == -1)
302: fatal("%s: dup: %s", __progname, strerror(errno));
303: close(STDIN_FILENO);
304: close(STDOUT_FILENO);
305: sanitise_stdfd(); /* resets to /dev/null */
306:
1.4 djm 307: if ((req = sshbuf_new()) == NULL)
1.1 djm 308: fatal("%s: sshbuf_new failed", __progname);
309: if (ssh_msg_recv(in, req) < 0)
310: fatal("ssh_msg_recv failed");
311: close(in);
1.11 ! djm 312: debug_f("received message len %zu", sshbuf_len(req));
1.1 djm 313:
314: if ((r = sshbuf_get_u8(req, &version)) != 0)
1.11 ! djm 315: fatal_r(r, "%s: parse version", __progname);
1.1 djm 316: if (version != SSH_SK_HELPER_VERSION) {
317: fatal("unsupported version: received %d, expected %d",
318: version, SSH_SK_HELPER_VERSION);
319: }
320:
1.8 djm 321: if ((r = sshbuf_get_u32(req, &rtype)) != 0 ||
322: (r = sshbuf_get_u8(req, &log_stderr)) != 0 ||
323: (r = sshbuf_get_u32(req, &ll)) != 0)
1.11 ! djm 324: fatal_r(r, "%s: parse", __progname);
1.8 djm 325:
326: if (!vflag && log_level_name((LogLevel)ll) != NULL)
327: log_init(__progname, (LogLevel)ll, log_facility, log_stderr);
1.1 djm 328:
1.4 djm 329: switch (rtype) {
330: case SSH_SK_HELPER_SIGN:
331: resp = process_sign(req);
332: break;
333: case SSH_SK_HELPER_ENROLL:
334: resp = process_enroll(req);
1.5 djm 335: break;
336: case SSH_SK_HELPER_LOAD_RESIDENT:
337: resp = process_load_resident(req);
1.4 djm 338: break;
339: default:
340: fatal("%s: unsupported request type %u", __progname, rtype);
341: }
342: sshbuf_free(req);
1.11 ! djm 343: debug_f("reply len %zu", sshbuf_len(resp));
1.1 djm 344:
345: if (ssh_msg_send(out, SSH_SK_HELPER_VERSION, resp) == -1)
346: fatal("ssh_msg_send failed");
1.4 djm 347: sshbuf_free(resp);
1.1 djm 348: close(out);
349:
350: return (0);
351: }
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