markus@openbsd.org | 2c55744 | 2019-11-12 19:33:08 +0000 | [diff] [blame] | 1 | /* $OpenBSD: ssh-sk-helper.c,v 1.3 2019/11/12 19:33:08 markus Exp $ */ |
djm@openbsd.org | 07da39f | 2019-10-31 21:22:01 +0000 | [diff] [blame] | 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 |
| 21 | * to ssh-pkcs11-helper.c but considerably simpler as the signing operation |
| 22 | * for this case are stateless. |
| 23 | * |
| 24 | * It receives a signing request (key, provider, message, flags) from |
| 25 | * stdin, attempts to perform a signature using the security key provider |
| 26 | * and returns the resultant signature via stdout. |
| 27 | * |
| 28 | * In the future, this program might gain additional functions to support |
| 29 | * FIDO2 tokens such as enumerating resident keys. When this happens it will |
| 30 | * be necessary to crank SSH_SK_HELPER_VERSION below. |
| 31 | */ |
| 32 | |
| 33 | #include "includes.h" |
| 34 | |
| 35 | #include <stdarg.h> |
| 36 | #include <stdio.h> |
| 37 | #include <stdlib.h> |
| 38 | #include <string.h> |
| 39 | #include <unistd.h> |
| 40 | #include <errno.h> |
| 41 | |
| 42 | #include "xmalloc.h" |
| 43 | #include "log.h" |
| 44 | #include "sshkey.h" |
| 45 | #include "authfd.h" |
| 46 | #include "misc.h" |
| 47 | #include "sshbuf.h" |
| 48 | #include "msg.h" |
| 49 | #include "uidswap.h" |
| 50 | #include "sshkey.h" |
| 51 | #include "ssherr.h" |
| 52 | #include "ssh-sk.h" |
| 53 | |
Damien Miller | 764d51e | 2019-11-01 13:34:49 +1100 | [diff] [blame] | 54 | #ifdef ENABLE_SK |
djm@openbsd.org | 07da39f | 2019-10-31 21:22:01 +0000 | [diff] [blame] | 55 | extern char *__progname; |
| 56 | |
| 57 | int |
| 58 | main(int argc, char **argv) |
| 59 | { |
| 60 | SyslogFacility log_facility = SYSLOG_FACILITY_AUTH; |
| 61 | LogLevel log_level = SYSLOG_LEVEL_ERROR; |
| 62 | struct sshbuf *req, *resp, *kbuf; |
| 63 | struct sshkey *key; |
| 64 | uint32_t compat; |
| 65 | const u_char *message; |
| 66 | u_char version, *sig; |
| 67 | size_t msglen, siglen; |
| 68 | char *provider; |
| 69 | int in, out, ch, r, log_stderr = 0; |
| 70 | |
| 71 | sanitise_stdfd(); |
| 72 | log_init(__progname, log_level, log_facility, log_stderr); |
| 73 | |
| 74 | while ((ch = getopt(argc, argv, "v")) != -1) { |
| 75 | switch (ch) { |
| 76 | case 'v': |
| 77 | log_stderr = 1; |
| 78 | if (log_level == SYSLOG_LEVEL_ERROR) |
| 79 | log_level = SYSLOG_LEVEL_DEBUG1; |
| 80 | else if (log_level < SYSLOG_LEVEL_DEBUG3) |
| 81 | log_level++; |
| 82 | break; |
| 83 | default: |
| 84 | fprintf(stderr, "usage: %s [-v]\n", __progname); |
| 85 | exit(1); |
| 86 | } |
| 87 | } |
| 88 | log_init(__progname, log_level, log_facility, log_stderr); |
| 89 | |
| 90 | /* |
| 91 | * Rearrange our file descriptors a little; we don't trust the |
| 92 | * providers not to fiddle with stdin/out. |
| 93 | */ |
| 94 | closefrom(STDERR_FILENO + 1); |
| 95 | if ((in = dup(STDIN_FILENO)) == -1 || (out = dup(STDOUT_FILENO)) == -1) |
| 96 | fatal("%s: dup: %s", __progname, strerror(errno)); |
| 97 | close(STDIN_FILENO); |
| 98 | close(STDOUT_FILENO); |
| 99 | sanitise_stdfd(); /* resets to /dev/null */ |
| 100 | |
| 101 | if ((req = sshbuf_new()) == NULL || (resp = sshbuf_new()) == NULL) |
| 102 | fatal("%s: sshbuf_new failed", __progname); |
| 103 | if (ssh_msg_recv(in, req) < 0) |
| 104 | fatal("ssh_msg_recv failed"); |
| 105 | close(in); |
| 106 | debug("%s: received message len %zu", __progname, sshbuf_len(req)); |
| 107 | |
| 108 | if ((r = sshbuf_get_u8(req, &version)) != 0) |
| 109 | fatal("%s: buffer error: %s", __progname, ssh_err(r)); |
| 110 | if (version != SSH_SK_HELPER_VERSION) { |
| 111 | fatal("unsupported version: received %d, expected %d", |
| 112 | version, SSH_SK_HELPER_VERSION); |
| 113 | } |
| 114 | if ((r = sshbuf_froms(req, &kbuf)) != 0 || |
| 115 | (r = sshkey_private_deserialize(kbuf, &key)) != 0) |
| 116 | fatal("Unable to parse key: %s", ssh_err(r)); |
markus@openbsd.org | 2c55744 | 2019-11-12 19:33:08 +0000 | [diff] [blame] | 117 | if (!sshkey_is_sk(key)) |
djm@openbsd.org | 07da39f | 2019-10-31 21:22:01 +0000 | [diff] [blame] | 118 | fatal("Unsupported key type %s", sshkey_ssh_name(key)); |
| 119 | |
| 120 | if ((r = sshbuf_get_cstring(req, &provider, NULL)) != 0 || |
| 121 | (r = sshbuf_get_string_direct(req, &message, &msglen)) != 0 || |
| 122 | (r = sshbuf_get_u32(req, &compat)) != 0) |
| 123 | fatal("%s: buffer error: %s", __progname, ssh_err(r)); |
| 124 | if (sshbuf_len(req) != 0) |
| 125 | fatal("%s: trailing data in request", __progname); |
| 126 | |
| 127 | debug("%s: ready to sign with key %s, provider %s: " |
| 128 | "msg len %zu, compat 0x%lx", __progname, sshkey_type(key), |
| 129 | provider, msglen, (u_long)compat); |
| 130 | |
markus@openbsd.org | e03a29e | 2019-11-12 19:30:50 +0000 | [diff] [blame] | 131 | if ((r = sshsk_sign(provider, key, &sig, &siglen, |
djm@openbsd.org | 07da39f | 2019-10-31 21:22:01 +0000 | [diff] [blame] | 132 | message, msglen, compat)) != 0) |
| 133 | fatal("Signing failed: %s", ssh_err(r)); |
| 134 | |
| 135 | /* send reply */ |
| 136 | if ((r = sshbuf_put_string(resp, sig, siglen)) != 0) |
| 137 | fatal("%s: buffer error: %s", __progname, ssh_err(r)); |
| 138 | debug("%s: reply len %zu", __progname, sshbuf_len(resp)); |
| 139 | if (ssh_msg_send(out, SSH_SK_HELPER_VERSION, resp) == -1) |
| 140 | fatal("ssh_msg_send failed"); |
| 141 | close(out); |
| 142 | |
| 143 | return (0); |
| 144 | } |
Damien Miller | 764d51e | 2019-11-01 13:34:49 +1100 | [diff] [blame] | 145 | #else /* ENABLE_SK */ |
| 146 | #include <stdio.h> |
| 147 | |
| 148 | int |
| 149 | main(int argc, char **argv) |
| 150 | { |
| 151 | fprintf(stderr, "ssh-sk-helper: disabled at compile time\n"); |
| 152 | return -1; |
| 153 | } |
| 154 | #endif /* ENABLE_SK */ |