Annotation of src/usr.bin/ssh/ssh-sk-helper.c, Revision 1.1
1.1 ! djm 1: /* $OpenBSD$ */
! 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 <stdarg.h>
! 34: #include <stdio.h>
! 35: #include <stdlib.h>
! 36: #include <string.h>
! 37: #include <unistd.h>
! 38: #include <errno.h>
! 39:
! 40: #include "xmalloc.h"
! 41: #include "log.h"
! 42: #include "sshkey.h"
! 43: #include "authfd.h"
! 44: #include "misc.h"
! 45: #include "sshbuf.h"
! 46: #include "msg.h"
! 47: #include "uidswap.h"
! 48: #include "sshkey.h"
! 49: #include "ssherr.h"
! 50: #include "ssh-sk.h"
! 51:
! 52: extern char *__progname;
! 53:
! 54: int
! 55: main(int argc, char **argv)
! 56: {
! 57: SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
! 58: LogLevel log_level = SYSLOG_LEVEL_ERROR;
! 59: struct sshbuf *req, *resp, *kbuf;
! 60: struct sshkey *key;
! 61: uint32_t compat;
! 62: const u_char *message;
! 63: u_char version, *sig;
! 64: size_t msglen, siglen;
! 65: char *provider;
! 66: int in, out, ch, r, log_stderr = 0;
! 67:
! 68: sanitise_stdfd();
! 69: log_init(__progname, log_level, log_facility, log_stderr);
! 70:
! 71: while ((ch = getopt(argc, argv, "v")) != -1) {
! 72: switch (ch) {
! 73: case 'v':
! 74: log_stderr = 1;
! 75: if (log_level == SYSLOG_LEVEL_ERROR)
! 76: log_level = SYSLOG_LEVEL_DEBUG1;
! 77: else if (log_level < SYSLOG_LEVEL_DEBUG3)
! 78: log_level++;
! 79: break;
! 80: default:
! 81: fprintf(stderr, "usage: %s [-v]\n", __progname);
! 82: exit(1);
! 83: }
! 84: }
! 85: log_init(__progname, log_level, log_facility, log_stderr);
! 86:
! 87: /*
! 88: * Rearrange our file descriptors a little; we don't trust the
! 89: * providers not to fiddle with stdin/out.
! 90: */
! 91: closefrom(STDERR_FILENO + 1);
! 92: if ((in = dup(STDIN_FILENO)) == -1 || (out = dup(STDOUT_FILENO)) == -1)
! 93: fatal("%s: dup: %s", __progname, strerror(errno));
! 94: close(STDIN_FILENO);
! 95: close(STDOUT_FILENO);
! 96: sanitise_stdfd(); /* resets to /dev/null */
! 97:
! 98: if ((req = sshbuf_new()) == NULL || (resp = sshbuf_new()) == NULL)
! 99: fatal("%s: sshbuf_new failed", __progname);
! 100: if (ssh_msg_recv(in, req) < 0)
! 101: fatal("ssh_msg_recv failed");
! 102: close(in);
! 103: debug("%s: received message len %zu", __progname, sshbuf_len(req));
! 104:
! 105: if ((r = sshbuf_get_u8(req, &version)) != 0)
! 106: fatal("%s: buffer error: %s", __progname, ssh_err(r));
! 107: if (version != SSH_SK_HELPER_VERSION) {
! 108: fatal("unsupported version: received %d, expected %d",
! 109: version, SSH_SK_HELPER_VERSION);
! 110: }
! 111: if ((r = sshbuf_froms(req, &kbuf)) != 0 ||
! 112: (r = sshkey_private_deserialize(kbuf, &key)) != 0)
! 113: fatal("Unable to parse key: %s", ssh_err(r));
! 114: if (sshkey_type_plain(key->type) != KEY_ECDSA_SK)
! 115: fatal("Unsupported key type %s", sshkey_ssh_name(key));
! 116:
! 117: if ((r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
! 118: (r = sshbuf_get_string_direct(req, &message, &msglen)) != 0 ||
! 119: (r = sshbuf_get_u32(req, &compat)) != 0)
! 120: fatal("%s: buffer error: %s", __progname, ssh_err(r));
! 121: if (sshbuf_len(req) != 0)
! 122: fatal("%s: trailing data in request", __progname);
! 123:
! 124: debug("%s: ready to sign with key %s, provider %s: "
! 125: "msg len %zu, compat 0x%lx", __progname, sshkey_type(key),
! 126: provider, msglen, (u_long)compat);
! 127:
! 128: if ((r = sshsk_ecdsa_sign(provider, key, &sig, &siglen,
! 129: message, msglen, compat)) != 0)
! 130: fatal("Signing failed: %s", ssh_err(r));
! 131:
! 132: /* send reply */
! 133: if ((r = sshbuf_put_string(resp, sig, siglen)) != 0)
! 134: fatal("%s: buffer error: %s", __progname, ssh_err(r));
! 135: debug("%s: reply len %zu", __progname, sshbuf_len(resp));
! 136: if (ssh_msg_send(out, SSH_SK_HELPER_VERSION, resp) == -1)
! 137: fatal("ssh_msg_send failed");
! 138: close(out);
! 139:
! 140: return (0);
! 141: }
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