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Diffstat (limited to '')
| -rw-r--r-- | ssh-sk-client.c | 449 |
1 files changed, 449 insertions, 0 deletions
diff --git a/ssh-sk-client.c b/ssh-sk-client.c new file mode 100644 index 0000000..8d7e6c3 --- /dev/null +++ b/ssh-sk-client.c @@ -0,0 +1,449 @@ +/* $OpenBSD: ssh-sk-client.c,v 1.7 2020/01/23 07:10:22 dtucker Exp $ */ +/* + * Copyright (c) 2019 Google LLC + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +#include "includes.h" + +#include <sys/types.h> +#include <sys/socket.h> +#include <sys/wait.h> + +#include <fcntl.h> +#include <limits.h> +#include <errno.h> +#include <signal.h> +#include <stdarg.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#include "log.h" +#include "ssherr.h" +#include "sshbuf.h" +#include "sshkey.h" +#include "msg.h" +#include "digest.h" +#include "pathnames.h" +#include "ssh-sk.h" +#include "misc.h" + +/* #define DEBUG_SK 1 */ + +static int +start_helper(int *fdp, pid_t *pidp, void (**osigchldp)(int)) +{ + void (*osigchld)(int); + int oerrno, pair[2], r = SSH_ERR_INTERNAL_ERROR; + pid_t pid; + char *helper, *verbosity = NULL; + + *fdp = -1; + *pidp = 0; + *osigchldp = SIG_DFL; + + helper = getenv("SSH_SK_HELPER"); + if (helper == NULL || strlen(helper) == 0) + helper = _PATH_SSH_SK_HELPER; + if (access(helper, X_OK) != 0) { + oerrno = errno; + error("%s: helper \"%s\" unusable: %s", __func__, helper, + strerror(errno)); + errno = oerrno; + return SSH_ERR_SYSTEM_ERROR; + } +#ifdef DEBUG_SK + verbosity = "-vvv"; +#endif + + /* Start helper */ + if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) { + error("socketpair: %s", strerror(errno)); + return SSH_ERR_SYSTEM_ERROR; + } + osigchld = ssh_signal(SIGCHLD, SIG_DFL); + if ((pid = fork()) == -1) { + oerrno = errno; + error("fork: %s", strerror(errno)); + close(pair[0]); + close(pair[1]); + ssh_signal(SIGCHLD, osigchld); + errno = oerrno; + return SSH_ERR_SYSTEM_ERROR; + } + if (pid == 0) { + if ((dup2(pair[1], STDIN_FILENO) == -1) || + (dup2(pair[1], STDOUT_FILENO) == -1)) { + error("%s: dup2: %s", __func__, ssh_err(r)); + _exit(1); + } + close(pair[0]); + close(pair[1]); + closefrom(STDERR_FILENO + 1); + debug("%s: starting %s %s", __func__, helper, + verbosity == NULL ? "" : verbosity); + execlp(helper, helper, verbosity, (char *)NULL); + error("%s: execlp: %s", __func__, strerror(errno)); + _exit(1); + } + close(pair[1]); + + /* success */ + debug3("%s: started pid=%ld", __func__, (long)pid); + *fdp = pair[0]; + *pidp = pid; + *osigchldp = osigchld; + return 0; +} + +static int +reap_helper(pid_t pid) +{ + int status, oerrno; + + debug3("%s: pid=%ld", __func__, (long)pid); + + errno = 0; + while (waitpid(pid, &status, 0) == -1) { + if (errno == EINTR) { + errno = 0; + continue; + } + oerrno = errno; + error("%s: waitpid: %s", __func__, strerror(errno)); + errno = oerrno; + return SSH_ERR_SYSTEM_ERROR; + } + if (!WIFEXITED(status)) { + error("%s: helper exited abnormally", __func__); + return SSH_ERR_AGENT_FAILURE; + } else if (WEXITSTATUS(status) != 0) { + error("%s: helper exited with non-zero exit status", __func__); + return SSH_ERR_AGENT_FAILURE; + } + return 0; +} + +static int +client_converse(struct sshbuf *msg, struct sshbuf **respp, u_int type) +{ + int oerrno, fd, r2, ll, r = SSH_ERR_INTERNAL_ERROR; + u_int rtype, rerr; + pid_t pid; + u_char version; + void (*osigchld)(int); + struct sshbuf *req = NULL, *resp = NULL; + *respp = NULL; + + if ((r = start_helper(&fd, &pid, &osigchld)) != 0) + return r; + + if ((req = sshbuf_new()) == NULL || (resp = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + /* Request preamble: type, log_on_stderr, log_level */ + ll = log_level_get(); + if ((r = sshbuf_put_u32(req, type)) != 0 || + (r = sshbuf_put_u8(req, log_is_on_stderr() != 0)) != 0 || + (r = sshbuf_put_u32(req, ll < 0 ? 0 : ll)) != 0 || + (r = sshbuf_putb(req, msg)) != 0) { + error("%s: build: %s", __func__, ssh_err(r)); + goto out; + } + if ((r = ssh_msg_send(fd, SSH_SK_HELPER_VERSION, req)) != 0) { + error("%s: send: %s", __func__, ssh_err(r)); + goto out; + } + if ((r = ssh_msg_recv(fd, resp)) != 0) { + error("%s: receive: %s", __func__, ssh_err(r)); + goto out; + } + if ((r = sshbuf_get_u8(resp, &version)) != 0) { + error("%s: parse version: %s", __func__, ssh_err(r)); + goto out; + } + if (version != SSH_SK_HELPER_VERSION) { + error("%s: unsupported version: got %u, expected %u", + __func__, version, SSH_SK_HELPER_VERSION); + r = SSH_ERR_INVALID_FORMAT; + goto out; + } + if ((r = sshbuf_get_u32(resp, &rtype)) != 0) { + error("%s: parse message type: %s", __func__, ssh_err(r)); + goto out; + } + if (rtype == SSH_SK_HELPER_ERROR) { + if ((r = sshbuf_get_u32(resp, &rerr)) != 0) { + error("%s: parse error: %s", __func__, ssh_err(r)); + goto out; + } + debug("%s: helper returned error -%u", __func__, rerr); + /* OpenSSH error values are negative; encoded as -err on wire */ + if (rerr == 0 || rerr >= INT_MAX) + r = SSH_ERR_INTERNAL_ERROR; + else + r = -(int)rerr; + goto out; + } else if (rtype != type) { + error("%s: helper returned incorrect message type %u, " + "expecting %u", __func__, rtype, type); + r = SSH_ERR_INTERNAL_ERROR; + goto out; + } + /* success */ + r = 0; + out: + oerrno = errno; + close(fd); + if ((r2 = reap_helper(pid)) != 0) { + if (r == 0) { + r = r2; + oerrno = errno; + } + } + if (r == 0) { + *respp = resp; + resp = NULL; + } + sshbuf_free(req); + sshbuf_free(resp); + ssh_signal(SIGCHLD, osigchld); + errno = oerrno; + return r; + +} + +int +sshsk_sign(const char *provider, struct sshkey *key, + u_char **sigp, size_t *lenp, const u_char *data, size_t datalen, + u_int compat, const char *pin) +{ + int oerrno, r = SSH_ERR_INTERNAL_ERROR; + char *fp = NULL; + struct sshbuf *kbuf = NULL, *req = NULL, *resp = NULL; + + *sigp = NULL; + *lenp = 0; + +#ifndef ENABLE_SK + return SSH_ERR_KEY_TYPE_UNKNOWN; +#endif + + if ((kbuf = sshbuf_new()) == NULL || + (req = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + + if ((r = sshkey_private_serialize(key, kbuf)) != 0) { + error("%s: serialize private key: %s", __func__, ssh_err(r)); + goto out; + } + if ((r = sshbuf_put_stringb(req, kbuf)) != 0 || + (r = sshbuf_put_cstring(req, provider)) != 0 || + (r = sshbuf_put_string(req, data, datalen)) != 0 || + (r = sshbuf_put_cstring(req, NULL)) != 0 || /* alg */ + (r = sshbuf_put_u32(req, compat)) != 0 || + (r = sshbuf_put_cstring(req, pin)) != 0) { + error("%s: compose: %s", __func__, ssh_err(r)); + goto out; + } + + if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, + SSH_FP_DEFAULT)) == NULL) { + error("%s: sshkey_fingerprint failed", __func__); + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if ((r = client_converse(req, &resp, SSH_SK_HELPER_SIGN)) != 0) + goto out; + + if ((r = sshbuf_get_string(resp, sigp, lenp)) != 0) { + error("%s: parse signature: %s", __func__, ssh_err(r)); + r = SSH_ERR_INVALID_FORMAT; + goto out; + } + if (sshbuf_len(resp) != 0) { + error("%s: trailing data in response", __func__); + r = SSH_ERR_INVALID_FORMAT; + goto out; + } + /* success */ + r = 0; + out: + oerrno = errno; + if (r != 0) { + freezero(*sigp, *lenp); + *sigp = NULL; + *lenp = 0; + } + sshbuf_free(kbuf); + sshbuf_free(req); + sshbuf_free(resp); + errno = oerrno; + return r; +} + +int +sshsk_enroll(int type, const char *provider_path, const char *device, + const char *application, const char *userid, uint8_t flags, + const char *pin, struct sshbuf *challenge_buf, + struct sshkey **keyp, struct sshbuf *attest) +{ + int oerrno, r = SSH_ERR_INTERNAL_ERROR; + struct sshbuf *kbuf = NULL, *abuf = NULL, *req = NULL, *resp = NULL; + struct sshkey *key = NULL; + + *keyp = NULL; + if (attest != NULL) + sshbuf_reset(attest); + +#ifndef ENABLE_SK + return SSH_ERR_KEY_TYPE_UNKNOWN; +#endif + + if (type < 0) + return SSH_ERR_INVALID_ARGUMENT; + + if ((abuf = sshbuf_new()) == NULL || + (kbuf = sshbuf_new()) == NULL || + (req = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + + if ((r = sshbuf_put_u32(req, (u_int)type)) != 0 || + (r = sshbuf_put_cstring(req, provider_path)) != 0 || + (r = sshbuf_put_cstring(req, device)) != 0 || + (r = sshbuf_put_cstring(req, application)) != 0 || + (r = sshbuf_put_cstring(req, userid)) != 0 || + (r = sshbuf_put_u8(req, flags)) != 0 || + (r = sshbuf_put_cstring(req, pin)) != 0 || + (r = sshbuf_put_stringb(req, challenge_buf)) != 0) { + error("%s: compose: %s", __func__, ssh_err(r)); + goto out; + } + + if ((r = client_converse(req, &resp, SSH_SK_HELPER_ENROLL)) != 0) + goto out; + + if ((r = sshbuf_get_stringb(resp, kbuf)) != 0 || + (r = sshbuf_get_stringb(resp, abuf)) != 0) { + error("%s: parse signature: %s", __func__, ssh_err(r)); + r = SSH_ERR_INVALID_FORMAT; + goto out; + } + if (sshbuf_len(resp) != 0) { + error("%s: trailing data in response", __func__); + r = SSH_ERR_INVALID_FORMAT; + goto out; + } + if ((r = sshkey_private_deserialize(kbuf, &key)) != 0) { + error("Unable to parse private key: %s", ssh_err(r)); + goto out; + } + if (attest != NULL && (r = sshbuf_putb(attest, abuf)) != 0) { + error("%s: buffer error: %s", __func__, ssh_err(r)); + goto out; + } + + /* success */ + r = 0; + *keyp = key; + key = NULL; + out: + oerrno = errno; + sshkey_free(key); + sshbuf_free(kbuf); + sshbuf_free(abuf); + sshbuf_free(req); + sshbuf_free(resp); + errno = oerrno; + return r; +} + +int +sshsk_load_resident(const char *provider_path, const char *device, + const char *pin, struct sshkey ***keysp, size_t *nkeysp) +{ + int oerrno, r = SSH_ERR_INTERNAL_ERROR; + struct sshbuf *kbuf = NULL, *req = NULL, *resp = NULL; + struct sshkey *key = NULL, **keys = NULL, **tmp; + size_t i, nkeys = 0; + + *keysp = NULL; + *nkeysp = 0; + + if ((resp = sshbuf_new()) == NULL || + (kbuf = sshbuf_new()) == NULL || + (req = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + + if ((r = sshbuf_put_cstring(req, provider_path)) != 0 || + (r = sshbuf_put_cstring(req, device)) != 0 || + (r = sshbuf_put_cstring(req, pin)) != 0) { + error("%s: compose: %s", __func__, ssh_err(r)); + goto out; + } + + if ((r = client_converse(req, &resp, SSH_SK_HELPER_LOAD_RESIDENT)) != 0) + goto out; + + while (sshbuf_len(resp) != 0) { + /* key, comment */ + if ((r = sshbuf_get_stringb(resp, kbuf)) != 0 || + (r = sshbuf_get_cstring(resp, NULL, NULL)) != 0) { + error("%s: parse signature: %s", __func__, ssh_err(r)); + r = SSH_ERR_INVALID_FORMAT; + goto out; + } + if ((r = sshkey_private_deserialize(kbuf, &key)) != 0) { + error("Unable to parse private key: %s", ssh_err(r)); + goto out; + } + if ((tmp = recallocarray(keys, nkeys, nkeys + 1, + sizeof(*keys))) == NULL) { + error("%s: recallocarray keys failed", __func__); + goto out; + } + debug("%s: keys[%zu]: %s %s", __func__, + nkeys, sshkey_type(key), key->sk_application); + keys = tmp; + keys[nkeys++] = key; + key = NULL; + } + + /* success */ + r = 0; + *keysp = keys; + *nkeysp = nkeys; + keys = NULL; + nkeys = 0; + out: + oerrno = errno; + for (i = 0; i < nkeys; i++) + sshkey_free(keys[i]); + free(keys); + sshkey_free(key); + sshbuf_free(kbuf); + sshbuf_free(req); + sshbuf_free(resp); + errno = oerrno; + return r; +} |