|
- /* $OpenBSD: ssh-sk-client.c,v 1.12 2022/01/14 03:34:00 djm 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];
- 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_f("helper \"%s\" unusable: %s", 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_f("dup2: %s", strerror(errno));
- _exit(1);
- }
- close(pair[0]);
- close(pair[1]);
- closefrom(STDERR_FILENO + 1);
- debug_f("starting %s %s", helper,
- verbosity == NULL ? "" : verbosity);
- execlp(helper, helper, verbosity, (char *)NULL);
- error_f("execlp: %s", strerror(errno));
- _exit(1);
- }
- close(pair[1]);
-
- /* success */
- debug3_f("started pid=%ld", (long)pid);
- *fdp = pair[0];
- *pidp = pid;
- *osigchldp = osigchld;
- return 0;
- }
-
- static int
- reap_helper(pid_t pid)
- {
- int status, oerrno;
-
- debug3_f("pid=%ld", (long)pid);
-
- errno = 0;
- while (waitpid(pid, &status, 0) == -1) {
- if (errno == EINTR) {
- errno = 0;
- continue;
- }
- oerrno = errno;
- error_f("waitpid: %s", strerror(errno));
- errno = oerrno;
- return SSH_ERR_SYSTEM_ERROR;
- }
- if (!WIFEXITED(status)) {
- error_f("helper exited abnormally");
- return SSH_ERR_AGENT_FAILURE;
- } else if (WEXITSTATUS(status) != 0) {
- error_f("helper exited with non-zero exit status");
- 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_fr(r, "compose");
- goto out;
- }
- if ((r = ssh_msg_send(fd, SSH_SK_HELPER_VERSION, req)) != 0) {
- error_fr(r, "send");
- goto out;
- }
- if ((r = ssh_msg_recv(fd, resp)) != 0) {
- error_fr(r, "receive");
- goto out;
- }
- if ((r = sshbuf_get_u8(resp, &version)) != 0) {
- error_fr(r, "parse version");
- goto out;
- }
- if (version != SSH_SK_HELPER_VERSION) {
- error_f("unsupported version: got %u, expected %u",
- version, SSH_SK_HELPER_VERSION);
- r = SSH_ERR_INVALID_FORMAT;
- goto out;
- }
- if ((r = sshbuf_get_u32(resp, &rtype)) != 0) {
- error_fr(r, "parse message type");
- goto out;
- }
- if (rtype == SSH_SK_HELPER_ERROR) {
- if ((r = sshbuf_get_u32(resp, &rerr)) != 0) {
- error_fr(r, "parse");
- goto out;
- }
- debug_f("helper returned error -%u", 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_f("helper returned incorrect message type %u, "
- "expecting %u", 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;
- 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_fr(r, "encode key");
- 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_fr(r, "compose");
- 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_fr(r, "parse signature");
- r = SSH_ERR_INVALID_FORMAT;
- goto out;
- }
- if (sshbuf_len(resp) != 0) {
- error_f("trailing data in response");
- 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_fr(r, "compose");
- 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_fr(r, "parse");
- r = SSH_ERR_INVALID_FORMAT;
- goto out;
- }
- if (sshbuf_len(resp) != 0) {
- error_f("trailing data in response");
- r = SSH_ERR_INVALID_FORMAT;
- goto out;
- }
- if ((r = sshkey_private_deserialize(kbuf, &key)) != 0) {
- error_fr(r, "encode");
- goto out;
- }
- if (attest != NULL && (r = sshbuf_putb(attest, abuf)) != 0) {
- error_fr(r, "encode attestation information");
- 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;
- }
-
- static void
- sshsk_free_resident_key(struct sshsk_resident_key *srk)
- {
- if (srk == NULL)
- return;
- sshkey_free(srk->key);
- freezero(srk->user_id, srk->user_id_len);
- free(srk);
- }
-
-
- void
- sshsk_free_resident_keys(struct sshsk_resident_key **srks, size_t nsrks)
- {
- size_t i;
-
- if (srks == NULL || nsrks == 0)
- return;
-
- for (i = 0; i < nsrks; i++)
- sshsk_free_resident_key(srks[i]);
- free(srks);
- }
-
- int
- sshsk_load_resident(const char *provider_path, const char *device,
- const char *pin, u_int flags, struct sshsk_resident_key ***srksp,
- size_t *nsrksp)
- {
- int oerrno, r = SSH_ERR_INTERNAL_ERROR;
- struct sshbuf *kbuf = NULL, *req = NULL, *resp = NULL;
- struct sshkey *key = NULL;
- struct sshsk_resident_key *srk = NULL, **srks = NULL, **tmp;
- u_char *userid = NULL;
- size_t userid_len = 0, nsrks = 0;
-
- *srksp = NULL;
- *nsrksp = 0;
-
- if ((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 ||
- (r = sshbuf_put_u32(req, flags)) != 0) {
- error_fr(r, "compose");
- goto out;
- }
-
- if ((r = client_converse(req, &resp, SSH_SK_HELPER_LOAD_RESIDENT)) != 0)
- goto out;
-
- while (sshbuf_len(resp) != 0) {
- /* key, comment, user_id */
- if ((r = sshbuf_get_stringb(resp, kbuf)) != 0 ||
- (r = sshbuf_get_cstring(resp, NULL, NULL)) != 0 ||
- (r = sshbuf_get_string(resp, &userid, &userid_len)) != 0) {
- error_fr(r, "parse");
- r = SSH_ERR_INVALID_FORMAT;
- goto out;
- }
- if ((r = sshkey_private_deserialize(kbuf, &key)) != 0) {
- error_fr(r, "decode key");
- goto out;
- }
- if ((srk = calloc(1, sizeof(*srk))) == NULL) {
- error_f("calloc failed");
- goto out;
- }
- srk->key = key;
- key = NULL;
- srk->user_id = userid;
- srk->user_id_len = userid_len;
- userid = NULL;
- userid_len = 0;
- if ((tmp = recallocarray(srks, nsrks, nsrks + 1,
- sizeof(*srks))) == NULL) {
- error_f("recallocarray keys failed");
- goto out;
- }
- debug_f("srks[%zu]: %s %s uidlen %zu", nsrks,
- sshkey_type(srk->key), srk->key->sk_application,
- srk->user_id_len);
- srks = tmp;
- srks[nsrks++] = srk;
- srk = NULL;
- }
-
- /* success */
- r = 0;
- *srksp = srks;
- *nsrksp = nsrks;
- srks = NULL;
- nsrks = 0;
- out:
- oerrno = errno;
- sshsk_free_resident_key(srk);
- sshsk_free_resident_keys(srks, nsrks);
- freezero(userid, userid_len);
- sshkey_free(key);
- sshbuf_free(kbuf);
- sshbuf_free(req);
- sshbuf_free(resp);
- errno = oerrno;
- return r;
- }
|