From d21434766764d5babf99fc3937c19b625c0f6334 Mon Sep 17 00:00:00 2001 From: "djm@openbsd.org" Date: Fri, 13 Dec 2019 20:16:56 +0000 Subject: [PATCH] upstream: actually commit the ssh-sk-helper client code; ok markus OpenBSD-Commit-ID: fd2ea776a5bbbf4d452989d3c3054cf25a5e0589 --- ssh-sk-client.c | 323 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 323 insertions(+) create mode 100644 ssh-sk-client.c diff --git a/ssh-sk-client.c b/ssh-sk-client.c new file mode 100644 index 000000000..35e268472 --- /dev/null +++ b/ssh-sk-client.c @@ -0,0 +1,323 @@ +/* $OpenBSD: ssh-sk-client.c,v 1.1 2019/12/13 20:16:56 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 +#include +#include + +#include +#include +#include +#include +#include +#include +#include + +#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" + +/* #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; +#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 = signal(SIGCHLD, SIG_DFL); + if ((pid = fork()) == -1) { + oerrno = errno; + error("fork: %s", strerror(errno)); + close(pair[0]); + close(pair[1]); + 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 *req, struct sshbuf **respp) +{ + int oerrno, fd, r2, r = SSH_ERR_INTERNAL_ERROR; + pid_t pid; + u_char version; + void (*osigchld)(int); + struct sshbuf *resp = NULL; + + *respp = NULL; + + if ((r = start_helper(&fd, &pid, &osigchld)) != 0) + return r; + + if ((resp = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + 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; + } + /* 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(resp); + 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) +{ + int oerrno, r = SSH_ERR_INTERNAL_ERROR; + char *fp = NULL; + struct sshbuf *kbuf = NULL, *req = NULL, *resp = NULL; + + *sigp = NULL; + *lenp = 0; + + 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_u32(req, SSH_SK_HELPER_SIGN)) != 0 || + (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) { + 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)) != 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 *application, + uint8_t flags, 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); + + 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, SSH_SK_HELPER_ENROLL)) != 0 || + (r = sshbuf_put_u32(req, (u_int)type)) != 0 || + (r = sshbuf_put_cstring(req, provider_path)) != 0 || + (r = sshbuf_put_cstring(req, application)) != 0 || + (r = sshbuf_put_u8(req, flags)) != 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)) != 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; +}