upstream: actually commit the ssh-sk-helper client code; ok markus

OpenBSD-Commit-ID: fd2ea776a5bbbf4d452989d3c3054cf25a5e0589

diff --git a/ssh-sk-client.c b/ssh-sk-client.c
new file mode 100644 (file)
index 0000000..35e2684
--- /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 <sys/types.h>
+#include <sys/socket.h>
+#include <sys/wait.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"
+
+/* #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;
+}