]> git.ipfire.org Git - thirdparty/openssh-portable.git/commitdiff
upstream: ssh-agent support for U2F/FIDO keys
authordjm@openbsd.org <djm@openbsd.org>
Thu, 31 Oct 2019 21:22:01 +0000 (21:22 +0000)
committerDamien Miller <djm@mindrot.org>
Thu, 31 Oct 2019 22:46:09 +0000 (09:46 +1100)
feedback & ok markus@

OpenBSD-Commit-ID: bb544a44bc32e45d2ec8bf652db2046f38360acb

Makefile.in
pathnames.h
ssh-agent.1
ssh-agent.c
ssh-sk-helper.c [new file with mode: 0644]
ssh-sk.h

index bac522ad2070335cd0057dbdd099569f6fd2d8e3..c4b4b935722df7c1b21f6776936f456f5d9a530f 100644 (file)
@@ -24,6 +24,7 @@ ASKPASS_PROGRAM=$(libexecdir)/ssh-askpass
 SFTP_SERVER=$(libexecdir)/sftp-server
 SSH_KEYSIGN=$(libexecdir)/ssh-keysign
 SSH_PKCS11_HELPER=$(libexecdir)/ssh-pkcs11-helper
+SSH_SK_HELPER=$(libexecdir)/ssh-sk-helper
 PRIVSEP_PATH=@PRIVSEP_PATH@
 SSH_PRIVSEP_USER=@SSH_PRIVSEP_USER@
 STRIP_OPT=@STRIP_OPT@
@@ -35,6 +36,7 @@ PATHS= -DSSHDIR=\"$(sysconfdir)\" \
        -D_PATH_SFTP_SERVER=\"$(SFTP_SERVER)\" \
        -D_PATH_SSH_KEY_SIGN=\"$(SSH_KEYSIGN)\" \
        -D_PATH_SSH_PKCS11_HELPER=\"$(SSH_PKCS11_HELPER)\" \
+       -D_PATH_SSH_SK_HELPER=\"$(SSH_SK_HELPER)\" \
        -D_PATH_SSH_PIDDIR=\"$(piddir)\" \
        -D_PATH_PRIVSEP_CHROOT_DIR=\"$(PRIVSEP_PATH)\"
 
@@ -60,7 +62,7 @@ EXEEXT=@EXEEXT@
 MANFMT=@MANFMT@
 MKDIR_P=@MKDIR_P@
 
-TARGETS=ssh$(EXEEXT) sshd$(EXEEXT) ssh-add$(EXEEXT) ssh-keygen$(EXEEXT) ssh-keyscan${EXEEXT} ssh-keysign${EXEEXT} ssh-pkcs11-helper$(EXEEXT) ssh-agent$(EXEEXT) scp$(EXEEXT) sftp-server$(EXEEXT) sftp$(EXEEXT)
+TARGETS=ssh$(EXEEXT) sshd$(EXEEXT) ssh-add$(EXEEXT) ssh-keygen$(EXEEXT) ssh-keyscan${EXEEXT} ssh-keysign${EXEEXT} ssh-pkcs11-helper$(EXEEXT) ssh-agent$(EXEEXT) scp$(EXEEXT) sftp-server$(EXEEXT) sftp$(EXEEXT) ssh-sk-helper$(EXEEXT)
 
 XMSS_OBJS=\
        ssh-xmss.o \
@@ -199,6 +201,9 @@ ssh-keysign$(EXEEXT): $(LIBCOMPAT) libssh.a ssh-keysign.o readconf.o uidswap.o c
 ssh-pkcs11-helper$(EXEEXT): $(LIBCOMPAT) libssh.a ssh-pkcs11-helper.o ssh-pkcs11.o
        $(LD) -o $@ ssh-pkcs11-helper.o ssh-pkcs11.o $(LDFLAGS) -lssh -lopenbsd-compat -lssh -lopenbsd-compat $(LIBS)
 
+ssh-sk-helper$(EXEEXT): $(LIBCOMPAT) libssh.a ssh-sk-helper.o
+       $(LD) -o $@ ssh-sk-helper.o $(LDFLAGS) -lssh -lopenbsd-compat -lssh -lopenbsd-compat $(LIBS)
+
 ssh-keyscan$(EXEEXT): $(LIBCOMPAT) libssh.a ssh-keyscan.o
        $(LD) -o $@ ssh-keyscan.o $(LDFLAGS) -lssh -lopenbsd-compat -lssh $(LIBS)
 
@@ -350,6 +355,7 @@ install-files:
        $(INSTALL) -m 0755 $(STRIP_OPT) sshd$(EXEEXT) $(DESTDIR)$(sbindir)/sshd$(EXEEXT)
        $(INSTALL) -m 4711 $(STRIP_OPT) ssh-keysign$(EXEEXT) $(DESTDIR)$(SSH_KEYSIGN)$(EXEEXT)
        $(INSTALL) -m 0755 $(STRIP_OPT) ssh-pkcs11-helper$(EXEEXT) $(DESTDIR)$(SSH_PKCS11_HELPER)$(EXEEXT)
+       $(INSTALL) -m 0755 $(STRIP_OPT) ssh-sk-helper$(EXEEXT) $(DESTDIR)$(SSH_SK_HELPER)$(EXEEXT)
        $(INSTALL) -m 0755 $(STRIP_OPT) sftp$(EXEEXT) $(DESTDIR)$(bindir)/sftp$(EXEEXT)
        $(INSTALL) -m 0755 $(STRIP_OPT) sftp-server$(EXEEXT) $(DESTDIR)$(SFTP_SERVER)$(EXEEXT)
        $(INSTALL) -m 644 ssh.1.out $(DESTDIR)$(mandir)/$(mansubdir)1/ssh.1
@@ -426,6 +432,7 @@ uninstall:
        -rm -r $(DESTDIR)$(SFTP_SERVER)$(EXEEXT)
        -rm -f $(DESTDIR)$(SSH_KEYSIGN)$(EXEEXT)
        -rm -f $(DESTDIR)$(SSH_PKCS11_HELPER)$(EXEEXT)
+       -rm -f $(DESTDIR)$(SSH_SK_HELPER)$(EXEEXT)
        -rm -f $(DESTDIR)$(mandir)/$(mansubdir)1/ssh.1
        -rm -f $(DESTDIR)$(mandir)/$(mansubdir)1/scp.1
        -rm -f $(DESTDIR)$(mandir)/$(mansubdir)1/ssh-add.1
@@ -616,10 +623,10 @@ interop-tests t-exec file-tests: regress-prep regress-binaries $(TARGETS)
        TEST_SSH_SSHADD="$${BUILDDIR}/ssh-add"; \
        TEST_SSH_SSHKEYGEN="$${BUILDDIR}/ssh-keygen"; \
        TEST_SSH_SSHPKCS11HELPER="$${BUILDDIR}/ssh-pkcs11-helper"; \
+       TEST_SSH_SSHSKHELPER="$${BUILDDIR}/ssh-sk-helper"; \
        TEST_SSH_SSHKEYSCAN="$${BUILDDIR}/ssh-keyscan"; \
        TEST_SSH_SFTP="$${BUILDDIR}/sftp"; \
        TEST_SSH_SFTPSERVER="$${BUILDDIR}/sftp-server"; \
-       TEST_SSH_SSHPKCS11HELPER="$${BUILDDIR}/ssh-pkcs11-helper"; \
        TEST_SSH_PLINK="plink"; \
        TEST_SSH_PUTTYGEN="puttygen"; \
        TEST_SSH_CONCH="conch"; \
index 2e0c7b15b33b4a982f6a0443bd78489beca9558e..3a1bd197768fb60279ae7e5012880ee8601e6a3d 100644 (file)
@@ -1,4 +1,4 @@
-/* $OpenBSD: pathnames.h,v 1.29 2019/10/31 21:15:14 djm Exp $ */
+/* $OpenBSD: pathnames.h,v 1.30 2019/10/31 21:22:01 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
 #define _PATH_SSH_PKCS11_HELPER                "/usr/libexec/ssh-pkcs11-helper"
 #endif
 
+/* Location of ssh-sk-helper to support keys in security keys */
+#ifndef _PATH_SSH_SK_HELPER
+#define _PATH_SSH_SK_HELPER            "/usr/libexec/ssh-sk-helper"
+#endif
+
 /* xauth for X11 forwarding */
 #ifndef _PATH_XAUTH
 #define _PATH_XAUTH                    "/usr/X11R6/bin/xauth"
index 83b2b41c846cbbb6630ef99c227b3b618e7b1bcd..7719384fefe622d4000d0a8a093dde45b3865a32 100644 (file)
@@ -1,4 +1,4 @@
-.\" $OpenBSD: ssh-agent.1,v 1.64 2016/11/30 06:54:26 jmc Exp $
+.\" $OpenBSD: ssh-agent.1,v 1.65 2019/10/31 21:22:01 djm Exp $
 .\"
 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -34,7 +34,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: November 30 2016 $
+.Dd $Mdocdate: October 31 2019 $
 .Dt SSH-AGENT 1
 .Os
 .Sh NAME
@@ -46,7 +46,7 @@
 .Op Fl \&Dd
 .Op Fl a Ar bind_address
 .Op Fl E Ar fingerprint_hash
-.Op Fl P Ar pkcs11_whitelist
+.Op Fl P Ar provider_whitelist
 .Op Fl t Ar life
 .Op Ar command Op Ar arg ...
 .Nm ssh-agent
@@ -122,15 +122,17 @@ The default is
 Kill the current agent (given by the
 .Ev SSH_AGENT_PID
 environment variable).
-.It Fl P Ar pkcs11_whitelist
-Specify a pattern-list of acceptable paths for PKCS#11 shared libraries
-that may be added using the
+.It Fl P Ar provider_whitelist
+Specify a pattern-list of acceptable paths for PKCS#11 and security key shared
+libraries that may be used with the
 .Fl s
-option to
+or
+.Fl S
+options to
 .Xr ssh-add 1 .
-The default is to allow loading PKCS#11 libraries from
+The default is to allow loading libraries from
 .Dq /usr/lib/*,/usr/local/lib/* .
-PKCS#11 libraries that do not match the whitelist will be refused.
+Libraries that do not match the whitelist will be refused.
 See PATTERNS in
 .Xr ssh_config 5
 for a description of pattern-list syntax.
index e500591a9a24d944c9e032ccad65a9d97a473f02..6bf9536fb5e8eef811206f6b97b90c5f121075e0 100644 (file)
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-agent.c,v 1.237 2019/06/28 13:35:04 deraadt Exp $ */
+/* $OpenBSD: ssh-agent.c,v 1.238 2019/10/31 21:22:01 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -41,6 +41,7 @@
 #include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/socket.h>
+#include <sys/wait.h>
 #ifdef HAVE_SYS_TIME_H
 # include <sys/time.h>
 #endif
 #include "digest.h"
 #include "ssherr.h"
 #include "match.h"
-
-#ifdef ENABLE_PKCS11
+#include "msg.h"
+#include "pathnames.h"
 #include "ssh-pkcs11.h"
-#endif
+#include "ssh-sk.h"
 
-#ifndef DEFAULT_PKCS11_WHITELIST
-# define DEFAULT_PKCS11_WHITELIST "/usr/lib*/*,/usr/local/lib*/*"
+#ifndef DEFAULT_PROVIDER_WHITELIST
+# define DEFAULT_PROVIDER_WHITELIST "/usr/lib*/*,/usr/local/lib*/*"
 #endif
 
 /* Maximum accepted message length */
@@ -123,6 +124,7 @@ typedef struct identity {
        char *provider;
        time_t death;
        u_int confirm;
+       char *sk_provider;
 } Identity;
 
 struct idtable {
@@ -146,8 +148,8 @@ pid_t cleanup_pid = 0;
 char socket_name[PATH_MAX];
 char socket_dir[PATH_MAX];
 
-/* PKCS#11 path whitelist */
-static char *pkcs11_whitelist;
+/* PKCS#11/Security key path whitelist */
+static char *provider_whitelist;
 
 /* locking */
 #define LOCK_SIZE      32
@@ -189,6 +191,7 @@ free_identity(Identity *id)
        sshkey_free(id->key);
        free(id->provider);
        free(id->comment);
+       free(id->sk_provider);
        free(id);
 }
 
@@ -278,6 +281,121 @@ agent_decode_alg(struct sshkey *key, u_int flags)
        return NULL;
 }
 
+static int
+provider_sign(const char *provider, struct sshkey *key,
+    u_char **sigp, size_t *lenp,
+    const u_char *data, size_t datalen,
+    const char *alg, u_int compat)
+{
+       int status, pair[2], r = SSH_ERR_INTERNAL_ERROR;
+       pid_t pid;
+       char *helper, *verbosity = NULL;
+       struct sshbuf *kbuf, *req, *resp;
+       u_char version;
+
+       debug3("%s: start for provider %s", __func__, provider);
+
+       *sigp = NULL;
+       *lenp = 0;
+
+       helper = getenv("SSH_SK_HELPER");
+       if (helper == NULL || strlen(helper) == 0)
+               helper = _PATH_SSH_SK_HELPER;
+       if (log_level_get() >= SYSLOG_LEVEL_DEBUG1)
+               verbosity = "-vvv";
+
+       /* Start helper */
+       if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) {
+               error("socketpair: %s", strerror(errno));
+               return SSH_ERR_SYSTEM_ERROR;
+       }
+       if ((pid = fork()) == -1) {
+               error("fork: %s", strerror(errno));
+               close(pair[0]);
+               close(pair[1]);
+               return SSH_ERR_SYSTEM_ERROR;
+       }
+       if (pid == 0) {
+               if ((dup2(pair[1], STDIN_FILENO) == -1) ||
+                   (dup2(pair[1], STDOUT_FILENO) == -1))
+                       fatal("%s: dup2: %s", __func__, ssh_err(r));
+               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);
+               fatal("%s: execlp: %s", __func__, strerror(errno));
+       }
+       close(pair[1]);
+
+       if ((kbuf = sshbuf_new()) == NULL ||
+           (req = sshbuf_new()) == NULL ||
+           (resp = sshbuf_new()) == NULL)
+               fatal("%s: sshbuf_new failed", __func__);
+
+       if ((r = sshkey_private_serialize(key, kbuf)) != 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_u32(req, compat)) != 0)
+               fatal("%s: compose: %s", __func__, ssh_err(r));
+       if ((r = ssh_msg_send(pair[0], SSH_SK_HELPER_VERSION, req)) != 0) {
+               error("%s: send: %s", __func__, ssh_err(r));
+               goto out;
+       }
+       if ((r = ssh_msg_recv(pair[0], 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_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:
+       while (waitpid(pid, &status, 0) == -1) {
+               if (errno != EINTR)
+                       fatal("%s: waitpid: %s", __func__, ssh_err(r));
+       }
+       if (!WIFEXITED(status)) {
+               error("%s: helper %s exited abnormally", __func__, helper);
+               if (r == 0)
+                       r = SSH_ERR_SYSTEM_ERROR;
+       } else if (WEXITSTATUS(status) != 0) {
+               error("%s: helper %s exited with non-zero exit status",
+                   __func__, helper);
+               if (r == 0)
+                       r = SSH_ERR_SYSTEM_ERROR;
+       }
+       if (r != 0) {
+               freezero(*sigp, *lenp);
+               *sigp = NULL;
+               *lenp = 0;
+       }
+       sshbuf_free(kbuf);
+       sshbuf_free(req);
+       sshbuf_free(resp);
+       return r;
+}
+
 /* ssh2 only */
 static void
 process_sign_request2(SocketEntry *e)
@@ -308,10 +426,19 @@ process_sign_request2(SocketEntry *e)
                verbose("%s: user refused key", __func__);
                goto send;
        }
-       if ((r = sshkey_sign(id->key, &signature, &slen,
-           data, dlen, agent_decode_alg(key, flags), compat)) != 0) {
-               error("%s: sshkey_sign: %s", __func__, ssh_err(r));
-               goto send;
+       if (id->sk_provider != NULL) {
+               if ((r = provider_sign(id->sk_provider, id->key, &signature,
+                   &slen, data, dlen, agent_decode_alg(key, flags),
+                   compat)) != 0) {
+                       error("%s: sshkey_sign: %s", __func__, ssh_err(r));
+                       goto send;
+               }
+       } else {
+               if ((r = sshkey_sign(id->key, &signature, &slen,
+                   data, dlen, agent_decode_alg(key, flags), compat)) != 0) {
+                       error("%s: sshkey_sign: %s", __func__, ssh_err(r));
+                       goto send;
+               }
        }
        /* Success */
        ok = 0;
@@ -411,7 +538,7 @@ process_add_identity(SocketEntry *e)
        Identity *id;
        int success = 0, confirm = 0;
        u_int seconds, maxsign;
-       char *comment = NULL;
+       char *fp, *comment = NULL, *ext_name = NULL, *sk_provider = NULL;
        time_t death = 0;
        struct sshkey *k = NULL;
        u_char ctype;
@@ -456,15 +583,58 @@ process_add_identity(SocketEntry *e)
                                goto err;
                        }
                        break;
+               case SSH_AGENT_CONSTRAIN_EXTENSION:
+                       if ((r = sshbuf_get_cstring(e->request,
+                           &ext_name, NULL)) != 0) {
+                               error("%s: cannot parse extension: %s",
+                                   __func__, ssh_err(r));
+                               goto err;
+                       }
+                       debug("%s: constraint ext %s", __func__, ext_name);
+                       if (strcmp(ext_name, "sk-provider@openssh.com") == 0) {
+                               if (sk_provider != NULL) {
+                                       error("%s already set", ext_name);
+                                       goto err;
+                               }
+                               if ((r = sshbuf_get_cstring(e->request,
+                                   &sk_provider, NULL)) != 0) {
+                                       error("%s: cannot parse %s: %s",
+                                           __func__, ext_name, ssh_err(r));
+                                       goto err;
+                               }
+                       } else {
+                               error("%s: unsupported constraint \"%s\"",
+                                   __func__, ext_name);
+                               goto err;
+                       }
+                       free(ext_name);
+                       break;
                default:
                        error("%s: Unknown constraint %d", __func__, ctype);
  err:
+                       free(sk_provider);
+                       free(ext_name);
                        sshbuf_reset(e->request);
                        free(comment);
                        sshkey_free(k);
                        goto send;
                }
        }
+       if (sk_provider != NULL) {
+               if (sshkey_type_plain(k->type) != KEY_ECDSA_SK) {
+                       error("Cannot add provider: %s is not a security key",
+                           sshkey_type(k));
+                       free(sk_provider);
+                       goto send;
+               }
+               if (match_pattern_list(sk_provider,
+                   provider_whitelist, 0) != 1) {
+                       error("Refusing add key: provider %s not whitelisted",
+                           sk_provider);
+                       free(sk_provider);
+                       goto send;
+               }
+       }
 
        success = 1;
        if (lifetime && !death)
@@ -478,11 +648,21 @@ process_add_identity(SocketEntry *e)
                /* key state might have been updated */
                sshkey_free(id->key);
                free(id->comment);
+               free(id->sk_provider);
        }
        id->key = k;
        id->comment = comment;
        id->death = death;
        id->confirm = confirm;
+       id->sk_provider = sk_provider;
+
+       if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
+           SSH_FP_DEFAULT)) == NULL)
+               fatal("%s: sshkey_fingerprint failed", __func__);
+       debug("%s: add %s %s \"%.100s\" (life: %u) (confirm: %u) "
+           "(provider: %s)", __func__, sshkey_ssh_name(k), fp, comment,
+           seconds, confirm, sk_provider == NULL ? "none" : sk_provider);
+       free(fp);
 send:
        send_status(e, success);
 }
@@ -600,7 +780,7 @@ process_add_smartcard_key(SocketEntry *e)
                    provider, strerror(errno));
                goto send;
        }
-       if (match_pattern_list(canonical_provider, pkcs11_whitelist, 0) != 1) {
+       if (match_pattern_list(canonical_provider, provider_whitelist, 0) != 1) {
                verbose("refusing PKCS#11 add of \"%.100s\": "
                    "provider not whitelisted", canonical_provider);
                goto send;
@@ -1079,7 +1259,7 @@ usage(void)
 {
        fprintf(stderr,
            "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
-           "                 [-P pkcs11_whitelist] [-t life] [command [arg ...]]\n"
+           "                 [-P provider_whitelist] [-t life] [command [arg ...]]\n"
            "       ssh-agent [-c | -s] -k\n");
        exit(1);
 }
@@ -1137,9 +1317,9 @@ main(int ac, char **av)
                        k_flag++;
                        break;
                case 'P':
-                       if (pkcs11_whitelist != NULL)
+                       if (provider_whitelist != NULL)
                                fatal("-P option already specified");
-                       pkcs11_whitelist = xstrdup(optarg);
+                       provider_whitelist = xstrdup(optarg);
                        break;
                case 's':
                        if (c_flag)
@@ -1175,8 +1355,8 @@ main(int ac, char **av)
        if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
                usage();
 
-       if (pkcs11_whitelist == NULL)
-               pkcs11_whitelist = xstrdup(DEFAULT_PKCS11_WHITELIST);
+       if (provider_whitelist == NULL)
+               provider_whitelist = xstrdup(DEFAULT_PROVIDER_WHITELIST);
 
        if (ac == 0 && !c_flag && !s_flag) {
                shell = getenv("SHELL");
diff --git a/ssh-sk-helper.c b/ssh-sk-helper.c
new file mode 100644 (file)
index 0000000..0a0c92a
--- /dev/null
@@ -0,0 +1,143 @@
+/* $OpenBSD: ssh-sk-helper.c,v 1.1 2019/10/31 21:22:01 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.
+ */
+
+/*
+ * This is a tiny program used to isolate the address space used for
+ * security key middleware signing operations from ssh-agent. It is similar
+ * to ssh-pkcs11-helper.c but considerably simpler as the signing operation
+ * for this case are stateless.
+ *
+ * It receives a signing request (key, provider, message, flags) from
+ * stdin, attempts to perform a signature using the security key provider
+ * and returns the resultant signature via stdout.
+ *
+ * In the future, this program might gain additional functions to support
+ * FIDO2 tokens such as enumerating resident keys. When this happens it will
+ * be necessary to crank SSH_SK_HELPER_VERSION below.
+ */
+
+#include "includes.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "xmalloc.h"
+#include "log.h"
+#include "sshkey.h"
+#include "authfd.h"
+#include "misc.h"
+#include "sshbuf.h"
+#include "msg.h"
+#include "uidswap.h"
+#include "sshkey.h"
+#include "ssherr.h"
+#include "ssh-sk.h"
+
+extern char *__progname;
+
+int
+main(int argc, char **argv)
+{
+       SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
+       LogLevel log_level = SYSLOG_LEVEL_ERROR;
+       struct sshbuf *req, *resp, *kbuf;
+       struct sshkey *key;
+       uint32_t compat;
+       const u_char *message;
+       u_char version, *sig;
+       size_t msglen, siglen;
+       char *provider;
+       int in, out, ch, r, log_stderr = 0;
+
+       sanitise_stdfd();
+       log_init(__progname, log_level, log_facility, log_stderr);
+
+       while ((ch = getopt(argc, argv, "v")) != -1) {
+               switch (ch) {
+               case 'v':
+                       log_stderr = 1;
+                       if (log_level == SYSLOG_LEVEL_ERROR)
+                               log_level = SYSLOG_LEVEL_DEBUG1;
+                       else if (log_level < SYSLOG_LEVEL_DEBUG3)
+                               log_level++;
+                       break;
+               default:
+                       fprintf(stderr, "usage: %s [-v]\n", __progname);
+                       exit(1);
+               }
+       }
+       log_init(__progname, log_level, log_facility, log_stderr);
+
+       /*
+        * Rearrange our file descriptors a little; we don't trust the
+        * providers not to fiddle with stdin/out.
+        */
+       closefrom(STDERR_FILENO + 1);
+       if ((in = dup(STDIN_FILENO)) == -1 || (out = dup(STDOUT_FILENO)) == -1)
+               fatal("%s: dup: %s", __progname, strerror(errno));
+       close(STDIN_FILENO);
+       close(STDOUT_FILENO);
+       sanitise_stdfd(); /* resets to /dev/null */
+
+       if ((req = sshbuf_new()) == NULL || (resp = sshbuf_new()) == NULL)
+               fatal("%s: sshbuf_new failed", __progname);
+       if (ssh_msg_recv(in, req) < 0)
+               fatal("ssh_msg_recv failed");
+       close(in);
+       debug("%s: received message len %zu", __progname, sshbuf_len(req));
+
+       if ((r = sshbuf_get_u8(req, &version)) != 0)
+               fatal("%s: buffer error: %s", __progname, ssh_err(r));
+       if (version != SSH_SK_HELPER_VERSION) {
+               fatal("unsupported version: received %d, expected %d",
+                   version, SSH_SK_HELPER_VERSION);
+       }
+       if ((r = sshbuf_froms(req, &kbuf)) != 0 ||
+           (r = sshkey_private_deserialize(kbuf, &key)) != 0)
+               fatal("Unable to parse key: %s", ssh_err(r));
+       if (sshkey_type_plain(key->type) != KEY_ECDSA_SK)
+               fatal("Unsupported key type %s", sshkey_ssh_name(key));
+
+       if ((r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
+           (r = sshbuf_get_string_direct(req, &message, &msglen)) != 0 ||
+           (r = sshbuf_get_u32(req, &compat)) != 0)
+               fatal("%s: buffer error: %s", __progname, ssh_err(r));
+       if (sshbuf_len(req) != 0)
+               fatal("%s: trailing data in request", __progname);
+
+       debug("%s: ready to sign with key %s, provider %s: "
+           "msg len %zu, compat 0x%lx", __progname, sshkey_type(key),
+           provider, msglen, (u_long)compat);
+
+       if ((r = sshsk_ecdsa_sign(provider, key, &sig, &siglen,
+           message, msglen, compat)) != 0)
+               fatal("Signing failed: %s", ssh_err(r));
+
+       /* send reply */
+       if ((r = sshbuf_put_string(resp, sig, siglen)) != 0)
+               fatal("%s: buffer error: %s", __progname, ssh_err(r));
+       debug("%s: reply len %zu", __progname, sshbuf_len(resp));
+       if (ssh_msg_send(out, SSH_SK_HELPER_VERSION, resp) == -1)
+               fatal("ssh_msg_send failed");
+       close(out);
+
+       return (0);
+}
index 7c1d2b927bb178f1ce1f3f54a5360857bcb31ab0..5033e6f6858739ede7a192a1f77c91993d50ce23 100644 (file)
--- a/ssh-sk.h
+++ b/ssh-sk.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-sk.h,v 1.1 2019/10/31 21:16:20 djm Exp $ */
+/* $OpenBSD: ssh-sk.h,v 1.2 2019/10/31 21:22:01 djm Exp $ */
 /*
  * Copyright (c) 2019 Google LLC
  *
@@ -21,6 +21,9 @@
 struct sshbuf;
 struct sshkey;
 
+/* Version of protocol between ssh-agent and ssh-sk-helper */
+#define SSH_SK_HELPER_VERSION  1
+
 /*
  * Enroll (generate) a new security-key hosted private key via the specified
  * provider middleware.