mirror of git://anongit.mindrot.org/openssh.git
upstream: perform security key enrollment via ssh-sk-helper too.
This means that ssh-keygen no longer needs to link against ssh-sk-helper, and only ssh-sk-helper needs libfido2 and /dev/uhid* access; feedback & ok markus@ OpenBSD-Commit-ID: 9464233fab95708d2ff059f8bee29c0d1f270800
This commit is contained in:
djm@openbsd.org
Damien Miller
parent
612b1dd1ec
commit
611073fb40
160
ssh-sk-helper.c
160
ssh-sk-helper.c
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@ -1,4 +1,4 @@
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/* $OpenBSD: ssh-sk-helper.c,v 1.3 2019/11/12 19:33:08 markus Exp $ */
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/* $OpenBSD: ssh-sk-helper.c,v 1.4 2019/12/13 19:11:14 djm Exp $ */
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/*
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* Copyright (c) 2019 Google LLC
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*
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@ -18,20 +18,16 @@
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/*
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* This is a tiny program used to isolate the address space used for
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* security key middleware signing operations from ssh-agent. It is similar
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* to ssh-pkcs11-helper.c but considerably simpler as the signing operation
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* for this case are stateless.
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* to ssh-pkcs11-helper.c but considerably simpler as the operations for
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* security keys are stateless.
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*
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* It receives a signing request (key, provider, message, flags) from
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* stdin, attempts to perform a signature using the security key provider
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* and returns the resultant signature via stdout.
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*
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* In the future, this program might gain additional functions to support
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* FIDO2 tokens such as enumerating resident keys. When this happens it will
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* be necessary to crank SSH_SK_HELPER_VERSION below.
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* Please crank SSH_SK_HELPER_VERSION in sshkey.h for any incompatible
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* protocol changes.
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*/
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#include "includes.h"
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#include <limits.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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@ -54,19 +50,112 @@
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#ifdef ENABLE_SK
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extern char *__progname;
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static struct sshbuf *
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process_sign(struct sshbuf *req)
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{
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int r = SSH_ERR_INTERNAL_ERROR;
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struct sshbuf *resp, *kbuf;
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struct sshkey *key;
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uint32_t compat;
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const u_char *message;
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u_char *sig;
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size_t msglen, siglen;
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char *provider;
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if ((r = sshbuf_froms(req, &kbuf)) != 0 ||
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(r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
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(r = sshbuf_get_string_direct(req, &message, &msglen)) != 0 ||
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(r = sshbuf_get_cstring(req, NULL, NULL)) != 0 || /* alg */
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(r = sshbuf_get_u32(req, &compat)) != 0)
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fatal("%s: buffer error: %s", __progname, ssh_err(r));
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if (sshbuf_len(req) != 0)
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fatal("%s: trailing data in request", __progname);
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if ((r = sshkey_private_deserialize(kbuf, &key)) != 0)
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fatal("Unable to parse private key: %s", ssh_err(r));
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if (!sshkey_is_sk(key))
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fatal("Unsupported key type %s", sshkey_ssh_name(key));
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debug("%s: ready to sign with key %s, provider %s: "
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"msg len %zu, compat 0x%lx", __progname, sshkey_type(key),
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provider, msglen, (u_long)compat);
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if ((r = sshsk_sign(provider, key, &sig, &siglen,
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message, msglen, compat)) != 0)
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fatal("Signing failed: %s", ssh_err(r));
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if ((resp = sshbuf_new()) == NULL)
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fatal("%s: sshbuf_new failed", __progname);
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if ((r = sshbuf_put_string(resp, sig, siglen)) != 0)
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fatal("%s: buffer error: %s", __progname, ssh_err(r));
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sshbuf_free(kbuf);
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free(provider);
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return resp;
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}
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static struct sshbuf *
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process_enroll(struct sshbuf *req)
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{
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int r;
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u_int type;
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char *provider;
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char *application;
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uint8_t flags;
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struct sshbuf *challenge, *attest, *kbuf, *resp;
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struct sshkey *key;
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if ((resp = sshbuf_new()) == NULL ||
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(attest = sshbuf_new()) == NULL ||
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(kbuf = sshbuf_new()) == NULL)
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fatal("%s: sshbuf_new failed", __progname);
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if ((r = sshbuf_get_u32(req, &type)) != 0 ||
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(r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
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(r = sshbuf_get_cstring(req, &application, NULL)) != 0 ||
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(r = sshbuf_get_u8(req, &flags)) != 0 ||
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(r = sshbuf_froms(req, &challenge)) != 0)
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fatal("%s: buffer error: %s", __progname, ssh_err(r));
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if (sshbuf_len(req) != 0)
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fatal("%s: trailing data in request", __progname);
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if (type > INT_MAX)
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fatal("%s: bad type %u", __progname, type);
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if (sshbuf_len(challenge) == 0) {
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sshbuf_free(challenge);
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challenge = NULL;
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}
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if ((r = sshsk_enroll((int)type, provider, application, flags,
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challenge, &key, attest)) != 0)
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fatal("%s: sshsk_enroll failed: %s", __progname, ssh_err(r));
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if ((r = sshkey_private_serialize(key, kbuf)) != 0)
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fatal("%s: serialize private key: %s", __progname, ssh_err(r));
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if ((r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
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(r = sshbuf_put_stringb(resp, attest)) != 0)
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fatal("%s: buffer error: %s", __progname, ssh_err(r));
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sshkey_free(key);
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sshbuf_free(kbuf);
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sshbuf_free(attest);
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sshbuf_free(challenge);
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free(provider);
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free(application);
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return resp;
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}
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int
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main(int argc, char **argv)
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{
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SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
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LogLevel log_level = SYSLOG_LEVEL_ERROR;
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struct sshbuf *req, *resp, *kbuf;
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struct sshkey *key;
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uint32_t compat;
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const u_char *message;
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u_char version, *sig;
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size_t msglen, siglen;
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char *provider;
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int in, out, ch, r, log_stderr = 0;
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u_int rtype;
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uint8_t version;
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sanitise_stdfd();
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log_init(__progname, log_level, log_facility, log_stderr);
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close(STDOUT_FILENO);
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sanitise_stdfd(); /* resets to /dev/null */
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if ((req = sshbuf_new()) == NULL || (resp = sshbuf_new()) == NULL)
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if ((req = sshbuf_new()) == NULL)
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fatal("%s: sshbuf_new failed", __progname);
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if (ssh_msg_recv(in, req) < 0)
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fatal("ssh_msg_recv failed");
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fatal("unsupported version: received %d, expected %d",
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version, SSH_SK_HELPER_VERSION);
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}
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if ((r = sshbuf_froms(req, &kbuf)) != 0 ||
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(r = sshkey_private_deserialize(kbuf, &key)) != 0)
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fatal("Unable to parse key: %s", ssh_err(r));
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if (!sshkey_is_sk(key))
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fatal("Unsupported key type %s", sshkey_ssh_name(key));
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if ((r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
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(r = sshbuf_get_string_direct(req, &message, &msglen)) != 0 ||
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(r = sshbuf_get_u32(req, &compat)) != 0)
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if ((r = sshbuf_get_u32(req, &rtype)) != 0)
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fatal("%s: buffer error: %s", __progname, ssh_err(r));
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if (sshbuf_len(req) != 0)
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fatal("%s: trailing data in request", __progname);
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debug("%s: ready to sign with key %s, provider %s: "
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"msg len %zu, compat 0x%lx", __progname, sshkey_type(key),
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provider, msglen, (u_long)compat);
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if ((r = sshsk_sign(provider, key, &sig, &siglen,
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message, msglen, compat)) != 0)
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fatal("Signing failed: %s", ssh_err(r));
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/* send reply */
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if ((r = sshbuf_put_string(resp, sig, siglen)) != 0)
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fatal("%s: buffer error: %s", __progname, ssh_err(r));
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switch (rtype) {
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case SSH_SK_HELPER_SIGN:
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resp = process_sign(req);
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break;
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case SSH_SK_HELPER_ENROLL:
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resp = process_enroll(req);
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break;
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default:
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fatal("%s: unsupported request type %u", __progname, rtype);
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}
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sshbuf_free(req);
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debug("%s: reply len %zu", __progname, sshbuf_len(resp));
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if (ssh_msg_send(out, SSH_SK_HELPER_VERSION, resp) == -1)
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fatal("ssh_msg_send failed");
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sshbuf_free(resp);
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close(out);
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return (0);
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8
sshkey.h
8
sshkey.h
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@ -1,4 +1,4 @@
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/* $OpenBSD: sshkey.h,v 1.41 2019/12/13 19:09:10 djm Exp $ */
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/* $OpenBSD: sshkey.h,v 1.42 2019/12/13 19:11:14 djm Exp $ */
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/*
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* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
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#define SSH_KEY_MAX_SIGN_DATA_SIZE (1 << 20)
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/* Version of protocol expected from ssh-sk-helper */
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#define SSH_SK_HELPER_VERSION 1
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#define SSH_SK_HELPER_VERSION 2
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/* ssh-sk-helper messages */
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#define SSH_SK_HELPER_SIGN 1
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#define SSH_SK_HELPER_ENROLL 2
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struct sshbuf;
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