449 lines
10 KiB
C
449 lines
10 KiB
C
/* $OpenBSD: ssh-sk-client.c,v 1.8 2020/10/18 11:32:02 djm Exp $ */
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/*
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* Copyright (c) 2019 Google LLC
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "includes.h"
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <sys/wait.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <errno.h>
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#include <signal.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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#include <string.h>
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#include <unistd.h>
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#include "log.h"
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#include "ssherr.h"
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#include "sshbuf.h"
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#include "sshkey.h"
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#include "msg.h"
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#include "digest.h"
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#include "pathnames.h"
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#include "ssh-sk.h"
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#include "misc.h"
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/* #define DEBUG_SK 1 */
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static int
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start_helper(int *fdp, pid_t *pidp, void (**osigchldp)(int))
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{
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void (*osigchld)(int);
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int oerrno, pair[2];
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pid_t pid;
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char *helper, *verbosity = NULL;
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*fdp = -1;
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*pidp = 0;
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*osigchldp = SIG_DFL;
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helper = getenv("SSH_SK_HELPER");
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if (helper == NULL || strlen(helper) == 0)
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helper = _PATH_SSH_SK_HELPER;
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if (access(helper, X_OK) != 0) {
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oerrno = errno;
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error_f("helper \"%s\" unusable: %s", helper, strerror(errno));
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errno = oerrno;
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return SSH_ERR_SYSTEM_ERROR;
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}
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#ifdef DEBUG_SK
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verbosity = "-vvv";
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#endif
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/* Start helper */
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if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) {
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error("socketpair: %s", strerror(errno));
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return SSH_ERR_SYSTEM_ERROR;
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}
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osigchld = ssh_signal(SIGCHLD, SIG_DFL);
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if ((pid = fork()) == -1) {
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oerrno = errno;
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error("fork: %s", strerror(errno));
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close(pair[0]);
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close(pair[1]);
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ssh_signal(SIGCHLD, osigchld);
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errno = oerrno;
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return SSH_ERR_SYSTEM_ERROR;
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}
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if (pid == 0) {
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if ((dup2(pair[1], STDIN_FILENO) == -1) ||
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(dup2(pair[1], STDOUT_FILENO) == -1)) {
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error_f("dup2: %s", strerror(errno));
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_exit(1);
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}
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close(pair[0]);
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close(pair[1]);
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closefrom(STDERR_FILENO + 1);
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debug_f("starting %s %s", helper,
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verbosity == NULL ? "" : verbosity);
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execlp(helper, helper, verbosity, (char *)NULL);
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error_f("execlp: %s", strerror(errno));
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_exit(1);
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}
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close(pair[1]);
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/* success */
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debug3_f("started pid=%ld", (long)pid);
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*fdp = pair[0];
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*pidp = pid;
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*osigchldp = osigchld;
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return 0;
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}
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static int
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reap_helper(pid_t pid)
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{
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int status, oerrno;
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debug3_f("pid=%ld", (long)pid);
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errno = 0;
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while (waitpid(pid, &status, 0) == -1) {
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if (errno == EINTR) {
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errno = 0;
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continue;
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}
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oerrno = errno;
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error_f("waitpid: %s", strerror(errno));
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errno = oerrno;
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return SSH_ERR_SYSTEM_ERROR;
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}
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if (!WIFEXITED(status)) {
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error_f("helper exited abnormally");
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return SSH_ERR_AGENT_FAILURE;
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} else if (WEXITSTATUS(status) != 0) {
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error_f("helper exited with non-zero exit status");
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return SSH_ERR_AGENT_FAILURE;
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}
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return 0;
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}
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static int
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client_converse(struct sshbuf *msg, struct sshbuf **respp, u_int type)
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{
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int oerrno, fd, r2, ll, r = SSH_ERR_INTERNAL_ERROR;
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u_int rtype, rerr;
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pid_t pid;
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u_char version;
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void (*osigchld)(int);
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struct sshbuf *req = NULL, *resp = NULL;
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*respp = NULL;
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if ((r = start_helper(&fd, &pid, &osigchld)) != 0)
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return r;
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if ((req = sshbuf_new()) == NULL || (resp = sshbuf_new()) == NULL) {
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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/* Request preamble: type, log_on_stderr, log_level */
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ll = log_level_get();
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if ((r = sshbuf_put_u32(req, type)) != 0 ||
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(r = sshbuf_put_u8(req, log_is_on_stderr() != 0)) != 0 ||
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(r = sshbuf_put_u32(req, ll < 0 ? 0 : ll)) != 0 ||
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(r = sshbuf_putb(req, msg)) != 0) {
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error_fr(r, "compose");
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goto out;
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}
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if ((r = ssh_msg_send(fd, SSH_SK_HELPER_VERSION, req)) != 0) {
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error_fr(r, "send");
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goto out;
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}
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if ((r = ssh_msg_recv(fd, resp)) != 0) {
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error_fr(r, "receive");
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goto out;
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}
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if ((r = sshbuf_get_u8(resp, &version)) != 0) {
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error_fr(r, "parse version");
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goto out;
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}
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if (version != SSH_SK_HELPER_VERSION) {
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error_f("unsupported version: got %u, expected %u",
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version, SSH_SK_HELPER_VERSION);
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if ((r = sshbuf_get_u32(resp, &rtype)) != 0) {
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error_fr(r, "parse message type");
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goto out;
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}
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if (rtype == SSH_SK_HELPER_ERROR) {
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if ((r = sshbuf_get_u32(resp, &rerr)) != 0) {
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error_fr(r, "parse");
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goto out;
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}
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debug_f("helper returned error -%u", rerr);
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/* OpenSSH error values are negative; encoded as -err on wire */
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if (rerr == 0 || rerr >= INT_MAX)
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r = SSH_ERR_INTERNAL_ERROR;
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else
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r = -(int)rerr;
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goto out;
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} else if (rtype != type) {
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error_f("helper returned incorrect message type %u, "
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"expecting %u", rtype, type);
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r = SSH_ERR_INTERNAL_ERROR;
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goto out;
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}
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/* success */
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r = 0;
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out:
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oerrno = errno;
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close(fd);
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if ((r2 = reap_helper(pid)) != 0) {
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if (r == 0) {
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r = r2;
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oerrno = errno;
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}
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}
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if (r == 0) {
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*respp = resp;
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resp = NULL;
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}
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sshbuf_free(req);
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sshbuf_free(resp);
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ssh_signal(SIGCHLD, osigchld);
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errno = oerrno;
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return r;
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}
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int
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sshsk_sign(const char *provider, struct sshkey *key,
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u_char **sigp, size_t *lenp, const u_char *data, size_t datalen,
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u_int compat, const char *pin)
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{
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int oerrno, r = SSH_ERR_INTERNAL_ERROR;
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char *fp = NULL;
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struct sshbuf *kbuf = NULL, *req = NULL, *resp = NULL;
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*sigp = NULL;
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*lenp = 0;
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#ifndef ENABLE_SK
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return SSH_ERR_KEY_TYPE_UNKNOWN;
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#endif
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if ((kbuf = sshbuf_new()) == NULL ||
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(req = sshbuf_new()) == NULL) {
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((r = sshkey_private_serialize(key, kbuf)) != 0) {
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error_fr(r, "encode key");
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goto out;
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}
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if ((r = sshbuf_put_stringb(req, kbuf)) != 0 ||
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(r = sshbuf_put_cstring(req, provider)) != 0 ||
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(r = sshbuf_put_string(req, data, datalen)) != 0 ||
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(r = sshbuf_put_cstring(req, NULL)) != 0 || /* alg */
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(r = sshbuf_put_u32(req, compat)) != 0 ||
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(r = sshbuf_put_cstring(req, pin)) != 0) {
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error_fr(r, "compose");
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goto out;
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}
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if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
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SSH_FP_DEFAULT)) == NULL) {
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error_f("sshkey_fingerprint failed");
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((r = client_converse(req, &resp, SSH_SK_HELPER_SIGN)) != 0)
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goto out;
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if ((r = sshbuf_get_string(resp, sigp, lenp)) != 0) {
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error_fr(r, "parse signature");
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if (sshbuf_len(resp) != 0) {
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error_f("trailing data in response");
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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/* success */
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r = 0;
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out:
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oerrno = errno;
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if (r != 0) {
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freezero(*sigp, *lenp);
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*sigp = NULL;
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*lenp = 0;
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}
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sshbuf_free(kbuf);
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sshbuf_free(req);
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sshbuf_free(resp);
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errno = oerrno;
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return r;
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}
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int
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sshsk_enroll(int type, const char *provider_path, const char *device,
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const char *application, const char *userid, uint8_t flags,
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const char *pin, struct sshbuf *challenge_buf,
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struct sshkey **keyp, struct sshbuf *attest)
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{
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int oerrno, r = SSH_ERR_INTERNAL_ERROR;
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struct sshbuf *kbuf = NULL, *abuf = NULL, *req = NULL, *resp = NULL;
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struct sshkey *key = NULL;
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*keyp = NULL;
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if (attest != NULL)
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sshbuf_reset(attest);
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#ifndef ENABLE_SK
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return SSH_ERR_KEY_TYPE_UNKNOWN;
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#endif
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if (type < 0)
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return SSH_ERR_INVALID_ARGUMENT;
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if ((abuf = sshbuf_new()) == NULL ||
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(kbuf = sshbuf_new()) == NULL ||
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(req = sshbuf_new()) == NULL) {
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((r = sshbuf_put_u32(req, (u_int)type)) != 0 ||
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(r = sshbuf_put_cstring(req, provider_path)) != 0 ||
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(r = sshbuf_put_cstring(req, device)) != 0 ||
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(r = sshbuf_put_cstring(req, application)) != 0 ||
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(r = sshbuf_put_cstring(req, userid)) != 0 ||
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(r = sshbuf_put_u8(req, flags)) != 0 ||
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(r = sshbuf_put_cstring(req, pin)) != 0 ||
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(r = sshbuf_put_stringb(req, challenge_buf)) != 0) {
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error_fr(r, "compose");
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goto out;
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}
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if ((r = client_converse(req, &resp, SSH_SK_HELPER_ENROLL)) != 0)
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goto out;
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if ((r = sshbuf_get_stringb(resp, kbuf)) != 0 ||
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(r = sshbuf_get_stringb(resp, abuf)) != 0) {
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error_fr(r, "parse");
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if (sshbuf_len(resp) != 0) {
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error_f("trailing data in response");
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if ((r = sshkey_private_deserialize(kbuf, &key)) != 0) {
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error_fr(r, "encode");
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goto out;
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}
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if (attest != NULL && (r = sshbuf_putb(attest, abuf)) != 0) {
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error_fr(r, "encode attestation information");
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goto out;
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}
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/* success */
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r = 0;
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*keyp = key;
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key = NULL;
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out:
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oerrno = errno;
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sshkey_free(key);
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sshbuf_free(kbuf);
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sshbuf_free(abuf);
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sshbuf_free(req);
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sshbuf_free(resp);
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errno = oerrno;
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return r;
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}
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int
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sshsk_load_resident(const char *provider_path, const char *device,
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const char *pin, struct sshkey ***keysp, size_t *nkeysp)
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{
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int oerrno, r = SSH_ERR_INTERNAL_ERROR;
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struct sshbuf *kbuf = NULL, *req = NULL, *resp = NULL;
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struct sshkey *key = NULL, **keys = NULL, **tmp;
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size_t i, nkeys = 0;
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*keysp = NULL;
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*nkeysp = 0;
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if ((resp = sshbuf_new()) == NULL ||
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(kbuf = sshbuf_new()) == NULL ||
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(req = sshbuf_new()) == NULL) {
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((r = sshbuf_put_cstring(req, provider_path)) != 0 ||
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(r = sshbuf_put_cstring(req, device)) != 0 ||
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(r = sshbuf_put_cstring(req, pin)) != 0) {
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error_fr(r, "compose");
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goto out;
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}
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if ((r = client_converse(req, &resp, SSH_SK_HELPER_LOAD_RESIDENT)) != 0)
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goto out;
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while (sshbuf_len(resp) != 0) {
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/* key, comment */
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if ((r = sshbuf_get_stringb(resp, kbuf)) != 0 ||
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(r = sshbuf_get_cstring(resp, NULL, NULL)) != 0) {
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error_fr(r, "parse signature");
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if ((r = sshkey_private_deserialize(kbuf, &key)) != 0) {
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error_fr(r, "decode key");
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goto out;
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}
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if ((tmp = recallocarray(keys, nkeys, nkeys + 1,
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sizeof(*keys))) == NULL) {
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error_f("recallocarray keys failed");
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goto out;
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}
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debug_f("keys[%zu]: %s %s", nkeys, sshkey_type(key),
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key->sk_application);
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keys = tmp;
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keys[nkeys++] = key;
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key = NULL;
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}
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/* success */
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r = 0;
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*keysp = keys;
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*nkeysp = nkeys;
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keys = NULL;
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nkeys = 0;
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out:
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oerrno = errno;
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for (i = 0; i < nkeys; i++)
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sshkey_free(keys[i]);
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free(keys);
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sshkey_free(key);
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sshbuf_free(kbuf);
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sshbuf_free(req);
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sshbuf_free(resp);
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errno = oerrno;
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return r;
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}
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