/* $NetBSD: ssh-sk-client.c,v 1.6.4.2 2023/12/25 12:31:08 martin Exp $ */ /* $OpenBSD: ssh-sk-client.c,v 1.12 2022/01/14 03:34:00 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 "includes.h" __RCSID("$NetBSD: ssh-sk-client.c,v 1.6.4.2 2023/12/25 12:31:08 martin Exp $"); #include #include #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" #include "misc.h" /* #define DEBUG_SK 1 */ static int start_helper(int *fdp, pid_t *pidp, void (**osigchldp)(int)) { void (*osigchld)(int); int oerrno, pair[2]; pid_t pid; const 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; if (access(helper, X_OK) != 0) { oerrno = errno; error_f("helper \"%s\" unusable: %s", helper, strerror(errno)); errno = oerrno; return SSH_ERR_SYSTEM_ERROR; } #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 = ssh_signal(SIGCHLD, SIG_DFL); if ((pid = fork()) == -1) { oerrno = errno; error("fork: %s", strerror(errno)); close(pair[0]); close(pair[1]); ssh_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_f("dup2: %s", strerror(errno)); _exit(1); } close(pair[0]); close(pair[1]); closefrom(STDERR_FILENO + 1); debug_f("starting %s %s", helper, verbosity == NULL ? "" : verbosity); execlp(helper, helper, verbosity, (char *)NULL); error_f("execlp: %s", strerror(errno)); _exit(1); } close(pair[1]); /* success */ debug3_f("started pid=%ld", (long)pid); *fdp = pair[0]; *pidp = pid; *osigchldp = osigchld; return 0; } static int reap_helper(pid_t pid) { int status, oerrno; debug3_f("pid=%ld", (long)pid); errno = 0; while (waitpid(pid, &status, 0) == -1) { if (errno == EINTR) { errno = 0; continue; } oerrno = errno; error_f("waitpid: %s", strerror(errno)); errno = oerrno; return SSH_ERR_SYSTEM_ERROR; } if (!WIFEXITED(status)) { error_f("helper exited abnormally"); return SSH_ERR_AGENT_FAILURE; } else if (WEXITSTATUS(status) != 0) { error_f("helper exited with non-zero exit status"); return SSH_ERR_AGENT_FAILURE; } return 0; } static int client_converse(struct sshbuf *msg, struct sshbuf **respp, u_int type) { int oerrno, fd, r2, ll, r = SSH_ERR_INTERNAL_ERROR; u_int rtype, rerr; pid_t pid; u_char version; void (*osigchld)(int); struct sshbuf *req = NULL, *resp = NULL; *respp = NULL; if ((r = start_helper(&fd, &pid, &osigchld)) != 0) return r; if ((req = sshbuf_new()) == NULL || (resp = sshbuf_new()) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } /* Request preamble: type, log_on_stderr, log_level */ ll = log_level_get(); if ((r = sshbuf_put_u32(req, type)) != 0 || (r = sshbuf_put_u8(req, log_is_on_stderr() != 0)) != 0 || (r = sshbuf_put_u32(req, (uint32_t)(ll < 0 ? 0 : ll))) != 0 || (r = sshbuf_putb(req, msg)) != 0) { error_fr(r, "compose"); goto out; } if ((r = ssh_msg_send(fd, SSH_SK_HELPER_VERSION, req)) != 0) { error_fr(r, "send"); goto out; } if ((r = ssh_msg_recv(fd, resp)) != 0) { error_fr(r, "receive"); goto out; } if ((r = sshbuf_get_u8(resp, &version)) != 0) { error_fr(r, "parse version"); goto out; } if (version != SSH_SK_HELPER_VERSION) { error_f("unsupported version: got %u, expected %u", version, SSH_SK_HELPER_VERSION); r = SSH_ERR_INVALID_FORMAT; goto out; } if ((r = sshbuf_get_u32(resp, &rtype)) != 0) { error_fr(r, "parse message type"); goto out; } if (rtype == SSH_SK_HELPER_ERROR) { if ((r = sshbuf_get_u32(resp, &rerr)) != 0) { error_fr(r, "parse"); goto out; } debug_f("helper returned error -%u", rerr); /* OpenSSH error values are negative; encoded as -err on wire */ if (rerr == 0 || rerr >= INT_MAX) r = SSH_ERR_INTERNAL_ERROR; else r = -(int)rerr; goto out; } else if (rtype != type) { error_f("helper returned incorrect message type %u, " "expecting %u", rtype, type); r = SSH_ERR_INTERNAL_ERROR; 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(req); sshbuf_free(resp); ssh_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, const char *pin) { int oerrno, r = SSH_ERR_INTERNAL_ERROR; 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_fr(r, "encode key"); goto out; } if ((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 || (r = sshbuf_put_cstring(req, pin)) != 0) { error_fr(r, "compose"); goto out; } if ((r = client_converse(req, &resp, SSH_SK_HELPER_SIGN)) != 0) goto out; if ((r = sshbuf_get_string(resp, sigp, lenp)) != 0) { error_fr(r, "parse signature"); r = SSH_ERR_INVALID_FORMAT; goto out; } if (sshbuf_len(resp) != 0) { error_f("trailing data in response"); 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 *device, const char *application, const char *userid, uint8_t flags, const char *pin, 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, (u_int)type)) != 0 || (r = sshbuf_put_cstring(req, provider_path)) != 0 || (r = sshbuf_put_cstring(req, device)) != 0 || (r = sshbuf_put_cstring(req, application)) != 0 || (r = sshbuf_put_cstring(req, userid)) != 0 || (r = sshbuf_put_u8(req, flags)) != 0 || (r = sshbuf_put_cstring(req, pin)) != 0 || (r = sshbuf_put_stringb(req, challenge_buf)) != 0) { error_fr(r, "compose"); goto out; } if ((r = client_converse(req, &resp, SSH_SK_HELPER_ENROLL)) != 0) goto out; if ((r = sshbuf_get_stringb(resp, kbuf)) != 0 || (r = sshbuf_get_stringb(resp, abuf)) != 0) { error_fr(r, "parse"); r = SSH_ERR_INVALID_FORMAT; goto out; } if (sshbuf_len(resp) != 0) { error_f("trailing data in response"); r = SSH_ERR_INVALID_FORMAT; goto out; } if ((r = sshkey_private_deserialize(kbuf, &key)) != 0) { error_fr(r, "encode"); goto out; } if (attest != NULL && (r = sshbuf_putb(attest, abuf)) != 0) { error_fr(r, "encode attestation information"); 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; } static void sshsk_free_resident_key(struct sshsk_resident_key *srk) { if (srk == NULL) return; sshkey_free(srk->key); freezero(srk->user_id, srk->user_id_len); free(srk); } void sshsk_free_resident_keys(struct sshsk_resident_key **srks, size_t nsrks) { size_t i; if (srks == NULL || nsrks == 0) return; for (i = 0; i < nsrks; i++) sshsk_free_resident_key(srks[i]); free(srks); } int sshsk_load_resident(const char *provider_path, const char *device, const char *pin, u_int flags, struct sshsk_resident_key ***srksp, size_t *nsrksp) { int oerrno, r = SSH_ERR_INTERNAL_ERROR; struct sshbuf *kbuf = NULL, *req = NULL, *resp = NULL; struct sshkey *key = NULL; struct sshsk_resident_key *srk = NULL, **srks = NULL, **tmp; u_char *userid = NULL; size_t userid_len = 0, nsrks = 0; *srksp = NULL; *nsrksp = 0; if ((kbuf = sshbuf_new()) == NULL || (req = sshbuf_new()) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } if ((r = sshbuf_put_cstring(req, provider_path)) != 0 || (r = sshbuf_put_cstring(req, device)) != 0 || (r = sshbuf_put_cstring(req, pin)) != 0 || (r = sshbuf_put_u32(req, flags)) != 0) { error_fr(r, "compose"); goto out; } if ((r = client_converse(req, &resp, SSH_SK_HELPER_LOAD_RESIDENT)) != 0) goto out; while (sshbuf_len(resp) != 0) { /* key, comment, user_id */ if ((r = sshbuf_get_stringb(resp, kbuf)) != 0 || (r = sshbuf_get_cstring(resp, NULL, NULL)) != 0 || (r = sshbuf_get_string(resp, &userid, &userid_len)) != 0) { error_fr(r, "parse"); r = SSH_ERR_INVALID_FORMAT; goto out; } if ((r = sshkey_private_deserialize(kbuf, &key)) != 0) { error_fr(r, "decode key"); goto out; } if ((srk = calloc(1, sizeof(*srk))) == NULL) { error_f("calloc failed"); goto out; } srk->key = key; key = NULL; srk->user_id = userid; srk->user_id_len = userid_len; userid = NULL; userid_len = 0; if ((tmp = recallocarray(srks, nsrks, nsrks + 1, sizeof(*srks))) == NULL) { error_f("recallocarray keys failed"); goto out; } debug_f("srks[%zu]: %s %s uidlen %zu", nsrks, sshkey_type(srk->key), srk->key->sk_application, srk->user_id_len); srks = tmp; srks[nsrks++] = srk; srk = NULL; } /* success */ r = 0; *srksp = srks; *nsrksp = nsrks; srks = NULL; nsrks = 0; out: oerrno = errno; sshsk_free_resident_key(srk); sshsk_free_resident_keys(srks, nsrks); freezero(userid, userid_len); sshkey_free(key); sshbuf_free(kbuf); sshbuf_free(req); sshbuf_free(resp); errno = oerrno; return r; }