Edit
IABSD.fr/src/usr.bin/ssh/authfd.c
djm
- usr.bin/ssh/authfd.c
-
/* $OpenBSD: authfd.c,v 1.134 2023/12/18 14:46:56 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland * All rights reserved * Functions for connecting the local authentication agent. * * As far as I am concerned, the code I have written for this software * can be used freely for any purpose. Any derived versions of this * software must be clearly marked as such, and if the derived work is * incompatible with the protocol description in the RFC file, it must be * called by a name other than "ssh" or "Secure Shell". * * SSH2 implementation, * Copyright (c) 2000 Markus Friedl. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include <sys/types.h> #include <sys/un.h> #include <sys/socket.h> #include <fcntl.h> #include <stdlib.h> #include <signal.h> #include <string.h> #include <stdarg.h> #include <unistd.h> #include <errno.h> #include "xmalloc.h" #include "ssh.h" #include "sshbuf.h" #include "sshkey.h" #include "authfd.h" #include "cipher.h" #include "log.h" #include "atomicio.h" #include "misc.h" #include "ssherr.h" #define MAX_AGENT_IDENTITIES 2048 /* Max keys in agent reply */ #define MAX_AGENT_REPLY_LEN (256 * 1024) /* Max bytes in agent reply */ /* macro to check for "agent failure" message */ #define agent_failed(x) \ ((x == SSH_AGENT_FAILURE) || \ (x == SSH_COM_AGENT2_FAILURE) || \ (x == SSH2_AGENT_FAILURE)) /* Convert success/failure response from agent to a err.h status */ static int decode_reply(u_char type) { if (agent_failed(type)) return SSH_ERR_AGENT_FAILURE; else if (type == SSH_AGENT_SUCCESS) return 0; else return SSH_ERR_INVALID_FORMAT; } /* * Opens an authentication socket at the provided path and stores the file * descriptor in fdp. Returns 0 on success and an error on failure. */ int ssh_get_authentication_socket_path(const char *authsocket, int *fdp) { int sock, oerrno; struct sockaddr_un sunaddr; debug3_f("path '%s'", authsocket); memset(&sunaddr, 0, sizeof(sunaddr)); sunaddr.sun_family = AF_UNIX; strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) return SSH_ERR_SYSTEM_ERROR; /* close on exec */ if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1 || connect(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) == -1) { oerrno = errno; close(sock); errno = oerrno; return SSH_ERR_SYSTEM_ERROR; } if (fdp != NULL) *fdp = sock; else close(sock); return 0; } /* * Opens the default authentication socket and stores the file descriptor in * fdp. Returns 0 on success and an error on failure. */ int ssh_get_authentication_socket(int *fdp) { const char *authsocket; if (fdp != NULL) *fdp = -1; authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); if (authsocket == NULL || *authsocket == '\0') return SSH_ERR_AGENT_NOT_PRESENT; return ssh_get_authentication_socket_path(authsocket, fdp); } /* Communicate with agent: send request and read reply */ static int ssh_request_reply(int sock, struct sshbuf *request, struct sshbuf *reply) { int r; size_t l, len; char buf[1024]; /* Get the length of the message, and format it in the buffer. */ len = sshbuf_len(request); POKE_U32(buf, len); /* Send the length and then the packet to the agent. */ if (atomicio(vwrite, sock, buf, 4) != 4 || atomicio(vwrite, sock, sshbuf_mutable_ptr(request), sshbuf_len(request)) != sshbuf_len(request)) return SSH_ERR_AGENT_COMMUNICATION; /* * Wait for response from the agent. First read the length of the * response packet. */ if (atomicio(read, sock, buf, 4) != 4) return SSH_ERR_AGENT_COMMUNICATION; /* Extract the length, and check it for sanity. */ len = PEEK_U32(buf); if (len > MAX_AGENT_REPLY_LEN) return SSH_ERR_INVALID_FORMAT; /* Read the rest of the response in to the buffer. */ sshbuf_reset(reply); while (len > 0) { l = len; if (l > sizeof(buf)) l = sizeof(buf); if (atomicio(read, sock, buf, l) != l) return SSH_ERR_AGENT_COMMUNICATION; if ((r = sshbuf_put(reply, buf, l)) != 0) return r; len -= l; } return 0; } /* Communicate with agent: sent request, read and decode status reply */ static int ssh_request_reply_decode(int sock, struct sshbuf *request) { struct sshbuf *reply; int r; u_char type; if ((reply = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((r = ssh_request_reply(sock, request, reply)) != 0 || (r = sshbuf_get_u8(reply, &type)) != 0 || (r = decode_reply(type)) != 0) goto out; /* success */ r = 0; out: sshbuf_free(reply); return r; } /* * Closes the agent socket if it should be closed (depends on how it was * obtained). The argument must have been returned by * ssh_get_authentication_socket(). */ void ssh_close_authentication_socket(int sock) { if (getenv(SSH_AUTHSOCKET_ENV_NAME)) close(sock); } /* Lock/unlock agent */ int ssh_lock_agent(int sock, int lock, const char *password) { int r; u_char type = lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK; struct sshbuf *msg; if ((msg = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((r = sshbuf_put_u8(msg, type)) != 0 || (r = sshbuf_put_cstring(msg, password)) != 0 || (r = ssh_request_reply_decode(sock, msg)) != 0) goto out; /* success */ r = 0; out: sshbuf_free(msg); return r; } static int deserialise_identity2(struct sshbuf *ids, struct sshkey **keyp, char **commentp) { int r; char *comment = NULL; const u_char *blob; size_t blen; if ((r = sshbuf_get_string_direct(ids, &blob, &blen)) != 0 || (r = sshbuf_get_cstring(ids, &comment, NULL)) != 0) goto out; if ((r = sshkey_from_blob(blob, blen, keyp)) != 0) goto out; if (commentp != NULL) { *commentp = comment; comment = NULL; } r = 0; out: free(comment); return r; } /* * Fetch list of identities held by the agent. */ int ssh_fetch_identitylist(int sock, struct ssh_identitylist **idlp) { u_char type; u_int32_t num, i; struct sshbuf *msg; struct ssh_identitylist *idl = NULL; int r; /* * Send a message to the agent requesting for a list of the * identities it can represent. */ if ((msg = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_REQUEST_IDENTITIES)) != 0) goto out; if ((r = ssh_request_reply(sock, msg, msg)) != 0) goto out; /* Get message type, and verify that we got a proper answer. */ if ((r = sshbuf_get_u8(msg, &type)) != 0) goto out; if (agent_failed(type)) { r = SSH_ERR_AGENT_FAILURE; goto out; } else if (type != SSH2_AGENT_IDENTITIES_ANSWER) { r = SSH_ERR_INVALID_FORMAT; goto out; } /* Get the number of entries in the response and check it for sanity. */ if ((r = sshbuf_get_u32(msg, &num)) != 0) goto out; if (num > MAX_AGENT_IDENTITIES) { r = SSH_ERR_INVALID_FORMAT; goto out; } if (num == 0) { r = SSH_ERR_AGENT_NO_IDENTITIES; goto out; } /* Deserialise the response into a list of keys/comments */ if ((idl = calloc(1, sizeof(*idl))) == NULL || (idl->keys = calloc(num, sizeof(*idl->keys))) == NULL || (idl->comments = calloc(num, sizeof(*idl->comments))) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } for (i = 0; i < num;) { if ((r = deserialise_identity2(msg, &(idl->keys[i]), &(idl->comments[i]))) != 0) { if (r == SSH_ERR_KEY_TYPE_UNKNOWN) { /* Gracefully skip unknown key types */ num--; continue; } else goto out; } i++; } idl->nkeys = num; *idlp = idl; idl = NULL; r = 0; out: sshbuf_free(msg); if (idl != NULL) ssh_free_identitylist(idl); return r; } void ssh_free_identitylist(struct ssh_identitylist *idl) { size_t i; if (idl == NULL) return; for (i = 0; i < idl->nkeys; i++) { if (idl->keys != NULL) sshkey_free(idl->keys[i]); if (idl->comments != NULL) free(idl->comments[i]); } free(idl->keys); free(idl->comments); free(idl); } /* * Check if the ssh agent has a given key. * Returns 0 if found, or a negative SSH_ERR_* error code on failure. */ int ssh_agent_has_key(int sock, const struct sshkey *key) { int r, ret = SSH_ERR_KEY_NOT_FOUND; size_t i; struct ssh_identitylist *idlist = NULL; if ((r = ssh_fetch_identitylist(sock, &idlist)) != 0) { return r; } for (i = 0; i < idlist->nkeys; i++) { if (sshkey_equal_public(idlist->keys[i], key)) { ret = 0; break; } } ssh_free_identitylist(idlist); return ret; } /* * Sends a challenge (typically from a server via ssh(1)) to the agent, * and waits for a response from the agent. * Returns true (non-zero) if the agent gave the correct answer, zero * otherwise. */ /* encode signature algorithm in flag bits, so we can keep the msg format */ static u_int agent_encode_alg(const struct sshkey *key, const char *alg) { if (alg != NULL && sshkey_type_plain(key->type) == KEY_RSA) { if (strcmp(alg, "rsa-sha2-256") == 0 || strcmp(alg, "rsa-sha2-256-cert-v01@openssh.com") == 0) return SSH_AGENT_RSA_SHA2_256; if (strcmp(alg, "rsa-sha2-512") == 0 || strcmp(alg, "rsa-sha2-512-cert-v01@openssh.com") == 0) return SSH_AGENT_RSA_SHA2_512; } return 0; } /* ask agent to sign data, returns err.h code on error, 0 on success */ int ssh_agent_sign(int sock, const struct sshkey *key, u_char **sigp, size_t *lenp, const u_char *data, size_t datalen, const char *alg, u_int compat) { struct sshbuf *msg; u_char *sig = NULL, type = 0; size_t len = 0; u_int flags = 0; int r = SSH_ERR_INTERNAL_ERROR; *sigp = NULL; *lenp = 0; if (datalen > SSH_KEY_MAX_SIGN_DATA_SIZE) return SSH_ERR_INVALID_ARGUMENT; if ((msg = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; flags |= agent_encode_alg(key, alg); if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 || (r = sshkey_puts(key, msg)) != 0 || (r = sshbuf_put_string(msg, data, datalen)) != 0 || (r = sshbuf_put_u32(msg, flags)) != 0) goto out; if ((r = ssh_request_reply(sock, msg, msg)) != 0) goto out; if ((r = sshbuf_get_u8(msg, &type)) != 0) goto out; if (agent_failed(type)) { r = SSH_ERR_AGENT_FAILURE; goto out; } else if (type != SSH2_AGENT_SIGN_RESPONSE) { r = SSH_ERR_INVALID_FORMAT; goto out; } if ((r = sshbuf_get_string(msg, &sig, &len)) != 0) goto out; /* Check what we actually got back from the agent. */ if ((r = sshkey_check_sigtype(sig, len, alg)) != 0) goto out; /* success */ *sigp = sig; *lenp = len; sig = NULL; len = 0; r = 0; out: freezero(sig, len); sshbuf_free(msg); return r; } /* Encode key for a message to the agent. */ static int encode_dest_constraint_hop(struct sshbuf *m, const struct dest_constraint_hop *dch) { struct sshbuf *b; u_int i; int r; if ((b = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((r = sshbuf_put_cstring(b, dch->user)) != 0 || (r = sshbuf_put_cstring(b, dch->hostname)) != 0 || (r = sshbuf_put_string(b, NULL, 0)) != 0) /* reserved */ goto out; for (i = 0; i < dch->nkeys; i++) { if ((r = sshkey_puts(dch->keys[i], b)) != 0 || (r = sshbuf_put_u8(b, dch->key_is_ca[i] != 0)) != 0) goto out; } if ((r = sshbuf_put_stringb(m, b)) != 0) goto out; /* success */ r = 0; out: sshbuf_free(b); return r; } static int encode_dest_constraint(struct sshbuf *m, const struct dest_constraint *dc) { struct sshbuf *b; int r; if ((b = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((r = encode_dest_constraint_hop(b, &dc->from)) != 0 || (r = encode_dest_constraint_hop(b, &dc->to)) != 0 || (r = sshbuf_put_string(b, NULL, 0)) != 0) /* reserved */ goto out; if ((r = sshbuf_put_stringb(m, b)) != 0) goto out; /* success */ r = 0; out: sshbuf_free(b); return r; } static int encode_constraints(struct sshbuf *m, u_int life, u_int confirm, u_int maxsign, const char *provider, struct dest_constraint **dest_constraints, size_t ndest_constraints, int cert_only, struct sshkey **certs, size_t ncerts) { int r; struct sshbuf *b = NULL; size_t i; if (life != 0) { if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_LIFETIME)) != 0 || (r = sshbuf_put_u32(m, life)) != 0) goto out; } if (confirm != 0) { if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_CONFIRM)) != 0) goto out; } if (maxsign != 0) { if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_MAXSIGN)) != 0 || (r = sshbuf_put_u32(m, maxsign)) != 0) goto out; } if (provider != NULL) { if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_EXTENSION)) != 0 || (r = sshbuf_put_cstring(m, "sk-provider@openssh.com")) != 0 || (r = sshbuf_put_cstring(m, provider)) != 0) goto out; } if (dest_constraints != NULL && ndest_constraints > 0) { if ((b = sshbuf_new()) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } for (i = 0; i < ndest_constraints; i++) { if ((r = encode_dest_constraint(b, dest_constraints[i])) != 0) goto out; } if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_EXTENSION)) != 0 || (r = sshbuf_put_cstring(m, "restrict-destination-v00@openssh.com")) != 0 || (r = sshbuf_put_stringb(m, b)) != 0) goto out; sshbuf_free(b); b = NULL; } if (ncerts != 0) { if ((b = sshbuf_new()) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } for (i = 0; i < ncerts; i++) { if ((r = sshkey_puts(certs[i], b)) != 0) goto out; } if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_EXTENSION)) != 0 || (r = sshbuf_put_cstring(m, "associated-certs-v00@openssh.com")) != 0 || (r = sshbuf_put_u8(m, cert_only != 0)) != 0 || (r = sshbuf_put_stringb(m, b)) != 0) goto out; sshbuf_free(b); b = NULL; } r = 0; out: sshbuf_free(b); return r; } /* * Adds an identity to the authentication server. * This call is intended only for use by ssh-add(1) and like applications. */ int ssh_add_identity_constrained(int sock, struct sshkey *key, const char *comment, u_int life, u_int confirm, u_int maxsign, const char *provider, struct dest_constraint **dest_constraints, size_t ndest_constraints) { struct sshbuf *msg; int r, constrained = (life || confirm || maxsign || provider || dest_constraints); u_char type; if ((msg = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; switch (key->type) { #ifdef WITH_OPENSSL case KEY_RSA: case KEY_RSA_CERT: case KEY_DSA: case KEY_DSA_CERT: case KEY_ECDSA: case KEY_ECDSA_CERT: case KEY_ECDSA_SK: case KEY_ECDSA_SK_CERT: #endif case KEY_ED25519: case KEY_ED25519_CERT: case KEY_ED25519_SK: case KEY_ED25519_SK_CERT: case KEY_XMSS: case KEY_XMSS_CERT: type = constrained ? SSH2_AGENTC_ADD_ID_CONSTRAINED : SSH2_AGENTC_ADD_IDENTITY; if ((r = sshbuf_put_u8(msg, type)) != 0 || (r = sshkey_private_serialize_maxsign(key, msg, maxsign, 0)) != 0 || (r = sshbuf_put_cstring(msg, comment)) != 0) goto out; break; default: r = SSH_ERR_INVALID_ARGUMENT; goto out; } if (constrained && (r = encode_constraints(msg, life, confirm, maxsign, provider, dest_constraints, ndest_constraints, 0, NULL, 0)) != 0) goto out; if ((r = ssh_request_reply_decode(sock, msg)) != 0) goto out; /* success */ r = 0; out: sshbuf_free(msg); return r; } /* * Removes an identity from the authentication server. * This call is intended only for use by ssh-add(1) and like applications. */ int ssh_remove_identity(int sock, const struct sshkey *key) { struct sshbuf *msg; int r; u_char *blob = NULL; size_t blen; if ((msg = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if (key->type != KEY_UNSPEC) { if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) goto out; if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_REMOVE_IDENTITY)) != 0 || (r = sshbuf_put_string(msg, blob, blen)) != 0) goto out; } else { r = SSH_ERR_INVALID_ARGUMENT; goto out; } if ((r = ssh_request_reply_decode(sock, msg)) != 0) goto out; /* success */ r = 0; out: if (blob != NULL) freezero(blob, blen); sshbuf_free(msg); return r; } /* * Add/remove an token-based identity from the authentication server. * This call is intended only for use by ssh-add(1) and like applications. */ int ssh_update_card(int sock, int add, const char *reader_id, const char *pin, u_int life, u_int confirm, struct dest_constraint **dest_constraints, size_t ndest_constraints, int cert_only, struct sshkey **certs, size_t ncerts) { struct sshbuf *msg; int r, constrained = (life || confirm || dest_constraints || certs); u_char type; if (add) { type = constrained ? SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED : SSH_AGENTC_ADD_SMARTCARD_KEY; } else type = SSH_AGENTC_REMOVE_SMARTCARD_KEY; if ((msg = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((r = sshbuf_put_u8(msg, type)) != 0 || (r = sshbuf_put_cstring(msg, reader_id)) != 0 || (r = sshbuf_put_cstring(msg, pin)) != 0) goto out; if (constrained && (r = encode_constraints(msg, life, confirm, 0, NULL, dest_constraints, ndest_constraints, cert_only, certs, ncerts)) != 0) goto out; if ((r = ssh_request_reply_decode(sock, msg)) != 0) goto out; /* success */ r = 0; out: sshbuf_free(msg); return r; } /* * Removes all identities from the agent. * This call is intended only for use by ssh-add(1) and like applications. * * This supports the SSH protocol 1 message to because, when clearing all * keys from an agent, we generally want to clear both protocol v1 and v2 * keys. */ int ssh_remove_all_identities(int sock, int version) { struct sshbuf *msg; u_char type = (version == 1) ? SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : SSH2_AGENTC_REMOVE_ALL_IDENTITIES; int r; if ((msg = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((r = sshbuf_put_u8(msg, type)) != 0) goto out; if ((r = ssh_request_reply_decode(sock, msg)) != 0) goto out; /* success */ r = 0; out: sshbuf_free(msg); return r; } /* Binds a session ID to a hostkey via the initial KEX signature. */ int ssh_agent_bind_hostkey(int sock, const struct sshkey *key, const struct sshbuf *session_id, const struct sshbuf *signature, int forwarding) { struct sshbuf *msg; int r; if (key == NULL || session_id == NULL || signature == NULL) return SSH_ERR_INVALID_ARGUMENT; if ((msg = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((r = sshbuf_put_u8(msg, SSH_AGENTC_EXTENSION)) != 0 || (r = sshbuf_put_cstring(msg, "session-bind@openssh.com")) != 0 || (r = sshkey_puts(key, msg)) != 0 || (r = sshbuf_put_stringb(msg, session_id)) != 0 || (r = sshbuf_put_stringb(msg, signature)) != 0 || (r = sshbuf_put_u8(msg, forwarding ? 1 : 0)) != 0) goto out; if ((r = ssh_request_reply_decode(sock, msg)) != 0) goto out; /* success */ r = 0; out: sshbuf_free(msg); return r; }