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-rw-r--r--authfd.c580
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diff --git a/authfd.c b/authfd.c
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+/* $OpenBSD: authfd.c,v 1.111 2018/07/09 21:59:10 markus 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 "includes.h"
+
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/socket.h>
+
+#include <fcntl.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <string.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 "compat.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;
+}
+
+/* Returns the number of the authentication fd, or -1 if there is none. */
+int
+ssh_get_authentication_socket(int *fdp)
+{
+ const char *authsocket;
+ int sock, oerrno;
+ struct sockaddr_un sunaddr;
+
+ if (fdp != NULL)
+ *fdp = -1;
+
+ authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
+ if (!authsocket)
+ return SSH_ERR_AGENT_NOT_PRESENT;
+
+ 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)) < 0)
+ return SSH_ERR_SYSTEM_ERROR;
+
+ /* close on exec */
+ if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1 ||
+ connect(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) < 0) {
+ oerrno = errno;
+ close(sock);
+ errno = oerrno;
+ return SSH_ERR_SYSTEM_ERROR;
+ }
+ if (fdp != NULL)
+ *fdp = sock;
+ else
+ close(sock);
+ return 0;
+}
+
+/* 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;
+}
+
+/*
+ * 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)
+ goto out;
+ if ((r = ssh_request_reply(sock, msg, msg)) != 0)
+ goto out;
+ if ((r = sshbuf_get_u8(msg, &type)) != 0)
+ goto out;
+ r = decode_reply(type);
+ 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);
+}
+
+/*
+ * 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 && key->type == KEY_RSA) {
+ if (strcmp(alg, "rsa-sha2-256") == 0)
+ return SSH_AGENT_RSA_SHA2_256;
+ else if (strcmp(alg, "rsa-sha2-512") == 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_constraints(struct sshbuf *m, u_int life, u_int confirm, u_int maxsign)
+{
+ int r;
+
+ 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;
+ }
+ r = 0;
+ out:
+ 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, const struct sshkey *key,
+ const char *comment, u_int life, u_int confirm, u_int maxsign)
+{
+ struct sshbuf *msg;
+ int r, constrained = (life || confirm || maxsign);
+ 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:
+#endif
+ case KEY_ED25519:
+ case KEY_ED25519_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,
+ NULL)) != 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)) != 0)
+ goto out;
+ if ((r = ssh_request_reply(sock, msg, msg)) != 0)
+ goto out;
+ if ((r = sshbuf_get_u8(msg, &type)) != 0)
+ goto out;
+ r = decode_reply(type);
+ 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, struct sshkey *key)
+{
+ struct sshbuf *msg;
+ int r;
+ u_char type, *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(sock, msg, msg)) != 0)
+ goto out;
+ if ((r = sshbuf_get_u8(msg, &type)) != 0)
+ goto out;
+ r = decode_reply(type);
+ out:
+ if (blob != NULL) {
+ explicit_bzero(blob, blen);
+ free(blob);
+ }
+ 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 sshbuf *msg;
+ int r, constrained = (life || confirm);
+ 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)) != 0)
+ goto out;
+ if ((r = ssh_request_reply(sock, msg, msg)) != 0)
+ goto out;
+ if ((r = sshbuf_get_u8(msg, &type)) != 0)
+ goto out;
+ r = decode_reply(type);
+ 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(sock, msg, msg)) != 0)
+ goto out;
+ if ((r = sshbuf_get_u8(msg, &type)) != 0)
+ goto out;
+ r = decode_reply(type);
+ out:
+ sshbuf_free(msg);
+ return r;
+}
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