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2058 lines (1850 loc) · 63.3 KB
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/*
* auth.c - Authentication with SSH protocols
*
* This file is part of the SSH Library
*
* Copyright (c) 2003-2013 by Aris Adamantiadis <aris@0xbadc0de.be>
* Copyright (c) 2008-2013 Andreas Schneider <asn@cryptomilk.org>
*
* The SSH Library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The SSH Library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the SSH Library; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#include "config.h"
#include <stdio.h>
#include <string.h>
#ifndef _WIN32
#include <netinet/in.h>
#include <arpa/inet.h>
#endif
#include "libssh/priv.h"
#include "libssh/crypto.h"
#include "libssh/ssh2.h"
#include "libssh/buffer.h"
#include "libssh/agent.h"
#include "libssh/misc.h"
#include "libssh/packet.h"
#include "libssh/session.h"
#include "libssh/keys.h"
#include "libssh/auth.h"
#include "libssh/pki.h"
#include "libssh/gssapi.h"
#include "libssh/legacy.h"
/**
* @defgroup libssh_auth The SSH authentication functions.
* @ingroup libssh
*
* Functions to authenticate with a server.
*
* @{
*/
/**
* @internal
*
* @brief Ask for access to the ssh-userauth service.
*
* @param[in] session The SSH session handle.
*
* @returns SSH_OK on success, SSH_ERROR on error.
* @returns SSH_AGAIN on nonblocking mode, if calling that function
* again is necessary
*/
static int ssh_userauth_request_service(ssh_session session)
{
int rc;
rc = ssh_service_request(session, "ssh-userauth");
if ((rc != SSH_OK) && (rc != SSH_AGAIN)) {
SSH_LOG(SSH_LOG_WARN,
"Failed to request \"ssh-userauth\" service");
}
return rc;
}
static int ssh_auth_response_termination(void *user)
{
ssh_session session = (ssh_session)user;
switch (session->auth.state) {
case SSH_AUTH_STATE_NONE:
case SSH_AUTH_STATE_KBDINT_SENT:
case SSH_AUTH_STATE_GSSAPI_REQUEST_SENT:
case SSH_AUTH_STATE_GSSAPI_TOKEN:
case SSH_AUTH_STATE_GSSAPI_MIC_SENT:
case SSH_AUTH_STATE_PUBKEY_AUTH_SENT:
case SSH_AUTH_STATE_PUBKEY_OFFER_SENT:
case SSH_AUTH_STATE_PASSWORD_AUTH_SENT:
case SSH_AUTH_STATE_AUTH_NONE_SENT:
return 0;
default:
return 1;
}
}
static const char *ssh_auth_get_current_method(ssh_session session)
{
const char *method = "unknown";
switch (session->auth.current_method) {
case SSH_AUTH_METHOD_NONE:
method = "none";
break;
case SSH_AUTH_METHOD_PASSWORD:
method = "password";
break;
case SSH_AUTH_METHOD_PUBLICKEY:
method = "publickey";
break;
case SSH_AUTH_METHOD_HOSTBASED:
method = "hostbased";
break;
case SSH_AUTH_METHOD_INTERACTIVE:
method = "keyboard interactive";
break;
case SSH_AUTH_METHOD_GSSAPI_MIC:
method = "gssapi";
break;
default:
break;
}
return method;
}
/**
* @internal
* @brief Wait for a response of an authentication function.
*
* @param[in] session The SSH session.
*
* @returns SSH_AUTH_SUCCESS Authentication success, or pubkey accepted
* SSH_AUTH_PARTIAL Authentication succeeded but another mean
* of authentication is needed.
* SSH_AUTH_INFO Data for keyboard-interactive
* SSH_AUTH_AGAIN In nonblocking mode, call has to be made again
* SSH_AUTH_ERROR Error during the process.
*/
static int ssh_userauth_get_response(ssh_session session)
{
int rc = SSH_AUTH_ERROR;
rc = ssh_handle_packets_termination(session, SSH_TIMEOUT_USER,
ssh_auth_response_termination, session);
if (rc == SSH_ERROR) {
return SSH_AUTH_ERROR;
}
if (!ssh_auth_response_termination(session)) {
return SSH_AUTH_AGAIN;
}
switch(session->auth.state) {
case SSH_AUTH_STATE_ERROR:
rc = SSH_AUTH_ERROR;
break;
case SSH_AUTH_STATE_FAILED:
rc = SSH_AUTH_DENIED;
break;
case SSH_AUTH_STATE_INFO:
rc = SSH_AUTH_INFO;
break;
case SSH_AUTH_STATE_PARTIAL:
rc = SSH_AUTH_PARTIAL;
break;
case SSH_AUTH_STATE_PK_OK:
case SSH_AUTH_STATE_SUCCESS:
rc = SSH_AUTH_SUCCESS;
break;
case SSH_AUTH_STATE_KBDINT_SENT:
case SSH_AUTH_STATE_GSSAPI_REQUEST_SENT:
case SSH_AUTH_STATE_GSSAPI_TOKEN:
case SSH_AUTH_STATE_GSSAPI_MIC_SENT:
case SSH_AUTH_STATE_PUBKEY_OFFER_SENT:
case SSH_AUTH_STATE_PUBKEY_AUTH_SENT:
case SSH_AUTH_STATE_PASSWORD_AUTH_SENT:
case SSH_AUTH_STATE_AUTH_NONE_SENT:
case SSH_AUTH_STATE_NONE:
/* not reached */
rc = SSH_AUTH_ERROR;
break;
}
return rc;
}
/**
* @internal
*
* @brief Handles a SSH_USERAUTH_BANNER packet.
*
* This banner should be shown to user prior to authentication
*/
SSH_PACKET_CALLBACK(ssh_packet_userauth_banner) {
ssh_string banner;
(void)type;
(void)user;
banner = ssh_buffer_get_ssh_string(packet);
if (banner == NULL) {
SSH_LOG(SSH_LOG_WARN,
"Invalid SSH_USERAUTH_BANNER packet");
} else {
SSH_LOG(SSH_LOG_DEBUG,
"Received SSH_USERAUTH_BANNER packet");
if (session->banner != NULL)
SSH_STRING_FREE(session->banner);
session->banner = banner;
}
return SSH_PACKET_USED;
}
/**
* @internal
*
* @brief Handles a SSH_USERAUTH_FAILURE packet.
*
* This handles the complete or partial authentication failure.
*/
SSH_PACKET_CALLBACK(ssh_packet_userauth_failure) {
const char *current_method = ssh_auth_get_current_method(session);
char *auth_methods = NULL;
uint8_t partial = 0;
int rc;
(void) type;
(void) user;
rc = ssh_buffer_unpack(packet, "sb", &auth_methods, &partial);
if (rc != SSH_OK) {
ssh_set_error(session, SSH_FATAL,
"Invalid SSH_MSG_USERAUTH_FAILURE message");
session->auth.state = SSH_AUTH_STATE_ERROR;
goto end;
}
if (partial) {
session->auth.state = SSH_AUTH_STATE_PARTIAL;
SSH_LOG(SSH_LOG_INFO,
"Partial success for '%s'. Authentication that can continue: %s",
current_method,
auth_methods);
} else {
session->auth.state = SSH_AUTH_STATE_FAILED;
ssh_set_error(session, SSH_REQUEST_DENIED,
"Access denied for '%s'. Authentication that can continue: %s",
current_method,
auth_methods);
SSH_LOG(SSH_LOG_INFO,
"%s",
ssh_get_error(session));
}
session->auth.supported_methods = 0;
if (strstr(auth_methods, "password") != NULL) {
session->auth.supported_methods |= SSH_AUTH_METHOD_PASSWORD;
}
if (strstr(auth_methods, "keyboard-interactive") != NULL) {
session->auth.supported_methods |= SSH_AUTH_METHOD_INTERACTIVE;
}
if (strstr(auth_methods, "publickey") != NULL) {
session->auth.supported_methods |= SSH_AUTH_METHOD_PUBLICKEY;
}
if (strstr(auth_methods, "hostbased") != NULL) {
session->auth.supported_methods |= SSH_AUTH_METHOD_HOSTBASED;
}
if (strstr(auth_methods, "gssapi-with-mic") != NULL) {
session->auth.supported_methods |= SSH_AUTH_METHOD_GSSAPI_MIC;
}
end:
session->auth.current_method = SSH_AUTH_METHOD_UNKNOWN;
SAFE_FREE(auth_methods);
return SSH_PACKET_USED;
}
/**
* @internal
*
* @brief Handles a SSH_USERAUTH_SUCCESS packet.
*
* It is also used to communicate the new to the upper levels.
*/
SSH_PACKET_CALLBACK(ssh_packet_userauth_success)
{
struct ssh_crypto_struct *crypto = NULL;
(void)packet;
(void)type;
(void)user;
SSH_LOG(SSH_LOG_DEBUG, "Authentication successful");
SSH_LOG(SSH_LOG_TRACE, "Received SSH_USERAUTH_SUCCESS");
session->auth.state = SSH_AUTH_STATE_SUCCESS;
session->session_state = SSH_SESSION_STATE_AUTHENTICATED;
session->flags |= SSH_SESSION_FLAG_AUTHENTICATED;
crypto = ssh_packet_get_current_crypto(session, SSH_DIRECTION_OUT);
if (crypto != NULL && crypto->delayed_compress_out) {
SSH_LOG(SSH_LOG_DEBUG, "Enabling delayed compression OUT");
crypto->do_compress_out = 1;
}
crypto = ssh_packet_get_current_crypto(session, SSH_DIRECTION_IN);
if (crypto != NULL && crypto->delayed_compress_in) {
SSH_LOG(SSH_LOG_DEBUG, "Enabling delayed compression IN");
crypto->do_compress_in = 1;
}
/* Reset errors by previous authentication methods. */
ssh_reset_error(session);
session->auth.current_method = SSH_AUTH_METHOD_UNKNOWN;
return SSH_PACKET_USED;
}
/**
* @internal
*
* @brief Handles a SSH_USERAUTH_PK_OK or SSH_USERAUTH_INFO_REQUEST packet.
*
* Since the two types of packets share the same code, additional work is done
* to understand if we are in a public key or keyboard-interactive context.
*/
SSH_PACKET_CALLBACK(ssh_packet_userauth_pk_ok) {
int rc;
SSH_LOG(SSH_LOG_TRACE,
"Received SSH_USERAUTH_PK_OK/INFO_REQUEST/GSSAPI_RESPONSE");
if (session->auth.state == SSH_AUTH_STATE_KBDINT_SENT) {
/* Assuming we are in keyboard-interactive context */
SSH_LOG(SSH_LOG_TRACE,
"keyboard-interactive context, "
"assuming SSH_USERAUTH_INFO_REQUEST");
rc = ssh_packet_userauth_info_request(session,type,packet,user);
#ifdef WITH_GSSAPI
} else if (session->auth.state == SSH_AUTH_STATE_GSSAPI_REQUEST_SENT) {
rc = ssh_packet_userauth_gssapi_response(session, type, packet, user);
#endif
} else if (session->auth.state == SSH_AUTH_STATE_PUBKEY_OFFER_SENT) {
session->auth.state = SSH_AUTH_STATE_PK_OK;
SSH_LOG(SSH_LOG_TRACE, "Assuming SSH_USERAUTH_PK_OK");
rc = SSH_PACKET_USED;
} else {
session->auth.state = SSH_AUTH_STATE_ERROR;
SSH_LOG(SSH_LOG_TRACE, "SSH_USERAUTH_PK_OK received in wrong state");
rc = SSH_PACKET_USED;
}
return rc;
}
/**
* @brief Get available authentication methods from the server.
*
* This requires the function ssh_userauth_none() to be called before the
* methods are available. The server MAY return a list of methods that may
* continue.
*
* @param[in] session The SSH session.
*
* @param[in] username Deprecated, set to NULL.
*
* @returns A bitfield of the following values:
* - SSH_AUTH_METHOD_PASSWORD
* - SSH_AUTH_METHOD_PUBLICKEY
* - SSH_AUTH_METHOD_HOSTBASED
* - SSH_AUTH_METHOD_INTERACTIVE
*
* @warning Other reserved flags may appear in future versions.
* @see ssh_userauth_none()
*/
int ssh_userauth_list(ssh_session session, const char *username)
{
(void) username; /* unused */
if (session == NULL) {
return 0;
}
return session->auth.supported_methods;
}
/**
* @brief Try to authenticate through the "none" method.
*
* @param[in] session The ssh session to use.
*
* @param[in] username The username, this SHOULD be NULL.
*
* @returns SSH_AUTH_ERROR: A serious error happened.\n
* SSH_AUTH_DENIED: Authentication failed: use another method\n
* SSH_AUTH_PARTIAL: You've been partially authenticated, you still
* have to use another method\n
* SSH_AUTH_SUCCESS: Authentication success\n
* SSH_AUTH_AGAIN: In nonblocking mode, you've got to call this again
* later.
*
* @note Most server implementations do not permit changing the username during
* authentication. The username should only be set with ssh_options_set() only
* before you connect to the server.
*/
int ssh_userauth_none(ssh_session session, const char *username)
{
int rc;
switch (session->pending_call_state) {
case SSH_PENDING_CALL_NONE:
break;
case SSH_PENDING_CALL_AUTH_NONE:
goto pending;
default:
ssh_set_error(session, SSH_FATAL,
"Wrong state (%d) during pending SSH call",
session->pending_call_state);
return SSH_AUTH_ERROR;
}
rc = ssh_userauth_request_service(session);
if (rc == SSH_AGAIN) {
return SSH_AUTH_AGAIN;
} else if (rc == SSH_ERROR) {
return SSH_AUTH_ERROR;
}
/* request */
rc = ssh_buffer_pack(session->out_buffer, "bsss",
SSH2_MSG_USERAUTH_REQUEST,
username ? username : session->opts.username,
"ssh-connection",
"none"
);
if (rc < 0) {
goto fail;
}
session->auth.current_method = SSH_AUTH_METHOD_NONE;
session->auth.state = SSH_AUTH_STATE_AUTH_NONE_SENT;
session->pending_call_state = SSH_PENDING_CALL_AUTH_NONE;
rc = ssh_packet_send(session);
if (rc == SSH_ERROR) {
return SSH_AUTH_ERROR;
}
pending:
rc = ssh_userauth_get_response(session);
if (rc != SSH_AUTH_AGAIN) {
session->pending_call_state = SSH_PENDING_CALL_NONE;
}
return rc;
fail:
ssh_set_error_oom(session);
ssh_buffer_reinit(session->out_buffer);
return SSH_AUTH_ERROR;
}
/**
* @brief Try to authenticate with the given public key.
*
* To avoid unnecessary processing and user interaction, the following method
* is provided for querying whether authentication using the 'pubkey' would
* be possible.
*
* @param[in] session The SSH session.
*
* @param[in] username The username, this SHOULD be NULL.
*
* @param[in] pubkey The public key to try.
*
* @return SSH_AUTH_ERROR: A serious error happened.\n
* SSH_AUTH_DENIED: The server doesn't accept that public key as an
* authentication token. Try another key or another
* method.\n
* SSH_AUTH_PARTIAL: You've been partially authenticated, you still
* have to use another method.\n
* SSH_AUTH_SUCCESS: The public key is accepted, you want now to use
* ssh_userauth_publickey().\n
* SSH_AUTH_AGAIN: In nonblocking mode, you've got to call this again
* later.
*
* @note Most server implementations do not permit changing the username during
* authentication. The username should only be set with ssh_options_set() only
* before you connect to the server.
*/
int ssh_userauth_try_publickey(ssh_session session,
const char *username,
const ssh_key pubkey)
{
ssh_string pubkey_s = NULL;
const char *sig_type_c = NULL;
bool allowed;
int rc;
if (session == NULL) {
return SSH_AUTH_ERROR;
}
if (pubkey == NULL || !ssh_key_is_public(pubkey)) {
ssh_set_error(session, SSH_FATAL, "Invalid pubkey");
return SSH_AUTH_ERROR;
}
switch(session->pending_call_state) {
case SSH_PENDING_CALL_NONE:
break;
case SSH_PENDING_CALL_AUTH_OFFER_PUBKEY:
goto pending;
default:
ssh_set_error(session,
SSH_FATAL,
"Wrong state (%d) during pending SSH call",
session->pending_call_state);
return SSH_AUTH_ERROR;
}
/* Check if the given public key algorithm is allowed */
sig_type_c = ssh_key_get_signature_algorithm(session, pubkey->type);
if (sig_type_c == NULL) {
ssh_set_error(session, SSH_REQUEST_DENIED,
"Invalid key type (unknown)");
return SSH_AUTH_DENIED;
}
rc = ssh_key_algorithm_allowed(session, sig_type_c);
if (!rc) {
ssh_set_error(session, SSH_REQUEST_DENIED,
"The key algorithm '%s' is not allowed to be used by"
" PUBLICKEY_ACCEPTED_TYPES configuration option",
sig_type_c);
return SSH_AUTH_DENIED;
}
allowed = ssh_key_size_allowed(session, pubkey);
if (!allowed) {
ssh_set_error(session, SSH_REQUEST_DENIED,
"The '%s' key type of size %d is not allowed by "
"RSA_MIN_SIZE", sig_type_c, ssh_key_size(pubkey));
return SSH_AUTH_DENIED;
}
rc = ssh_userauth_request_service(session);
if (rc == SSH_AGAIN) {
return SSH_AUTH_AGAIN;
} else if (rc == SSH_ERROR) {
return SSH_AUTH_ERROR;
}
/* public key */
rc = ssh_pki_export_pubkey_blob(pubkey, &pubkey_s);
if (rc < 0) {
goto fail;
}
/* request */
rc = ssh_buffer_pack(session->out_buffer, "bsssbsS",
SSH2_MSG_USERAUTH_REQUEST,
username ? username : session->opts.username,
"ssh-connection",
"publickey",
0, /* private key ? */
sig_type_c, /* algo */
pubkey_s /* public key */
);
if (rc < 0) {
goto fail;
}
SSH_STRING_FREE(pubkey_s);
session->auth.current_method = SSH_AUTH_METHOD_PUBLICKEY;
session->auth.state = SSH_AUTH_STATE_PUBKEY_OFFER_SENT;
session->pending_call_state = SSH_PENDING_CALL_AUTH_OFFER_PUBKEY;
rc = ssh_packet_send(session);
if (rc == SSH_ERROR) {
return SSH_AUTH_ERROR;
}
pending:
rc = ssh_userauth_get_response(session);
if (rc != SSH_AUTH_AGAIN) {
session->pending_call_state = SSH_PENDING_CALL_NONE;
}
return rc;
fail:
SSH_STRING_FREE(pubkey_s);
ssh_set_error_oom(session);
ssh_buffer_reinit(session->out_buffer);
return SSH_AUTH_ERROR;
}
/**
* @brief Authenticate with public/private key or certificate.
*
* @param[in] session The SSH session.
*
* @param[in] username The username, this SHOULD be NULL.
*
* @param[in] privkey The private key for authentication.
*
* @return SSH_AUTH_ERROR: A serious error happened.\n
* SSH_AUTH_DENIED: The server doesn't accept that public key as an
* authentication token. Try another key or another
* method.\n
* SSH_AUTH_PARTIAL: You've been partially authenticated, you still
* have to use another method.\n
* SSH_AUTH_SUCCESS: The public key is accepted.\n
* SSH_AUTH_AGAIN: In nonblocking mode, you've got to call this again
* later.
*
* @note Most server implementations do not permit changing the username during
* authentication. The username should only be set with ssh_options_set() only
* before you connect to the server.
*/
int ssh_userauth_publickey(ssh_session session,
const char *username,
const ssh_key privkey)
{
ssh_string str = NULL;
bool allowed;
int rc;
const char *sig_type_c = NULL;
enum ssh_keytypes_e key_type;
enum ssh_digest_e hash_type;
if (session == NULL) {
return SSH_AUTH_ERROR;
}
if (privkey == NULL || !ssh_key_is_private(privkey)) {
ssh_set_error(session, SSH_FATAL, "Invalid private key");
return SSH_AUTH_ERROR;
}
switch(session->pending_call_state) {
case SSH_PENDING_CALL_NONE:
break;
case SSH_PENDING_CALL_AUTH_PUBKEY:
goto pending;
default:
ssh_set_error(session,
SSH_FATAL,
"Bad call during pending SSH call in ssh_userauth_try_publickey");
return SSH_AUTH_ERROR;
}
/* Cert auth requires presenting the cert type name (*-cert@openssh.com) */
key_type = privkey->cert != NULL ? privkey->cert_type : privkey->type;
/* Check if the given public key algorithm is allowed */
sig_type_c = ssh_key_get_signature_algorithm(session, key_type);
if (sig_type_c == NULL) {
ssh_set_error(session, SSH_REQUEST_DENIED,
"Invalid key type (unknown)");
return SSH_AUTH_DENIED;
}
rc = ssh_key_algorithm_allowed(session, sig_type_c);
if (!rc) {
ssh_set_error(session, SSH_REQUEST_DENIED,
"The key algorithm '%s' is not allowed to be used by"
" PUBLICKEY_ACCEPTED_TYPES configuration option",
sig_type_c);
return SSH_AUTH_DENIED;
}
allowed = ssh_key_size_allowed(session, privkey);
if (!allowed) {
ssh_set_error(session, SSH_REQUEST_DENIED,
"The '%s' key type of size %d is not allowed by "
"RSA_MIN_SIZE", sig_type_c, ssh_key_size(privkey));
return SSH_AUTH_DENIED;
}
rc = ssh_userauth_request_service(session);
if (rc == SSH_AGAIN) {
return SSH_AUTH_AGAIN;
} else if (rc == SSH_ERROR) {
return SSH_AUTH_ERROR;
}
/* get public key or cert */
rc = ssh_pki_export_pubkey_blob(privkey, &str);
if (rc < 0) {
goto fail;
}
/* request */
rc = ssh_buffer_pack(session->out_buffer, "bsssbsS",
SSH2_MSG_USERAUTH_REQUEST,
username ? username : session->opts.username,
"ssh-connection",
"publickey",
1, /* private key */
sig_type_c, /* algo */
str /* public key or cert */
);
if (rc < 0) {
goto fail;
}
SSH_STRING_FREE(str);
/* Get the hash type to be used in the signature based on the key type */
hash_type = ssh_key_type_to_hash(session, privkey->type);
/* sign the buffer with the private key */
str = ssh_pki_do_sign(session, session->out_buffer, privkey, hash_type);
if (str == NULL) {
goto fail;
}
rc = ssh_buffer_add_ssh_string(session->out_buffer, str);
SSH_STRING_FREE(str);
str = NULL;
if (rc < 0) {
goto fail;
}
session->auth.current_method = SSH_AUTH_METHOD_PUBLICKEY;
session->auth.state = SSH_AUTH_STATE_PUBKEY_AUTH_SENT;
session->pending_call_state = SSH_PENDING_CALL_AUTH_PUBKEY;
rc = ssh_packet_send(session);
if (rc == SSH_ERROR) {
return SSH_AUTH_ERROR;
}
pending:
rc = ssh_userauth_get_response(session);
if (rc != SSH_AUTH_AGAIN) {
session->pending_call_state = SSH_PENDING_CALL_NONE;
}
return rc;
fail:
SSH_STRING_FREE(str);
ssh_set_error_oom(session);
ssh_buffer_reinit(session->out_buffer);
return SSH_AUTH_ERROR;
}
static int ssh_userauth_agent_publickey(ssh_session session,
const char *username,
ssh_key pubkey)
{
ssh_string pubkey_s = NULL;
ssh_string sig_blob = NULL;
const char *sig_type_c = NULL;
bool allowed;
int rc;
switch(session->pending_call_state) {
case SSH_PENDING_CALL_NONE:
break;
case SSH_PENDING_CALL_AUTH_AGENT:
goto pending;
default:
ssh_set_error(session,
SSH_FATAL,
"Bad call during pending SSH call in ssh_userauth_try_publickey");
return SSH_ERROR;
}
rc = ssh_userauth_request_service(session);
if (rc == SSH_AGAIN) {
return SSH_AUTH_AGAIN;
} else if (rc == SSH_ERROR) {
return SSH_AUTH_ERROR;
}
/* public key */
rc = ssh_pki_export_pubkey_blob(pubkey, &pubkey_s);
if (rc < 0) {
goto fail;
}
/* Check if the given public key algorithm is allowed */
sig_type_c = ssh_key_get_signature_algorithm(session, pubkey->type);
if (sig_type_c == NULL) {
ssh_set_error(session, SSH_REQUEST_DENIED,
"Invalid key type (unknown)");
SSH_STRING_FREE(pubkey_s);
return SSH_AUTH_DENIED;
}
rc = ssh_key_algorithm_allowed(session, sig_type_c);
if (!rc) {
ssh_set_error(session, SSH_REQUEST_DENIED,
"The key algorithm '%s' is not allowed to be used by"
" PUBLICKEY_ACCEPTED_TYPES configuration option",
sig_type_c);
SSH_STRING_FREE(pubkey_s);
return SSH_AUTH_DENIED;
}
allowed = ssh_key_size_allowed(session, pubkey);
if (!allowed) {
ssh_set_error(session, SSH_REQUEST_DENIED,
"The '%s' key type of size %d is not allowed by "
"RSA_MIN_SIZE", sig_type_c, ssh_key_size(pubkey));
SSH_STRING_FREE(pubkey_s);
return SSH_AUTH_DENIED;
}
/* request */
rc = ssh_buffer_pack(session->out_buffer, "bsssbsS",
SSH2_MSG_USERAUTH_REQUEST,
username ? username : session->opts.username,
"ssh-connection",
"publickey",
1, /* private key */
sig_type_c, /* algo */
pubkey_s /* public key */
);
SSH_STRING_FREE(pubkey_s);
if (rc < 0) {
goto fail;
}
/* sign the buffer with the private key */
sig_blob = ssh_pki_do_sign_agent(session, session->out_buffer, pubkey);
if (sig_blob == NULL) {
goto fail;
}
rc = ssh_buffer_add_ssh_string(session->out_buffer, sig_blob);
SSH_STRING_FREE(sig_blob);
if (rc < 0) {
goto fail;
}
session->auth.current_method = SSH_AUTH_METHOD_PUBLICKEY;
session->auth.state = SSH_AUTH_STATE_PUBKEY_AUTH_SENT;
session->pending_call_state = SSH_PENDING_CALL_AUTH_AGENT;
rc = ssh_packet_send(session);
if (rc == SSH_ERROR) {
return SSH_AUTH_ERROR;
}
pending:
rc = ssh_userauth_get_response(session);
if (rc != SSH_AUTH_AGAIN) {
session->pending_call_state = SSH_PENDING_CALL_NONE;
}
return rc;
fail:
ssh_set_error_oom(session);
ssh_buffer_reinit(session->out_buffer);
SSH_STRING_FREE(pubkey_s);
return SSH_AUTH_ERROR;
}
enum ssh_agent_state_e {
SSH_AGENT_STATE_NONE = 0,
SSH_AGENT_STATE_PUBKEY,
SSH_AGENT_STATE_AUTH
};
struct ssh_agent_state_struct {
enum ssh_agent_state_e state;
ssh_key pubkey;
char *comment;
};
/* Internal function */
void ssh_agent_state_free(void *data)
{
struct ssh_agent_state_struct *state = data;
if (state) {
SSH_STRING_FREE_CHAR(state->comment);
ssh_key_free(state->pubkey);
free (state);
}
}
/**
* @brief Try to do public key authentication with ssh agent.
*
* @param[in] session The ssh session to use.
*
* @param[in] username The username, this SHOULD be NULL.
*
* @return SSH_AUTH_ERROR: A serious error happened.\n
* SSH_AUTH_DENIED: The server doesn't accept that public key as an
* authentication token. Try another key or another
* method.\n
* SSH_AUTH_PARTIAL: You've been partially authenticated, you still
* have to use another method.\n
* SSH_AUTH_SUCCESS: The public key is accepted, you want now to use
* ssh_userauth_publickey().\n
* SSH_AUTH_AGAIN: In nonblocking mode, you've got to call this again
* later.
*
* @note Most server implementations do not permit changing the username during
* authentication. The username should only be set with ssh_options_set() only
* before you connect to the server.
*/
int ssh_userauth_agent(ssh_session session,
const char *username)
{
int rc = SSH_AUTH_ERROR;
struct ssh_agent_state_struct *state;
if (session == NULL) {
return SSH_AUTH_ERROR;
}
if (!ssh_agent_is_running(session)) {
return SSH_AUTH_DENIED;
}
if (!session->agent_state) {
session->agent_state = malloc(sizeof(struct ssh_agent_state_struct));
if (!session->agent_state) {
ssh_set_error_oom(session);
return SSH_AUTH_ERROR;
}
ZERO_STRUCTP(session->agent_state);
session->agent_state->state=SSH_AGENT_STATE_NONE;
}
state = session->agent_state;
if (state->pubkey == NULL) {
state->pubkey = ssh_agent_get_first_ident(session, &state->comment);
}
if (state->pubkey == NULL) {
return SSH_AUTH_DENIED;
}
while (state->pubkey != NULL) {
if (state->state == SSH_AGENT_STATE_NONE) {
SSH_LOG(SSH_LOG_DEBUG,
"Trying identity %s", state->comment);
}
if (state->state == SSH_AGENT_STATE_NONE ||
state->state == SSH_AGENT_STATE_PUBKEY) {
rc = ssh_userauth_try_publickey(session, username, state->pubkey);
if (rc == SSH_AUTH_ERROR) {
ssh_agent_state_free (state);
session->agent_state = NULL;
return rc;
} else if (rc == SSH_AUTH_AGAIN) {
state->state = SSH_AGENT_STATE_PUBKEY;
return rc;
} else if (rc != SSH_AUTH_SUCCESS) {
SSH_LOG(SSH_LOG_DEBUG,
"Public key of %s refused by server", state->comment);
SSH_STRING_FREE_CHAR(state->comment);
state->comment = NULL;
ssh_key_free(state->pubkey);
state->pubkey = ssh_agent_get_next_ident(session, &state->comment);
state->state = SSH_AGENT_STATE_NONE;
continue;
}
SSH_LOG(SSH_LOG_DEBUG,
"Public key of %s accepted by server", state->comment);
state->state = SSH_AGENT_STATE_AUTH;
}
if (state->state == SSH_AGENT_STATE_AUTH) {
rc = ssh_userauth_agent_publickey(session, username, state->pubkey);
if (rc == SSH_AUTH_AGAIN)
return rc;
SSH_STRING_FREE_CHAR(state->comment);
state->comment = NULL;
if (rc == SSH_AUTH_ERROR || rc == SSH_AUTH_PARTIAL) {
ssh_agent_state_free (session->agent_state);
session->agent_state = NULL;
return rc;
} else if (rc != SSH_AUTH_SUCCESS) {
SSH_LOG(SSH_LOG_INFO,
"Server accepted public key but refused the signature");
ssh_key_free(state->pubkey);
state->pubkey = ssh_agent_get_next_ident(session, &state->comment);
state->state = SSH_AGENT_STATE_NONE;
continue;
}
ssh_agent_state_free (session->agent_state);
session->agent_state = NULL;
return SSH_AUTH_SUCCESS;
}
}
ssh_agent_state_free (session->agent_state);
session->agent_state = NULL;
return rc;
}
enum ssh_auth_auto_state_e {
SSH_AUTH_AUTO_STATE_NONE = 0,
SSH_AUTH_AUTO_STATE_PUBKEY,
SSH_AUTH_AUTO_STATE_KEY_IMPORTED,
SSH_AUTH_AUTO_STATE_PUBKEY_ACCEPTED