httpntlm.c

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/*
 * Copyright (C) 2017 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
FILE_SECBOOT ( PERMITTED );

/**
 * @file
 *
 * Hyper Text Transfer Protocol (HTTP) NTLM authentication
 *
 */

#include <string.h>
#include <errno.h>
#include <ipxe/uri.h>
#include <ipxe/base64.h>
#include <ipxe/ntlm.h>
#include <ipxe/netbios.h>
#include <ipxe/http.h>

struct http_authentication http_ntlm_auth __http_authentication;

/** Workstation name used for NTLM authentication */
static const char http_ntlm_workstation[] = "iPXE";

/**
 * Parse HTTP "WWW-Authenticate" header for NTLM authentication
 *
 * @v http              HTTP transaction
 * @v line              Remaining header line
 * @ret rc              Return status code
 */
static int http_parse_ntlm_auth ( struct http_transaction *http, char *line ) {
        struct http_response_auth_ntlm *rsp = &http->response.auth.ntlm;
        char *copy;
        int len;
        int rc;

        /* Create temporary copy of Base64-encoded challenge message */
        copy = strdup ( line );
        if ( ! copy ) {
                rc = -ENOMEM;
                goto err_alloc;
        }

        /* Decode challenge message, overwriting the original */
        len = base64_decode ( copy, line, strlen ( line ) );
        if ( len < 0 ) {
                rc = len;
                DBGC ( http, "HTTP %p could not decode NTLM challenge "
                       "\"%s\": %s\n", http, copy, strerror ( rc ) );
                goto err_decode;
        }

        /* Parse challenge, if present */
        if ( len ) {
                rsp->challenge = ( ( void * ) line );
                if ( ( rc = ntlm_challenge ( rsp->challenge, len,
                                             &rsp->info ) ) != 0 ) {
                        DBGC ( http, "HTTP %p could not parse NTLM challenge: "
                               "%s\n", http, strerror ( rc ) );
                        goto err_challenge;
                }
        }

        /* Allow HTTP request to be retried if the request had not
         * already tried authentication.  Note that NTLM requires an
         * additional round trip to obtain the challenge message,
         * which is not present in the initial WWW-Authenticate.
         */
        if ( ( http->request.auth.auth == NULL ) ||
             ( ( http->request.auth.auth == &http_ntlm_auth ) &&
               ( http->request.auth.ntlm.len == 0 ) && len ) ) {
                http->response.flags |= HTTP_RESPONSE_RETRY;
        }

        /* Success */
        rc = 0;

 err_challenge:
 err_decode:
        free ( copy );
 err_alloc:
        return rc;
}

/**
 * Perform HTTP NTLM authentication
 *
 * @v http              HTTP transaction
 * @ret rc              Return status code
 */
static int http_ntlm_authenticate ( struct http_transaction *http ) {
        struct http_request_auth_ntlm *req = &http->request.auth.ntlm;
        struct http_response_auth_ntlm *rsp = &http->response.auth.ntlm;
        struct ntlm_key key;
        const char *domain;
        char *username;
        const char *password;

        /* If we have no challenge yet, then just send a Negotiate message */
        if ( ! rsp->challenge ) {
                DBGC ( http, "HTTP %p sending NTLM Negotiate\n", http );
                return 0;
        }

        /* Record username */
        if ( ! http->uri->user ) {
                DBGC ( http, "HTTP %p has no username for NTLM "
                       "authentication\n", http );
                return -EACCES;
        }
        req->username = http->uri->user;
        password = ( http->uri->password ? http->uri->password : "" );

        /* Split NetBIOS [domain\]username */
        username = ( ( char * ) req->username );
        domain = netbios_domain ( &username );

        /* Generate key */
        ntlm_key ( domain, username, password, &key );

        /* Generate responses */
        ntlm_response ( &rsp->info, &key, NULL, &req->lm, &req->nt );

        /* Calculate Authenticate message length */
        req->len = ntlm_authenticate_len ( &rsp->info, domain, username,
                                           http_ntlm_workstation );

        /* Restore NetBIOS [domain\]username */
        netbios_domain_undo ( domain, username );

        return 0;
}

/**
 * Construct HTTP "Authorization" header for NTLM authentication
 *
 * @v http              HTTP transaction
 * @v buf               Buffer
 * @v len               Length of buffer
 * @ret len             Length of header value, or negative error
 */
static int http_format_ntlm_auth ( struct http_transaction *http,
                                   char *buf, size_t len ) {
        struct http_request_auth_ntlm *req = &http->request.auth.ntlm;
        struct http_response_auth_ntlm *rsp = &http->response.auth.ntlm;
        struct ntlm_authenticate *auth;
        const char *domain;
        char *username;
        size_t check;

        /* If we have no challenge yet, then just send a Negotiate message */
        if ( ! rsp->challenge ) {
                return base64_encode ( &ntlm_negotiate,
                                       sizeof ( ntlm_negotiate ), buf, len );
        }

        /* Skip allocation if just calculating length */
        if ( ! len )
                return base64_encoded_len ( req->len );

        /* Allocate temporary buffer for Authenticate message */
        auth = malloc ( req->len );
        if ( ! auth )
                return -ENOMEM;

        /* Split NetBIOS [domain\]username */
        username = ( ( char * ) req->username );
        domain = netbios_domain ( &username );

        /* Construct raw Authenticate message */
        check = ntlm_authenticate ( &rsp->info, domain, username,
                                    http_ntlm_workstation, &req->lm,
                                    &req->nt, auth );
        assert ( check == req->len );

        /* Restore NetBIOS [domain\]username */
        netbios_domain_undo ( domain, username );

        /* Base64-encode Authenticate message */
        len = base64_encode ( auth, req->len, buf, len );

        /* Free raw Authenticate message */
        free ( auth );

        return len;
}

/** HTTP NTLM authentication scheme */
struct http_authentication http_ntlm_auth __http_authentication = {
        .name = "NTLM",
        .parse = http_parse_ntlm_auth,
        .authenticate = http_ntlm_authenticate,
        .format = http_format_ntlm_auth,
};

/* Drag in HTTP authentication support */
REQUIRING_SYMBOL ( http_ntlm_auth );
REQUIRE_OBJECT ( httpauth );