1/*
2 * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26/*
27 * jexec for J2SE
28 *
29 * jexec is used by the system to allow execution of JAR files.
30 *    Essentially jexec needs to run java and
31 *    needs to be a native ISA executable (not a shell script), although
32 *    this native ISA executable requirement was a mistake that will be fixed.
33 *    (<ISA> is sparc or i386 or amd64).
34 *
35 *    When you execute a jar file, jexec is executed by the system as follows:
36 *      /usr/java/jre/lib/<ISA>/jexec -jar JARFILENAME
37 *    so this just needs to be turned into:
38 *      /usr/java/jre/bin/java -jar JARFILENAME
39 *
40 * Solaris systems (new 7's and all 8's) will be looking for jexec at:
41 *      /usr/java/jre/lib/<ISA>/jexec
42 * Older systems may need to add this to their /etc/system file:
43 *      set javaexec:jexec="/usr/java/jre/lib/<ISA>/jexec"
44 *     and reboot the machine for this to work.
45 *
46 * This source should be compiled as:
47 *      cc -o jexec jexec.c
48 *
49 * And jexec should be placed at the following location of the installation:
50 *      <INSTALLATIONDIR>/jre/lib/<ISA>/jexec  (for Solaris)
51 *      <INSTALLATIONDIR>/lib/jexec            (for Linux)
52 *
53 * NOTE: Unless <INSTALLATIONDIR> is the "default" JDK on the system
54 *       (i.e. /usr/java -> <INSTALLATIONDIR>), this jexec will not be
55 *       found.  The 1.2 java is only the default on Solaris 8 and
56 *       on systems where the 1.2 packages were installed and no 1.1
57 *       java was found.
58 *
59 * NOTE: You must use 1.2 jar to build your jar files. The system
60 *       doesn't seem to pick up 1.1 jar files.
61 *
62 * NOTE: We don't need to set LD_LIBRARY_PATH here, even though we
63 *       are running the actual java binary because the java binary will
64 *       look for it's libraries through it's own runpath, which uses
65 *       $ORIGIN.
66 *
67 * NOTE: This jexec should NOT have any special .so library needs because
68 *       it appears that this executable will NOT get the $ORIGIN of jexec
69 *       but the $ORIGIN of the jar file being executed. Be careful to keep
70 *       this program simple and with no .so dependencies.
71 */
72
73#include <stdlib.h>
74#include <stdio.h>
75#include <unistd.h>
76#include <string.h>
77#include <limits.h>
78#include <errno.h>
79#ifdef __linux__
80#  include <sys/types.h>
81#  include <sys/stat.h>
82#  include <fcntl.h>
83#  include "jni.h"
84#  include "manifest_info.h"
85#endif
86
87static const int CRAZY_EXEC = ENOEXEC;
88static const int BAD_MAGIC  = ENOEXEC;
89
90static const char * BAD_EXEC_MSG     = "jexec failed";
91static const char * CRAZY_EXEC_MSG   = "missing args";
92static const char * MISSING_JAVA_MSG = "can't locate java";
93static const char * BAD_ARG_MSG      = "incorrect number of arguments";
94static const char * MEM_FAILED_MSG   = "memory allocation failed";
95#ifdef __linux__
96static const char * BAD_PATHNAME_MSG = "invalid path";
97static const char * BAD_FILE_MSG     = "invalid file";
98static const char * BAD_MAGIC_MSG    = "invalid file (bad magic number)";
99#endif
100static const char * UNKNOWN_ERROR    = "unknown error";
101
102/* Define a constant that represents the number of directories to pop off the
103 * current location to find the java binary */
104#ifdef __linux__
105static const int RELATIVE_DEPTH = 2;
106#else /* Solaris */
107static const int RELATIVE_DEPTH = 3;
108#endif
109
110/* path to java after popping */
111static const char * BIN_PATH = "/bin/java";
112
113/* flag used when running JAR files */
114static const char * JAR_FLAG = "-jar";
115
116
117#ifdef __linux__
118/* largest possible size for a local file header */
119static const size_t CHUNK_SIZE = 65535;
120
121/* smallest possible size for a local file header */
122static const ssize_t MIN_SIZE = LOCHDR + 1 + 4;
123#endif
124
125
126int main(int argc, const char * argv[]);
127void errorExit(int error, const char * message);
128int getJavaPath(const char * path, char * buf, int depth);
129#ifdef __linux__
130const char * isJar(const char * path);
131#endif
132
133
134/*
135 * This is the main entry point.  This program (jexec) will attempt to execute
136 * a JAR file by finding the Java program (java), relative to its own location.
137 * The exact location of the Java program depends on the platform, i.e.
138 *
139 *      <INSTALLATIONDIR>/jre/lib/<ISA>/jexec  (for Solaris)
140 *      <INSTALLATIONDIR>/lib/jexec            (for Linux JDK)
141 *
142 * Once the Java program is found, this program copies any remaining arguments
143 * into another array, which is then used to exec the Java program.
144 *
145 * On Linux this program does some additional steps.  When copying the array of
146 * args, it is necessary to insert the "-jar" flag between arg[0], the program
147 * name, and the original arg[1], which is presumed to be a path to a JAR file.
148 * It is also necessary to verify that the original arg[1] really is a JAR file.
149 * (These steps are unnecessary on Solaris because they are taken care of by
150 * the kernel.)
151 */
152int main(int argc, const char * argv[]) {
153    /* We need to exec the original arguments using java, instead of jexec.
154     * Also, for Linux, it is necessary to add the "-jar" argument between
155     * the new arg[0], and the old arg[1].  To do this we will create a new
156     * args array. */
157    char          java[PATH_MAX + 1];    /* path to java binary  */
158    const char ** nargv = NULL;          /* new args array       */
159    int           nargc = 0;             /* new args array count */
160    int           argi  = 0;             /* index into old array */
161    size_t        alen  = 0;             /* length of new array */
162
163    /* Make sure we have something to work with */
164    if ((argc < 1) || (argv == NULL)) {
165        /* Shouldn't happen... */
166        errorExit(CRAZY_EXEC, CRAZY_EXEC_MSG);
167    }
168
169    /* Get the path to the java binary, which is in a known position relative
170     * to our current position, which is in argv[0]. */
171    if (getJavaPath(argv[argi++], java, RELATIVE_DEPTH) != 0) {
172        errorExit(errno, MISSING_JAVA_MSG);
173    }
174    alen = (argc + 2) * (sizeof (const char *));
175    if (alen <= 0 || alen > INT_MAX / sizeof(char *)) {
176        errorExit(errno, BAD_ARG_MSG);
177    }
178    nargv = (const char **) malloc(alen);
179    if (nargv == NULL) {
180        errorExit(errno, MEM_FAILED_MSG);
181    }
182    nargv[nargc++] = java;
183
184#ifdef __linux__
185    /* The "-jar" flag is already in the original args list on Solaris,
186     * so it only needs to be added on Linux. */
187    nargv[nargc++] = JAR_FLAG;
188#endif
189
190    if (argc >= 2) {
191        const char * jarfile = argv[argi++];
192        const char * message = NULL;
193
194#ifdef __linux__
195        /* On Linux we also need to make sure argv[1] is really a JAR
196         * file (this will also resolve any symlinks, which helps). */
197        char jarPath[PATH_MAX + 1];
198
199        if (realpath(jarfile, jarPath) == NULL) {
200            errorExit(errno, BAD_PATHNAME_MSG);
201        }
202
203        message = isJar(jarPath);
204        if (message != NULL) {
205            errorExit(errno, message);
206        }
207
208        jarfile = jarPath;
209#endif
210        /* the next argument is the path to the JAR file */
211        nargv[nargc++] = jarfile;
212    }
213
214    /* finally copy any remaining arguments */
215    while (argi < argc) {
216        nargv[nargc++] = argv[argi++];
217    }
218
219    /* finally add one last terminating null */
220    nargv[nargc++] = NULL;
221
222    /* It's time to exec the java binary with the new arguments.  It
223     * is possible that we've reached this point without actually
224     * having a JAR file argument (i.e. if argc < 2), but we still
225     * want to exec the java binary, since that will take care of
226     * displaying the correct usage. */
227    execv(java, (char * const *) nargv);
228
229    /* If the exec worked, this process would have been replaced
230     * by the new process.  So any code reached beyond this point
231     * implies an error in the exec. */
232    free(nargv);
233    errorExit(errno, BAD_EXEC_MSG);
234    return 0; // keep the compiler happy
235}
236
237
238/*
239 * Exit the application by setting errno, and writing a message.
240 *
241 * Parameters:
242 *     error   - errno is set to this value, and it is used to exit.
243 *     message - the message to write.
244 */
245void errorExit(int error, const char * message) {
246    if (error != 0) {
247        errno = error;
248        perror((message != NULL) ? message : UNKNOWN_ERROR);
249    }
250
251    exit((error == 0) ? 0 : 1);
252}
253
254
255/*
256 * Get the path to the java binary that should be relative to the current path.
257 *
258 * Parameters:
259 *     path  - the input path that the java binary that should be relative to.
260 *     buf   - a buffer of size PATH_MAX or greater that the java path is
261 *             copied to.
262 *     depth - the number of names to trim off the current path, including the
263 *             name of this program.
264 *
265 * Returns:
266 *     This function returns 0 on success; otherwise it returns the value of
267 *     errno.
268 */
269int getJavaPath(const char * path, char * buf, int depth) {
270    int result = 0;
271
272    /* Get the full path to this program.  Depending on whether this is Solaris
273     * or Linux, this will be something like,
274     *
275     *     <FOO>/jre/lib/<ISA>/jexec  (for Solaris)
276     *     <FOO>/lib/jexec            (for Linux)
277     */
278    if (realpath(path, buf) != NULL) {
279        int count = 0;
280
281        /* Pop off the filename, and then subdirectories for each level of
282         * depth */
283        for (count = 0; count < depth; count++) {
284            *(strrchr(buf, '/')) = '\0';
285        }
286
287        /* Append the relative location of java, creating something like,
288         *
289         *     <FOO>/jre/bin/java  (for Solaris)
290         *     <FOO>/bin/java      (for Linux)
291         */
292        strcat(buf, BIN_PATH);
293    }
294    else {
295        /* Failed to get the path */
296        result = errno;
297    }
298
299    return (result);
300}
301
302
303#ifdef __linux__
304/*
305 * Check if the given file is a JAR file.
306 *
307 * Parameters:
308 *     path  - the path to the file to check for JAR magic.
309 *
310 * Returns:
311 *     This function return NULL on success.  Otherwise, errno is set, and it
312 *     returns a message that indicates what caused the failure.
313 */
314const char * isJar(const char * path) {
315    const char * result = BAD_FILE_MSG;
316
317    int fd = open(path, O_RDONLY);
318    if (fd != -1) {
319        unsigned char buf[CHUNK_SIZE];
320
321        ssize_t count = read(fd, buf, CHUNK_SIZE);
322        if (count >= MIN_SIZE) {
323            result = BAD_MAGIC_MSG;
324
325            // be sure the file is at least a ZIP file
326            if (LOCSIG_AT(buf)) {
327
328                off_t flen  = LOCNAM(buf);
329                off_t xlen  = LOCEXT(buf);
330                off_t start = LOCHDR + flen;
331                off_t end   = start  + xlen;
332
333                if (end <= count) {
334                    end -= 4; // make sure there are 4 bytes to read at start
335                    while (start <= end) {
336                        off_t xhid  = SH(buf, start);
337                        off_t xdlen = SH(buf, start + 2);
338
339                        start += 4 + xdlen;
340                        if (xhid == 0xcafe) {
341                            // found the JAR magic
342                            result = NULL;
343                            break;
344                        }
345                    }
346                }
347            }
348        }
349
350        if (result != NULL) {
351            errno = BAD_MAGIC;
352        }
353
354        close (fd);
355    }
356
357    return (result);
358}
359#endif
360