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1.1 marc 20:
1.3 marc 21: <h2><font color=#e00000>Building an OpenBSD port</font></h2>
1.1 marc 22:
23: So you've just compiled your favorite software package on your
24: OpenBSD machine and you want to share your effort by turning
25: it into a standard port. What to do?
26: <p>
1.9 marc 27: First look at the porting information on this page. Then check
28: out the referenced documents, especially the OpenBSD porting
1.14 espie 29: <a href="checklist.html">checklist</a>.
1.1 marc 30: <p>
1.9 marc 31: Test, then re-test, and finally test again!
32: <p>
33: Submit the port. Create a gzipped tarball of the port directory.
34: You can then either place it on a public FTP or HTTP server, sending
35: its address to <a href=mailto:ports@openbsd.org>ports@openbsd.org</a>
36: or send the port mime encoded to the same address. Pick whichever
37: method works best for you.
1.1 marc 38: <p>
39: <h3><font color=#0000e0>Available Porting Information</font></h3>
40: <ul>
41: <li>The file <code>/usr/share/mk/bsd.port.mk</code>. This is the
42: system ports makefile included at the end of each individual
43: port makefile. Read the comments at the start of the makefile.
44: They do a good job of describing the available make options.
45: <li>The
1.13 art 46: <a href="http://www.netbsd.org/Documentation/software/packages.html">
47: NetBSD Package System</a> documentation. This document describes
48: NetBSD's version of the FreeBSD ports system and is quite helpful.
1.8 marc 49: <li>Section 19.2.5 of the
1.1 marc 50: <a href="http://www.freebsd.org/handbook/porting.html">FreeBSD
51: Handbook</a>. This is the FreeBSD porting bible.
1.9 marc 52: <li>OpenBSD porting <a href="checklist.html">checklist</a>.
1.15 espie 53: <li><a href="audio-port.html">Porting audio applications to OpenBSD</a>.
1.1 marc 54: <li>The OpenBSD ports mailing list,
55: <a href="mailto:ports@openbsd.org">ports@OpenBSD.ORG</a>.
56: </ul>
57: <h3><font color=#0000e0>OpenBSD Porting Policy</font></h3>
58: <ul>
59: <li>OpenBSD does NOT use /usr/local/etc/rc.d.<br>
1.7 espie 60: <code>/usr/local</code> is often shared between several machines
1.15 espie 61: thanks to NFS. For this reason, configuration files that are specific
62: to a given machine can't be stored under <code>/usr/local</code>,
63: <code>/etc</code> is the central repository for per machine
64: configuration files. Moreover, OpenBSD policy is to never update
65: files under <code>/etc</code> automatically. Ports that need some
66: specific boot setup should advise the administrator about what to do
67: instead of blindly installing files.
1.1 marc 68: <li>OpenBSD does NOT compress man pages.
69: <li>OpenBSD does NOT require <code>-lcrypt</code>.<br>
70: DES encryption is part of the standard <code>libc</code>.
1.10 espie 71: <li>OpenBSD is strongly security-oriented. You should read and understand
72: this page's <a href="#security">security section</a>.
73: <li>Be sure to add the <code>$</code><code>OpenBSD$</code> CVS tag to
74: the Makefile. If importing a port from another system be sure to
75: leave their tag in the Makefile, too. However, replace the FreeBSD
76: <code>$</code><code>Id$</code> tag with the
77: <code>$</code><code>FreeBSD$</code> tag.
78: <li>The goal is to get all ported applications to support OpenBSD. To
79: achieve this goal you <strong>must</strong> feed any OpenBSD patches
80: back to the application maintainer.
81: </ul>
82: <a name=security>
83: <h3><font color=#0000e0>Security recommendations</font></h3>
84: There are many security problems to worry about. If
1.2 marc 85: you are not absolutely sure of what you are doing please request
1.1 marc 86: help from the <a href="mailto:ports@openbsd.org">ports</a> mailing
87: list.
1.10 espie 88:
89: <ul>
90: <li>Do <emph>not</emph> use alpha or beta code when preparing a port. Use the
91: latest regular or patch release.
92:
1.1 marc 93: <li>Any software to be installed as a server should be scanned
94: for buffer overflows, especially unsafe use of
95: <code>strcat/strcpy/strcmp/sprintf</code>. In general,
96: <code>sprintf</code> should be replaced with <code>snprintf</code>.
1.10 espie 97:
1.17 ! espie 98: <li>Never use filenames instead of true security. There are numerous race
1.10 espie 99: conditions where you don't have proper control. For instance, an attacker
100: who already has user privileges on your machines may replace files in
101: <code>/tmp</code> with symbolic links to more strategic files, such as
1.15 espie 102: <code>/etc/passwd</code>.
1.16 espie 103:
104: <li>For instance, both <code>fopen</code> and <code>freopen</code>
105: <strong>create a new file or open an existing file</strong> for
106: writing. An attacker may create a symbolic link from
107: <code>/etc/paswd</code> to <code>/tmp/addrpool_dump</code>. The
108: instant you open it, your password file is hosed. Yes, even with
109: an <code>unlink</code> right before. You only narrow the window
110: of opportunity. Use <code>open</code> with
111: <code>O_CREAT|O_EXCLUDE</code> and <code>fdopen</code> instead.
1.15 espie 112:
1.16 espie 113: <li>Another very common problem is the <code>mktemp</code>
1.17 ! espie 114: function. Heed the warnings of the bsd linker about its uses.
1.15 espie 115: <strong>These must be fixed</strong>.
116: This is not quite as simple as <code>s/mktemp/mkstemp/g</code>. <br>
117: Refer to the <code>mktemp(3)</code> man page of OpenBSD current
118: for more indications.
119: Correct code using <code>mkstemp</code> includes the source to
120: <code>ed</code> or <code>mail</code>.
121: A rare instance of code that uses <code>mktemp</code> correctly
122: can be found in the <code>rsync</code> port.
1.10 espie 123:
124: <li>Just because you can read it doesn't mean you should. A well-known hole
125: of this nature was the <code>startx</code> problem. As a setuid program,
126: you could launch startx with any file as a script. If the file was not
127: a valid shell script, a syntax error message would follow, along with the
128: first line of the offending file, without any further permission check.
129: Pretty handy to grab the first line of a shadow passwd file, considering
1.12 deraadt 130: these often start with root entry. Do not open your file, and then do
131: an <code>fstat</code> on the open descriptor to check if you should have
1.15 espie 132: been able to open it (or the attacker will play with /dev/rst0 and rewind
1.12 deraadt 133: your tape) -- open it with the correct uid/gid/grouplist set.
1.10 espie 134:
135: <li>Don't use anything that forks a shell in setuid programs before dropping
1.15 espie 136: your privileges. This includes <code>popen</code> and
137: <code>system</code>.
1.10 espie 138: Use <code>fork</code>, <code>pipe</code> and <code>execve</code> instead.
139:
1.15 espie 140: <li>Pass open descriptors instead of filenames to other programs to
141: avoid race conditions. Even if a program does not accept file
142: descriptors, you can still use <code>/dev/fd/0</code>.
1.10 espie 143:
1.15 espie 144: <li>Access rights are attached to file descriptors. If you need setuid rights
1.10 espie 145: to open a file, open that file, then drop your privileges. You can still
146: access the open descriptor, but you have less to worry about. This is
147: double-edged: even after dropping privileges, you should still watch out
148: for those descriptors.
149:
150: <li>Avoid root setuid as much as you can. Basically, root can do anything,
1.15 espie 151: but root rights are very rarely needed, except maybe to create
152: socket ports with a number under 1024. It is arguably better to
153: keep that under <code>inetd</code>
1.10 espie 154: control and just add the relevant entries to <code>inetd.conf</code>.
155: You must know the appropriate magic for writing daemons to achieve that.
1.15 espie 156: It could be argued that you have no business writing setuid programs
157: if you don't know how to do that.
1.10 espie 158:
1.15 espie 159: <li>Use setgid instead of setuid. Apart from those specific files needed
160: by setgid programs, most files are not group-writable. Hence, a
161: security problem in a setgid program won't compromise your system as
162: much: with only group rights, the worst an intruder will be able to
163: do is hack a games score table or some such.
1.10 espie 164: See the <code>xkobo</code> port for an instance of such a change.
165:
1.15 espie 166: <li>Don't trust group-writable files. Even though they are audited,
167: setgid programs are not perceived as important potential security
168: holes. Hence stuff they can tamper with shouldn't be considered
169: sensitive information.
170:
171: <li>Don't trust your environment ! This involves simple things such as
172: your <code>PATH</code> (never use <code>system</code> with an
173: unqualified name, avoid <code>execvp</code>), but also more subtle
174: items such as your locale, timezone, termcap, and so on.
175: Be aware of transitivity: even though you're taking full precautions,
176: programs you call directly won't necessarily. <strong>Never</strong>
177: use <code>system</code> in privileged programs, build your command
178: line, a controlled environment, and call <code>execve</code> directly.
179: The <code>perlsec</code> man page is a good tutorial on such problems.
180:
181: <li>Never used setuid shell-scripts. These are inherently insecure.
182: Wrap them into some C code that ensures a proper environment.
183: On the other hand, OpenBSD features secure perl scripts.
184:
185: <li>Beware the dynamic loader. If you are running setuid, it will only
186: use trusted libraries that were scanned with ldconfig.
187: Setgid is not enough.
188:
189: <li>Dynamic libraries are tricky. C++ code sets a similar problem.
190: Basically, libraries may take some action based upon your environment
191: before your main program even gets to check its setuid status.
192: OpenBSD <code>issetugid</code> addresses this problem, from the
193: library writer point of view. Don't try to port libraries unless you
194: understand this issue thoroughly.
1.10 espie 195: </ul>
196: <h3><font color=#0000e0>Generic porting hints</font></h3>
197: <ul>
198: <li><code>__OpenBSD__</code> should be used sparingly, if at all.
199: Constructs that look like
200: <pre>
201: #if defined(__NetBSD__) || defined(__FreeBSD__)
202: </pre>
203: are often inappropriate. Don't add blindly <code>__OpenBSD__</code>
204: to it. Instead, try to figure out what's going on, and what actual
205: feature is needed. Manual pages are often useful, as they include
206: historic comments, stating when a particular feature was incorporated
207: into BSD. Checking the numeric value of <code>BSD</code> against known
208: releases is often the right way. See
1.17 ! espie 209: <a href="ftp://ftp.netbsd.org/pub/NetBSD/packages/pkgsrc/Packages.txt">the NetBSD package guide</a>
1.10 espie 210: for more information.
211: <li>Defining <code>BSD</code> is a bad idea. Try to include <code>sys/param.h</code>.
212: This not only defines <code>BSD</code>, it also gives it a proper value.
213: The right code fragment should look like:
214: <pre>
215: #if (defined(__unix__) || defined(unix)) && !defined(USG)
216: #include <sys/param.h>
217: #endif
218: </pre>
219: <li>Test for features, not for specific OSes. In the long run, it is much
1.15 espie 220: better to test whether <code>tcgetattr</code> works than whether
221: you're running under BSD 4.3 or later, or SystemVR4. These kind of
222: tests just confuse the issue. The way to go about it is, for instance,
223: to test for one particular system, set up a slew of
224: <code>HAVE_TCGETATTR</code> defines, then proceed to the next system.
225: This technique separates features tests from specific OSes.
226: In a hurry, another porter can just add the whole set of
227: <code>-DHAVE_XXX</code> defines to the Makefile. One may also write
228: or add to a configure script to check for that feature and add it
229: automatically. As an example not to follow, check nethack 3.2.2
230: source: it assumes loads of things based on the system type. Most
231: of these assumptions are obsolete and no longer reflect reality:
232: POSIX functions are more useful than older BSD versus SystemV
233: differences, to the point that some traditional bsd functions are
1.10 espie 234: now only supported through compatibility libraries.
235:
236: <li>Avoid include files that include other includes that... First, because
1.15 espie 237: this is inefficient. Your project will end up including a file that
238: includes everything. Also, because it makes some problems difficult
239: to fix. It becomes harder to <em>not</em> include one particular file
240: at a given point.
1.10 espie 241:
242: <li>Avoid bizarre macro tricks. Undefining a macro that was defined by a
243: header file is a bad idea. Defining macros to get some specific behavior
1.15 espie 244: from an include file is also a bad idea: compilation modes should be
245: global. If you want POSIX behavior, say so, and
246: <code>#define POSIX_C_SOURCE</code>
1.10 espie 247: throughout the whole project, not when you feel like it.
248:
249: <li>Don't ever write system function prototypes. All modern systems,
250: OpenBSD included, have a standard location for these prototypes. Likely
1.15 espie 251: places include <code>unistd.h</code>, <code>fcntl.h</code> or
252: <code>termios.h</code>.
253: The man page frequently states where the prototype can be found.
254: You might need another slew of <code>HAVE_XXX</code> macros to
255: procure the right file. Don't worry about including the same file
256: twice, include files have guards that prevent all kinds of nastiness.<br>
1.10 espie 257: If some broken system needs you to write the prototype, don't impose
1.15 espie 258: on all other systems. Roll-your-own prototypes will break because they
259: may use types that are equivalent on your system, but are not portable
260: to other systems (<code>unsigned long</code> instead of
261: <code>size_t</code>), or get some <code>const</code> status wrong.
262: Also, some compilers, such as OpenBSD's own gcc,
1.10 espie 263: are able to do a better job with some very frequent functions such as
264: <code>strlen</code> if you include the right header file.
265:
266: <li>Don't use the name of a standard system function for anything else.
1.15 espie 267: If you want to write your own function, give it its own name, and
268: call that function everywhere. If you wish to revert to the
269: default system function, you just need to comment your code out,
270: and define your own name to the system function. Don't do it the
271: other way round. Code should look like this
1.10 espie 272: <pre>
273: /* prototype part */
274: #ifdef USE_OWN_GCVT
275: char *foo_gcvt(double number, size_t ndigit, char *buf);
276: #else
277: /* include correct file */
278: #include <stdlib.h>
279: /* use system function */
280: #define foo_gcvt gcvt
281: #endif
282:
283: /* definition part */
284: #ifdef USE_OWN_GCVT
285: char *foo_gcvt(double number, size_t ndigit, char *buf)
286: {
1.15 espie 287: /* proper definition */
288: }
1.10 espie 289:
290: /* typical use */
291: s = foo_gcvt(n, 15, b);
292: </pre>
1.1 marc 293: </ul>
294: <h3><font color=#0000e0>Other Helpful Hints</font></h3>
295: <ul>
1.15 espie 296: <li>Recent versions of <code>bsd.port.mk</code> set the installers
297: path. Specifically, they set <code>/usr/bin</code> and
298: <code>/bin</code> to be searched <em>before</em>
299: <code>/usr/local/bin</code> and <code>/usr/X11R6/bin</code>.
300: <li>Do <em>NOT</em> generate shared libraries for <code>${MACHINE_ARCH} ==
1.1 marc 301: alpha</code>
302: <li>In OpenBSD <code>curses.h/libcurses/libtermlib</code> are the
303: ``new curses''. Change:<br>
1.15 espie 304: <code>ncurses.h ==> curses.h</code><br>
305: <code>-lncurses ==> -lcurses</code><br>
306: ``old (BSD) curses'' is available by defining
307: <code>_USE_OLD_CURSES_</code>
1.11 millert 308: before including <code>curses.h</code> (usually in a Makefile) and
1.15 espie 309: linking with <code>-locurses</code>.
1.11 millert 310: <li>In OpenBSD, terminal discipline has been upgraded from the older BSD
311: <code>sgtty</code> to the newer POSIX <code>tcgetattr</code> family.
1.15 espie 312: Avoid the older style in new code. Some code may define
313: <code>tcgetattr</code> to be a synonym for the older
314: <code>sgtty</code>, but this is at best a stopgap measure on OpenBSD.
315: The <code>xterm</code> source code is a very good example of
316: what not to do. Try to get your system functionality right: you
317: want a type that remembers the state of your terminal
318: (possible typedef), you want a function that extracts the current
319: state, and a function that sets the new state.
320: Functions that modify this state are more difficult, as they tend
321: to vary depending upon the system. Also, don't forget that you will
322: have to handle cases where you are not connected to a terminal,
323: and that you need to handle signals: not only termination, but
324: also background (<code>SIGTSTP</code>). You should always leave
325: the terminal in a sane state. Do your tests under an older shell,
326: such as sh, which does not reset the terminal in any way at
1.10 espie 327: program's termination.
1.15 espie 328: <li>The newer termcap/terminfo and curses, as included with OpenBSD,
329: include standard sequences for controlling color terminals. You
330: should use these if possible, reverting to standard ANSI color
331: sequences on other systems. However, some terminal descriptions
332: have not been updated yet, and you may need to be able to specify
333: these sequences manually. This is the way vim handles it. This is
334: not strictly necessary. Except for privileged programs, it is
335: generally possible to override a termcap definition through the
1.10 espie 336: <code>TERMCAP</code> variable and get it to work properly.
1.15 espie 337: <li>Signal semantics are tricky, and vary from one system to another.
338: Use <code>sigaction</code> to ensure a specific semantics, along
339: with other system calls referenced in the corresponding manpage.
1.1 marc 340: </ul>
341: <hr>
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