annotate INSTALL @ 1930:299f4f19ba19

Add /usr/sbin and /sbin to default root PATH When dropbear is used in a very restricted environment (such as in a initrd), the default user shell is often also very restricted and doesn't take care of setting the PATH so the user ends up with the PATH set by dropbear. Unfortunately, dropbear always sets "/usr/bin:/bin" as default PATH even for the root user which should have /usr/sbin and /sbin too. For a concrete instance of this problem, see the "Remote Unlocking" section in this tutorial: https://paxswill.com/blog/2013/11/04/encrypted-raspberry-pi/ It speaks of a bug in the initramfs script because it's written "blkid" instead of "/sbin/blkid"... this is just because the scripts from the initramfs do not expect to have a PATH without the sbin directories and because dropbear is not setting the PATH appropriately for the root user. I'm thus suggesting to use the attached patch to fix this misbehaviour (I did not test it, but it's easy enough). It might seem anecdotic but multiple Kali users have been bitten by this. From https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=903403
author Raphael Hertzog <hertzog@debian.org>
date Mon, 09 Jul 2018 16:27:53 +0200
parents f78e67527731
children
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1 Basic Dropbear build instructions:
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3 - Edit localoptions.h to set which features you want. Available options
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4 are described in default_options.h, these will be overridden by
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5 anything set in localoptions.h
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6 localoptions.h should be located in the build directory if you are
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7 building out of tree.
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9 - Configure for your system:
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10 ./configure (optionally with --disable-zlib or --disable-syslog,
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11 or --help for other options)
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13 (you'll need to first run "autoconf; autoheader" if you edit configure.ac)
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15 - Compile:
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17 make PROGRAMS="dropbear dbclient dropbearkey dropbearconvert scp"
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19 - Optionally install, or copy the binaries another way
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21 make install (/usr/local/bin is usual default):
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23 or
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25 make PROGRAMS="dropbear dbclient dropbearkey dropbearconvert scp" install
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27 (you can leave items out of the PROGRAMS list to avoid compiling them. If you
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28 recompile after changing the PROGRAMS list, you *MUST* "make clean" before
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29 recompiling - bad things will happen otherwise)
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31 DEVELOPING.md has some notes on other developer topics, including debugging.
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33 See MULTI for instructions on making all-in-one binaries.
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35 If you want to compile statically use ./configure --enable-static
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37 By default Dropbear adds various build flags that improve robustness
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38 against programming bugs (good for security). If these cause problems
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39 they can be disabled with ./configure --disable-harden
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41 Binaries can be stripped with "make strip"
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43 ============================================================================
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45 If you're compiling for a 386-class CPU, you will probably need to add
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46 CFLAGS=-DLTC_NO_BSWAP so that libtomcrypt doesn't use 486+ instructions.
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48 ============================================================================
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50 Compiling with uClibc:
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52 Firstly, make sure you have at least uclibc 0.9.17, as getusershell() in prior
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53 versions is broken. Also note that you may get strange issues if your uClibc
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54 headers don't match the library you are running with, ie the headers might
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55 say that shadow password support exists, but the libraries don't have it.
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57 Compiling for uClibc should be the same as normal, just set CC to the magic
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58 uClibc toolchain compiler (ie export CC=i386-uclibc-gcc or whatever).
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59 You can use "make STATIC=1" to make statically linked binaries, and it is
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60 advisable to strip the binaries too. If you're looking to make a small binary,
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61 you should remove unneeded ciphers and MD5, by editing localoptions.h
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63 It is possible to compile zlib in, by copying zlib.h and zconf.h into a
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64 subdirectory (ie zlibincludes), and
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66 export CFLAGS="-Izlibincludes -I../zlibincludes"
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67 export LDFLAGS=/usr/lib/libz.a
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69 before ./configure and make.
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71 If you disable zlib, you must explicitly disable compression for the client -
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72 OpenSSH is possibly buggy in this regard, it seems you need to disable it
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73 globally in ~/.ssh/config, not just in the host entry in that file.
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75 You may want to manually disable lastlog recording when using uClibc, configure
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76 with --disable-lastlog.
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78 One common problem is pty allocation. There are a number of types of pty
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79 allocation which can be used -- if they work properly, the end result is the
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80 same for each type. Running configure should detect the best type to use
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81 automatically, however for some systems, this may be incorrect. Some
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82 things to note:
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84 If your system expects /dev/pts to be mounted (this is a uClibc option),
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85 make sure that it is.
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87 Make sure that your libc headers match the library version you are using.
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89 If openpty() is being used (HAVE_OPENPTY defined in config.h) and it fails,
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90 you can try compiling with --disable-openpty. You will probably then need
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91 to create all the /dev/pty?? and /dev/tty?? devices, which can be
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92 problematic for devfs. In general, openpty() is the best way to allocate
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93 PTYs, so it's best to try and get it working.