Add Chacha20-Poly1305, AES128-GCM and AES256-GCM support (#93) * Add Chacha20-Poly1305 authenticated encryption * Add general AEAD approach. * Add [email protected] algo using LibTomCrypt chacha and poly1305 routines. Chacha20-Poly1305 is generally faster than AES256 on CPU w/o dedicated AES instructions, having the same key size. Compiling in will add ~5,5kB to binary size on x86-64. function old new delta chacha_crypt - 1397 +1397 _poly1305_block - 608 +608 poly1305_done - 595 +595 dropbear_chachapoly_crypt - 457 +457 .rodata 26976 27392 +416 poly1305_process - 290 +290 poly1305_init - 221 +221 chacha_setup - 218 +218 encrypt_packet 1068 1270 +202 dropbear_chachapoly_getlength - 147 +147 decrypt_packet 756 897 +141 chacha_ivctr64 - 137 +137 read_packet 543 637 +94 dropbear_chachapoly_start - 94 +94 read_kex_algos 792 880 +88 chacha_keystream - 69 +69 dropbear_mode_chachapoly - 48 +48 sshciphers 280 320 +40 dropbear_mode_none 24 48 +24 dropbear_mode_ctr 24 48 +24 dropbear_mode_cbc 24 48 +24 dropbear_chachapoly_mac - 24 +24 dropbear_chachapoly - 24 +24 gen_new_keys 848 854 +6 ------------------------------------------------------------------------------ (add/remove: 14/0 grow/shrink: 10/0 up/down: 5388/0) Total: 5388 bytes * Add AES128-GCM and AES256-GCM authenticated encryption * Add general AES-GCM mode. * Add [email protected] and [email protected] algo using LibTomCrypt gcm routines. AES-GCM is combination of AES CTR mode and GHASH, slower than AES-CTR on CPU w/o dedicated AES/GHASH instructions therefore disabled by default. Compiling in will add ~6kB to binary size on x86-64. function old new delta gcm_process - 1060 +1060 .rodata 26976 27808 +832 gcm_gf_mult - 820 +820 gcm_add_aad - 660 +660 gcm_shift_table - 512 +512 gcm_done - 471 +471 gcm_add_iv - 384 +384 gcm_init - 347 +347 dropbear_gcm_crypt - 309 +309 encrypt_packet 1068 1270 +202 decrypt_packet 756 897 +141 gcm_reset - 118 +118 read_packet 543 637 +94 read_kex_algos 792 880 +88 sshciphers 280 360 +80 gcm_mult_h - 80 +80 dropbear_gcm_start - 62 +62 dropbear_mode_gcm - 48 +48 dropbear_mode_none 24 48 +24 dropbear_mode_ctr 24 48 +24 dropbear_mode_cbc 24 48 +24 dropbear_ghash - 24 +24 dropbear_gcm_getlength - 24 +24 gen_new_keys 848 854 +6 ------------------------------------------------------------------------------ (add/remove: 14/0 grow/shrink: 10/0 up/down: 6434/0) Total: 6434 bytes

Basic Dropbear build instructions:

- Edit localoptions.h to set which features you want. Available options
  are described in default_options.h, these will be overridden by
  anything set in localoptions.h
  localoptions.h should be located in the build directory if you are
  building out of tree.

- If using a Mercurial or Git checkout, "autoconf; autoheader"

- Configure for your system:
  ./configure     (optionally with --disable-zlib or --disable-syslog,
                  or --help for other options)

- Compile:

  make PROGRAMS="dropbear dbclient dropbearkey dropbearconvert scp"

- Optionally install, or copy the binaries another way

  make install (/usr/local/bin is usual default):

  or

  make PROGRAMS="dropbear dbclient dropbearkey dropbearconvert scp" install

(you can leave items out of the PROGRAMS list to avoid compiling them. If you
recompile after changing the PROGRAMS list, you *MUST* "make clean" before
recompiling - bad things will happen otherwise)

See MULTI for instructions on making all-in-one binaries.

If you want to compile statically use ./configure --enable-static

By default Dropbear adds various build flags that improve robustness 
against programming bugs (good for security). If these cause problems
they can be disabled with ./configure --disable-harden

Binaries can be stripped with "make strip"

============================================================================

If you're compiling for a 386-class CPU, you will probably need to add
CFLAGS=-DLTC_NO_BSWAP so that libtomcrypt doesn't use 486+ instructions.

============================================================================

Compiling with uClibc:

Firstly, make sure you have at least uclibc 0.9.17, as getusershell() in prior
versions is broken. Also note that you may get strange issues if your uClibc
headers don't match the library you are running with, ie the headers might
say that shadow password support exists, but the libraries don't have it.

Compiling for uClibc should be the same as normal, just set CC to the magic
uClibc toolchain compiler (ie export CC=i386-uclibc-gcc or whatever).
You can use "make STATIC=1" to make statically linked binaries, and it is
advisable to strip the binaries too. If you're looking to make a small binary,
you should remove unneeded ciphers and MD5, by editing localoptions.h

It is possible to compile zlib in, by copying zlib.h and zconf.h into a
subdirectory (ie zlibincludes), and 

export CFLAGS="-Izlibincludes -I../zlibincludes"
export LDFLAGS=/usr/lib/libz.a

before ./configure and make.

If you disable zlib, you must explicitly disable compression for the client -
OpenSSH is possibly buggy in this regard, it seems you need to disable it
globally in ~/.ssh/config, not just in the host entry in that file.

You may want to manually disable lastlog recording when using uClibc, configure
with --disable-lastlog.

One common problem is pty allocation. There are a number of types of pty
allocation which can be used -- if they work properly, the end result is the
same for each type. Running configure should detect the best type to use
automatically, however for some systems, this may be incorrect. Some
things to note:

    If your system expects /dev/pts to be mounted (this is a uClibc option),
	make sure that it is.

	Make sure that your libc headers match the library version you are using.

	If openpty() is being used (HAVE_OPENPTY defined in config.h) and it fails,
	you can try compiling with --disable-openpty. You will probably then need
	to create all the /dev/pty?? and /dev/tty?? devices, which can be
	problematic for devfs. In general, openpty() is the best way to allocate
	PTYs, so it's best to try and get it working.