missing crypt on glibc 2.31

[thom-nic]

I am cross-compiling dropbear on Ubuntu host for arm-linux-gnueabihf target. I had been using Ubuntu Bionic (glibc 2.27) building dropbear release v2017.75. I want to upgrade to Ubuntu Focal host which uses glibc 2.31 and build the most recent dropbear release. It seems versions 2018+ fail on Ubuntu Focal host with the following:

During configure

configure: Using bundled libtomcrypt and libtommath
configure:
configure: crypt() not available, dropbear server will not have password authentication
configure:
configure: Now edit options.h to choose features.

Then during make:

make -C libtomcrypt
make[1]: Entering directory '/root/etx8-linux/recovery/dropbear/libtomcrypt'
arm-linux-gnueabihf-gcc -Isrc/headers/ -I./src/headers/ -I../ -I./../ -DLTC_SOURCE -I../libtommath/ -I./../libtommath/ -I./libtomcrypt/src/headers/ -DLOCALOPTIONS_H_EXISTS -I. -I.  -Os -W -Wall -Wno-pointer-sign -fno-strict-overflow -fPIE -fstack-protector-strong -D_FORTIFY_SOURCE=2 -DDROPBEAR_SERVER -DDROPBEAR_CLIENT -c src/ciphers/aes/aes.c -o src/ciphers/aes/aes.o
In file included from ../options.h:23,
                 from src/headers/tomcrypt_dropbear.h:2,
                 from src/headers/tomcrypt_custom.h:13,
                 from src/headers/tomcrypt.h:22,
                 from src/ciphers/aes/aes.c:31:
../sysoptions.h:237:3: error: #error "DROPBEAR_SVR_PASSWORD_AUTH requires `crypt()'."
  237 |  #error "DROPBEAR_SVR_PASSWORD_AUTH requires `crypt()'."
      |   ^~~~~
make[1]: *** [Makefile:246: src/ciphers/aes/aes.o] Error 1
make[1]: Leaving directory '/root/etx8-linux/recovery/dropbear/libtomcrypt'
make: *** [Makefile:209: libtomcrypt/libtomcrypt.a] Error 2
Errors encountered, aborting!

As I understand from this thread crypt is no longer bundled in glibc. I have tried the various solutions in that post but to no avail. Wondering if someone can help me with directions for building against glibc 2.31.

I have tried adding the following to localoptions.h but it doesn't seem to help:

#define _GNU_SOURCE
#include <crypt.h>

My configure and make commands look like this:

./configure --host=arm-linux-gnueabihf --prefix=/usr \
      --disable-syslog \
      --enable-bundled-libtom \
      --disable-lastlog \
      --disable-utmp \
      --disable-utmpx \
      --disable-wtmp \
      --disable-wtmpx \
      --disable-zlib
make PROGRAMS="dropbear dbclient dropbearkey dropbearconvert scp"

I think maybe I need to add CFLAGS and LDFLAGS?

[mkj]

Since libcrypt is standalone you will need to install the armhf dev packages too.
From https://wiki.debian.org/Multiarch/HOWTO

dpkg --add-architecture armhf

Add these to /etc/apt/sources.list.d (the normal mirrors don't seem to have armhf)

deb [arch=armhf] http://ports.ubuntu.com/ focal main restricted
deb [arch=armhf] http://ports.ubuntu.com/ focal-updates main restricted

apt-get update (there may be 404s from armhf not existing on the normal mirror, you can probably solve that by adding [arch=amd64] to those lines in /etc/apt/sources.list)

apt install libcrypt-dev:armhf

Then Dropbear configure should run successfully.

[Doerthous]

I use another solution:

1. download standalone libcrypt from https://github.com/besser82/libxcrypt/
2. cross compile it with the following configurations (install to the cross-compiler directory):

   tar -xvf libxcrypt-4.4.28.tar.xz  
   cd libxcrypt-4.4.28
   ./configure --prefix=/usr/arm-linux-gnueabihf  CC=arm-linux-gnueabihf-gcc \
   --host=arm
   

3. compile dropbear

Environment:

• dropbear-dropbear-2022.82
• libxcrypt-4.4.28
• arm-linux-gnueabihf-gcc 9.4.0 (Ubuntu 9.4.0-1ubuntu1~20.04.1)

[harpreetsc1992]

I used the two approaches in the answer. I am still getting the same error. What information can I provide further in order to fix these issues?

[thom-nic]

mkj's solution worked for me. Are you building on Focal or Jammy host @harpreetsc1992?