Apache DBD Auth not working with mysql

Thanks Andreas for this report. Apparently the same problem happens in Eoan too. The minimal steps to reproduce are:

1. start a fresh LXD container
2. apt update
3. apt install apache2 libaprutil1-dbd-mysql
4. a2enmod authn_dbd (also enables the dbd module)
5. systemctl restart apache2
6. curl localhost => It works!
7. echo DBDriver mysql > /etc/apache2/conf-available/dbd_mysql.conf
8. a2enconf dbd_mysql
9. systemctl reload apache2

This last reload fails on Eoan and Focal with error:

apachectl[2695]: AH00526: Syntax error on line 1 of /etc/apache2/conf-enabled/dbd_mysql.conf:
apachectl[2695]: Can't load driver file apr_dbd_mysql.so
apachectl[2695]: Action 'graceful' failed.

but succeeds on Bionic.

This is still present six weeks later in the 20.04 daily build.
Running this with strace seems to indicate that indeed the library is successfully loaded:

openat(AT_FDCWD, "/usr/lib/x86_64-linux-gnu/apr-util-1/apr_dbd_mysql-1.so", O_RDONLY|O_CLOEXEC) = 7
read(7, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\20(\0\0\0\0\0\0"..., 832) = 832
fstat(7, {st_mode=S_IFREG|0644, st_size=27288, ...}) = 0
mmap(NULL, 29208, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 7, 0) = 0x7f90a4122000
mmap(0x7f90a4124000, 12288, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 7, 0x2000) = 0x7f90a4124000
mmap(0x7f90a4127000, 4096, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 7, 0x5000) = 0x7f90a4127000
mmap(0x7f90a4128000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 7, 0x5000) = 0x7f90a4128000
close(7) = 0
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 7
fstat(7, {st_mode=S_IFREG|0644, st_size=78933, ...}) = 0
mmap(NULL, 78933, PROT_READ, MAP_PRIVATE, 7, 0) = 0x7f90a410e000
close(7) = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libmysqlclient.so.21", O_RDONLY|O_CLOEXEC) = 7
read(7, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0 \222\2\0\0\0\0\0"..., 832) = 832
fstat(7, {st_mode=S_IFREG|0644, st_size=7256008, ...}) = 0
mmap(NULL, 7279960, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 7, 0) = 0x7f90a3a1c000
mprotect(0x7f90a3a43000, 3997696, PROT_NONE) = 0
mmap(0x7f90a3a43000, 942080, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 7, 0x27000) = 0x7f90a3a43000
mmap(0x7f90a3b29000, 3051520, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 7, 0x10d000) = 0x7f90a3b29000
mmap(0x7f90a3e13000, 3100672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 7, 0x3f6000) = 0x7f90a3e13000
mmap(0x7f90a4108000, 21848, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f90a4108000
close(7) = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libstdc++.so.6", O_RDONLY|O_CLOEXEC) = 7
read(7, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\240\341\t\0\0\0\0\0"..., 832) = 832
fstat(7, {st_mode=S_IFREG|0644, st_size=1952928, ...}) = 0
mmap(NULL, 1968128, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 7, 0) = 0x7f90a383b000
mprotect(0x7f90a38d1000, 1286144, PROT_NONE) = 0
mmap(0x7f90a38d1000, 983040, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 7, 0x96000) = 0x7f90a38d1000
mmap(0x7f90a39c1000, 299008, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 7, 0x186000) = 0x7f90a39c1000
mmap(0x7f90a3a0b000, 57344, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 7, 0x1cf000) = 0x7f90a3a0b000
mmap(0x7f90a3a19000, 10240, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f90a3a19000
close(7) = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libgcc_s.so.1", O_RDONLY|O_CLOEXEC) = 7
read(7, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\3405\0\0\0\0\0\0"..., 832) = 832
fstat(7, {st_mode=S_IFREG|0644, st_size=104984, ...}) = 0
mmap(NULL, 107600, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 7, 0) = 0x7f90a3820000
mmap(0x7f90a3823000, 73728, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 7, 0x...

The build logs show this:
/home/ubuntu/deb/apr-util/apr-util-1.6.1/dbd/apr_dbd_mysql.c:1267:5: warning: implicit declaration of function ‘my_init’; did you mean ‘mysql_init’? [-Wimplicit-function-declaration]
 1267 | my_init();
      | ^~~~~~~
      | mysql_init

Checking the mysql 8 release notes at https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-2.html we see:
"""
The my_init() function is no longer included in the list of symbols exported from libmysqlclient. It need not be called explicitly by client programs because it is called implicitly by other C API initialization functions.
"""

In the dbd/apr_dbd_mysql.c code, it is called like this:
static void dbd_mysql_init(apr_pool_t *pool)
{
#if MYSQL_VERSION_ID < 100000
    my_init();
#endif
    mysql_thread_init();

Dropping that my_init() call fixed the loading of the module for me. I'll publish a ppa for people to test.

PPA with builds for eoan and focal: https://launchpad.net/~ahasenack/+archive/ubuntu/mysql8-my-init/

Note: focal build does not have proposed enabled.

This bug was fixed in the package apr-util - 1.6.1-4ubuntu2

---------------
apr-util (1.6.1-4ubuntu2) focal; urgency=medium

  * d/p/mysql8-my_init.patch: don't call my_init() since it's not
    exported anymore since MySQL 8.0.2 (LP: #1859773)

 -- Andreas Hasenack <email address hidden> Wed, 04 Mar 2020 16:51:27 -0300

Hello Andreas, or anyone else affected,

Accepted apr-util into eoan-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/apr-util/1.6.1-4ubuntu0.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-eoan to verification-done-eoan. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-eoan. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

Tested the 1.6.1-4ubuntu0.1 version and it worked for me. After upgrading to 19.10 and newer MySQL, the apr_dbd_mysql.so would not load. All configuration, permissions, apache and apr-dbd packages seemed to be the same. Found this bug and did a one off install of the apr and apr-mysql .debs from proposed and everything works again.

This bug was fixed in the package apr-util - 1.6.1-4ubuntu0.1

---------------
apr-util (1.6.1-4ubuntu0.1) eoan; urgency=medium

  * d/p/mysql8-my_init.patch: don't call my_init() since it's not
    exported anymore since MySQL 8.0.2 (LP: #1859773)

 -- Andreas Hasenack <email address hidden> Wed, 04 Mar 2020 17:00:31 -0300

The verification of the Stable Release Update for apr-util has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.