libyajl not found. Build script not searching correct directories.

[RooHTaylor]

Describe the bug

When trying to ./configure --with-yajl YAJL can never be found. If I specify --with-yajl="/usr/include/yajl" it will find the YAJL headers, but still report that YAJL was not found. If I include multiple paths in --with-yajl="" it continues to find nothing.

I tried to uninstall libyajl-dev from my package manager and manually compile yajl from sources. I experieced the same results with any combination of /usr/local/{include,lib} in the path.

After some digging I found that ./build/yajl.m4 tries to use pkg-config to find YAJL first, and then falls back to directory scanning. However, it appears the list of directories to check is stored in YAJL_POSSIBLE_PATHS while the script is passing YAJL_POSSIBLE_LIB_NAMES to CHECK_FOR_YAJL_AT() on line 65.

# If pkg-config did not find anything useful, go over file lookup.
for x in ${YAJL_POSSIBLE_LIB_NAMES}; do
        CHECK_FOR_YAJL_AT(${x})
        if test -n "${YAJL_VERSION}"; then
            break
    fi
done

Reviewing the definition of CHECK_FOR_YAJL_AT() it expects 'path' as the first argumant, and then loops through the YAJL_POSSIBLE_EXTENSIONS and YAJL_POSSIBLE_LIB_NAMES inside the function to search that path.

AC_DEFUN([CHECK_FOR_YAJL_AT], [
    path=$1
    for y in ${YAJL_POSSIBLE_EXTENSIONS}; do
        for z in ${YAJL_POSSIBLE_LIB_NAMES}; do
...

By modifying the loop defined on line 65 to loop over YAJL_POSSIBLE_PATHS instead of YAJL_POSSIBLE_LIB_NAMES and running ./build.sh again, YAJL is found correctly.

Additionally, if multiple directories are provided, for example --with-yajl="<dir1> <dir2>", they are not all searched. Instead they are treated as a single directory. In the yajl.m4 file on line 73 the script checks for --with-yajl with an argument and passes the argument to CHECK_FOR_YAJL_AT() as a path. Instead, it would be optimal to loop over provided paths and search each one.

Logs and dumps

There was no useful log information. The config.log simply reported that YAJL could not be found and/or that sometimes the headers were found, but that YAJL still was not found. There was no indication that paths were being checked at all.

To Reproduce

Steps to reproduce the behavior:

sudo apt install -y libyajl-dev
git clone --recursive [email protected]:owasp-modsecurity/ModSecurity.git
cd ModSecurity
./build.sh
./configure --with-yajl

You can try any combination of paths in --with-yajl and it fails to find it.

Expected behavior

Obviously the expected behaviour is that YAJL should be found if specifying --with-yajl.

Server (please complete the following information):

• ModSecurity version: 3.0.13
• OS (and distro): Debian 12.9

[airween]

Hi @RooHTaylor,

thanks for reporting this.

When I read your comment my first idea was try to build the library without --with-yajl option - but then I saw you tried that.

Yes, that seems like a bug in build system, and if I'm right you successfully solved that issue - would you mind to send a PR to fix that?

[airween]

Closing as completed through #3335 - thanks again @RooHTaylor.