Support PCRE2

[martinhsv]

This pull request provides initial support for PCRE2 on an experimental basis. (Closes #2668 )

To use PCRE2 with nginx and ModSecurity you need to:

• use a version of nginx that supports it (e.g. nginx v1.21.5 or 1.21.6)
• use a version of the connector (ModSecurity-nginx) at or later than owasp-modsecurity/ModSecurity-nginx@1c32794
• include the --with-pcre2 option when running ModSecurity's ./configure

[istiak101]

Do I need to pass the PCRE2 path too? Explicit --with-pcre2=yes didn't work.

checking for libpcre config script... no
configure: *** pcre library not found.
configure: error: pcre library is required

I don't know it's using build/pcre.m4 instead of build/pcre2.m4

Compiling with PCRE1 works.

[istiak101]

So PCRE1 config binary location is /usr/bin/pcre-config and PCRE2 config binary /usr/bin/pcre2-config.
In PCRE1 the config script is detected correctly but not with PCRE2.

[dvershinin]

@istiak101 @martinhsv apparently there's a bug somewhere.

--with-pcre2 only compiles fine if both pcre1 and pcre2 devel libs installed. And the resulting binary links with both, which is incorrect, of course.

If only pcre2 devel is installed on the system, the error message during configure is always configure: error: pcre library is required.

See filed new bug #2750

[martinhsv]

Hello @istiak101 ,

As @dvershinin has noted, the dependency on pcre1 has not been removed even if you specifically want to use pcre2. But beyond that, does it work if you just use (although =yes should work too):

./configure --with-pcre2

[istiak101]

Hello @martinhsv,

Yes if install both pcre-devel and pcre2-devel it works.