Re: Reverse String (or get 2nd level domain sample)?

[Jarno Huuskonen]

Hi,

On Fri, Jun 29, Baptiste wrote:
> converters are just simple C functions, (or could be Lua code as well), and
> are quite trivial to write.
> Instead of creating a converter that reverse the order of chars in a
> string, I would rather patch current "word" converter to support negative
> integers.
> IE: -2 would means you extract the second word, starting at the end of the
> string.

No need to patch "word" for negative indexes. The functionality is
already there:
commit 9631a28275b7c04f441f7d1c3706a765586844e7
Author: Marcin Deranek 
Date:   Mon Apr 16 14:30:46 2018 +0200

MEDIUM: sample: Extend functionality for field/word converters

Extend functionality of field/word converters, so it's possible
to extract field(s)/word(s) counting from the beginning/end and/or
extract multiple fields/words (including separators) eg.

str(f1_f2_f3__f5),field(2,_,2)  # f2_f3
str(f1_f2_f3__f5),field(2,_,0)  # f2_f3__f5
str(f1_f2_f3__f5),field(-2,_,3) # f2_f3_
str(f1_f2_f3__f5),field(-3,_,0) # f1_f2_f3

str(w1_w2_w3___w4),word(3,_,2)  # w3___w4
str(w1_w2_w3___w4),word(2,_,0)  # w2_w3___w4
str(w1_w2_w3___w4),word(-2,_,3) # w1_w2_w3
str(w1_w2_w3___w4),word(-3,_,0) # w1_w2;

-Jarno

> On Mon, Jun 25, 2018 at 12:29 PM, Daniel Schneller <
> daniel.schnel...@centerdevice.com> wrote:
> 
> > Hi!
> >
> > Just double checking to make sure I am not simply blind: Is there a way to
> > reverse a string using a sample converter?
> >
> > Background: I need to extract just the second level domain from the host
> > header. So for sub.sample.example.com I need to fetch "example".
> >
> > Using the "word" converter and a "." as the separator I can get at the
> > individual components, but because the number of nested subdomains varies,
> > I cannot use that directly.
> >
> > My idea was to just reverse the full domain (removing a potential port
> > number first), get word(2) and reverse again. Is that possible? Or is there
> > an even better function I can use? I am thinking this must be a common use
> > case, but googling "haproxy" and "reverse" will naturally turn up lots of
> > results talking about "reverse proxying".
> >
> > If possible, I would like to avoid using maps to keep this thing as
> > generic as possible.
> >
> > Thanks a lot!
> >
> > Daniel

-- 
Jarno Huuskonen

Re: Reverse String (or get 2nd level domain sample)?

[Baptiste]

Hi,

converters are just simple C functions, (or could be Lua code as well), and
are quite trivial to write.
Instead of creating a converter that reverse the order of chars in a
string, I would rather patch current "word" converter to support negative
integers.
IE: -2 would means you extract the second word, starting at the end of the
string.

Baptiste



On Mon, Jun 25, 2018 at 12:29 PM, Daniel Schneller <
daniel.schnel...@centerdevice.com> wrote:

> Hi!
>
> Just double checking to make sure I am not simply blind: Is there a way to
> reverse a string using a sample converter?
>
> Background: I need to extract just the second level domain from the host
> header. So for sub.sample.example.com I need to fetch "example".
>
> Using the "word" converter and a "." as the separator I can get at the
> individual components, but because the number of nested subdomains varies,
> I cannot use that directly.
>
> My idea was to just reverse the full domain (removing a potential port
> number first), get word(2) and reverse again. Is that possible? Or is there
> an even better function I can use? I am thinking this must be a common use
> case, but googling "haproxy" and "reverse" will naturally turn up lots of
> results talking about "reverse proxying".
>
> If possible, I would like to avoid using maps to keep this thing as
> generic as possible.
>
> Thanks a lot!
>
> Daniel
>
>
> --
> Daniel Schneller
> Principal Cloud Engineer
>
> CenterDevice GmbH
> Rheinwerkallee 3
> 53227 Bonn
> www.centerdevice.com
>
> __
> Geschäftsführung: Dr. Patrick Peschlow, Dr. Lukas Pustina, Michael
> Rosbach, Handelsregister-Nr.: HRB 18655, HR-Gericht: Bonn,
> USt-IdNr.: DE-815299431
>
> Diese E-Mail einschließlich evtl. beigefügter Dateien enthält vertrauliche
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> dieser E-Mail ist nicht gestattet.
>
>
>

Re: Reverse String (or get 2nd level domain sample)?

[Daniel Schneller]

Hi again!

I found a working config using the map_regm converter.
I think it is somewhat overcomplicated for what it is supposed to achieve, but 
for now it works.

Leaving this here for reference:

# Remove port numbers from the Host header -- we do not rely on different 
ports for the same domain, and this makes ACL matching clearer
http-request replace-value Host '(.*):.*' '\1'

# Store the (now port-free) request Host in a transaction scoped variable 
for use in response ACLs
http-request set-var(txn.host) req.hdr(Host)

# Store the 2nd level domain (lower case) as the distributor. This uses a 
simple map file with just a single
# regex, because the inline regsub function does not support backrefs which 
are needed for variable number of subdomains.
http-request set-var(txn.distributor) 
var(txn.host),map_regm(distributors.map,"unknown"),lower

# Add a X-Distributor header for the application, overwriting anything the 
client may have claimed
http-request set-header X-Distributor %[var(txn.distributor)]

The distributors.map file contents looks like this:

(.*\.)+(.*)\.(.*) \2

Looks more complicated than it is. The first "(.*\.)+" greedily matches 
subdomains (in our case only domains with at least three parts are valid) and 
their trailing dots.
The second capture group matches the second level domain, followed by a dot, 
and then the final capture group "(.*)" for the top level domain.
The final one doesn't _have_ to be a group, because I drop the top level domain 
anyway. , but I find it more readable this way.

Anything that matches this regex is replaced with just the value of the 2nd 
capture group (i. e. the 2nd level domain).

(tested with haproxy 1.8, but this should also work with earlier versions IMO).

Cheers,
Daniel





> On 25. Jun 2018, at 12:29, Daniel Schneller 
>  wrote:
> 
> Hi!
> 
> Just double checking to make sure I am not simply blind: Is there a way to 
> reverse a string using a sample converter?
> 
> Background: I need to extract just the second level domain from the host 
> header. So for sub.sample.example.com  I need 
> to fetch "example".
> 
> Using the "word" converter and a "." as the separator I can get at the 
> individual components, but because the number of nested subdomains varies, I 
> cannot use that directly.
> 
> My idea was to just reverse the full domain (removing a potential port number 
> first), get word(2) and reverse again. Is that possible? Or is there an even 
> better function I can use? I am thinking this must be a common use case, but 
> googling "haproxy" and "reverse" will naturally turn up lots of results 
> talking about "reverse proxying".
> 
> If possible, I would like to avoid using maps to keep this thing as generic 
> as possible.
> 
> Thanks a lot!
> 
> Daniel
> 
> 
> --
> Daniel Schneller
> Principal Cloud Engineer
> 
> CenterDevice GmbH
> Rheinwerkallee 3
> 53227 Bonn
> www.centerdevice.com 
> 
> __
> Geschäftsführung: Dr. Patrick Peschlow, Dr. Lukas Pustina, Michael Rosbach, 
> Handelsregister-Nr.: HRB 18655, HR-Gericht: Bonn, USt-IdNr.: DE-815299431
> 
> Diese E-Mail einschließlich evtl. beigefügter Dateien enthält vertrauliche 
> und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige 
> Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie 
> bitte sofort den Absender und löschen Sie diese E-Mail und evtl. beigefügter 
> Dateien umgehend. Das unerlaubte Kopieren, Nutzen oder Öffnen evtl. 
> beigefügter Dateien sowie die unbefugte Weitergabe dieser E-Mail ist nicht 
> gestattet.
> 
> 



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Reverse String (or get 2nd level domain sample)?

[Daniel Schneller]

Hi!

Just double checking to make sure I am not simply blind: Is there a way to 
reverse a string using a sample converter?

Background: I need to extract just the second level domain from the host 
header. So for sub.sample.example.com  I need 
to fetch "example".

Using the "word" converter and a "." as the separator I can get at the 
individual components, but because the number of nested subdomains varies, I 
cannot use that directly.

My idea was to just reverse the full domain (removing a potential port number 
first), get word(2) and reverse again. Is that possible? Or is there an even 
better function I can use? I am thinking this must be a common use case, but 
googling "haproxy" and "reverse" will naturally turn up lots of results talking 
about "reverse proxying".

If possible, I would like to avoid using maps to keep this thing as generic as 
possible.

Thanks a lot!

Daniel


--
Daniel Schneller
Principal Cloud Engineer

CenterDevice GmbH
Rheinwerkallee 3
53227 Bonn
www.centerdevice.com

__
Geschäftsführung: Dr. Patrick Peschlow, Dr. Lukas Pustina, Michael Rosbach, 
Handelsregister-Nr.: HRB 18655, HR-Gericht: Bonn, USt-IdNr.: DE-815299431

Diese E-Mail einschließlich evtl. beigefügter Dateien enthält vertrauliche 
und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige 
Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie 
bitte sofort den Absender und löschen Sie diese E-Mail und evtl. beigefügter 
Dateien umgehend. Das unerlaubte Kopieren, Nutzen oder Öffnen evtl. beigefügter 
Dateien sowie die unbefugte Weitergabe dieser E-Mail ist nicht gestattet.




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