Create a TXT record for DKIM using Net::DNS

nethawk has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks, i tried adding a TXT record via Net::DNS to a testdomain but having problems with escaping the semicolon.

my $txtdata = "v=DKIM1; k=rsa; t=y;p=MIGfMA0GCSqGSIb3DQAFGQUAA4GNADCBi
+QKBgQDwWV9npEVjm10XoR1NIx174X/SR+BW8yd4RaXMk+pSDwNx0bFK8fPCXf7tLtFbjC
+mYldyhsrnrcloWPVlJkAy41xaTGUcXWpC2Onr/ScbkXa9cuREv4Fy4YmMpHoBKSHoE2JI
+8wBEe4oOoHPojT/b+HTNoZmxfkrYqk5eN5jnUewIDAQAB";

my $a = ";";
my $b = "\\" . ";";

# trying to escape the ;
$txtdata =~ s/$a/$b/g;

my $update = Net::DNS::Update->new("domain.com");
$update->push("update", rr_add("porgy._domainkey.domain.com 600 TXT '$
+txtdata'"));
$update->sign_tsig("keyname", "keysign");
my $res = Net::DNS::Resolver->new;
$res->nameservers("ns.domain2.com");
my $reply = $res->send($update);
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If i do a

host -a porgy._domainkey.domain.com ns.domain2.com
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I get the TXT record back, but the semicolon is more than once escaped as:

"v=DKIM1\\\; k=rsa\\\; t=y\\\;p=MIGfMA0GC..."
[download]

Anyone is seeing an error on my side ? Thanks

Comment on Create a TXT record for DKIM using Net::DNS Select or Download Code

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Re: Create a TXT record for DKIM using Net::DNS by ww (Archbishop) on Feb 10, 2009 at 01:13 UTC
Assuming you want the output to singly escape the semi-colons, thusly: `v=DKIM1\; k=rsa\; t=y\;p=MIGfMA0GCSqGSIb3DQAFG....` you don't need to interpolate anything other than the escape (slash). Try using single quotes in the assignments `my $a = ';';` `my $b = "\\" . ';';` "A petty consistency..." would suggest single-quoting a single slash, too, but run with ActiveState (w32), `strict` and `warnings`, that fails. `Can't find string terminator "'" anywhere before EOF at 742623.pl line 8.` If you escape the slash (eg: `<c>my $b = '\\' . ';';`, Perl will not complain.	[reply] [d/l] [select]
Re^2: Create a TXT record for DKIM using Net::DNS by almut (Canon) on Feb 10, 2009 at 02:09 UTC
`'\'` doesn't work because there has to be some way to escape a single quote in a single-quoted literal, which is done - as usual - using a backslash. BTW, I wouldn't know why using single quotes here should make a difference with respect to what the OP wants to achieve.... (As to the OP's problem, my suspicion is that Net::DNS is doing some escaping on its own — though I haven't verified it.)	[reply] [d/l]
Re^3: Create a TXT record for DKIM using Net::DNS by nethawk (Initiate) on Feb 10, 2009 at 10:51 UTC
I assume too, that Net::DNS is making "some" escaping itself, although http://www.net-dns.org/docs/Net/DNS/RR/TXT.html states: For some applications of the TXT RR the semicolon is relevant, you will need to escape it on input. If i don't do escaping on $txtdata, i get a FORMERR back from bind.	[reply]