Verify digital signature using php

Question

I have an email which is digitally signed.

email :

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

The below email has been digitally signed for test purposes. We will
now go on and save this signed email in our dms system.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.22 (MingW32)
Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/

iQEcBAEBAgAGBQJTnwd9AAoJEEWjhuB1kNr9dQcH/2YeZlHEfK/KOPg8XhpOY+4l
3camfFVya8JIzLHsOzhhdSqIItDr7VlGDrjrMgPPiD1abyy9zhcqZ18Kh8sUuFJV
/TA434rrnMJC0xmSzXl4uo+UagyNyCjzwR4TFCGP4Ob6SzPl/jxfrcfO5yXEdF1I
X6wgQUmnb3ZLczdPVXsKpwpVIGqX7diwe1CAZKxCmjZo9rr/MmDLLl7AjYq/WQDT
uOYqXs2IasOIiTGpYrqexBpDn1qRUNiKVgFSRUTfTjYGXYij9P635WTfeE1bQrn1
HpT9hKhipYPkFcELAor7asqAcnE0lc4Oy9NV2bUryss8ic/pkhiXvlohA3MpCDA=
=+IbK
-----END PGP SIGNATURE-----

Public Key:

-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v2.0.22 (MingW32)

mQENBFOfBmkBCAC6gH9rR185hiCADttaQeUp9Jc+4Zzx60E+ogWd33Tb1dNvK/IK
wqpnRpYI1CHVpqX0xWy8Ylcw3rLpPJ6BUzO3hWFLRMXAIXiemV/+VKrKysgm1Xdg
1PSAVfqmgkXLEEGGSj2OHNA0VVnl1G8AI8/SMpLqhS3PMz3X1nmBv4hLohugLla9
AVdYp6Me5OAWfjHswkUxCvc/fSh2ufFSnFxgjUibIyn+GP5qG8Wc+GjrBzTLzjA7
LvP198fWIHQ5w342F3WE8/9ec+1ir/a4japcFodRibXBEqltF+BXgk9pVcEXTd8O
FCxygrnSkWioj9Qf5uyjuKfV1F7Wq/Nu5uPZABEBAAG0JkFiaGluYXYgQWdnYXJ3
YWwgPGFiaGluYXZAdHJ1dGVjaC5vcmc+iQE/BBMBAgApBQJTnwZpAhsjBQkJZgGA
BwsJCAcDAgEGFQgCCQoLBBYCAwECHgECF4AACgkQRaOG4HWQ2v2F9Af/RAKCz0uo
xqrVe1MXqCe9ZCPSwlHGH4X4NtQbo7FTYy7K2fo9ucoKI4c2lHZA+Ef1K6BhZG34
IlXPSwy8nhTWJl7pi/xo7gEDlnHJMJCGvQcdtm4lkp39V2cy/Y0lS9V/EYmiesIX
tmPwwyYxo85jNsdmbjQKDTv5mcir9AebllCk2NlrxpyTO8oAnp1peHaHHq+U92e3
ZipHEiuAvE0U6WU/fA7tHoWoUor9AUm1hE5mSsyi+do4o/YJqGEgAss62v0npcBx
oyHoHum5XUgZ1kjvq40Mzkxo9N6vU7P7ULyt9FZylM+pk9XEqiz8IGTPW6JGiJS2
WmhJli2Szl1xgLkBDQRTnwZpAQgA27UvNu/m61pZwTBSQAVjLNJnJTlU4yh/DxKU
B3opw7JvvgXYB3VS9AyqSYaIJTcziCBZRewMH+WVpZwRk9SFMyeyNhuk9SGeGU9s
vyE5dGPa/U5zpvhaqn//CMdRr+wf6XeBKjzc9eKgWMrPLhzlHZ6kzLsbRsalOd4x
0M3aeO4SV00HFFfXVfJplNB8/zsHNNqtF5ACz9DX69p1GWJD6AAlu/s04xkkUScr
M2B5lHm6iU6NmfP1GeTD+rOyigcOrSlAL4QGIzGDfoDJOy9UYtk+YOv8UBa3IpG0
7sARkd+MZGUOgPWIDYQLiSi+9opFHtn4EzrvuUP3Zj1kN4ZUTwARAQABiQElBBgB
AgAPBQJTnwZpAhsMBQkJZgGAAAoJEEWjhuB1kNr9kHoIAKnjEAiH53ZrWYuummPR
PRztZL1K7LkxEAxQ00V+PMrg4wNlp1WW5Vl3X0jB5FqUTUmI/65MhoWa+Ucqg31c
pUOpw5OHK/cyrsscj+gL3nknhswWcvqBNQuiB8UO7Kt89yFYysA754sADKE+nDBM
D+kmlH4u3vvKep0hZ+gzvH3AOZDhijKJYN9zMMf/gtwZhlEm/N+yBpkP1sxcFsJ+
V5hduu4sqJnAcCWg3V/JXonAOZGPS/GE+wXt4Om1D/6RcBBtrBGwh/ezBFS/gSio
vGRcFzZYRhM1rMEu82raZ3ji3X/5fOjxvhSXdrajG3LX8s2gCk+a0nGDi3MYs5l0
p14=
=cn4r
-----END PGP PUBLIC KEY BLOCK-----

I want to write a program in php which will verify the digital signature. I have public key of the sender. I tried downloading GnuPG library from this site , but it is not getting downloaded.

Is there any other way? How should I do it? Any help will be appreciated.

Answer 1

PHP already brings a module for interfacing GnuPG , which is fairly easy to use.

GnuPG must already be installed, on Linux servers it usually is, on Windows machines I heard of getting PHP running together with GnuPG rather difficult.

For verifying signatures , use gnupg_verify(...) , example from the linked PHP documentation:

<?php
$plaintext = "";
$gpg = new gnupg();
// clearsigned
$info = $gpg -> verify($signed_text,false,$plaintext);
print_r($info);
// detached signature
$info = $gpg -> verify($signed_text,$signature);
print_r($info);
?>

You will have to import the signer's public key before verifying, if not done already.