CODEWITHSUNDEEP
phpopenssldigital-signaturepublic-key
John Turner
John Turner

Reputation: 45

Failure to verify openssl signatures in PHP

If I use openssl to create a new key pair, use the private key to sign some data, and use the public key to verify the signature... it works.

$ openssl genrsa -out mykey.pem 1024
$ openssl rsa -in mykey.pem -pubout > mypubkey.pem
$ echo 'It could be bunnies' > file.txt
$ openssl rsautl -sign -in file.txt -inkey mykey.pem -out sig.txt
$ openssl rsautl -verify -in sig.txt -inkey mypubkey.pem -pubin
It could be bunnies

However, if I try to verify the signature using the openssl library in php it fails.

$pubkey = openssl_pkey_get_public(file_get_contents('/var/key/mypubkey.pem')); 
$sig = file_get_contents('/var/key/sig.txt');
$data = file_get_contents('/var/key/file.txt');
$verifyResult = (openssl_verify($data, $sig, $pubkey) == 1);

Similar story with Crypt_RSA

$pubkey = file_get_contents('/var/test/mypubkey.pem');
$sig = file_get_contents('/var/test/sig.txt');
$data = file_get_contents('/var/test/file.txt');
$rsa = new Crypt_RSA();
$rsa->loadKey($pubkey);
$rsa->verify($data, $sig);
$verifyResult = $rsa->verify($data, $sig);

How do I get php to play nicely? These examples are simplified but accurate to my needs. In the real world I will only have the data, signature, and public key...

Upvotes: 2

Views: 3416

Answers (2)

user1350492
user1350492

Reputation: 94

For phpseclib, try $rsa->setSignatureMode(CRYPT_RSA_SIGNATURE_PKCS1) before calling $rsa->verify().

Upvotes: 1

John Turner
John Turner

Reputation: 45

I was really hoping someone would chime in with a definitive answer on the public key question. Seems like it should work. However, in the meantime, I've switched from a public key to a self-signed certificate. The openssl library in PHP seems happy with extracting an acceptable public key from that. Which means the real problem (verifying signed data) is solved for me. Server clients will now have the data, signature, and x.509 certificate.

Here are the code snippet(s).

$ openssl genrsa -out server.key 4096
$ openssl req -new -key server.key -out server.csr
$ openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt
$ openssl dgst -sha1 -sign server.key -out file.sha1 file.txt

...

$pubkey = openssl_pkey_get_public(file_get_contents('/var/key/server.crt')); 
$sig = file_get_contents('/var/key/file.sha1');
$data = file_get_contents('/var/key/file.txt');
$verifyResult = (openssl_verify($data, $sig, $pubkey) == 1);

Upvotes: 2

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