openssl_pkey_get_public

(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

openssl_pkey_get_public — Extract public key from certificate and prepare it for use

Descrizione

openssl_pkey_get_public(OpenSSLAsymmetricKey|OpenSSLCertificate|array|string $public_key): OpenSSLAsymmetricKey|false

openssl_pkey_get_public() extracts the public key from public_key and prepares it for use by other functions.

Elenco dei parametri

public_key

public_key can be one of the following:

an OpenSSLAsymmetricKey instance
a string having the format file://path/to/file.pem. The named file must contain a PEM encoded certificate/public key (it may contain both).
A PEM formatted public key.

Valori restituiti

Returns an OpenSSLAsymmetricKey instance on success, or false on error.

Log delle modifiche

Versione	Descrizione
8.0.0	On success, this function returns an OpenSSLAsymmetricKey instance now; previously, a resource of type `OpenSSL key` was returned.
8.0.0	`public_key` accepts an OpenSSLAsymmetricKey or OpenSSLCertificate instance now; previously, a resource of type `OpenSSL key` or `OpenSSL X.509` was accepted.

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User Contributed Notes 12 notes

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info at steyla dot com ¶

13 years ago


If you are trying to read a PKCS#1 RSA public key you run into trouble, because openssl wants the public key in X.509 style.

The PKCS#1 RSA public key

-----BEGIN RSA PUBLIC KEY-----
MIIBCgKCAQEAgYxTW5Yj+5QiQtlPMnS9kqQ/HVp+T2KtmvShe68cm8luR7Dampmb
[...]
cbn6n2FsV91BlEnrAKq65PGJxcwcH5+aJwIDAQAB
-----END RSA PUBLIC KEY-----

.. is  not readable while the X.509 style public key

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAgYxTW5Yj+5QiQtlPMnS9
[..]
JwIDAQAB
-----END PUBLIC KEY-----

is. You can use an easy (and dirty) work around to read the PKCS#1 RSA anyway. The first few bytes of the X.509 style public key contain header information and can shamelessly be copied.

In other words: Delete everything after the first 32 bytes from the above X.509 key (starting behind Q8A) and attach your PKCS#1 data, reformat to 64 bytes length and use it with openssl.

Please note: The above example only works for 2048 bit length.

Like I said - it's kind of dirty - but hey - if you're as desperate as I was.

Michaela

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Joey ¶

8 years ago


I spent a few hours raging with this function and hitting my head on the desk trying to get it to load a public PEM key.

This function can leave errors in openssl_error_string even if it succeeded so this can cause a lot of confusion further down. Especially if you're prototyping and haven't put full checks on return values in yet. The error will not be cleared either when calling other functions successfully.

To avoid confusion, you should always check the return result and only call openssl_error_string after calling an openssl function that returned failure (false).

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Anonymous ¶

17 years ago


you can get (and save to file) public key using openssl_pkey_get_details(resource $key ) function:



<?php

$pub_key = openssl_pkey_get_public(file_get_contents('./cert.crt'));

$keyData = openssl_pkey_get_details($pub_key);

file_put_contents('./key.pub', $keyData['key']);

?>

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GeniusLe at zslm dot org ¶

4 years ago


You may need to export a public key from the private key, because the public key provided by the key generated by other tools is in pem format, and we need openssh format

```
<?php
$public = openssl_pkey_get_details(openssl_pkey_get_private(OPENSSL_USER_PRIVATE_KYE))['key'];

// save $public

```

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Anonymous ¶

20 years ago


This documentation notes it can take a PEM-formatted private key, but as per bug #25614, this is not possible in any form. The function simply returns a FALSE.

The only thing you can get public keys out of are X.509 certificates.

Furthermore, there is NO way to export a public key into a PEM-encoded form.

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-1

dankybastard at hotmail ¶

19 years ago


You must also use the string representation of the certificate to get the public key resource:

$dn = array();  // use defaults
$res_privkey = openssl_pkey_new();
$res_csr = openssl_csr_new($dn, $res_privkey);
$res_cert = openssl_csr_sign($res_csr, null, $res_privkey, $ndays);

openssl_x509_export($res_cert, $str_cert);

$res_pubkey = openssl_pkey_get_public($str_cert);

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-5

ppostma1 ¶

13 years ago


found the cert/public key for 2048 bits is this format:



-----BEGIN PUBLIC KEY-----

X509 signature + PEM sig + modulus + 'ID' + exponent

-----END PUBLIC KEY-----



so the variables are:

-----BEGIN PUBLIC KEY-----

'MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8A' . 'MIIBCgKCAQEA' . $modulus . 'ID' . $exponent

-----END PUBLIC KEY-----



<?php wordwrap($cert, 64, "\r\n", true); ?>

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-8

igniweb dot net at gmail dot com ¶

6 years ago


To complete http://php.net/manual/fr/function.openssl-pkey-get-public.php#101513

Michaela code retranscription can be :

$key = str_replace([
    '-----BEGIN RSA PUBLIC KEY-----',
    '-----END RSA PUBLIC KEY-----',
    "\r\n",
    "\n",
], [
    '',
    '',
    "\n",
    ''
], $key);

$key = 'MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8A' . trim($key);

$key = "-----BEGIN PUBLIC KEY-----\n" . wordwrap($key, 64, "\n", true) . "\n-----END PUBLIC KEY-----";

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-6

VaD ¶

16 years ago


Small error in this code:

$pub_key = openssl_pkey_get_public(file_get_contents('./cert.crt'));
$keyData = openssl_pkey_get_details($pub_key);
file_put_contents('./key.pub', $keyData['key']);

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-8

thelen dot shar at gmail dot com ¶

15 years ago


Found it difficult to get my head around this due to lack of documentation.

But the process I followed for all this was:
Generate private key:
openssl genrsa -des3 -out private.pem 1024

Generate public key:
openssl rsa -in private.pem -out public.pem -outform PEM -pubout

Then in PHP:
$passphrase = 'somestring';
$key_private = openssl_get_privatekey(file_get_contents('private.pem'), $passphrase);
$key_public = openssl_get_publickey(file_get_contents('public.pem'));

Probably not the best way of doing it, but a lot simpler than the other examples on the site. I was having trouble getting the pubkey, it wasn't exactly specified very well, and I had made a mistake in generating it so it wasn't working for that reason as well.

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-11

Paul Clark ¶

14 years ago


Note this will read public keys from PEM formatted public keys as well:



<?php

$key = <<<EOF

-----BEGIN PUBLIC KEY-----

MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDXX/MsKEBLcLeKA1d/i7ufG1qs

qS97xFkIRSeX3TwmHic843AfVrzoh2pZUeOvK9ZLZQpHSM7DoHMYDGD1273+FvZX

Ypf5LiFtecfxko/Cku16zy6WAeCYVFjjlveBhwPmPCIk+qDRYeiIW05QE2XK+CuD

nJ7sxxXIJSSgD3Jo5wIDAQAB

-----END PUBLIC KEY-----

EOF;



print $key;

$res = openssl_pkey_get_public($key);

print_r(openssl_pkey_get_details($res));

?>



Note that contrary to the documentation, openssl_pkey_get_details() will *not* read PEM directly, and you have to go through this step.

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-14

Rurri ¶

12 years ago


If you have a 4096 bit key pair and are trying to use a public key that begins with:

-----BEGIN RSA PUBLIC KEY-----
 
and you need to convert it for this function to use, you can convert it by prepending the static header information:

MIICIjANBgkqhkiG9w0BAQEFAAOCAg8A

Such as:

$start_key = str_replace('-----BEGIN RSA PUBLIC KEY-----', '', $start_key);
$start_key = trim(str_replace('-----END RSA PUBLIC KEY-----', '', $start_key));
$key = 'MIICIjANBgkqhkiG9w0BAQEFAAOCAg8A' . str_replace("\n", '', $start_key);
$key = "-----BEGIN PUBLIC KEY-----\n" . wordwrap($key, 64, "\n", true) . "\n-----END PUBLIC KEY-----";

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