PHP : Get private key from a single line private key - php

Question

I am trying to create a JWT token. The other server is storing the public key in a single line and using that for validation.
Also, the public key being used for validation is in single line.
So, to generate the correct JWT token, what I think is I should also use the private key in a single line (may be with \n or may be without).
I am using openssl_sign to generate the token, which uses openssl_reource as key. I get that paramter from openssl_pkey_get_private.
But problem which happens in this case is, it either accepts the pem file path, or the key in PEM string format. So, if I pass the private_key as a single line, it doesn't give me the required output.
So, how can I resolve this. As I see other language libraries able to generate signature by passing private key in a single line.

Answer 1

In PHP the key can be formatted with line breaks or as a one-liner (with \n). Both works. In the following example I use a 512-bit encrypted RSA-key for simplicity (although in practice a larger key (>= 2048 bit) must be used for security reasons):
<?php
// Private key: 512 bit for simplicity
// Passphrase: MyPassphrase
// openssl genrsa -aes256 -out private.pem 512
$privKeyEnc = "-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-256-CBC,8F2D6F9594B3D379BF9D9748BD174458
RP2fyz1VNBKHiCadC5B9fjxV7z7AMAqbsN2vykFfPhdUFsxlJaecEeTMT7s6IbZN
Pr80+ljLjJ0SxJiK+j8DAc/Wrf+qyYUFcWbsvOhUIPyB5ww9+mEeIERJCigsyZJ7
k/Apau/BypdC9vCXKB3wM9FcmvP1g/ZwVoXfN3TIPEfWTktvuf74yFNoIaVbZAK/
+tzAGduu9wLkr6WTq4Isqy/IPjVCp9VwH1wNnz+hjkO7oELcCpFieIvAidUMKBR9
EdexLQCimbOl2wlfRNLincK8+FDOVWx6ElFFQlhzyWQCt8ed1fdiAggKxOco4Ww2
tFjIzaO4KXlbc9JFGd9PzigpftN/aHbk3c+x0E+3q5u8eySai4vgk38s1KaE7rn/
rarCgtGxOlbbTkI3opkjIrGlrsEyexKtS23mI/Dgcco=
-----END RSA PRIVATE KEY-----";
// One-liner using \n
$privKeyEnc_1Line = "-----BEGIN RSA PRIVATE KEY-----\nProc-Type: 4,ENCRYPTED\nDEK-Info: AES-256-CBC,8F2D6F9594B3D379BF9D9748BD174458\n\nRP2fyz1VNBKHiCadC5B9fjxV7z7AMAqbsN2vykFfPhdUFsxlJaecEeTMT7s6IbZN\nPr80+ljLjJ0SxJiK+j8DAc/Wrf+qyYUFcWbsvOhUIPyB5ww9+mEeIERJCigsyZJ7\nk/Apau/BypdC9vCXKB3wM9FcmvP1g/ZwVoXfN3TIPEfWTktvuf74yFNoIaVbZAK/\n+tzAGduu9wLkr6WTq4Isqy/IPjVCp9VwH1wNnz+hjkO7oELcCpFieIvAidUMKBR9\nEdexLQCimbOl2wlfRNLincK8+FDOVWx6ElFFQlhzyWQCt8ed1fdiAggKxOco4Ww2\ntFjIzaO4KXlbc9JFGd9PzigpftN/aHbk3c+x0E+3q5u8eySai4vgk38s1KaE7rn/\nrarCgtGxOlbbTkI3opkjIrGlrsEyexKtS23mI/Dgcco=\n-----END RSA PRIVATE KEY-----";
// Public key:
// Passphrase: MyPassphrase
// openssl rsa -in private.pem -outform PEM -pubout -out public.pem
$pubKey = "-----BEGIN PUBLIC KEY-----
MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAMjYQLbdIVgKX1mSyKijOIpmlB9YWui1
KoCniRNHUPEsxth+o9fZXZMo1gzh9ZlFs6VLiyU7kv2+5QElOnhNzwcCAwEAAQ==
-----END PUBLIC KEY-----";
// One-liner using \n
$pubKey_1Line = "-----BEGIN PUBLIC KEY-----\nMFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAMjYQLbdIVgKX1mSyKijOIpmlB9YWui1\nKoCniRNHUPEsxth+o9fZXZMo1gzh9ZlFs6VLiyU7kv2+5QElOnhNzwcCAwEAAQ==\n-----END PUBLIC KEY-----";
$dataToSign = 'The quick brown fox jumps over the lazy dog.';
// Signing
//$privateKey = openssl_pkey_get_private("$privKeyEnc", "MyPassphrase"); // also works
$privateKey = openssl_pkey_get_private("$privKeyEnc_1Line", "MyPassphrase");
openssl_sign($dataToSign, $signature, $privateKey, 'sha256');
$signatureBase64 = base64_encode($signature);
print("Signature (Base64): ".$signatureBase64."<br>");
// Verifying
$publicKey = openssl_pkey_get_public("$pubKey");
//$publicKey = openssl_pkey_get_public("$pubKey_1Line"); // also works
$verified = openssl_verify($dataToSign, $signature, $publicKey,'sha256');
print("Verification: ".$verified."<br>");
/*
Output:
Signature (Base64): KVuUd+xy6at0emmhF20rbiD9lWzIN9euwKbeEm7aMvxqEkJ68HrjAoDJ37R3QGPI24woXY3TON9pahAhx+YNhQ==
Verification: 1
*/
?>