Decrypt openssl-encrypted data?

[Philippe Lang]

Hi,

I'm trying to decode with pidCrypt some data which has been encrypted with openssl, and I have a few problems. Here is what I'm doing server-side:

# Generate encrypted private key.
openssl genrsa -aes256 -out private.key

# Extract public key from private key.
openssl rsa -in private.key -pubout > public.key

# Encrypt with public key, and encode in Base64
echo 'Hello Trac!' | openssl rsautl -encrypt -pubin -inkey public.key | base64 > encrypted_with_public_key

My goal is to decrypt the content of file "encrypted_with_public_key" with pidCrypt, the private key, and the password chosen to encrypt the private key.

Here is the javascript code I'm using:

:::javascript
// Get input data
private_key_encoded = $("div.password > .private_key_encoded").html();
password_encrypted_base64 = $("div.password > .encrypted_password").html();

// Parse the private key
params = certParser(private_key_encoded);

// Aes-cbc decoding
aes = new pidCrypt.AES.CBC();
salt = params.salt;
k_and_iv = aes.createKeyAndIv({password:data.password, salt:salt, bits:params.bits});
aes.initByValues(params.b64, k_and_iv.key, params.iv.toLowerCase(), {UTF8:false, A0_PAD:false, nBits:params.bits});
rsapem_decrypted = aes.decrypt();

// ASN1 Parsing
decryptedBytes = pidCryptUtil.toByteArray(rsapem_decrypted);
asn = pidCrypt.ASN1.decode(decryptedBytes);
asnTree = asn.toHexTree();

// RSA decoding
rsa = new pidCrypt.RSA();
// Set the private key based on the result of the ASN1 parsing
rsa.setPrivateKeyFromASN(asnTree);
// Prepare text to decode
ciphertext = pidCryptUtil.decodeBase64(pidCryptUtil.stripLineFeeds(password_encrypted_base64));
// Decode
plain = rsa.decrypt(pidCryptUtil.convertToHex(ciphertext));

alert('Data: ' + plain);

Plaintext return is always empty. But key decoding seems to work. Do you see any reason why this shouldn't work?

Thanks!

[Philippe Lang]

I was able to decode my rsa encrypted string by using a hack I still don't understand, after noticing a bunch of "f" at the end of the cipher, just before decryption.

:::javascript
ciphertext = ciphertext.substring(0, ciphertext.length - 9);

I might have unneeded trailing characters in my encoded string.

[Jonah (pidder)]

It might be a padding issue. Please try using PKCS#1 v1.5 (see https://www.openssl.org/docs/apps/rsautl.html).

We demonstrate a working example in this thread. Please let us know if this does not solve your issue.

Best,
Jonah

[Philippe Lang]

Hi,

I tried all combinations of openssl paddings, but none seems to work. In particular, here are the openssl options I have tried:

-pkcs: (the default) works with my hack, doesn't work without.
-oaep: doesn't work at all, with or without hack.
-ssl: works with my hack, doesn't work without.
-raw: doesn't work at all, with or without hack.

Using OpenSSL 1.0.1e 11 Feb 2013, on Debian SID.

[Philippe Lang]

Sorry, this was my fault from the beginning: I'm reading the encoded password through jquery, and I didn't take care of a few empty characters in the HTML file, which used to look like:

:::html
            <div class="hide encrypted_password">
VcKQBg6PNAfBtrBTmeE4m5xAiX/s42aCdj+vCh+oNaD5LqCa9v6kqz+cCp3Wg6U5LwSsIRT0SgAs
DF4NU7dgv2GSSkL6L9bpjOF7UP3CQlm96sMfhkGZ0P/Ka1EoGuxFe6A1WMOhL9BEw+twQm70OdpN
eP4/vS3PF5rSXuTruWY=
            </div>

Works fine like so:

:::html
            <div class="hide encrypted_password">
VcKQBg6PNAfBtrBTmeE4m5xAiX/s42aCdj+vCh+oNaD5LqCa9v6kqz+cCp3Wg6U5LwSsIRT0SgAs
DF4NU7dgv2GSSkL6L9bpjOF7UP3CQlm96sMfhkGZ0P/Ka1EoGuxFe6A1WMOhL9BEw+twQm70OdpN
eP4/vS3PF5rSXuTruWY=</div>

Sorry for that! :)

[Jonah (pidder)]

No problem and we're glad you have figured it out!