Decrypt openssl certificate - ssl

Question

I generated 3 keys / certificates using this script:
#!/bin/sh
AUTH='/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android#android.com'
if [ "$1" == "" ]; then
echo "Create a test certificate key."
echo "Usage: $0 NAME"
echo "Will generate NAME.pk8 and NAME.x509.pem"
echo " $AUTH"
exit
fi
openssl genrsa -3 -out $1.pem 2048
openssl req -new -x509 -key $1.pem -out $1.x509.pem -days 10000 \
-subj "$AUTH"
echo "Please enter the password for this key:"
openssl pkcs8 -in $1.pem -topk8 -outform DER -out $1.pk8 -passout stdin
The output is:
releasekey.pem
releasekey.pk8
releasekey.x509.pem
Then I'm trying to decrypt it using this command:
openssl pkcs8 -in ~/.android-certs/releasekey.pk8 -inform DER
So, the output is
alex-garmas-osx:android alex-garmash$ openssl pkcs8 -in ~/.android-
certs/releasekey.pk8 -inform DER
Enter Password:
-----BEGIN PRIVATE KEY-----
CONTENT OF PRIVATE KEY HERE
-----END PRIVATE KEY-----
And it works OK. releasekey.pk8 doesn't have a passphrase
When I do the same with the command:
openssl pkcs8 -in ~/.android-certs/releasekey.pk8 -inform DER -nocrypt
I have an error:
140735885419528:error:0D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag:tasn_dec.c:1200:
140735885419528:error:0D06C03A:asn1 encoding routines:ASN1_D2I_EX_PRIMITIVE:nested asn1 error:tasn_dec.c:768:
140735885419528:error:0D08303A:asn1 encoding routines:ASN1_TEMPLATE_NOEXP_D2I:nested asn1 error:tasn_dec.c:700:Field=version, Type=PKCS8_PRIV_KEY_INFO
In the documentation I see that I can use option -nocrypt, but why is it failing?
UPDATE
Many thanks to #bartonjs for the explanation. To solve this problem you need to add -nocrypt flag to the last command of the script, then you can use the command above to decrypt generated key
#!/bin/sh
AUTH='/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android#android.com'
if [ "$1" == "" ]; then
echo "Create a test certificate key."
echo "Usage: $0 NAME"
echo "Will generate NAME.pk8 and NAME.x509.pem"
echo " $AUTH"
exit
fi
openssl genrsa -3 -out $1.pem 2048
openssl req -new -x509 -key $1.pem -out $1.x509.pem -days 10000 \
-subj "$AUTH"
echo "Please enter the password for this key:"
openssl pkcs8 -in $1.pem -topk8 -outform DER -out $1.pk8 -passout stdin -nocrypt

Answer 1

You are getting prompted for the empty password, and it succeeds, and with -nocrypt it is failing.
There's a difference between "encrypted with the empty password" and "not encrypted" (though to a brute forcer, not much of one).
An unencrypted PKCS#8 blob looks like (ASN.1):
PrivateKeyInfo ::= SEQUENCE {
version Version,
privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
privateKey PrivateKey,
attributes [0] IMPLICIT Attributes OPTIONAL }
If it has been encrypted, then it's
EncryptedPrivateKeyInfo ::= SEQUENCE {
encryptionAlgorithm EncryptionAlgorithmIdentifier,
encryptedData EncryptedData }
EncryptionAlgorithmIdentifier ::= AlgorithmIdentifier
EncryptedData ::= OCTET STRING
So -nocrypt tells OpenSSL that it should expect the first structure directly, whereas yours looks like the second (notably, the first child of the SEQUENCE wasn't an INTEGER, but was another SEQUENCE).
And saying that your data was encrypted with the empty password doesn't mean it was encrypted with some sort of empty key. The creator of the PKCS#8 file almost certainly went through the trouble of picking a random salt to the PBKDF2 algorithm, which then gets combined with the empty password to produce an output. That data is still noise, just... easier to brute force noise than normal.