CODEWITHSUNDEEP
apachessl
M.N
M.N

Reputation: 11078

Do I need to convert .CER to .CRT for Apache SSL certificates? If so, how?

I need to setup an Apache 2 server with SSL.

I have my *.key file, but all the documentation I've found online, *.crt files are specified, and my CA only provided me with a *.cer file.

Are *.cer files the same as *.crt? If not, how can I convert CER to CRT format?

Upvotes: 180

Views: 607551

Answers (12)

Linh Vu
Linh Vu

Reputation: 970

.cer: binary DER format

.crt: base64 PEM format

.cer -> .crt (DER to PEM):

openssl x509 -inform DER -in certificate.cer -outform PEM -out certificate.crt

.crt -> .cer (PEM to DER):

openssl x509 -inform PEM -in certificate.crt -outform DER -out certificate.cer

Upvotes: 6

rinilnath
rinilnath

Reputation: 136

Here is one case that worked for me if we need to convert .cer to .crt, though both of them are contextually same

Generate crt file: openssl pkcs12 -in identity.p12 -nokeys -out mycertificate.crt

Generate key file: openssl pkcs12 -in identity.p12 -out mycertificate.key -nodes -nocerts

where we should have a valid private key (identity.p12) PKCS 12 format, this one i generated from keystore (.jks file) provided by CA (Certification Authority) who created my certificate.

Upvotes: 2

user65839
user65839

Reputation:

File extensions for cryptographic certificates aren't really as standardized as you'd expect. Windows by default treats double-clicking a .crt file as a request to import the certificate into the Windows Root Certificate store, but treats a .cer file as a request just to view the certificate. So, they're different in the sense that Windows has some inherent different meaning for what happens when you double click each type of file.

But the way that Windows handles them when you double-click them is about the only difference between the two. Both extensions just represent that it contains a public certificate. You can rename a certificate file to use one extension in place of the other in any system or configuration file that I've seen. And on non-Windows platforms (and even on Windows), people aren't particularly careful about which extension they use, and treat them both interchangeably, as there's no difference between them as long as the contents of the file are correct.

Making things more confusing is that there are two standard ways of storing certificate data in a file: One is a "binary" X.509 encoding, and the other is a "text" base64 encoding that usually starts with "-----BEGIN CERTIFICATE-----". These encode the same data but in different ways. Most systems accept both formats, but, if you need to, you can convert one to the other via openssl or other tools. The encoding within a certificate file is really independent of which extension somebody gave the file.

Upvotes: 157

Hugo L.M
Hugo L.M

Reputation: 1083

I use command:

openssl x509 -inform PEM -in certificate.cer -out certificate.crt

But CER is an X.509 certificate in binary form, DER encoded. CRT is a binary X.509 certificate, encapsulated in text (base-64) encoding.

Because of that, you maybe should use:

openssl x509 -inform DER -in certificate.cer -out certificate.crt

And then to import your certificate:

Copy your CA to dir:

/usr/local/share/ca-certificates/

Use command:

sudo cp foo.crt /usr/local/share/ca-certificates/foo.crt

Update the CA store:

sudo update-ca-certificates

Upvotes: 37

Liibo
Liibo

Reputation: 1341

Basically there are two CER certificate encoding types, DER and Base64. When type DER returns an error loading certificate (asn1 encoding routines), try the PEM and it shall work.

openssl x509 -inform DER -in certificate.cer -out certificate.crt

openssl x509 -inform PEM -in certificate.cer -out certificate.crt

Upvotes: 124

mburakkalkan
mburakkalkan

Reputation: 1178

If your cer file has binary format you must convert it by

openssl x509 -inform DER -in YOUR_CERTIFICATE.cer -out YOUR_CERTIFICATE.crt

Upvotes: 7

Dmitry G
Dmitry G

Reputation: 708

According to documentation mod_ssl:

SSLCertificateFile: 
   Name: SSLCertificateFile
   Description: Server PEM-encoded X.509 certificate file

Certificate file should be PEM-encoded X.509 Certificate file:

openssl x509 -inform DER -in certificate.cer -out certificate.pem

Upvotes: 56

Mutuma
Mutuma

Reputation: 1955

Just do

openssl x509 -req -days 365 -in server.cer -signkey server.key -out server.crt

Upvotes: -2

Alexander Presber
Alexander Presber

Reputation: 6625

The answer to the question how to convert a .cer file into a .crt file (they are encoded differently!) is:

openssl pkcs7 -print_certs -in certificate.cer -out certificate.crt

Upvotes: 17

Spawnrider
Spawnrider

Reputation: 1773

CER is an X.509 certificate in binary form, DER encoded.
CRT is a binary X.509 certificate, encapsulated in text (base-64) encoding.

It is not the same encoding.

Upvotes: 37

Karl Ward
Karl Ward

Reputation: 321

I assume that you have a .cer file containing PKCS#7-encoded certificate data and you want to convert it to PEM-encoded certificate data (typically a .crt or .pem file). For instance, a .cer file containing PKCS#7-encoded data looks like this: 

-----BEGIN PKCS7-----
MIIW4gYJKoZIhvcNAQcCoIIW0zCCFs8CAQExADALBgkqhkiG9w0BBwGggha1MIIH
...
POI9n9cd2cNgQ4xYDiKWL2KjLB+6rQXvqzJ4h6BUcxm1XAX5Uj5tLUUL9wqT6u0G
+bKhADEA
-----END PKCS7-----

PEM certificate data looks like this: 

-----BEGIN CERTIFICATE-----
MIIHNjCCBh6gAwIBAgIQAlBxtqKazsxUSR9QdWWxaDANBgkqhkiG9w0BAQUFADBm
...
nv72c/OV4nlyrvBLPoaS5JFUJvFUG8RfAEY=
-----END CERTIFICATE-----

There is an OpenSSL command that will convert .cer files (with PKCS#7 data) to the PEM data you may be expecting to encounter (the BEGIN CERTIFICATE block in the example above). You can coerce PKCS#7 data into PEM format by this command on a file we'll call certfile.cer:

openssl pkcs7 -text -in certfile.cer -print_certs -outform PEM -out certfile.pem

Note that a .cer or .pem file might contain one or more certificates (possibly the entire certificate chain).

Upvotes: 32

OtherDevOpsGene
OtherDevOpsGene

Reputation: 7451

The .cer and .crt file should be interchangable as far as importing them into a keystore.

Take a look at the contents of the .cer file. Erase anything before the -----BEGIN CERTIFICATE----- line and after the -----END CERTIFICATE----- line. You'll be left with the BEGIN/END lines with a bunch of Base64-encoded stuff between them.

-----BEGIN CERTIFICATE-----
MIIDQTCCAqqgAwIBAgIJALQea21f1bVjMA0GCSqGSIb3DQEBBQUAMIG1MQswCQYD
...
pfDACIDHTrwCk5OefMwArfEkSBo/
-----END CERTIFICATE-----

Then just import it into your keyfile using keytool.

keytool -import -alias myalias -keystore my.keystore -trustcacerts -file mycert.cer

Upvotes: 4

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