Convert your SSL from or to: crt, cer, pem, der, pfx, & p7b

[DaMysterious]

Convert your SSL file to other formats

If your server/device requires a different certificate format other than Base64 encoded X.509, a third party tool such as OpenSSL can be used to convert the certificates into the appropriate format.
OpenSSL commands to convert PEM formatted file

Convert PEM to DER

openssl x509 -outform der -in certificate.pem -out certificate.der

Convert PEM to P7B

openssl crl2pkcs7 -nocrl -certfile certificate.cer -out certificate.p7b -certfile CACert.cer

Convert PEM to PFX

openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt

OpenSSL commands to convert DER formatted file

Convert DER to PEM

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

OpenSSL commands to convert P7B formatted file

Convert P7B to PEM

openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer

Convert P7B to PFX

openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer 
openssl pkcs12 -export -in certificate.cer -inkey privateKey.key -out certificate.pfx -certfile CACert.cer

OpenSSL commands to convert PFX formatted file

Convert PFX to PEM

openssl pkcs12 -in certificate.pfx -out certificate.cer -nodes

[hotfuzz]

thanks for the tutorial, but i have ssl recently issued with me and by mistake i choose to install on windows and ssl company issued me ssl in .cer format and there is no CA certificate and .crt file, as i need to install it on the linux server.

I tried the above command but got errors:

21325:error:0D0690A4:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag:tasn_dec.c:1316:
21325:error:0D07802A:asn1 encoding routines:ASN1_ITEM_EX_D2I:nested asn1 error:tasn_dec.c:380:Type=X509

[DaMysterious]

CER Certificate has two types of encoding i.e DER and Base64.

If either one returns an error loading certificate i.e asn1 encoding routines, try the different one.

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

openssl x509 -inform PEM -in certificate.cer -out certificate.crt
[B][/B]

or try this:

  
 openssl pkcs7 -print_certs -in certificate.cer -out certificate.crt [B][/B]