PKCS12

pkcs12 − PKCS#12 file utility

openssl pkcs12 [−export] [−chain] [−inkey filename] [−certfile filename] [−name name] [−caname name] [−in filename] [−out filename] [−noout] [−nomacver] [−nocerts] [−clcerts] [−cacerts] [−nokeys] [−info] [−des | −des3 | −idea | −aes128 | −aes192 | −aes256 | −camellia128 | −camellia192 | −camellia256 | −nodes] [−noiter] [−maciter | −nomaciter | −nomac] [−twopass] [−descert] [−certpbe cipher] [−keypbe cipher] [−macalg digest] [−keyex] [−keysig] [−password arg] [−passin arg] [−passout arg] [−rand file(s)] [−CAfile file] [−CApath dir] [−CSP name]

The pkcs12 command allows PKCS#12 files (sometimes referred to as PFX files) to be created and parsed. PKCS#12 files are used by several programs including Netscape, MSIE and MS Outlook.

There are a lot of options the meaning of some depends of whether a PKCS#12 file is being created or parsed. By default a PKCS#12 file is parsed. A PKCS#12 file can be created by using the −export option (see below).

−in filename

This specifies filename of the PKCS#12 file to be parsed. Standard input is used by default.

−out filename

The filename to write certificates and private keys to, standard output by default. They are all written in PEM format.

−pass arg, −passin arg

the PKCS#12 file (i.e. input file) password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).

−passout arg

pass phrase source to encrypt any outputed private keys with. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).

−noout

this option inhibits output of the keys and certificates to the output file version of the PKCS#12 file.

−clcerts

only output client certificates (not CA certificates).

−cacerts

only output CA certificates (not client certificates).

−nocerts

no certificates at all will be output.

−nokeys

no private keys will be output.

−info

output additional information about the PKCS#12 file structure, algorithms used and iteration counts.

−des

use DES to encrypt private keys before outputting.

−des3

use triple DES to encrypt private keys before outputting, this is the default.

−idea

use IDEA to encrypt private keys before outputting.

−aes128, −aes192, −aes256

use AES to encrypt private keys before outputting.

−camellia128, −camellia192, −camellia256

use Camellia to encrypt private keys before outputting.

−nodes

don’t encrypt the private keys at all.

−nomacver

don’t attempt to verify the integrity MAC before reading the file.

−twopass

prompt for separate integrity and encryption passwords: most software always assumes these are the same so this option will render such PKCS#12 files unreadable.

−export

This option specifies that a PKCS#12 file will be created rather than parsed.

−out filename

This specifies filename to write the PKCS#12 file to. Standard output is used by default.

−in filename

The filename to read certificates and private keys from, standard input by default. They must all be in PEM format. The order doesn’t matter but one private key and its corresponding certificate should be present. If additional certificates are present they will also be included in the PKCS#12 file.

−inkey filename

file to read private key from. If not present then a private key must be present in the input file.

−name friendlyname

This specifies the "friendly name" for the certificate and private key. This name is typically displayed in list boxes by software importing the file.

−certfile filename

A filename to read additional certificates from.

−caname friendlyname

This specifies the "friendly name" for other certificates. This option may be used multiple times to specify names for all certificates in the order they appear. Netscape ignores friendly names on other certificates whereas MSIE displays them.

−pass arg, −passout arg

the PKCS#12 file (i.e. output file) password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).

−passin password

pass phrase source to decrypt any input private keys with. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).

−chain

if this option is present then an attempt is made to include the entire certificate chain of the user certificate. The standard CA store is used for this search. If the search fails it is considered a fatal error.

−descert

encrypt the certificate using triple DES , this may render the PKCS#12 file unreadable by some "export grade" software. By default the private key is encrypted using triple DES and the certificate using 40 bit RC2 .

−keypbe alg, −certpbe alg

these options allow the algorithm used to encrypt the private key and certificates to be selected. Any PKCS#5 v1.5 or PKCS#12 PBE algorithm name can be used (see NOTES section for more information). If a a cipher name (as output by the list-cipher-algorithms command is specified then it is used with PKCS#5 v2.0. For interoperability reasons it is advisable to only use PKCS#12 algorithms.

−keyex|−keysig

specifies that the private key is to be used for key exchange or just signing. This option is only interpreted by MSIE and similar MS software. Normally "export grade" software will only allow 512 bit RSA keys to be used for encryption purposes but arbitrary length keys for signing. The −keysig option marks the key for signing only. Signing only keys can be used for S/MIME signing, authenticode (ActiveX control signing) and SSL client authentication, however due to a bug only MSIE 5.0 and later support the use of signing only keys for SSL client authentication.

−macalg digest

specify the MAC digest algorithm. If not included them SHA1 will be used.

−nomaciter, −noiter

these options affect the iteration counts on the MAC and key algorithms. Unless you wish to produce files compatible with MSIE 4.0 you should leave these options alone.

To discourage attacks by using large dictionaries of common passwords the algorithm that derives keys from passwords can have an iteration count applied to it: this causes a certain part of the algorithm to be repeated and slows it down. The MAC is used to check the file integrity but since it will normally have the same password as the keys and certificates it could also be attacked. By default both MAC and encryption iteration counts are set to 2048, using these options the MAC and encryption iteration counts can be set to 1, since this reduces the file security you should not use these options unless you really have to. Most software supports both MAC and key iteration counts. MSIE 4.0 doesn’t support MAC iteration counts so it needs the −nomaciter option.

−maciter

This option is included for compatibility with previous versions, it used to be needed to use MAC iterations counts but they are now used by default.

−nomac

don’t attempt to provide the MAC integrity.

−rand file(s)

a file or files containing random data used to seed the random number generator, or an EGD socket (see RAND_egd(3)). Multiple files can be specified separated by a OS-dependent character. The separator is ; for MS-Windows, , for OpenVMS, and : for all others.

−CAfile file

CA storage as a file.

−CApath dir

CA storage as a directory. This directory must be a standard certificate directory: that is a hash of each subject name (using x509 −hash) should be linked to each certificate.

−CSP name

write name as a Microsoft CSP name.

Although there are a large number of options most of them are very rarely used. For PKCS#12 file parsing only −in and −out need to be used for PKCS#12 file creation −export and −name are also used.

If none of the −clcerts, −cacerts or −nocerts options are present then all certificates will be output in the order they appear in the input PKCS#12 files. There is no guarantee that the first certificate present is the one corresponding to the private key. Certain software which requires a private key and certificate and assumes the first certificate in the file is the one corresponding to the private key: this may not always be the case. Using the −clcerts option will solve this problem by only outputting the certificate corresponding to the private key. If the CA certificates are required then they can be output to a separate file using the −nokeys −cacerts options to just output CA certificates.

The −keypbe and −certpbe algorithms allow the precise encryption algorithms for private keys and certificates to be specified. Normally the defaults are fine but occasionally software can’t handle triple DES encrypted private keys, then the option −keypbe PBE−SHA1−RC2−40 can be used to reduce the private key encryption to 40 bit RC2 . A complete description of all algorithms is contained in the pkcs8 manual page.

Parse a PKCS#12 file and output it to a file:

 openssl pkcs12 −in file.p12 −out file.pem

Output only client certificates to a file:

 openssl pkcs12 −in file.p12 −clcerts −out file.pem

Don’t encrypt the private key:

 openssl pkcs12 −in file.p12 −out file.pem −nodes

Print some info about a PKCS#12 file:

 openssl pkcs12 −in file.p12 −info −noout

Create a PKCS#12 file:

 openssl pkcs12 −export −in file.pem −out file.p12 −name "My Certificate"

Include some extra certificates:

 openssl pkcs12 −export −in file.pem −out file.p12 −name "My Certificate" \
  −certfile othercerts.pem

Some would argue that the PKCS#12 standard is one big bug :−)

Versions of OpenSSL before 0.9.6a had a bug in the PKCS#12 key generation routines. Under rare circumstances this could produce a PKCS#12 file encrypted with an invalid key. As a result some PKCS#12 files which triggered this bug from other implementations ( MSIE or Netscape) could not be decrypted by OpenSSL and similarly OpenSSL could produce PKCS#12 files which could not be decrypted by other implementations. The chances of producing such a file are relatively small: less than 1 in 256.

A side effect of fixing this bug is that any old invalidly encrypted PKCS#12 files cannot no longer be parsed by the fixed version. Under such circumstances the pkcs12 utility will report that the MAC is OK but fail with a decryption error when extracting private keys.

This problem can be resolved by extracting the private keys and certificates from the PKCS#12 file using an older version of OpenSSL and recreating the PKCS#12 file from the keys and certificates using a newer version of OpenSSL. For example:

 old−openssl −in bad.p12 −out keycerts.pem
 openssl −in keycerts.pem −export −name "My PKCS#12 file" −out fixed.p12

pkcs8(1)