openssl/doc/man1/openssl.pod

=pod

=head1 NAME

openssl - OpenSSL command line program

=head1 SYNOPSIS

B<openssl>
I<command>
[ I<options> ... ]
[ I<parameters> ... ]

B<openssl>
B<list>
B<-standard-commands> |
B<-digest-commands> |
B<-cipher-commands> |
B<-cipher-algorithms> |
B<-digest-algorithms> |
B<-mac-algorithms> |
B<-public-key-algorithms>

B<openssl> B<no->I<XXX> [ I<options> ]

=head1 DESCRIPTION

OpenSSL is a cryptography toolkit implementing the Secure Sockets Layer (SSL
v2/v3) and Transport Layer Security (TLS v1) network protocols and related
cryptography standards required by them.

The B<openssl> program is a command line program for using the various
cryptography functions of OpenSSL's B<crypto> library from the shell.
It can be used for

 o  Creation and management of private keys, public keys and parameters
 o  Public key cryptographic operations
 o  Creation of X.509 certificates, CSRs and CRLs
 o  Calculation of Message Digests and Message Authentication Codes
 o  Encryption and Decryption with Ciphers
 o  SSL/TLS Client and Server Tests
 o  Handling of S/MIME signed or encrypted mail
 o  Timestamp requests, generation and verification

=head1 COMMAND SUMMARY

The B<openssl> program provides a rich variety of commands (I<command> in
the L</SYNOPSIS> above).
Each command can have many options and argument parameters, shown above as
I<options> and I<parameters>.

Detailed documentation and use cases for most standard subcommands are available
(e.g., L<openssl-x509(1)>).

The list options B<-standard-commands>, B<-digest-commands>,
and B<-cipher-commands> output a list (one entry per line) of the names
of all standard commands, message digest commands, or cipher commands,
respectively, that are available.

The list parameters B<-cipher-algorithms>, B<-digest-algorithms>,
and B<-mac-algorithms> list all cipher, message digest, and message
authentication code names, one entry per line. Aliases are listed as:

 from => to

The list parameter B<-public-key-algorithms> lists all supported public
key algorithms.

The command B<no->I<XXX> tests whether a command of the
specified name is available.  If no command named I<XXX> exists, it
returns 0 (success) and prints B<no->I<XXX>; otherwise it returns 1
and prints I<XXX>.  In both cases, the output goes to B<stdout> and
nothing is printed to B<stderr>.  Additional command line arguments
are always ignored.  Since for each cipher there is a command of the
same name, this provides an easy way for shell scripts to test for the
availability of ciphers in the B<openssl> program.  (B<no->I<XXX> is
not able to detect pseudo-commands such as B<quit>,
B<list>, or B<no->I<XXX> itself.)

=head2 Configuration Option

Many commands use an external configuration file for some or all of their
arguments and have a B<-config> option to specify that file.
The default name of the file is F<openssl.cnf> in the default certificate
storage area, which can be determined from the L<openssl-version(1)>
command. This can be used to load modules.
The environment variable B<OPENSSL_CONF> can be used to specify
a different location of the file.
See L<openssl-env(7)>.

=head2 Standard Commands

=over 4

=item B<asn1parse>

Parse an ASN.1 sequence.

=item B<ca>

Certificate Authority (CA) Management.

=item B<ciphers>

Cipher Suite Description Determination.

=item B<cms>

CMS (Cryptographic Message Syntax) command.

=item B<crl>

Certificate Revocation List (CRL) Management.

=item B<crl2pkcs7>

CRL to PKCS#7 Conversion.

=item B<dgst>

Message Digest calculation. MAC calculations are superseded by
L<openssl-mac(1)>.

=item B<dhparam>

Generation and Management of Diffie-Hellman Parameters. Superseded by
L<openssl-genpkey(1)> and L<openssl-pkeyparam(1)>.

=item B<dsa>

DSA Data Management.

=item B<dsaparam>

DSA Parameter Generation and Management. Superseded by
L<openssl-genpkey(1)> and L<openssl-pkeyparam(1)>.

=item B<ec>

EC (Elliptic curve) key processing.

=item B<ecparam>

EC parameter manipulation and generation.

=item B<enc>

Encryption, decryption, and encoding.

=item B<engine>

Engine (loadable module) information and manipulation.

=item B<errstr>

Error Number to Error String Conversion.

=item B<fipsinstall>

FIPS configuration installation.

=item B<gendsa>

Generation of DSA Private Key from Parameters. Superseded by
L<openssl-genpkey(1)> and L<openssl-pkey(1)>.

=item B<genpkey>

Generation of Private Key or Parameters.

=item B<genrsa>

Generation of RSA Private Key. Superseded by L<openssl-genpkey(1)>.

=item B<help>

Display information about a command's options.

=item B<info>

Display diverse information built into the OpenSSL libraries.

=item B<kdf>

Key Derivation Functions.

=item B<list>

List algorithms and features.

=item B<mac>

Message Authentication Code Calculation.

=item B<nseq>

Create or examine a Netscape certificate sequence.

=item B<ocsp>

Online Certificate Status Protocol command.

=item B<passwd>

Generation of hashed passwords.

=item B<pkcs12>

PKCS#12 Data Management.

=item B<pkcs7>

PKCS#7 Data Management.

=item B<pkcs8>

PKCS#8 format private key conversion command.

=item B<pkey>

Public and private key management.

=item B<pkeyparam>

Public key algorithm parameter management.

=item B<pkeyutl>

Public key algorithm cryptographic operation command.

=item B<prime>

Compute prime numbers.

=item B<provider>

Load and query providers.

=item B<rand>

Generate pseudo-random bytes.

=item B<rehash>

Create symbolic links to certificate and CRL files named by the hash values.

=item B<req>

PKCS#10 X.509 Certificate Signing Request (CSR) Management.

=item B<rsa>

RSA key management.

=item B<rsautl>

RSA command for signing, verification, encryption, and decryption. Superseded
by  L<openssl-pkeyutl(1)>.

=item B<s_client>

This implements a generic SSL/TLS client which can establish a transparent
connection to a remote server speaking SSL/TLS. It's intended for testing
purposes only and provides only rudimentary interface functionality but
internally uses mostly all functionality of the OpenSSL B<ssl> library.

=item B<s_server>

This implements a generic SSL/TLS server which accepts connections from remote
clients speaking SSL/TLS. It's intended for testing purposes only and provides
only rudimentary interface functionality but internally uses mostly all
functionality of the OpenSSL B<ssl> library.  It provides both an own command
line oriented protocol for testing SSL functions and a simple HTTP response
facility to emulate an SSL/TLS-aware webserver.

=item B<s_time>

SSL Connection Timer.

=item B<sess_id>

SSL Session Data Management.

=item B<smime>

S/MIME mail processing.

=item B<speed>

Algorithm Speed Measurement.

=item B<spkac>

SPKAC printing and generating command.

=item B<srp>

Maintain SRP password file.

=item B<storeutl>

Command to list and display certificates, keys, CRLs, etc.

=item B<ts>

Time Stamping Authority command.

=item B<verify>

X.509 Certificate Verification.

=item B<version>

OpenSSL Version Information.

=item B<x509>

X.509 Certificate Data Management.

=back

=head2 Message Digest Commands

=over 4

=item B<blake2b512>

BLAKE2b-512 Digest

=item B<blake2s256>

BLAKE2s-256 Digest

=item B<md2>

MD2 Digest

=item B<md4>

MD4 Digest

=item B<md5>

MD5 Digest

=item B<mdc2>

MDC2 Digest

=item B<rmd160>

RMD-160 Digest

=item B<sha1>

SHA-1 Digest

=item B<sha224>

SHA-2 224 Digest

=item B<sha256>

SHA-2 256 Digest

=item B<sha384>

SHA-2 384 Digest

=item B<sha512>

SHA-2 512 Digest

=item B<sha3-224>

SHA-3 224 Digest

=item B<sha3-256>

SHA-3 256 Digest

=item B<sha3-384>

SHA-3 384 Digest

=item B<sha3-512>

SHA-3 512 Digest

=item B<shake128>

SHA-3 SHAKE128 Digest

=item B<shake256>

SHA-3 SHAKE256 Digest

=item B<sm3>

SM3 Digest

=back

=head2 Encryption, Decryption, and Encoding Commands

The following aliases provide convenient access to the most used encodings
and ciphers.

Depending on how OpenSSL was configured and built, not all ciphers listed
here may be present. See L<openssl-enc(1)> for more information.

=over 4

=item B<aes128>, B<aes-128-cbc>, B<aes-128-cfb>, B<aes-128-ctr>, B<aes-128-ecb>, B<aes-128-ofb>

AES-128 Cipher

=item B<aes192>, B<aes-192-cbc>, B<aes-192-cfb>, B<aes-192-ctr>, B<aes-192-ecb>, B<aes-192-ofb>

AES-192 Cipher

=item B<aes256>, B<aes-256-cbc>, B<aes-256-cfb>, B<aes-256-ctr>, B<aes-256-ecb>, B<aes-256-ofb>

AES-256 Cipher

=item B<aria128>, B<aria-128-cbc>, B<aria-128-cfb>, B<aria-128-ctr>, B<aria-128-ecb>, B<aria-128-ofb>

Aria-128 Cipher

=item B<aria192>, B<aria-192-cbc>, B<aria-192-cfb>, B<aria-192-ctr>, B<aria-192-ecb>, B<aria-192-ofb>

Aria-192 Cipher

=item B<aria256>, B<aria-256-cbc>, B<aria-256-cfb>, B<aria-256-ctr>, B<aria-256-ecb>, B<aria-256-ofb>

Aria-256 Cipher

=item B<base64>

Base64 Encoding

=item B<bf>, B<bf-cbc>, B<bf-cfb>, B<bf-ecb>, B<bf-ofb>

Blowfish Cipher

=item B<camellia128>, B<camellia-128-cbc>, B<camellia-128-cfb>, B<camellia-128-ctr>, B<camellia-128-ecb>, B<camellia-128-ofb>

Camellia-128 Cipher

=item B<camellia192>, B<camellia-192-cbc>, B<camellia-192-cfb>, B<camellia-192-ctr>, B<camellia-192-ecb>, B<camellia-192-ofb>

Camellia-192 Cipher

=item B<camellia256>, B<camellia-256-cbc>, B<camellia-256-cfb>, B<camellia-256-ctr>, B<camellia-256-ecb>, B<camellia-256-ofb>

Camellia-256 Cipher

=item B<cast>, B<cast-cbc>

CAST Cipher

=item B<cast5-cbc>, B<cast5-cfb>, B<cast5-ecb>, B<cast5-ofb>

CAST5 Cipher

=item B<chacha20>

Chacha20 Cipher

=item B<des>, B<des-cbc>, B<des-cfb>, B<des-ecb>, B<des-ede>, B<des-ede-cbc>, B<des-ede-cfb>, B<des-ede-ofb>, B<des-ofb>

DES Cipher

=item B<des3>, B<desx>, B<des-ede3>, B<des-ede3-cbc>, B<des-ede3-cfb>, B<des-ede3-ofb>

Triple-DES Cipher

=item B<idea>, B<idea-cbc>, B<idea-cfb>, B<idea-ecb>, B<idea-ofb>

IDEA Cipher

=item B<rc2>, B<rc2-cbc>, B<rc2-cfb>, B<rc2-ecb>, B<rc2-ofb>

RC2 Cipher

=item B<rc4>

RC4 Cipher

=item B<rc5>, B<rc5-cbc>, B<rc5-cfb>, B<rc5-ecb>, B<rc5-ofb>

RC5 Cipher

=item B<seed>, B<seed-cbc>, B<seed-cfb>, B<seed-ecb>, B<seed-ofb>

SEED Cipher

=item B<sm4>, B<sm4-cbc>, B<sm4-cfb>, B<sm4-ctr>, B<sm4-ecb>, B<sm4-ofb>

SM4 Cipher

=back

=head1 OPTIONS

Details of which options are available depend on the specific command.
This section describes some common options with common behavior.

=head2 Common Options

=over 4

=item B<-help>

Provides a terse summary of all options.
If an option takes an argument, the "type" of argument is also given.

=item B<-->

This terminates the list of options. It is mostly useful if any filename
parameters start with a minus sign:

 openssl verify [flags...] -- -cert1.pem...

=back

=head2 Format Options

Several OpenSSL commands can take input or generate output in a variety
of formats.
Since OpenSSL 3.0 keys, single certificates, and CRLs can be read from
files in any of the B<DER>, B<PEM> or B<P12> formats,
while specifying their input format is no more needed.

The list of acceptable formats, and the default, is
described in each command documentation.  The list of formats is
described below. Both uppercase and lowercase are accepted.

=over 4

=item B<DER>

A binary format, encoded or parsed according to Distinguished Encoding Rules
(DER) of the ASN.1 data language.

=item B<ENGINE>

Used to specify that the cryptographic material is in an OpenSSL B<engine>.
An engine must be configured or specified using the B<-engine> option.
In addition, the B<-input> flag can be used to name a specific object in
the engine.
A password, such as the B<-passin> flag often must be specified as well.

=item B<P12>

A DER-encoded file containing a PKCS#12 object.
It might be necessary to provide a decryption password to retrieve
the private key.

=item B<PEM>

A text format defined in IETF RFC 1421 and IETF RFC 7468. Briefly, this is
a block of base-64 encoding (defined in IETF RFC 4648), with specific
lines used to mark the start and end:

 Text before the BEGIN line is ignored.
 ----- BEGIN object-type -----
 OT43gQKBgQC/2OHZoko6iRlNOAQ/tMVFNq7fL81GivoQ9F1U0Qr+DH3ZfaH8eIkX
 xT0ToMPJUzWAn8pZv0snA0um6SIgvkCuxO84OkANCVbttzXImIsL7pFzfcwV/ERK
 UM6j0ZuSMFOCr/lGPAoOQU0fskidGEHi1/kW+suSr28TqsyYZpwBDQ==
 ----- END object-type -----
 Text after the END line is also ignored

The I<object-type> must match the type of object that is expected.
For example a C<BEGIN X509 CERTIFICATE> will not match if the command
is trying to read a private key. The types supported include:

 ANY PRIVATE KEY
 CERTIFICATE
 CERTIFICATE REQUEST
 CMS
 DH PARAMETERS
 DSA PARAMETERS
 DSA PUBLIC KEY
 EC PARAMETERS
 EC PRIVATE KEY
 ECDSA PUBLIC KEY
 ENCRYPTED PRIVATE KEY
 PARAMETERS
 PKCS #7 SIGNED DATA
 PKCS7
 PRIVATE KEY
 PUBLIC KEY
 RSA PRIVATE KEY
 SSL SESSION PARAMETERS
 TRUSTED CERTIFICATE
 X509 CRL
 X9.42 DH PARAMETERS

The following legacy I<object-type>'s are also supported for compatibility
with earlier releases:

 DSA PRIVATE KEY
 NEW CERTIFICATE REQUEST
 RSA PUBLIC KEY
 X509 CERTIFICATE

=item B<SMIME>

An S/MIME object as described in IETF RFC 8551.
Earlier versions were known as CMS and are compatible.
Note that the parsing is simple and might fail to parse some legal data.

=back

The options to specify the format are as follows. Refer to the individual
man page to see which options are accepted.

=over 4

=item B<-inform> I<format>, B<-outform> I<format>

The format of the input or output streams.

=item B<-keyform> I<format>

Format of a private key input source.
The only value with effect is B<ENGINE>; all others have become obsolete.
See L<openssl(1)/Format Options> for details.

=item B<-CRLform> I<format>

Format of a CRL input source.

=back

=head2 Pass Phrase Options

Several commands accept password arguments, typically using B<-passin>
and B<-passout> for input and output passwords respectively. These allow
the password to be obtained from a variety of sources. Both of these
options take a single argument whose format is described below. If no
password argument is given and a password is required then the user is
prompted to enter one: this will typically be read from the current
terminal with echoing turned off.

Note that character encoding may be relevant, please see
L<passphrase-encoding(7)>.

=over 4

=item B<pass:>I<password>

The actual password is I<password>. Since the password is visible
to utilities (like 'ps' under Unix) this form should only be used
where security is not important.

=item B<env:>I<var>

Obtain the password from the environment variable I<var>. Since
the environment of other processes is visible on certain platforms
(e.g. ps under certain Unix OSes) this option should be used with caution.

=item B<file:>I<pathname>

The first line of I<pathname> is the password. If the same I<pathname>
argument is supplied to B<-passin> and B<-passout> arguments then the first
line will be used for the input password and the next line for the output
password. I<pathname> need not refer to a regular file: it could for example
refer to a device or named pipe.

=item B<fd:>I<number>

Read the password from the file descriptor I<number>. This can be used to
send the data via a pipe for example.

=item B<stdin>

Read the password from standard input.

=back

=head2 Trusted Certificate Options

Part of validating a certificate includes verifying that the chain of CA's
can be traced up to an existing trusted root.  The following options specify
how to list the trusted roots, also known as trust anchors.  A collection
of trusted roots is called a I<trust store>.

Note that OpenSSL does not provide a default set of trust anchors.  Many
Linux distributions include a system default and configure OpenSSL to point
to that.  Mozilla maintains an influential trust store that can be found at
L<https://www.mozilla.org/en-US/about/governance/policies/security-group/certs/>.

=over 4

=item B<-CAfile> I<file>

Load the specified file which contains one or more PEM-format certificates
of CA's that are trusted.

=item B<-no-CAfile>

Do not load the default file of trusted certificates.

=item B<-CApath> I<dir>

Use the specified directory as a list of trust certificates. That is,
files should be named with the hash of the X.509 SubjectName of each
certificate. This is so that the library can extract the IssuerName,
hash it, and directly lookup the file to get the issuer certificate.
See L<openssl-rehash(1)> for information on creating this type of directory.

=item B<-no-CApath>

Do not use the default directory of trusted certificates.

=item B<-CAstore> I<uri>

Use I<uri> as a store of trusted CA certificates.  The URI may
indicate a single certificate, as well as a collection of them.
With URIs in the C<file:> scheme, this acts as B<-CAfile> or
B<-CApath>, depending on if the URI indicates a single file or
directory.
See L<ossl_store-file(7)> for more information on the C<file:> scheme.

These certificates are also used when building the server certificate
chain (for example with L<openssl-s_server(1)>) or client certificate
chain (for example with L<openssl-s_time(1)>).

=item B<-no-CAstore>

Do not use the default store.

=back

=head2 Random State Options

Prior to OpenSSL 1.1.1, it was common for applications to store information
about the state of the random-number generator in a file that was loaded
at startup and rewritten upon exit. On modern operating systems, this is
generally no longer necessary as OpenSSL will seed itself from a trusted
entropy source provided by the operating system. These flags are still
supported for special platforms or circumstances that might require them.

It is generally an error to use the same seed file more than once and
every use of B<-rand> should be paired with B<-writerand>.

=over 4

=item B<-rand> I<files>

A file or files containing random data used to seed the random number
generator.
Multiple files can be specified separated by an OS-dependent character.
The separator is C<;> for MS-Windows, C<,> for OpenVMS, and C<:> for
all others. Another way to specify multiple files is to repeat this flag
with different filenames.

=item B<-writerand> I<file>

Writes the seed data to the specified I<file> upon exit.
This file can be used in a subsequent command invocation.

=back

=head2 Provider Options

With the move to provider based cryptographic operations in OpenSSL 3.0,
options were added to allow specific providers or sets of providers to be used.

=over 4

=item B<-provider> I<name>

Use the provider identified by I<name> and use all the methods it
implements (algorithms, key storage, etc.).  This option can be specified
multiple time to load more than one provider.

=item B<-provider-path> I<path>

Specify the search I<path> that is used to locate provider modules.  The format
of I<path> varies depending on the operating system being used.

=back

=head2 Extended Verification Options

Sometimes there may be more than one certificate chain leading to an
end-entity certificate.
This usually happens when a root or intermediate CA signs a certificate
for another a CA in other organization.
Another reason is when a CA might have intermediates that use two different
signature formats, such as a SHA-1 and a SHA-256 digest.

The following options can be used to provide data that will allow the
OpenSSL command to generate an alternative chain.

=over 4

=item B<-xkey> I<infile>, B<-xcert> I<infile>, B<-xchain>

Specify an extra certificate, private key and certificate chain. These behave
in the same manner as the B<-cert>, B<-key> and B<-cert_chain> options.  When
specified, the callback returning the first valid chain will be in use by the
client.

=item B<-xchain_build>

Specify whether the application should build the certificate chain to be
provided to the server for the extra certificates via the B<-xkey>,
B<-xcert>, and B<-xchain> options.

=item B<-xcertform> B<DER>|B<PEM>|B<P12>

The input format for the extra certificate.
This option has no effect and is retained for backward compatibility only.

=item B<-xkeyform> B<DER>|B<PEM>|B<P12>

The input format for the extra key.
This option has no effect and is retained for backward compatibility only.

=back

=head2 Verification Options

Many OpenSSL commands verify certificates. The details of how each
command handles errors are documented on the specific command page.

Verification is a complicated process, consisting of a number of separate
steps that are detailed in the following paragraphs.

First, a certificate chain is built up starting from the target certificate
and typically ending in a self-signed "root" CA certificate.
It is an error if the whole chain cannot be built up
unless the B<-partial_chain> option is given.
The chain is built up iteratively, looking up in turn
the certificate of the signer ("issuer") of the current certificate.
If a certificate is found that appears to be its own issuer
it is assumed to be the self-signed root, which must be trusted.

The process of looking up the issuer's certificate itself involves a number
of steps.
All available certificates with a subject name that matches the issuer
name of the current certificate are subject to further tests.
The relevant authority key identifier components of the current certificate
(if present) must match the subject key identifier (if present)
and issuer and serial number of the candidate issuer certificate.

The lookup first searches for issuer certificates in the trust store.
If it does not find a match there it consults
the list of untrusted "intermediate" CA certificates (if provided).
The last certificate (which typically is of a root CA) is always looked up
in the trusted certificate list; an exact match must be found there.

The second step is to check the extensions of every untrusted certificate
for consistency with the supplied purpose.
If the B<-purpose> option is not included then no checks are done.
The target or "leaf" certificate must have extensions compatible with the
supplied purpose and all other certificates must also be valid CA certificates.
The precise extensions required are described in more detail in
L<openssl-x509(1)/CERTIFICATE EXTENSIONS>.

The third step is to check the trust settings on the last certficate,
typically of a root CA.
It should be trusted for the supplied purpose.
For compatibility with previous versions of OpenSSL,
a certificate with no trust settings is considered to be valid for all purposes.

The fourth, and final, step is to check the validity of the certificate chain.
The validity period is checked against the system time
and the C<notBefore> and C<notAfter> dates in each certificate.
The B<-attime> flag may be used to specify a time other than "now."
The certificate signatures are also checked at this point
(except for the signature of the self-signed "root CA" certificate,
which is verified only if the B<-check_ss_sig> option is given).
When verifying a certificate signature
the keyUsage extension (if present) of the candidate issuer certificate
is checked to permit digitalSignature for signing proxy certificates
or to permit keyCertSign for signing other certificates, respectively.
If all operations complete successfully then certificate is considered
valid. If any operation fails then the certificate is not valid.

The details of the processing steps can be fine-tuned with the
following flags.

=over 4

=item B<-verbose>

Print extra information about the operations being performed.

=item B<-attime> I<timestamp>

Perform validation checks using time specified by I<timestamp> and not
current system time. I<timestamp> is the number of seconds since
January 1, 1970 (i.e., the Unix Epoch).

=item B<-no_check_time>

This option suppresses checking the validity period of certificates and CRLs
against the current time. If option B<-attime> is used to specify
a verification time, the check is not suppressed.

=item B<-x509_strict>

This disables non-compliant workarounds for broken certificates.

=item B<-ignore_critical>

Normally if an unhandled critical extension is present that is not
supported by OpenSSL the certificate is rejected (as required by RFC5280).
If this option is set critical extensions are ignored.

=item B<-issuer_checks>

Ignored.

=item B<-crl_check>

Checks end entity certificate validity by attempting to look up a valid CRL.
If a valid CRL cannot be found an error occurs.

=item B<-crl_check_all>

Checks the validity of B<all> certificates in the chain by attempting
to look up valid CRLs.

=item B<-use_deltas>

Enable support for delta CRLs.

=item B<-extended_crl>

Enable extended CRL features such as indirect CRLs and alternate CRL
signing keys.

=item B<-suiteB_128_only>, B<-suiteB_128>, B<-suiteB_192>

Enable the Suite B mode operation at 128 bit Level of Security, 128 bit or
192 bit, or only 192 bit Level of Security respectively.
See RFC6460 for details. In particular the supported signature algorithms are
reduced to support only ECDSA and SHA256 or SHA384 and only the elliptic curves
P-256 and P-384.

=item B<-auth_level> I<level>

Set the certificate chain authentication security level to I<level>.
The authentication security level determines the acceptable signature and
public key strength when verifying certificate chains.  For a certificate
chain to validate, the public keys of all the certificates must meet the
specified security I<level>.  The signature algorithm security level is
enforced for all the certificates in the chain except for the chain's
I<trust anchor>, which is either directly trusted or validated by means
other than its signature.  See L<SSL_CTX_set_security_level(3)> for the
definitions of the available levels.  The default security level is -1,
or "not set".  At security level 0 or lower all algorithms are acceptable.
Security level 1 requires at least 80-bit-equivalent security and is broadly
interoperable, though it will, for example, reject MD5 signatures or RSA
keys shorter than 1024 bits.

=item B<-partial_chain>

Allow verification to succeed even if a I<complete> chain cannot be built to a
self-signed trust-anchor, provided it is possible to construct a chain to a
trusted certificate that might not be self-signed.
This certificate may be self-issued or belong to an intermediate CA.

=item B<-check_ss_sig>

Verify the signature of
the last certificate in a chain if the certificate is supposedly self-signed.
This is prohibited and will result in an error if it is a non-conforming CA
certificate with key usage restrictions not including the keyCertSign bit.
This verification is disabled by default because it doesn't add any security.

=item B<-allow_proxy_certs>

Allow the verification of proxy certificates.

=item B<-trusted_first>

As of OpenSSL 1.1.0 this option is on by default and cannot be disabled.

When constructing the certificate chain, the trusted certificates specified
via B<-CAfile>, B<-CApath>, B<-CAstore> or B<-trusted> are always used
before any certificates specified via B<-untrusted>.

=item B<-no_alt_chains>

As of OpenSSL 1.1.0, since B<-trusted_first> always on, this option has no
effect.

=item B<-trusted> I<file>

Parse I<file> as a set of one or more certificates in PEM format.
All certificates must be self-signed, unless the
B<-partial_chain> option is specified.
This option implies the B<-no-CAfile>, B<-no-CApath>, and B<-no-CAstore> options
and it cannot be used with the B<-CAfile>, B<-CApath> or B<-CAstore> options, so
only certificates in the file are trust anchors.
This option may be used multiple times.

=item B<-untrusted> I<file>

Parse I<file> as a set of one or more certificates in PEM format.
All certificates are untrusted certificates (typically of intermedate CAs)
that may be used to
construct a certificate chain from the subject certificate to a trust anchor.
This option may be used multiple times.

=item B<-policy> I<arg>

Enable policy processing and add I<arg> to the user-initial-policy-set (see
RFC5280). The policy I<arg> can be an object name an OID in numeric form.
This argument can appear more than once.

=item B<-explicit_policy>

Set policy variable require-explicit-policy (see RFC5280).

=item B<-policy_check>

Enables certificate policy processing.

=item B<-policy_print>

Print out diagnostics related to policy processing.

=item B<-inhibit_any>

Set policy variable inhibit-any-policy (see RFC5280).

=item B<-inhibit_map>

Set policy variable inhibit-policy-mapping (see RFC5280).

=item B<-purpose> I<purpose>

The intended use for the certificate. If this option is not specified, this
command will not consider certificate purpose during chain verification.
Currently accepted uses are B<sslclient>, B<sslserver>, B<nssslserver>,
B<smimesign>, B<smimeencrypt>.

=item B<-verify_depth> I<num>

Limit the certificate chain to I<num> intermediate CA certificates.
A maximal depth chain can have up to I<num>+2 certificates, since neither the
end-entity certificate nor the trust-anchor certificate count against the
B<-verify_depth> limit.

=item B<-verify_email> I<email>

Verify if I<email> matches the email address in Subject Alternative Name or
the email in the subject Distinguished Name.

=item B<-verify_hostname> I<hostname>

Verify if I<hostname> matches DNS name in Subject Alternative Name or
Common Name in the subject certificate.

=item B<-verify_ip> I<ip>

Verify if I<ip> matches the IP address in Subject Alternative Name of
the subject certificate.

=item B<-verify_name> I<name>

Use default verification policies like trust model and required certificate
policies identified by I<name>.
The trust model determines which auxiliary trust or reject OIDs are applicable
to verifying the given certificate chain.
See the B<-addtrust> and B<-addreject> options for L<openssl-x509(1)>.
Supported policy names include: B<default>, B<pkcs7>, B<smime_sign>,
B<ssl_client>, B<ssl_server>.
These mimics the combinations of purpose and trust settings used in SSL, CMS
and S/MIME.
As of OpenSSL 1.1.0, the trust model is inferred from the purpose when not
specified, so the B<-verify_name> options are functionally equivalent to the
corresponding B<-purpose> settings.

=back

=head2 Name Format Options

OpenSSL provides fine-grain control over how the subject and issuer DN's are
displayed.
This is specified by using the B<-nameopt> option, which takes a
comma-separated list of options from the following set.
An option may be preceded by a minus sign, C<->, to turn it off.
The default value is C<oneline>.
The first four are the most commonly used.

=over 4

=item B<compat>

Display the name using an old format from previous OpenSSL versions.

=item B<RFC2253>

Display the name using the format defined in RFC 2253.
It is equivalent to B<esc_2253>, B<esc_ctrl>, B<esc_msb>, B<utf8>,
B<dump_nostr>, B<dump_unknown>, B<dump_der>, B<sep_comma_plus>, B<dn_rev>
and B<sname>.

=item B<oneline>

Display the name in one line, using a format that is more readable
RFC 2253.
It is equivalent to B<esc_2253>, B<esc_ctrl>, B<esc_msb>, B<utf8>,
B<dump_nostr>, B<dump_der>, B<use_quote>, B<sep_comma_plus_space>,
B<space_eq> and B<sname> options.

=item B<multiline>

Display the name using multiple lines.
It is equivalent to B<esc_ctrl>, B<esc_msb>, B<sep_multiline>, B<space_eq>,
B<lname> and B<align>.

=item B<esc_2253>

Escape the "special" characters in a field, as required by RFC 2253.
That is, any of the characters C<,+"E<lt>E<gt>;>, C<#> at the beginning of
a string and leading or trailing spaces.

=item B<esc_2254>

Escape the "special" characters in a field as required by RFC 2254 in a field.
That is, the B<NUL> character and of C<()*>.

=item B<esc_ctrl>

Escape non-printable ASCII characters, codes less than 0x20 (space)
or greater than 0x7F (DELETE). They are displayed using RFC 2253 C<\XX>
notation where B<XX> are the two hex digits representing the character value.

=item B<esc_msb>

Escape any characters with the most significant bit set, that is with
values larger than 127, as described in B<esc_ctrl>.

=item B<use_quote>

Escapes some characters by surrounding the entire string with quotation
marks, C<">.
Without this option, individual special characters are preceded with
a backslash character, C<\>.

=item B<utf8>

Convert all strings to UTF-8 format first as required by RFC 2253.
If the output device is UTF-8 compatible, then using this option (and
not setting B<esc_msb>) may give the correct display of multibyte
characters.
If this option is not set, then multibyte characters larger than 0xFF
will be output as C<\UXXXX> for 16 bits or C<\WXXXXXXXX> for 32 bits.
In addition, any UTF8Strings will be converted to their character form first.

=item B<ignore_type>

This option does not attempt to interpret multibyte characters in any
way. That is, the content octets are merely dumped as though one octet
represents each character. This is useful for diagnostic purposes but
will result in rather odd looking output.

=item B<show_type>

Display the type of the ASN1 character string before the value,
such as C<BMPSTRING: Hello World>.

=item B<dump_der>

Any fields that would be output in hex format are displayed using
the DER encoding of the field.
If not set, just the content octets are displayed.
Either way, the B<#XXXX...> format of RFC 2253 is used.

=item B<dump_nostr>

Dump non-character strings, such as ASN.1 B<OCTET STRING>.
If this option is not set, then non character string types will be displayed
as though each content octet represents a single character.

=item B<dump_all>

Dump all fields. When this used with B<dump_der>, this allows the
DER encoding of the structure to be unambiguously determined.

=item B<dump_unknown>

Dump any field whose OID is not recognised by OpenSSL.

=item B<sep_comma_plus>, B<sep_comma_plus_space>, B<sep_semi_plus_space>,
B<sep_multiline>

Specify the field separators. The first word is used between the
Relative Distinguished Names (RDNs) and the second is between
multiple Attribute Value Assertions (AVAs). Multiple AVAs are
very rare and their use is discouraged.
The options ending in "space" additionally place a space after the separator to make it more readable.
The B<sep_multiline> starts each field on its own line, and uses "plus space"
for the AVA separator.
It also indents the fields by four characters.
The default value is B<sep_comma_plus_space>.

=item B<dn_rev>

Reverse the fields of the DN as required by RFC 2253.
This also reverses the order of multiple AVAs in a field, but this is
permissible as there is no ordering on values.

=item B<nofname>, B<sname>, B<lname>, B<oid>

Specify how the field name is displayed.
B<nofname> does not display the field at all.
B<sname> uses the "short name" form (CN for commonName for example).
B<lname> uses the long form.
B<oid> represents the OID in numerical form and is useful for
diagnostic purpose.

=item B<align>

Align field values for a more readable output. Only usable with
B<sep_multiline>.

=item B<space_eq>

Places spaces round the equal sign, C<=>, character which follows the field
name.

=back

=head2 TLS Version Options

Several commands use SSL, TLS, or DTLS. By default, the commands use TLS and
clients will offer the lowest and highest protocol version they support,
and servers will pick the highest version that the client offers that is also
supported by the server.

The options below can be used to limit which protocol versions are used,
and whether TCP (SSL and TLS) or UDP (DTLS) is used.
Note that not all protocols and flags may be available, depending on how
OpenSSL was built.

=over 4

=item B<-ssl3>, B<-tls1>, B<-tls1_1>, B<-tls1_2>, B<-tls1_3>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>

These options require or disable the use of the specified SSL or TLS protocols.
When a specific TLS version is required, only that version will be offered or
accepted.
Only one specific protocol can be given and it cannot be combined with any of
the B<no_> options.

=item B<-dtls>, B<-dtls1>, B<-dtls1_2>

These options specify to use DTLS instead of DLTS.
With B<-dtls>, clients will negotiate any supported DTLS protocol version.
Use the B<-dtls1> or B<-dtls1_2> options to support only DTLS1.0 or DTLS1.2,
respectively.

=back

=head2 Engine Options

=over 4

=item B<-engine> I<id>

Use the engine identified by I<id> and use all the methods it
implements (algorithms, key storage, etc.), unless specified otherwise in
the command-specific documentation or it is configured to do so, as described
in L<config(5)/Engine Configuration Module>.

=back

=head1 ENVIRONMENT

The OpenSSL library can be take some configuration parameters from the
environment.  Some of these variables are listed below.  For information
about specific commands, see L<openssl-engine(1)>, L<openssl-provider(1)>,
L<openssl-rehash(1)>, and L<tsget(1)>.

For information about the use of environment variables in configuration,
see L<config(5)/ENVIRONMENT>.

For information about querying or specifying CPU architecture flags, see
L<OPENSSL_ia32cap(3)>, and L<OPENSSL_s390xcap(3)>.

For information about all environment variables used by the OpenSSL libraries,
see L<openssl-env(7)>.

=over 4

=item B<OPENSSL_TRACE=>I<name>[,...]

Enable tracing output of OpenSSL library, by name.
This output will only make sense if you know OpenSSL internals well.
Also, it might not give you any output at all, depending on how
OpenSSL was built.

The value is a comma separated list of names, with the following
available:

=over 4

=item B<TRACE>

The tracing functionality.

=item B<TLS>

General SSL/TLS.

=item B<TLS_CIPHER>

SSL/TLS cipher.

=item B<CONF>

Show details about provider and engine configuration.

=item B<ENGINE_TABLE>

The function that is used by RSA, DSA (etc) code to select registered
ENGINEs, cache defaults and functional references (etc), will generate
debugging summaries.

=item B<ENGINE_REF_COUNT>

Reference counts in the ENGINE structure will be monitored with a line
of generated for each change.

=item B<PKCS5V2>

PKCS#5 v2 keygen.

=item B<PKCS12_KEYGEN>

PKCS#12 key generation.

=item B<PKCS12_DECRYPT>

PKCS#12 decryption.

=item B<X509V3_POLICY>

Generates the complete policy tree at various point during X.509 v3
policy evaluation.

=item B<BN_CTX>

BIGNUM context.

=back

=back

=head1 SEE ALSO

L<openssl-asn1parse(1)>,
L<openssl-ca(1)>,
L<openssl-ciphers(1)>,
L<openssl-cms(1)>,
L<openssl-crl(1)>,
L<openssl-crl2pkcs7(1)>,
L<openssl-dgst(1)>,
L<openssl-dhparam(1)>,
L<openssl-dsa(1)>,
L<openssl-dsaparam(1)>,
L<openssl-ec(1)>,
L<openssl-ecparam(1)>,
L<openssl-enc(1)>,
L<openssl-engine(1)>,
L<openssl-errstr(1)>,
L<openssl-gendsa(1)>,
L<openssl-genpkey(1)>,
L<openssl-genrsa(1)>,
L<openssl-kdf(1)>,
L<openssl-mac(1)>,
L<openssl-nseq(1)>,
L<openssl-ocsp(1)>,
L<openssl-passwd(1)>,
L<openssl-pkcs12(1)>,
L<openssl-pkcs7(1)>,
L<openssl-pkcs8(1)>,
L<openssl-pkey(1)>,
L<openssl-pkeyparam(1)>,
L<openssl-pkeyutl(1)>,
L<openssl-prime(1)>,
L<openssl-rand(1)>,
L<openssl-rehash(1)>,
L<openssl-req(1)>,
L<openssl-rsa(1)>,
L<openssl-rsautl(1)>,
L<openssl-s_client(1)>,
L<openssl-s_server(1)>,
L<openssl-s_time(1)>,
L<openssl-sess_id(1)>,
L<openssl-smime(1)>,
L<openssl-speed(1)>,
L<openssl-spkac(1)>,
L<openssl-srp(1)>,
L<openssl-storeutl(1)>,
L<openssl-ts(1)>,
L<openssl-verify(1)>,
L<openssl-version(1)>,
L<openssl-x509(1)>,
L<config(5)>,
L<crypto(7)>,
L<openssl-env(7)>.
L<ssl(7)>,
L<x509v3_config(5)>


=head1 HISTORY

The B<list> -I<XXX>B<-algorithms> options were added in OpenSSL 1.0.0;
For notes on the availability of other commands, see their individual
manual pages.

The B<-issuer_checks> option is deprecated as of OpenSSL 1.1.0 and
is silently ignored.

The B<-xcertform> and B<-xkeyform> options
are obsolete since OpenSSL 3.0 and have no effect.

The interactive mode, which could be invoked by running C<openssl>
with no further arguments, was removed in OpenSSL 3.0, and running
that program with no arguments is now equivalent to C<openssl help>.

=head1 COPYRIGHT

Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.

=cut