541 lines
16 KiB
Text
541 lines
16 KiB
Text
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=pod
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=head1 NAME
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x509 - Certificate display and signing utility
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=head1 SYNOPSIS
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B<openssl> B<x509>
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[B<-inform DER|PEM|NET>]
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[B<-outform DER|PEM|NET>]
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[B<-keyform DER|PEM>]
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[B<-CAform DER|PEM>]
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[B<-CAkeyform DER|PEM>]
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[B<-in filename>]
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[B<-out filename>]
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[B<-serial>]
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[B<-hash>]
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[B<-subject>]
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[B<-issuer>]
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[B<-startdate>]
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[B<-enddate>]
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[B<-purpose>]
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[B<-dates>]
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[B<-modulus>]
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[B<-fingerprint>]
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[B<-alias>]
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[B<-noout>]
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[B<-trustout>]
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[B<-clrtrust>]
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[B<-clrreject>]
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[B<-addtrust arg>]
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[B<-addreject arg>]
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[B<-setalias arg>]
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[B<-days arg>]
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[B<-signkey filename>]
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[B<-x509toreq>]
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[B<-req>]
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[B<-CA filename>]
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[B<-CAkey filename>]
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[B<-CAcreateserial>]
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[B<-CAserial filename>]
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[B<-text>]
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[B<-C>]
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[B<-md2|-md5|-sha1|-mdc2>]
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[B<-clrext>]
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[B<-extfile filename>]
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[B<-extensions section>]
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=head1 DESCRIPTION
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The B<x509> command is a multi purpose certificate utility. It can be
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used to display certificate information, convert certificates to
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various forms, sign certificate requests like a "mini CA" or edit
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certificate trust settings.
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Since there are a large number of options they will split up into
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various sections.
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=head1 INPUT, OUTPUT AND GENERAL PURPOSE OPTIONS
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=over 4
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=item B<-inform DER|PEM|NET>
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This specifies the input format normally the command will expect an X509
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certificate but this can change if other options such as B<-req> are
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present. The DER format is the DER encoding of the certificate and PEM
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is the base64 encoding of the DER encoding with header and footer lines
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added. The NET option is an obscure Netscape server format that is now
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obsolete.
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=item B<-outform DER|PEM|NET>
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This specifies the output format, the options have the same meaning as the
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B<-inform> option.
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=item B<-in filename>
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This specifies the input filename to read a certificate from or standard input
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if this option is not specified.
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=item B<-out filename>
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This specifies the output filename to write to or standard output by
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default.
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=item B<-md2|-md5|-sha1|-mdc2>
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the digest to use. This affects any signing or display option that uses a message
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digest, such as the B<-fingerprint>, B<-signkey> and B<-CA> options. If not
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specified then MD5 is used. If the key being used to sign with is a DSA key then
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this option has no effect: SHA1 is always used with DSA keys.
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=back
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=head1 DISPLAY OPTIONS
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Note: the B<-alias> and B<-purpose> options are also display options
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but are described in the B<TRUST OPTIONS> section.
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=over 4
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=item B<-text>
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prints out the certificate in text form. Full details are output including the
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public key, signature algorithms, issuer and subject names, serial number
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any extensions present and any trust settings.
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=item B<-noout>
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this option prevents output of the encoded version of the request.
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=item B<-modulus>
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this option prints out the value of the modulus of the public key
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contained in the certificate.
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=item B<-serial>
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outputs the certificate serial number.
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=item B<-hash>
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outputs the "hash" of the certificate subject name. This is used in OpenSSL to
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form an index to allow certificates in a directory to be looked up by subject
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name.
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=item B<-subject>
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outputs the subject name.
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=item B<-issuer>
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outputs the issuer name.
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=item B<-startdate>
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prints out the start date of the certificate, that is the notBefore date.
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=item B<-enddate>
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prints out the expiry date of the certificate, that is the notAfter date.
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=item B<-dates>
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prints out the start and expiry dates of a certificate.
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=item B<-fingerprint>
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prints out the digest of the DER encoded version of the whole certificate.
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=item B<-C>
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this outputs the certificate in the form of a C source file.
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=back
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=head1 TRUST SETTINGS
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Please note these options are currently experimental and may well change.
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A B<trusted certificate> is an ordinary certificate which has several
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additional pieces of information attached to it such as the permitted
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and prohibited uses of the certificate and an "alias".
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Normally when a certificate is being verified at least one certificate
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must be "trusted". By default a trusted certificate must be stored
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locally and must be a root CA: any certificate chain ending in this CA
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is then usable for any purpose.
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Trust settings currently are only used with a root CA. They allow a finer
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control over the purposes the root CA can be used for. For example a CA
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may be trusted for SSL client but not SSL server use.
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See the description of the B<verify> utility for more information on the
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meaning of trust settings.
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Future versions of OpenSSL will recognise trust settings on any
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certificate: not just root CAs.
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=over 4
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=item B<-trustout>
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this causes B<x509> to output a B<trusted> certificate. An ordinary
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or trusted certificate can be input but by default an ordinary
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certificate is output and any trust settings are discarded. With the
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B<-trustout> option a trusted certificate is output. A trusted
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certificate is automatically output if any trust settings are modified.
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=item B<-setalias arg>
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sets the alias of the certificate. This will allow the certificate
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to be referred to using a nickname for example "Steve's Certificate".
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=item B<-alias>
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outputs the certificate alias, if any.
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=item B<-clrtrust>
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clears all the permitted or trusted uses of the certificate.
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=item B<-clrreject>
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clears all the prohibited or rejected uses of the certificate.
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=item B<-addtrust arg>
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adds a trusted certificate use. Currently acceptable values
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are B<all> (any purpose), B<sslclient> (SSL client use), B<sslserver>
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(SSL server use) B<email> (S/MIME email) and B<objsign> (Object signing).
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=item B<-addreject arg>
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adds a prohibited use. It accepts the same values as the B<-addtrust>
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option.
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=item B<-purpose>
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this option performs tests on the certificate extensions and outputs
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the results. For a more complete description see the B<CERTIFICATE
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EXTENSIONS> section.
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=back
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=head1 SIGNING OPTIONS
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The B<x509> utility can be used to sign certificates and requests: it
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can thus behave like a "mini CA".
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=over 4
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=item B<-signkey filename>
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this option causes the input file to be self signed using the supplied
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private key.
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If the input file is a certificate it sets the issuer name to the
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subject name (i.e. makes it self signed) changes the public key to the
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supplied value and changes the start and end dates. The start date is
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set to the current time and the end date is set to a value determined
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by the B<-days> option. Any certificate extensions are retained unless
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the B<-clrext> option is supplied.
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If the input is a certificate request then a self signed certificate
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is created using the supplied private key using the subject name in
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the request.
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=item B<-clrext>
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delete any extensions from a certificate. This option is used when a
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certificate is being created from another certificate (for example with
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the B<-signkey> or the B<-CA> options). Normally all extensions are
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retained.
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=item B<-keyform PEM|DER>
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specifies the format (DER or PEM) of the private key file used in the
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B<-signkey> option.
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=item B<-days arg>
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specifies the number of days to make a certificate valid for. The default
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is 30 days.
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=item B<-x509toreq>
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converts a certificate into a certificate request. The B<-signkey> option
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is used to pass the required private key.
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=item B<-req>
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by default a certificate is expected on input. With this option a
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certificate request is expected instead.
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=item B<-CA filename>
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specifies the CA certificate to be used for signing. When this option is
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present B<x509> behaves like a "mini CA". The input file is signed by this
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CA using this option: that is its issuer name is set to the subject name
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of the CA and it is digitally signed using the CAs private key.
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This option is normally combined with the B<-req> option. Without the
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B<-req> option the input is a certificate which must be self signed.
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=item B<-CAkey filename>
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sets the CA private key to sign a certificate with. If this option is
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not specified then it is assumed that the CA private key is present in
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the CA certificate file.
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=item B<-CAserial filename>
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sets the CA serial number file to use.
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When the B<-CA> option is used to sign a certificate it uses a serial
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number specified in a file. This file consist of one line containing
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an even number of hex digits with the serial number to use. After each
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use the serial number is incremented and written out to the file again.
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The default filename consists of the CA certificate file base name with
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".srl" appended. For example if the CA certificate file is called
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"mycacert.pem" it expects to find a serial number file called "mycacert.srl".
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=item B<-CAcreateserial filename>
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with this option the CA serial number file is created if it does not exist:
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it will contain the serial number "01". Normally if the B<-CA> option is
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specified and the serial number file does not exist it is an error.
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=item B<-extfile filename>
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file containing certificate extensions to use. If not specified then
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no extensions are added to the certificate.
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=item B<-extensions section>
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the section to add certificate extensions from. If this option is not
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specified then the extensions should either be contained in the unnamed
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(default) section or the default section should contain a variable called
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"extensions" which contains the section to use.
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=back
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=head1 EXAMPLES
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Note: in these examples the '\' means the example should be all on one
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line.
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Display the contents of a certificate:
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openssl x509 -in cert.pem -noout -text
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Display the certificate serial number:
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openssl x509 -in cert.pem -noout -serial
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Display the certificate MD5 fingerprint:
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openssl x509 -in cert.pem -noout -fingerprint
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Display the certificate SHA1 fingerprint:
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openssl x509 -sha1 -in cert.pem -noout -fingerprint
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Convert a certificate from PEM to DER format:
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openssl x509 -in cert.pem -inform PEM -out cert.der -outform DER
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Convert a certificate to a certificate request:
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openssl x509 -x509toreq -in cert.pem -out req.pem -signkey key.pem
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Convert a certificate request into a self signed certificate using
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extensions for a CA:
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openssl x509 -req -in careq.pem -config openssl.cnf -extensions v3_ca \
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-signkey key.pem -out cacert.pem
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Sign a certificate request using the CA certificate above and add user
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certificate extensions:
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openssl x509 -req -in req.pem -config openssl.cnf -extensions v3_usr \
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-CA cacert.pem -CAkey key.pem -CAcreateserial
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Set a certificate to be trusted for SSL client use and change set its alias to
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"Steve's Class 1 CA"
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openssl x509 -in cert.pem -addtrust sslclient \
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-alias "Steve's Class 1 CA" -out trust.pem
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=head1 NOTES
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The PEM format uses the header and footer lines:
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-----BEGIN CERTIFICATE----
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-----END CERTIFICATE----
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it will also handle files containing:
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-----BEGIN X509 CERTIFICATE----
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-----END X509 CERTIFICATE----
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Trusted certificates have the lines
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-----BEGIN TRUSTED CERTIFICATE----
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-----END TRUSTED CERTIFICATE----
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The B<-fingerprint> option takes the digest of the DER encoded certificate.
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This is commonly called a "fingerprint". Because of the nature of message
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digests the fingerprint of a certificate is unique to that certificate and
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two certificates with the same fingerprint can be considered to be the same.
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The Netscape fingerprint uses MD5 whereas MSIE uses SHA1.
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=head1 CERTIFICATE EXTENSIONS
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The B<-purpose> option checks the certificate extensions and determines
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what the certificate can be used for. The actual checks done are rather
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complex and include various hacks and workarounds to handle broken
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certificates and software.
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The same code is used when verifying untrusted certificates in chains
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so this section is useful if a chain is rejected by the verify code.
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The basicConstraints extension CA flag is used to determine whether the
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certificate can be used as a CA. If the CA flag is true then it is a CA,
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if the CA flag is false then it is not a CA. B<All> CAs should have the
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CA flag set to true.
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If the basicConstraints extension is absent then the certificate is
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considered to be a "possible CA" other extensions are checked according
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to the intended use of the certificate. A warning is given in this case
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because the certificate should really not be regarded as a CA: however
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it is allowed to be a CA to work around some broken software.
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If the certificate is a V1 certificate (and thus has no extensions) and
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it is self signed it is also assumed to be a CA but a warning is again
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given: this is to work around the problem of Verisign roots which are V1
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self signed certificates.
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If the keyUsage extension is present then additional restraints are
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made on the uses of the certificate. A CA certificate B<must> have the
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keyCertSign bit set if the keyUsage extension is present.
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The extended key usage extension places additional restrictions on the
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certificate uses. If this extension is present (whether critical or not)
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the key can only be used for the purposes specified.
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A complete description of each test is given below. The comments about
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basicConstraints and keyUsage and V1 certificates above apply to B<all>
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CA certificates.
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=over 4
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=item B<SSL Client>
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The extended key usage extension must be absent or include the "web client
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authentication" OID. keyUsage must be absent or it must have the
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digitalSignature bit set. Netscape certificate type must be absent or it must
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have the SSL client bit set.
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=item B<SSL Client CA>
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The extended key usage extension must be absent or include the "web client
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authentication" OID. Netscape certificate type must be absent or it must have
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the SSL CA bit set: this is used as a work around if the basicConstraints
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extension is absent.
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=item B<SSL Server>
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The extended key usage extension must be absent or include the "web server
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authentication" and/or one of the SGC OIDs. keyUsage must be absent or it
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must have the digitalSignature, the keyEncipherment set or both bits set.
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Netscape certificate type must be absent or have the SSL server bit set.
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=item B<SSL Server CA>
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The extended key usage extension must be absent or include the "web server
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authentication" and/or one of the SGC OIDs. Netscape certificate type must
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be absent or the SSL CA bit must be set: this is used as a work around if the
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basicConstraints extension is absent.
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=item B<Netscape SSL Server>
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For Netscape SSL clients to connect to an SSL server it must have the
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keyEncipherment bit set if the keyUsage extension is present. This isn't
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always valid because some cipher suites use the key for digital signing.
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Otherwise it is the same as a normal SSL server.
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=item B<Common S/MIME Client Tests>
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The extended key usage extension must be absent or include the "email
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protection" OID. Netscape certificate type must be absent or should have the
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S/MIME bit set. If the S/MIME bit is not set in netscape certificate type
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then the SSL client bit is tolerated as an alternative but a warning is shown:
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this is because some Verisign certificates don't set the S/MIME bit.
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=item B<S/MIME Signing>
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In addition to the common S/MIME client tests the digitalSignature bit must
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be set if the keyUsage extension is present.
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=item B<S/MIME Encryption>
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In addition to the common S/MIME tests the keyEncipherment bit must be set
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if the keyUsage extension is present.
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=item B<S/MIME CA>
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The extended key usage extension must be absent or include the "email
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protection" OID. Netscape certificate type must be absent or must have the
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S/MIME CA bit set: this is used as a work around if the basicConstraints
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extension is absent.
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=item B<CRL Signing>
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The keyUsage extension must be absent or it must have the CRL signing bit
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set.
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=item B<CRL Signing CA>
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The normal CA tests apply. Except in this case the basicConstraints extension
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must be present.
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=back
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=head1 BUGS
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The way DNs are printed is in a "historical SSLeay" format which doesn't
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follow any published standard. It should follow some standard like RFC2253
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or RFC1779 with options to make the stuff more readable.
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Extensions in certificates are not transferred to certificate requests and
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vice versa.
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It is possible to produce invalid certificates or requests by specifying the
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wrong private key or using inconsistent options in some cases: these should
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be checked.
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There should be options to explicitly set such things as start and end
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dates rather than an offset from the current time.
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The code to implement the verify behaviour described in the B<TRUST SETTINGS>
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is currently being developed. It thus describes the intended behavior rather
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than the current behaviour. It is hoped that it will represent reality in
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OpenSSL 0.9.5 and later.
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=head1 SEE ALSO
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req(1), ca(1), genrsa(1), gendsa(1), verify(1)
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=cut
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