From 52261db09ef9dbf5abc95baed22722c5c332f9f7 Mon Sep 17 00:00:00 2001
From: Rob Austein <sra@hactrn.net>
Date: Tue, 20 Jun 2006 17:33:26 +0000
Subject: Pulling OpenSSL 0.9.8b into trunk

svn path=/openssl/trunk; revision=3
---
 openssl/trunk/doc/apps/x509.pod | 832 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 832 insertions(+)
 create mode 100644 openssl/trunk/doc/apps/x509.pod

(limited to 'openssl/trunk/doc/apps/x509.pod')

diff --git a/openssl/trunk/doc/apps/x509.pod b/openssl/trunk/doc/apps/x509.pod
new file mode 100644
index 00000000..a46378f0
--- /dev/null
+++ b/openssl/trunk/doc/apps/x509.pod
@@ -0,0 +1,832 @@
+
+=pod
+
+=head1 NAME
+
+x509 - Certificate display and signing utility
+
+=head1 SYNOPSIS
+
+B<openssl> B<x509>
+[B<-inform DER|PEM|NET>]
+[B<-outform DER|PEM|NET>]
+[B<-keyform DER|PEM>]
+[B<-CAform DER|PEM>]
+[B<-CAkeyform DER|PEM>]
+[B<-in filename>]
+[B<-out filename>]
+[B<-serial>]
+[B<-hash>]
+[B<-subject_hash>]
+[B<-issuer_hash>]
+[B<-subject>]
+[B<-issuer>]
+[B<-nameopt option>]
+[B<-email>]
+[B<-startdate>]
+[B<-enddate>]
+[B<-purpose>]
+[B<-dates>]
+[B<-modulus>]
+[B<-fingerprint>]
+[B<-alias>]
+[B<-noout>]
+[B<-trustout>]
+[B<-clrtrust>]
+[B<-clrreject>]
+[B<-addtrust arg>]
+[B<-addreject arg>]
+[B<-setalias arg>]
+[B<-days arg>]
+[B<-set_serial n>]
+[B<-signkey filename>]
+[B<-x509toreq>]
+[B<-req>]
+[B<-CA filename>]
+[B<-CAkey filename>]
+[B<-CAcreateserial>]
+[B<-CAserial filename>]
+[B<-text>]
+[B<-C>]
+[B<-md2|-md5|-sha1|-mdc2>]
+[B<-clrext>]
+[B<-extfile filename>]
+[B<-extensions section>]
+[B<-engine id>]
+
+=head1 DESCRIPTION
+
+The B<x509> command is a multi purpose certificate utility. It can be
+used to display certificate information, convert certificates to
+various forms, sign certificate requests like a "mini CA" or edit
+certificate trust settings.
+
+Since there are a large number of options they will split up into
+various sections.
+
+=head1 OPTIONS
+
+=head2 INPUT, OUTPUT AND GENERAL PURPOSE OPTIONS
+
+=over 4
+
+=item B<-inform DER|PEM|NET>
+
+This specifies the input format normally the command will expect an X509
+certificate but this can change if other options such as B<-req> are
+present. The DER format is the DER encoding of the certificate and PEM
+is the base64 encoding of the DER encoding with header and footer lines
+added. The NET option is an obscure Netscape server format that is now
+obsolete.
+
+=item B<-outform DER|PEM|NET>
+
+This specifies the output format, the options have the same meaning as the 
+B<-inform> option.
+
+=item B<-in filename>
+
+This specifies the input filename to read a certificate from or standard input
+if this option is not specified.
+
+=item B<-out filename>
+
+This specifies the output filename to write to or standard output by
+default.
+
+=item B<-md2|-md5|-sha1|-mdc2>
+
+the digest to use. This affects any signing or display option that uses a message
+digest, such as the B<-fingerprint>, B<-signkey> and B<-CA> options. If not
+specified then SHA1 is used. If the key being used to sign with is a DSA key
+then this option has no effect: SHA1 is always used with DSA keys.
+
+=item B<-engine id>
+
+specifying an engine (by it's unique B<id> string) will cause B<req>
+to attempt to obtain a functional reference to the specified engine,
+thus initialising it if needed. The engine will then be set as the default
+for all available algorithms.
+
+=back
+
+=head2 DISPLAY OPTIONS
+
+Note: the B<-alias> and B<-purpose> options are also display options
+but are described in the B<TRUST SETTINGS> section.
+
+=over 4
+
+=item B<-text>
+
+prints out the certificate in text form. Full details are output including the
+public key, signature algorithms, issuer and subject names, serial number
+any extensions present and any trust settings.
+
+=item B<-certopt option>
+
+customise the output format used with B<-text>. The B<option> argument can be
+a single option or multiple options separated by commas. The B<-certopt> switch
+may be also be used more than once to set multiple options. See the B<TEXT OPTIONS>
+section for more information.
+
+=item B<-noout>
+
+this option prevents output of the encoded version of the request.
+
+=item B<-modulus>
+
+this option prints out the value of the modulus of the public key
+contained in the certificate.
+
+=item B<-serial>
+
+outputs the certificate serial number.
+
+=item B<-subject_hash>
+
+outputs the "hash" of the certificate subject name. This is used in OpenSSL to
+form an index to allow certificates in a directory to be looked up by subject
+name.
+
+=item B<-issuer_hash>
+
+outputs the "hash" of the certificate issuer name.
+
+=item B<-hash>
+
+synonym for "-hash" for backward compatibility reasons.
+
+=item B<-subject>
+
+outputs the subject name.
+
+=item B<-issuer>
+
+outputs the issuer name.
+
+=item B<-nameopt option>
+
+option which determines how the subject or issuer names are displayed. The
+B<option> argument can be a single option or multiple options separated by
+commas.  Alternatively the B<-nameopt> switch may be used more than once to
+set multiple options. See the B<NAME OPTIONS> section for more information.
+
+=item B<-email>
+
+outputs the email address(es) if any.
+
+=item B<-startdate>
+
+prints out the start date of the certificate, that is the notBefore date.
+
+=item B<-enddate>
+
+prints out the expiry date of the certificate, that is the notAfter date.
+
+=item B<-dates>
+
+prints out the start and expiry dates of a certificate.
+
+=item B<-fingerprint>
+
+prints out the digest of the DER encoded version of the whole certificate
+(see digest options).
+
+=item B<-C>
+
+this outputs the certificate in the form of a C source file.
+
+=back
+
+=head2 TRUST SETTINGS
+
+Please note these options are currently experimental and may well change.
+
+A B<trusted certificate> is an ordinary certificate which has several
+additional pieces of information attached to it such as the permitted
+and prohibited uses of the certificate and an "alias".
+
+Normally when a certificate is being verified at least one certificate
+must be "trusted". By default a trusted certificate must be stored
+locally and must be a root CA: any certificate chain ending in this CA
+is then usable for any purpose.
+
+Trust settings currently are only used with a root CA. They allow a finer
+control over the purposes the root CA can be used for. For example a CA
+may be trusted for SSL client but not SSL server use.
+
+See the description of the B<verify> utility for more information on the
+meaning of trust settings.
+
+Future versions of OpenSSL will recognize trust settings on any
+certificate: not just root CAs.
+
+
+=over 4
+
+=item B<-trustout>
+
+this causes B<x509> to output a B<trusted> certificate. An ordinary
+or trusted certificate can be input but by default an ordinary
+certificate is output and any trust settings are discarded. With the
+B<-trustout> option a trusted certificate is output. A trusted
+certificate is automatically output if any trust settings are modified.
+
+=item B<-setalias arg>
+
+sets the alias of the certificate. This will allow the certificate
+to be referred to using a nickname for example "Steve's Certificate".
+
+=item B<-alias>
+
+outputs the certificate alias, if any.
+
+=item B<-clrtrust>
+
+clears all the permitted or trusted uses of the certificate.
+
+=item B<-clrreject>
+
+clears all the prohibited or rejected uses of the certificate.
+
+=item B<-addtrust arg>
+
+adds a trusted certificate use. Any object name can be used here
+but currently only B<clientAuth> (SSL client use), B<serverAuth>
+(SSL server use) and B<emailProtection> (S/MIME email) are used.
+Other OpenSSL applications may define additional uses.
+
+=item B<-addreject arg>
+
+adds a prohibited use. It accepts the same values as the B<-addtrust>
+option.
+
+=item B<-purpose>
+
+this option performs tests on the certificate extensions and outputs
+the results. For a more complete description see the B<CERTIFICATE
+EXTENSIONS> section.
+
+=back
+
+=head2 SIGNING OPTIONS
+
+The B<x509> utility can be used to sign certificates and requests: it
+can thus behave like a "mini CA".
+
+=over 4
+
+=item B<-signkey filename>
+
+this option causes the input file to be self signed using the supplied
+private key. 
+
+If the input file is a certificate it sets the issuer name to the
+subject name (i.e.  makes it self signed) changes the public key to the
+supplied value and changes the start and end dates. The start date is
+set to the current time and the end date is set to a value determined
+by the B<-days> option. Any certificate extensions are retained unless
+the B<-clrext> option is supplied.
+
+If the input is a certificate request then a self signed certificate
+is created using the supplied private key using the subject name in
+the request.
+
+=item B<-clrext>
+
+delete any extensions from a certificate. This option is used when a
+certificate is being created from another certificate (for example with
+the B<-signkey> or the B<-CA> options). Normally all extensions are
+retained.
+
+=item B<-keyform PEM|DER>
+
+specifies the format (DER or PEM) of the private key file used in the
+B<-signkey> option.
+
+=item B<-days arg>
+
+specifies the number of days to make a certificate valid for. The default
+is 30 days.
+
+=item B<-x509toreq>
+
+converts a certificate into a certificate request. The B<-signkey> option
+is used to pass the required private key.
+
+=item B<-req>
+
+by default a certificate is expected on input. With this option a
+certificate request is expected instead.
+
+=item B<-set_serial n>
+
+specifies the serial number to use. This option can be used with either
+the B<-signkey> or B<-CA> options. If used in conjunction with the B<-CA>
+option the serial number file (as specified by the B<-CAserial> or
+B<-CAcreateserial> options) is not used.
+
+The serial number can be decimal or hex (if preceded by B<0x>). Negative
+serial numbers can also be specified but their use is not recommended.
+
+=item B<-CA filename>
+
+specifies the CA certificate to be used for signing. When this option is
+present B<x509> behaves like a "mini CA". The input file is signed by this
+CA using this option: that is its issuer name is set to the subject name
+of the CA and it is digitally signed using the CAs private key.
+
+This option is normally combined with the B<-req> option. Without the
+B<-req> option the input is a certificate which must be self signed.
+
+=item B<-CAkey filename>
+
+sets the CA private key to sign a certificate with. If this option is
+not specified then it is assumed that the CA private key is present in
+the CA certificate file.
+
+=item B<-CAserial filename>
+
+sets the CA serial number file to use.
+
+When the B<-CA> option is used to sign a certificate it uses a serial
+number specified in a file. This file consist of one line containing
+an even number of hex digits with the serial number to use. After each
+use the serial number is incremented and written out to the file again.
+
+The default filename consists of the CA certificate file base name with
+".srl" appended. For example if the CA certificate file is called 
+"mycacert.pem" it expects to find a serial number file called "mycacert.srl".
+
+=item B<-CAcreateserial>
+
+with this option the CA serial number file is created if it does not exist:
+it will contain the serial number "02" and the certificate being signed will
+have the 1 as its serial number. Normally if the B<-CA> option is specified
+and the serial number file does not exist it is an error.
+
+=item B<-extfile filename>
+
+file containing certificate extensions to use. If not specified then
+no extensions are added to the certificate.
+
+=item B<-extensions section>
+
+the section to add certificate extensions from. If this option is not
+specified then the extensions should either be contained in the unnamed
+(default) section or the default section should contain a variable called
+"extensions" which contains the section to use.
+
+=back
+
+=head2 NAME OPTIONS
+
+The B<nameopt> command line switch determines how the subject and issuer
+names are displayed. If no B<nameopt> switch is present the default "oneline"
+format is used which is compatible with previous versions of OpenSSL.
+Each option is described in detail below, all options can be preceded by
+a B<-> to turn the option off. Only the first four will normally be used.
+
+=over 4
+
+=item B<compat>
+
+use the old format. This is equivalent to specifying no name options at all.
+
+=item B<RFC2253>
+
+displays names compatible with RFC2253 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>
+
+a oneline format which is more readable than RFC2253. It is equivalent to
+specifying the  B<esc_2253>, B<esc_ctrl>, B<esc_msb>, B<utf8>, B<dump_nostr>,
+B<dump_der>, B<use_quote>, B<sep_comma_plus_spc>, B<spc_eq> and B<sname>
+options.
+
+=item B<multiline>
+
+a multiline format. It is equivalent B<esc_ctrl>, B<esc_msb>, B<sep_multiline>,
+B<spc_eq>, B<lname> and B<align>.
+
+=item B<esc_2253>
+
+escape the "special" characters required by RFC2253 in a field That is
+B<,+"E<lt>E<gt>;>. Additionally B<#> is escaped at the beginning of a string
+and a space character at the beginning or end of a string.
+
+=item B<esc_ctrl>
+
+escape control characters. That is those with ASCII values less than
+0x20 (space) and the delete (0x7f) character. They are escaped using the
+RFC2253 \XX notation (where XX are two hex digits representing the
+character value).
+
+=item B<esc_msb>
+
+escape characters with the MSB set, that is with ASCII values larger than
+127.
+
+=item B<use_quote>
+
+escapes some characters by surrounding the whole string with B<"> characters,
+without the option all escaping is done with the B<\> character.
+
+=item B<utf8>
+
+convert all strings to UTF8 format first. This is required by RFC2253. If
+you are lucky enough to have a UTF8 compatible terminal then the use
+of this option (and B<not> setting B<esc_msb>) may result in the correct
+display of multibyte (international) characters. Is this option is not
+present then multibyte characters larger than 0xff will be represented
+using the format \UXXXX for 16 bits and \WXXXXXXXX for 32 bits.
+Also if this option is off any UTF8Strings will be converted to their
+character form first.
+
+=item B<no_type>
+
+this option does not attempt to interpret multibyte characters in any
+way. That is their 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>
+
+show the type of the ASN1 character string. The type precedes the
+field contents. For example "BMPSTRING: Hello World".
+
+=item B<dump_der>
+
+when this option is set any fields that need to be hexdumped will
+be dumped using the DER encoding of the field. Otherwise just the
+content octets will be displayed. Both options use the RFC2253
+B<#XXXX...> format.
+
+=item B<dump_nostr>
+
+dump non character string types (for example 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. This option when used with B<dump_der> 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>
+
+these options determine the field separators. The first character is
+between RDNs and the second between multiple 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> uses a linefeed character for
+the RDN separator and a spaced B<+> for the AVA separator. It also
+indents the fields by four characters.
+
+=item B<dn_rev>
+
+reverse the fields of the DN. This is required by RFC2253. As a side
+effect this also reverses the order of multiple AVAs but this is
+permissible.
+
+=item B<nofname>, B<sname>, B<lname>, B<oid>
+
+these options alter 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<spc_eq>
+
+places spaces round the B<=> character which follows the field
+name.
+
+=back
+
+=head2 TEXT OPTIONS
+
+As well as customising the name output format, it is also possible to
+customise the actual fields printed using the B<certopt> options when
+the B<text> option is present. The default behaviour is to print all fields.
+
+=over 4
+
+=item B<compatible>
+
+use the old format. This is equivalent to specifying no output options at all.
+
+=item B<no_header>
+
+don't print header information: that is the lines saying "Certificate" and "Data".
+
+=item B<no_version>
+
+don't print out the version number.
+
+=item B<no_serial>
+
+don't print out the serial number.
+
+=item B<no_signame>
+
+don't print out the signature algorithm used.
+
+=item B<no_validity>
+
+don't print the validity, that is the B<notBefore> and B<notAfter> fields.
+
+=item B<no_subject>
+
+don't print out the subject name.
+
+=item B<no_issuer>
+
+don't print out the issuer name.
+
+=item B<no_pubkey>
+
+don't print out the public key.
+
+=item B<no_sigdump>
+
+don't give a hexadecimal dump of the certificate signature.
+
+=item B<no_aux>
+
+don't print out certificate trust information.
+
+=item B<no_extensions>
+
+don't print out any X509V3 extensions.
+
+=item B<ext_default>
+
+retain default extension behaviour: attempt to print out unsupported certificate extensions.
+
+=item B<ext_error>
+
+print an error message for unsupported certificate extensions.
+
+=item B<ext_parse>
+
+ASN1 parse unsupported extensions.
+
+=item B<ext_dump>
+
+hex dump unsupported extensions.
+
+=item B<ca_default>
+
+the value used by the B<ca> utility, equivalent to B<no_issuer>, B<no_pubkey>, B<no_header>,
+B<no_version>, B<no_sigdump> and B<no_signame>.
+
+=back
+
+=head1 EXAMPLES
+
+Note: in these examples the '\' means the example should be all on one
+line.
+
+Display the contents of a certificate:
+
+ openssl x509 -in cert.pem -noout -text
+
+Display the certificate serial number:
+
+ openssl x509 -in cert.pem -noout -serial
+
+Display the certificate subject name:
+
+ openssl x509 -in cert.pem -noout -subject
+
+Display the certificate subject name in RFC2253 form:
+
+ openssl x509 -in cert.pem -noout -subject -nameopt RFC2253
+
+Display the certificate subject name in oneline form on a terminal
+supporting UTF8:
+
+ openssl x509 -in cert.pem -noout -subject -nameopt oneline,-escmsb
+
+Display the certificate MD5 fingerprint:
+
+ openssl x509 -in cert.pem -noout -fingerprint
+
+Display the certificate SHA1 fingerprint:
+
+ openssl x509 -sha1 -in cert.pem -noout -fingerprint
+
+Convert a certificate from PEM to DER format:
+
+ openssl x509 -in cert.pem -inform PEM -out cert.der -outform DER
+
+Convert a certificate to a certificate request:
+
+ openssl x509 -x509toreq -in cert.pem -out req.pem -signkey key.pem
+
+Convert a certificate request into a self signed certificate using
+extensions for a CA:
+
+ openssl x509 -req -in careq.pem -extfile openssl.cnf -extensions v3_ca \
+	-signkey key.pem -out cacert.pem
+
+Sign a certificate request using the CA certificate above and add user
+certificate extensions:
+
+ openssl x509 -req -in req.pem -extfile openssl.cnf -extensions v3_usr \
+	-CA cacert.pem -CAkey key.pem -CAcreateserial
+
+
+Set a certificate to be trusted for SSL client use and change set its alias to
+"Steve's Class 1 CA"
+
+ openssl x509 -in cert.pem -addtrust clientAuth \
+	-setalias "Steve's Class 1 CA" -out trust.pem
+
+=head1 NOTES
+
+The PEM format uses the header and footer lines:
+
+ -----BEGIN CERTIFICATE-----
+ -----END CERTIFICATE-----
+
+it will also handle files containing:
+
+ -----BEGIN X509 CERTIFICATE-----
+ -----END X509 CERTIFICATE-----
+
+Trusted certificates have the lines
+
+ -----BEGIN TRUSTED CERTIFICATE-----
+ -----END TRUSTED CERTIFICATE-----
+
+The conversion to UTF8 format used with the name options assumes that
+T61Strings use the ISO8859-1 character set. This is wrong but Netscape
+and MSIE do this as do many certificates. So although this is incorrect
+it is more likely to display the majority of certificates correctly.
+
+The B<-fingerprint> option takes the digest of the DER encoded certificate.
+This is commonly called a "fingerprint". Because of the nature of message
+digests the fingerprint of a certificate is unique to that certificate and
+two certificates with the same fingerprint can be considered to be the same.
+
+The Netscape fingerprint uses MD5 whereas MSIE uses SHA1.
+
+The B<-email> option searches the subject name and the subject alternative
+name extension. Only unique email addresses will be printed out: it will
+not print the same address more than once.
+
+=head1 CERTIFICATE EXTENSIONS
+
+The B<-purpose> option checks the certificate extensions and determines
+what the certificate can be used for. The actual checks done are rather
+complex and include various hacks and workarounds to handle broken
+certificates and software.
+
+The same code is used when verifying untrusted certificates in chains
+so this section is useful if a chain is rejected by the verify code.
+
+The basicConstraints extension CA flag is used to determine whether the
+certificate can be used as a CA. If the CA flag is true then it is a CA,
+if the CA flag is false then it is not a CA. B<All> CAs should have the
+CA flag set to true.
+
+If the basicConstraints extension is absent then the certificate is
+considered to be a "possible CA" other extensions are checked according
+to the intended use of the certificate. A warning is given in this case
+because the certificate should really not be regarded as a CA: however
+it is allowed to be a CA to work around some broken software.
+
+If the certificate is a V1 certificate (and thus has no extensions) and
+it is self signed it is also assumed to be a CA but a warning is again
+given: this is to work around the problem of Verisign roots which are V1
+self signed certificates.
+
+If the keyUsage extension is present then additional restraints are
+made on the uses of the certificate. A CA certificate B<must> have the
+keyCertSign bit set if the keyUsage extension is present.
+
+The extended key usage extension places additional restrictions on the
+certificate uses. If this extension is present (whether critical or not)
+the key can only be used for the purposes specified.
+
+A complete description of each test is given below. The comments about
+basicConstraints and keyUsage and V1 certificates above apply to B<all>
+CA certificates.
+
+
+=over 4
+
+=item B<SSL Client>
+
+The extended key usage extension must be absent or include the "web client
+authentication" OID.  keyUsage must be absent or it must have the
+digitalSignature bit set. Netscape certificate type must be absent or it must
+have the SSL client bit set.
+
+=item B<SSL Client CA>
+
+The extended key usage extension must be absent or include the "web client
+authentication" OID. Netscape certificate type must be absent or it must have
+the SSL CA bit set: this is used as a work around if the basicConstraints
+extension is absent.
+
+=item B<SSL Server>
+
+The extended key usage extension must be absent or include the "web server
+authentication" and/or one of the SGC OIDs.  keyUsage must be absent or it
+must have the digitalSignature, the keyEncipherment set or both bits set.
+Netscape certificate type must be absent or have the SSL server bit set.
+
+=item B<SSL Server CA>
+
+The extended key usage extension must be absent or include the "web server
+authentication" and/or one of the SGC OIDs.  Netscape certificate type must
+be absent or the SSL CA bit must be set: this is used as a work around if the
+basicConstraints extension is absent.
+
+=item B<Netscape SSL Server>
+
+For Netscape SSL clients to connect to an SSL server it must have the
+keyEncipherment bit set if the keyUsage extension is present. This isn't
+always valid because some cipher suites use the key for digital signing.
+Otherwise it is the same as a normal SSL server.
+
+=item B<Common S/MIME Client Tests>
+
+The extended key usage extension must be absent or include the "email
+protection" OID. Netscape certificate type must be absent or should have the
+S/MIME bit set. If the S/MIME bit is not set in netscape certificate type
+then the SSL client bit is tolerated as an alternative but a warning is shown:
+this is because some Verisign certificates don't set the S/MIME bit.
+
+=item B<S/MIME Signing>
+
+In addition to the common S/MIME client tests the digitalSignature bit must
+be set if the keyUsage extension is present.
+
+=item B<S/MIME Encryption>
+
+In addition to the common S/MIME tests the keyEncipherment bit must be set
+if the keyUsage extension is present.
+
+=item B<S/MIME CA>
+
+The extended key usage extension must be absent or include the "email
+protection" OID. Netscape certificate type must be absent or must have the
+S/MIME CA bit set: this is used as a work around if the basicConstraints
+extension is absent. 
+
+=item B<CRL Signing>
+
+The keyUsage extension must be absent or it must have the CRL signing bit
+set.
+
+=item B<CRL Signing CA>
+
+The normal CA tests apply. Except in this case the basicConstraints extension
+must be present.
+
+=back
+
+=head1 BUGS
+
+Extensions in certificates are not transferred to certificate requests and
+vice versa.
+
+It is possible to produce invalid certificates or requests by specifying the
+wrong private key or using inconsistent options in some cases: these should
+be checked.
+
+There should be options to explicitly set such things as start and end
+dates rather than an offset from the current time.
+
+The code to implement the verify behaviour described in the B<TRUST SETTINGS>
+is currently being developed. It thus describes the intended behaviour rather
+than the current behaviour. It is hoped that it will represent reality in
+OpenSSL 0.9.5 and later.
+
+=head1 SEE ALSO
+
+L<req(1)|req(1)>, L<ca(1)|ca(1)>, L<genrsa(1)|genrsa(1)>,
+L<gendsa(1)|gendsa(1)>, L<verify(1)|verify(1)>
+
+=head1 HISTORY
+
+Before OpenSSL 0.9.8, the default digest for RSA keys was MD5.
+
+=cut
-- 
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