2 This is some preliminary documentation for OpenSSL.
6 OpenSSL X509V3 extension configuration
7 X509V3 Extension code: programmers guide
11 ==============================================================================
12 OpenSSL X509V3 extension configuration
13 ==============================================================================
15 OpenSSL X509V3 extension configuration: preliminary documentation.
19 For OpenSSL 0.9.2 the extension code has be considerably enhanced. It is now
20 possible to add and print out common X509 V3 certificate and CRL extensions.
24 For most simple applications you don't need to know too much about extensions:
25 the default openssl.cnf values will usually do sensible things.
27 If you want to know more you can initially quickly look through the sections
28 describing how the standard OpenSSL utilities display and add extensions and
29 then the list of supported extensions.
31 For more technical information about the meaning of extensions see:
33 http://www.imc.org/ietf-pkix/
34 http://home.netscape.com/eng/security/certs.html
38 Extension values are automatically printed out for supported extensions.
40 openssl x509 -in cert.pem -text
41 openssl crl -in crl.pem -text
43 will give information in the extension printout, for example:
46 X509v3 Basic Constraints:
48 X509v3 Subject Key Identifier:
49 73:FE:F7:59:A7:E1:26:84:44:D6:44:36:EE:79:1A:95:7C:B1:4B:15
50 X509v3 Authority Key Identifier:
51 keyid:73:FE:F7:59:A7:E1:26:84:44:D6:44:36:EE:79:1A:95:7C:B1:4B:15, DirName:/C=AU/ST=Some-State/O=Internet Widgits Pty Ltd/Email=email@1.address/Email=email@2.address, serial:00
53 Certificate Sign, CRL Sign
54 X509v3 Subject Alternative Name:
55 email:email@1.address, email:email@2.address
59 The OpenSSL utilities 'ca' and 'req' can now have extension sections listing
60 which certificate extensions to include. In each case a line:
62 x509_extensions = extension_section
64 indicates which section contains the extensions. In the case of 'req' the
65 extension section is used when the -x509 option is present to create a
66 self signed root certificate.
68 The 'x509' utility also supports extensions when it signs a certificate.
69 The -extfile option is used to set the configuration file containing the
70 extensions. In this case a line with:
72 extensions = extension_section
74 in the nameless (default) section is used. If no such line is included then
75 it uses the default section.
77 You can also add extensions to CRLs: a line
79 crl_extensions = crl_extension_section
81 will include extensions when the -gencrl option is used with the 'ca' utility.
82 You can add any extension to a CRL but of the supported extensions only
83 issuerAltName and authorityKeyIdentifier make any real sense. Note: these are
84 CRL extensions NOT CRL *entry* extensions which cannot currently be generated.
85 CRL entry extensions can be displayed.
87 NB. At this time Netscape Communicator rejects V2 CRLs: to get an old V1 CRL
88 you should not include a crl_extensions line in the configuration file.
90 As with all configuration files you can use the inbuilt environment expansion
91 to allow the values to be passed in the environment. Therefore if you have
92 several extension sections used for different purposes you can have a line:
94 x509_extensions = $ENV::ENV_EXT
96 and set the ENV_EXT environment variable before calling the relevant utility.
100 Extensions have the basic form:
102 extension_name=[critical,] extension_options
104 the use of the critical option makes the extension critical. Extreme caution
105 should be made when using the critical flag. If an extension is marked
106 as critical then any client that does not understand the extension should
107 reject it as invalid. Some broken software will reject certificates which
108 have *any* critical extensions (these violates PKIX but we have to live
111 There are three main types of extension: string extensions, multi-valued
112 extensions, and raw extensions.
114 String extensions simply have a string which contains either the value itself
115 or how it is obtained.
119 nsComment="This is a Comment"
121 Multi-valued extensions have a short form and a long form. The short form
122 is a list of names and values:
124 basicConstraints=critical,CA:true,pathlen:1
126 The long form allows the values to be placed in a separate section:
128 basicConstraints=critical,@bs_section
135 Both forms are equivalent. However it should be noted that in some cases the
136 same name can appear multiple times, for example,
138 subjectAltName=email:steve@here,email:steve@there
140 in this case an equivalent long form is:
142 subjectAltName=@alt_section
149 This is because the configuration file code cannot handle the same name
150 occurring twice in the same section.
152 The syntax of raw extensions is governed by the extension code: it can
153 for example contain data in multiple sections. The correct syntax to
154 use is defined by the extension code itself: check out the certificate
155 policies extension for an example.
157 In addition it is also possible to use the word DER to include arbitrary
158 data in any extension.
160 1.2.3.4=critical,DER:01:02:03:04
163 The value following DER is a hex dump of the DER encoding of the extension
164 Any extension can be placed in this form to override the default behaviour.
167 basicConstraints=critical,DER:00:01:02:03
169 WARNING: DER should be used with caution. It is possible to create totally
170 invalid extensions unless care is taken.
172 CURRENTLY SUPPORTED EXTENSIONS.
174 If you aren't sure about extensions then they can be largely ignored: its only
175 when you want to do things like restrict certificate usage when you need to
178 The only extension that a beginner might want to look at is Basic Constraints.
179 If in addition you want to try Netscape object signing the you should also
180 look at Netscape Certificate Type.
182 Literal String extensions.
184 In each case the 'value' of the extension is placed directly in the
185 extension. Currently supported extensions in this category are: nsBaseUrl,
186 nsRevocationUrl, nsCaRevocationUrl, nsRenewalUrl, nsCaPolicyUrl,
187 nsSslServerName and nsComment.
191 nsComment="This is a test comment"
195 Bit string extensions just consist of a list of supported bits, currently
196 two extensions are in this category: PKIX keyUsage and the Netscape specific
199 nsCertType (netscape certificate type) takes the flags: client, server, email,
200 objsign, reserved, sslCA, emailCA, objCA.
202 keyUsage (PKIX key usage) takes the flags: digitalSignature, nonRepudiation,
203 keyEncipherment, dataEncipherment, keyAgreement, keyCertSign, cRLSign,
204 encipherOnly, decipherOnly.
210 keyUsage=digitalSignature, nonRepudiation
212 Hints on Netscape Certificate Type.
214 Other than Basic Constraints this is the only extension a beginner might
215 want to use, if you want to try Netscape object signing, otherwise it can
218 If you want a certificate that can be used just for object signing then:
222 will do the job. If you want to use it as a normal end user and server
223 certificate as well then
225 nsCertType=objsign,email,server
227 is more appropriate. You cannot use a self signed certificate for object
228 signing (well Netscape signtool can but it cheats!) so you need to create
229 a CA certificate and sign an end user certificate with it.
231 Side note: If you want to conform to the Netscape specifications then you
232 should really also set:
236 in the *CA* certificate for just an object signing CA and
238 nsCertType=objCA,emailCA,sslCA
240 for everything. Current Netscape software doesn't enforce this so it can
245 This is generally the only extension you need to worry about for simple
246 applications. If you want your certificate to be usable as a CA certificate
247 (in addition to an end user certificate) then you set this to:
249 basicConstraints=CA:TRUE
251 if you want to be certain the certificate cannot be used as a CA then do:
253 basicConstraints=CA:FALSE
255 The rest of this section describes more advanced usage.
257 Basic constraints is a multi-valued extension that supports a CA and an
258 optional pathlen option. The CA option takes the values true and false and
259 pathlen takes an integer. Note if the CA option is false the pathlen option
262 The pathlen parameter indicates the maximum number of CAs that can appear
263 below this one in a chain. So if you have a CA with a pathlen of zero it can
264 only be used to sign end user certificates and not further CAs. This all
265 assumes that the software correctly interprets this extension of course.
269 basicConstraints=CA:TRUE
270 basicConstraints=critical,CA:TRUE, pathlen:0
272 NOTE: for a CA to be considered valid it must have the CA option set to
273 TRUE. An end user certificate MUST NOT have the CA value set to true.
274 According to PKIX recommendations it should exclude the extension entirely,
275 however some software may require CA set to FALSE for end entity certificates.
279 This extensions consists of a list of usages.
281 These can either be object short names of the dotted numerical form of OIDs.
282 While any OID can be used only certain values make sense. In particular the
283 following PKIX, NS and MS values are meaningful:
287 serverAuth SSL/TLS Web Server Authentication.
288 clientAuth SSL/TLS Web Client Authentication.
289 codeSigning Code signing.
290 emailProtection E-mail Protection (S/MIME).
291 timeStamping Trusted Timestamping
292 msCodeInd Microsoft Individual Code Signing (authenticode)
293 msCodeCom Microsoft Commercial Code Signing (authenticode)
294 msCTLSign Microsoft Trust List Signing
295 msSGC Microsoft Server Gated Crypto
296 msEFS Microsoft Encrypted File System
297 nsSGC Netscape Server Gated Crypto
299 For example, under IE5 a CA can be used for any purpose: by including a list
300 of the above usages the CA can be restricted to only authorised uses.
302 Note: software packages may place additional interpretations on certificate
303 use, in particular some usages may only work for selected CAs. Don't for example
304 expect just including msSGC or nsSGC will automatically mean that a certificate
305 can be used for SGC ("step up" encryption) otherwise anyone could use it.
309 extendedKeyUsage=critical,codeSigning,1.2.3.4
310 extendedKeyUsage=nsSGC,msSGC
312 Subject Key Identifier.
314 This is really a string extension and can take two possible values. Either
315 a hex string giving details of the extension value to include or the word
316 'hash' which then automatically follow PKIX guidelines in selecting and
317 appropriate key identifier. The use of the hex string is strongly discouraged.
319 Example: subjectKeyIdentifier=hash
321 Authority Key Identifier.
323 The authority key identifier extension permits two options. keyid and issuer:
324 both can take the optional value "always".
326 If the keyid option is present an attempt is made to copy the subject key
327 identifier from the parent certificate. If the value "always" is present
328 then an error is returned if the option fails.
330 The issuer option copies the issuer and serial number from the issuer
331 certificate. Normally this will only be done if the keyid option fails or
332 is not included: the "always" flag will always include the value.
334 Subject Alternative Name.
336 The subject alternative name extension allows various literal values to be
337 included in the configuration file. These include "email" (an email address)
338 "URI" a uniform resource indicator, "DNS" (a DNS domain name), RID (a
339 registered ID: OBJECT IDENTIFIER) and IP (and IP address).
341 Also the email option include a special 'copy' value. This will automatically
342 include and email addresses contained in the certificate subject name in
347 subjectAltName=email:copy,email:my@other.address,URL:http://my.url.here/
348 subjectAltName=email:my@other.address,RID:1.2.3.4
350 Issuer Alternative Name.
352 The issuer alternative name option supports all the literal options of
353 subject alternative name. It does *not* support the email:copy option because
354 that would not make sense. It does support an additional issuer:copy option
355 that will copy all the subject alternative name values from the issuer
356 certificate (if possible).
358 CRL distribution points.
360 This is a multi-valued extension that supports all the literal options of
361 subject alternative name. Of the few software packages that currently interpret
362 this extension most only interpret the URI option.
364 Currently each option will set a new DistributionPoint with the fullName
365 field set to the given value.
367 Other fields like cRLissuer and reasons cannot currently be set or displayed:
368 at this time no examples were available that used these fields.
370 If you see this extension with <UNSUPPORTED> when you attempt to print it out
371 or it doesn't appear to display correctly then let me know, including the
372 certificate (mail me at steve@openssl.org) .
376 crlDistributionPoints=URI:http://www.myhost.com/myca.crl
377 crlDistributionPoints=URI:http://www.my.com/my.crl,URI:http://www.oth.com/my.crl
379 Certificate Policies.
381 This is a RAW extension. It attempts to display the contents of this extension:
382 unfortunately this extension is often improperly encoded.
384 The certificate policies extension will rarely be used in practice: few
385 software packages interpret it correctly or at all. IE5 does partially
386 support this extension: but it needs the 'ia5org' option because it will
387 only correctly support a broken encoding. Of the options below only the
388 policy OID, explicitText and CPS options are displayed with IE5.
390 All the fields of this extension can be set by using the appropriate syntax.
392 If you follow the PKIX recommendations of not including any qualifiers and just
393 using only one OID then you just include the value of that OID. Multiple OIDs
394 can be set separated by commas, for example:
396 certificatePolicies= 1.2.4.5, 1.1.3.4
398 If you wish to include qualifiers then the policy OID and qualifiers need to
399 be specified in a separate section: this is done by using the @section syntax
400 instead of a literal OID value.
402 The section referred to must include the policy OID using the name
403 policyIdentifier, cPSuri qualifiers can be included using the syntax:
407 userNotice qualifiers can be set using the syntax:
409 userNotice.nnn=@notice
411 The value of the userNotice qualifier is specified in the relevant section.
412 This section can include explicitText, organization and noticeNumbers
413 options. explicitText and organization are text strings, noticeNumbers is a
414 comma separated list of numbers. The organization and noticeNumbers options
415 (if included) must BOTH be present. If you use the userNotice option with IE5
416 then you need the 'ia5org' option at the top level to modify the encoding:
417 otherwise it will not be interpreted properly.
421 certificatePolicies=ia5org,1.2.3.4,1.5.6.7.8,@polsect
425 policyIdentifier = 1.3.5.8
426 CPS.1="http://my.host.name/"
427 CPS.2="http://my.your.name/"
432 explicitText="Explicit Text Here"
433 organization="Organisation Name"
434 noticeNumbers=1,2,3,4
436 TECHNICAL NOTE: the ia5org option changes the type of the 'organization' field,
437 according to PKIX it should be of type DisplayText but Verisign uses an
438 IA5STRING and IE5 needs this too.
440 Display only extensions.
442 Some extensions are only partially supported and currently are only displayed
443 but cannot be set. These include private key usage period, CRL number, and
446 ==============================================================================
447 X509V3 Extension code: programmers guide
448 ==============================================================================
450 The purpose of the extension code is twofold. It allows an extension to be
451 created from a string or structure describing its contents and it prints out an
452 extension in a human or machine readable form.
454 1. Initialisation and cleanup.
456 No special initialisation is needed before calling the extension functions.
457 You used to have to call X509V3_add_standard_extensions(); but this is no longer
458 required and this function no longer does anything.
460 void X509V3_EXT_cleanup(void);
462 This function should be called to cleanup the extension code if any custom
463 extensions have been added. If no custom extensions have been added then this
464 call does nothing. After this call all custom extension code is freed up but
465 you can still use the standard extensions.
467 2. Printing and parsing extensions.
469 The simplest way to print out extensions is via the standard X509 printing
470 routines: if you use the standard X509_print() function, the supported
471 extensions will be printed out automatically.
473 The following functions allow finer control over extension display:
475 int X509V3_EXT_print(BIO *out, X509_EXTENSION *ext, int flag, int indent);
476 int X509V3_EXT_print_fp(FILE *out, X509_EXTENSION *ext, int flag, int indent);
478 These two functions print out an individual extension to a BIO or FILE pointer.
479 Currently the flag argument is unused and should be set to 0. The 'indent'
480 argument is the number of spaces to indent each line.
482 void *X509V3_EXT_d2i(X509_EXTENSION *ext);
484 This function parses an extension and returns its internal structure. The
485 precise structure you get back depends on the extension being parsed. If the
486 extension if basicConstraints you will get back a pointer to a
487 BASIC_CONSTRAINTS structure. Check out the source in crypto/x509v3 for more
488 details about the structures returned. The returned structure should be freed
489 after use using the relevant free function, BASIC_CONSTRAINTS_free() for
492 3. Generating extensions.
494 An extension will typically be generated from a configuration file, or some
495 other kind of configuration database.
497 int X509V3_EXT_add_conf(LHASH *conf, X509V3_CTX *ctx, char *section,
499 int X509V3_EXT_CRL_add_conf(LHASH *conf, X509V3_CTX *ctx, char *section,
502 These functions add all the extensions in the given section to the given
503 certificate or CRL. They will normally be called just before the certificate
504 or CRL is due to be signed. Both return 0 on error on non zero for success.
506 In each case 'conf' is the LHASH pointer of the configuration file to use
507 and 'section' is the section containing the extension details.
509 See the 'context functions' section for a description of the ctx parameter.
512 X509_EXTENSION *X509V3_EXT_conf(LHASH *conf, X509V3_CTX *ctx, char *name,
515 This function returns an extension based on a name and value pair, if the
516 pair will not need to access other sections in a config file (or there is no
517 config file) then the 'conf' parameter can be set to NULL.
519 X509_EXTENSION *X509V3_EXT_conf_nid(char *conf, X509V3_CTX *ctx, int nid,
522 This function creates an extension in the same way as X509V3_EXT_conf() but
523 takes the NID of the extension rather than its name.
525 For example to produce basicConstraints with the CA flag and a path length of
528 x = X509V3_EXT_conf_nid(NULL, NULL, NID_basic_constraints,"CA:TRUE,pathlen:10");
531 X509_EXTENSION *X509V3_EXT_i2d(int ext_nid, int crit, void *ext_struc);
533 This function sets up an extension from its internal structure. The ext_nid
534 parameter is the NID of the extension and 'crit' is the critical flag.
536 4. Context functions.
538 The following functions set and manipulate an extension context structure.
539 The purpose of the extension context is to allow the extension code to
540 access various structures relating to the "environment" of the certificate:
541 for example the issuers certificate or the certificate request.
543 void X509V3_set_ctx(X509V3_CTX *ctx, X509 *issuer, X509 *subject,
544 X509_REQ *req, X509_CRL *crl, int flags);
546 This function sets up an X509V3_CTX structure with details of the certificate
547 environment: specifically the issuers certificate, the subject certificate,
548 the certificate request and the CRL: if these are not relevant or not
549 available then they can be set to NULL. The 'flags' parameter should be set
552 X509V3_set_ctx_test(ctx)
554 This macro is used to set the 'ctx' structure to a 'test' value: this is to
555 allow the syntax of an extension (or configuration file) to be tested.
557 X509V3_set_ctx_nodb(ctx)
559 This macro is used when no configuration database is present.
561 void X509V3_set_conf_lhash(X509V3_CTX *ctx, LHASH *lhash);
563 This function is used to set the configuration database when it is an LHASH
564 structure: typically a configuration file.
566 The following functions are used to access a configuration database: they
567 should only be used in RAW extensions.
569 char * X509V3_get_string(X509V3_CTX *ctx, char *name, char *section);
571 This function returns the value of the parameter "name" in "section", or NULL
572 if there has been an error.
574 void X509V3_string_free(X509V3_CTX *ctx, char *str);
576 This function frees up the string returned by the above function.
578 STACK_OF(CONF_VALUE) * X509V3_get_section(X509V3_CTX *ctx, char *section);
580 This function returns a whole section as a STACK_OF(CONF_VALUE) .
582 void X509V3_section_free( X509V3_CTX *ctx, STACK_OF(CONF_VALUE) *section);
584 This function frees up the STACK returned by the above function.
586 Note: it is possible to use the extension code with a custom configuration
587 database. To do this the "db_meth" element of the X509V3_CTX structure should
588 be set to an X509V3_CTX_METHOD structure. This structure contains the following
591 char * (*get_string)(void *db, char *section, char *value);
592 STACK_OF(CONF_VALUE) * (*get_section)(void *db, char *section);
593 void (*free_string)(void *db, char * string);
594 void (*free_section)(void *db, STACK_OF(CONF_VALUE) *section);
596 these will be called and passed the 'db' element in the X509V3_CTX structure
597 to access the database. If a given function is not implemented or not required
598 it can be set to NULL.
600 5. String helper functions.
602 There are several "i2s" and "s2i" functions that convert structures to and
603 from ASCII strings. In all the "i2s" cases the returned string should be
604 freed using Free() after use. Since some of these are part of other extension
605 code they may take a 'method' parameter. Unless otherwise stated it can be
608 char *i2s_ASN1_OCTET_STRING(X509V3_EXT_METHOD *method, ASN1_OCTET_STRING *oct);
610 This returns a hex string from an ASN1_OCTET_STRING.
612 char * i2s_ASN1_INTEGER(X509V3_EXT_METHOD *meth, ASN1_INTEGER *aint);
613 char * i2s_ASN1_ENUMERATED(X509V3_EXT_METHOD *meth, ASN1_ENUMERATED *aint);
615 These return a string decimal representations of an ASN1_INTEGER and an
616 ASN1_ENUMERATED type, respectively.
618 ASN1_OCTET_STRING *s2i_ASN1_OCTET_STRING(X509V3_EXT_METHOD *method,
619 X509V3_CTX *ctx, char *str);
621 This converts an ASCII hex string to an ASN1_OCTET_STRING.
623 ASN1_INTEGER * s2i_ASN1_INTEGER(X509V3_EXT_METHOD *meth, char *value);
625 This converts a decimal ASCII string into an ASN1_INTEGER.
627 6. Multi valued extension helper functions.
629 The following functions can be used to manipulate STACKs of CONF_VALUE
630 structures, as used by multi valued extensions.
632 int X509V3_get_value_bool(CONF_VALUE *value, int *asn1_bool);
634 This function expects a boolean value in 'value' and sets 'asn1_bool' to
635 it. That is it sets it to 0 for FALSE or 0xff for TRUE. The following
636 strings are acceptable: "TRUE", "true", "Y", "y", "YES", "yes", "FALSE"
637 "false", "N", "n", "NO" or "no".
639 int X509V3_get_value_int(CONF_VALUE *value, ASN1_INTEGER **aint);
641 This accepts a decimal integer of arbitrary length and sets an ASN1_INTEGER.
643 int X509V3_add_value(const char *name, const char *value,
644 STACK_OF(CONF_VALUE) **extlist);
646 This simply adds a string name and value pair.
648 int X509V3_add_value_uchar(const char *name, const unsigned char *value,
649 STACK_OF(CONF_VALUE) **extlist);
651 The same as above but for an unsigned character value.
653 int X509V3_add_value_bool(const char *name, int asn1_bool,
654 STACK_OF(CONF_VALUE) **extlist);
656 This adds either "TRUE" or "FALSE" depending on the value of 'asn1_bool'
658 int X509V3_add_value_bool_nf(char *name, int asn1_bool,
659 STACK_OF(CONF_VALUE) **extlist);
661 This is the same as above except it adds nothing if asn1_bool is FALSE.
663 int X509V3_add_value_int(const char *name, ASN1_INTEGER *aint,
664 STACK_OF(CONF_VALUE) **extlist);
666 This function adds the value of the ASN1_INTEGER in decimal form.
668 7. Other helper functions.
672 ADDING CUSTOM EXTENSIONS.
674 Currently there are three types of supported extensions.
676 String extensions are simple strings where the value is placed directly in the
677 extensions, and the string returned is printed out.
679 Multi value extensions are passed a STACK_OF(CONF_VALUE) name and value pairs
680 or return a STACK_OF(CONF_VALUE).
682 Raw extensions are just passed a BIO or a value and it is the extensions
683 responsibility to handle all the necessary printing.
685 There are two ways to add an extension. One is simply as an alias to an already
686 existing extension. An alias is an extension that is identical in ASN1 structure
687 to an existing extension but has a different OBJECT IDENTIFIER. This can be
690 int X509V3_EXT_add_alias(int nid_to, int nid_from);
692 'nid_to' is the new extension NID and 'nid_from' is the already existing
695 Alternatively an extension can be written from scratch. This involves writing
696 the ASN1 code to encode and decode the extension and functions to print out and
697 generate the extension from strings. The relevant functions are then placed in
698 a X509V3_EXT_METHOD structure and int X509V3_EXT_add(X509V3_EXT_METHOD *ext);
701 The X509V3_EXT_METHOD structure is described below.
706 X509V3_EXT_NEW ext_new;
707 X509V3_EXT_FREE ext_free;
720 The elements have the following meanings.
722 ext_nid is the NID of the object identifier of the extension.
724 ext_flags is set of flags. Currently the only external flag is
725 X509V3_EXT_MULTILINE which means a multi valued extensions
726 should be printed on separate lines.
728 usr_data is an extension specific pointer to any relevant data. This
729 allows extensions to share identical code but have different
730 uses. An example of this is the bit string extension which uses
731 usr_data to contain a list of the bit names.
733 All the remaining elements are function pointers.
735 ext_new is a pointer to a function that allocates memory for the
736 extension ASN1 structure: for example ASN1_OBJECT_new().
738 ext_free is a pointer to a function that free up memory of the extension
739 ASN1 structure: for example ASN1_OBJECT_free().
741 d2i is the standard ASN1 function that converts a DER buffer into
742 the internal ASN1 structure: for example d2i_ASN1_IA5STRING().
744 i2d is the standard ASN1 function that converts the internal
745 structure into the DER representation: for example
746 i2d_ASN1_IA5STRING().
748 The remaining functions are depend on the type of extension. One i2X and
749 one X2i should be set and the rest set to NULL. The types set do not need
750 to match up, for example the extension could be set using the multi valued
751 v2i function and printed out using the raw i2r.
753 All functions have the X509V3_EXT_METHOD passed to them in the 'method'
754 parameter and an X509V3_CTX structure. Extension code can then access the
755 parent structure via the 'method' parameter to for example make use of the value
756 of usr_data. If the code needs to use detail relating to the request it can
757 use the 'ctx' parameter.
759 A note should be given here about the 'flags' member of the 'ctx' parameter.
760 If it has the value CTX_TEST then the configuration syntax is being checked
761 and no actual certificate or CRL exists. Therefore any attempt in the config
762 file to access such information should silently succeed. If the syntax is OK
763 then it should simply return a (possibly bogus) extension, otherwise it
766 char *i2s(struct v3_ext_method *method, void *ext);
768 This function takes the internal structure in the ext parameter and returns
769 a Malloc'ed string representing its value.
771 void * s2i(struct v3_ext_method *method, struct v3_ext_ctx *ctx, char *str);
773 This function takes the string representation in the ext parameter and returns
774 an allocated internal structure: ext_free() will be used on this internal
777 i2v and v2i handle a STACK_OF(CONF_VALUE):
786 Only the name and value members are currently used.
788 STACK_OF(CONF_VALUE) * i2v(struct v3_ext_method *method, void *ext);
790 This function is passed the internal structure in the ext parameter and
791 returns a STACK of CONF_VALUE structures. The values of name, value,
792 section and the structure itself will be freed up with Free after use.
793 Several helper functions are available to add values to this STACK.
795 void * v2i(struct v3_ext_method *method, struct v3_ext_ctx *ctx,
796 STACK_OF(CONF_VALUE) *values);
798 This function takes a STACK_OF(CONF_VALUE) structures and should set the
799 values of the external structure. This typically uses the name element to
800 determine which structure element to set and the value element to determine
801 what to set it to. Several helper functions are available for this
804 int i2r(struct v3_ext_method *method, void *ext, BIO *out, int indent);
806 This function is passed the internal extension structure in the ext parameter
807 and sends out a human readable version of the extension to out. The 'indent'
808 parameter should be noted to determine the necessary amount of indentation
809 needed on the output.
811 void * r2i(struct v3_ext_method *method, struct v3_ext_ctx *ctx, char *str);
813 This is just passed the string representation of the extension. It is intended
814 to be used for more elaborate extensions where the standard single and multi
815 valued options are insufficient. They can use the 'ctx' parameter to parse the
816 configuration database themselves. See the context functions section for details
819 Note: although this type takes the same parameters as the "r2s" function there
820 is a subtle difference. Whereas an "r2i" function can access a configuration
821 database an "s2i" function MUST NOT. This is so the internal code can safely
822 assume that an "s2i" function will work without a configuration database.
824 ==============================================================================
826 ==============================================================================
828 This section describes the internal PKCS#12 support. There are very few
829 differences between the old external library and the new internal code at
830 present. This may well change because the external library will not be updated
833 This version now includes a couple of high level PKCS#12 functions which
834 generally "do the right thing" and should make it much easier to handle PKCS#12
837 HIGH LEVEL FUNCTIONS.
839 For most applications you only need concern yourself with the high level
840 functions. They can parse and generate simple PKCS#12 files as produced by
841 Netscape and MSIE or indeed any compliant PKCS#12 file containing a single
842 private key and certificate pair.
844 1. Initialisation and cleanup.
846 No special initialisation is needed for the internal PKCS#12 library: the
847 standard SSLeay_add_all_algorithms() is sufficient. If you do not wish to
848 add all algorithms (you should at least add SHA1 though) then you can manually
849 initialise the PKCS#12 library with:
853 The memory allocated by the PKCS#12 library is freed up when EVP_cleanup() is
854 called or it can be directly freed with:
858 after this call (or EVP_cleanup() ) no more PKCS#12 library functions should
863 i2d_PKCS12_bio(bp, p12)
865 This writes out a PKCS12 structure to a BIO.
867 i2d_PKCS12_fp(fp, p12)
869 This is the same but for a FILE pointer.
871 d2i_PKCS12_bio(bp, p12)
873 This reads in a PKCS12 structure from a BIO.
875 d2i_PKCS12_fp(fp, p12)
877 This is the same but for a FILE pointer.
879 3. High level functions.
881 3.1 Parsing with PKCS12_parse().
883 int PKCS12_parse(PKCS12 *p12, char *pass, EVP_PKEY **pkey, X509 **cert,
886 This function takes a PKCS12 structure and a password (ASCII, null terminated)
887 and returns the private key, the corresponding certificate and any CA
888 certificates. If any of these is not required it can be passed as a NULL.
889 The 'ca' parameter should be either NULL, a pointer to NULL or a valid STACK
890 structure. Typically to read in a PKCS#12 file you might do:
892 p12 = d2i_PKCS12_fp(fp, NULL);
893 PKCS12_parse(p12, password, &pkey, &cert, NULL); /* CAs not wanted */
896 3.2 PKCS#12 creation with PKCS12_create().
898 PKCS12 *PKCS12_create(char *pass, char *name, EVP_PKEY *pkey, X509 *cert,
899 STACK *ca, int nid_key, int nid_cert, int iter,
900 int mac_iter, int keytype);
902 This function will create a PKCS12 structure from a given password, name,
903 private key, certificate and optional STACK of CA certificates. The remaining
904 5 parameters can be set to 0 and sensible defaults will be used.
906 The parameters nid_key and nid_cert are the key and certificate encryption
907 algorithms, iter is the encryption iteration count, mac_iter is the MAC
908 iteration count and keytype is the type of private key. If you really want
909 to know what these last 5 parameters do then read the low level section.
911 Typically to create a PKCS#12 file the following could be used:
913 p12 = PKCS12_create(pass, "My Certificate", pkey, cert, NULL, 0,0,0,0,0);
914 i2d_PKCS12_fp(fp, p12);
917 3.3 Changing a PKCS#12 structure password.
919 int PKCS12_newpass(PKCS12 *p12, char *oldpass, char *newpass);
921 This changes the password of an already existing PKCS#12 structure. oldpass
922 is the old password and newpass is the new one. An error occurs if the old
923 password is incorrect.
927 In some cases the high level functions do not provide the necessary
928 functionality. For example if you want to generate or parse more complex
929 PKCS#12 files. The sample pkcs12 application uses the low level functions
930 to display details about the internal structure of a PKCS#12 file.
934 This is a brief description of how a PKCS#12 file is represented internally:
935 some knowledge of PKCS#12 is assumed.
937 A PKCS#12 object contains several levels.
939 At the lowest level is a PKCS12_SAFEBAG. This can contain a certificate, a
940 CRL, a private key, encrypted or unencrypted, a set of safebags (so the
941 structure can be nested) or other secrets (not documented at present).
942 A safebag can optionally have attributes, currently these are: a unicode
943 friendlyName (a Unicode string) or a localKeyID (a string of bytes).
945 At the next level is an authSafe which is a set of safebags collected into
946 a PKCS#7 ContentInfo. This can be just plain data, or encrypted itself.
948 At the top level is the PKCS12 structure itself which contains a set of
949 authSafes in an embedded PKCS#7 Contentinfo of type data. In addition it
950 contains a MAC which is a kind of password protected digest to preserve
951 integrity (so any unencrypted stuff below can't be tampered with).
953 The reason for these levels is so various objects can be encrypted in various
954 ways. For example you might want to encrypt a set of private keys with
955 triple-DES and then include the related certificates either unencrypted or
956 with lower encryption. Yes it's the dreaded crypto laws at work again which
957 allow strong encryption on private keys and only weak encryption on other
960 To build one of these things you turn all certificates and keys into safebags
961 (with optional attributes). You collect the safebags into (one or more) STACKS
962 and convert these into authsafes (encrypted or unencrypted). The authsafes
963 are collected into a STACK and added to a PKCS12 structure. Finally a MAC
966 Pulling one apart is basically the reverse process. The MAC is verified against
967 the given password. The authsafes are extracted and each authsafe split into
968 a set of safebags (possibly involving decryption). Finally the safebags are
969 decomposed into the original keys and certificates and the attributes used to
970 match up private key and certificate pairs.
972 Anyway here are the functions that do the dirty work.
974 1. Construction functions.
976 1.1 Safebag functions.
978 M_PKCS12_x5092certbag(x509)
980 This macro takes an X509 structure and returns a certificate bag. The
981 X509 structure can be freed up after calling this function.
983 M_PKCS12_x509crl2certbag(crl)
985 As above but for a CRL.
987 PKCS8_PRIV_KEY_INFO *PKEY2PKCS8(EVP_PKEY *pkey)
989 Take a private key and convert it into a PKCS#8 PrivateKeyInfo structure.
990 Works for both RSA and DSA private keys. NB since the PKCS#8 PrivateKeyInfo
991 structure contains a private key data in plain text form it should be free'd
992 up as soon as it has been encrypted for security reasons (freeing up the
993 structure zeros out the sensitive data). This can be done with
994 PKCS8_PRIV_KEY_INFO_free().
996 PKCS8_add_keyusage(PKCS8_PRIV_KEY_INFO *p8, int usage)
998 This sets the key type when a key is imported into MSIE or Outlook 98. Two
999 values are currently supported: KEY_EX and KEY_SIG. KEY_EX is an exchange type
1000 key that can also be used for signing but its size is limited in the export
1001 versions of MS software to 512 bits, it is also the default. KEY_SIG is a
1002 signing only key but the keysize is unlimited (well 16K is supposed to work).
1003 If you are using the domestic version of MSIE then you can ignore this because
1004 KEY_EX is not limited and can be used for both.
1006 PKCS12_SAFEBAG *PKCS12_MAKE_KEYBAG(PKCS8_PRIV_KEY_INFO *p8)
1008 Convert a PKCS8 private key structure into a keybag. This routine embeds the
1009 p8 structure in the keybag so p8 should not be freed up or used after it is
1010 called. The p8 structure will be freed up when the safebag is freed.
1012 PKCS12_SAFEBAG *PKCS12_MAKE_SHKEYBAG(int pbe_nid, unsigned char *pass, int passlen, unsigned char *salt, int saltlen, int iter, PKCS8_PRIV_KEY_INFO *p8)
1014 Convert a PKCS#8 structure into a shrouded key bag (encrypted). p8 is not
1015 embedded and can be freed up after use.
1017 int PKCS12_add_localkeyid(PKCS12_SAFEBAG *bag, unsigned char *name, int namelen)
1018 int PKCS12_add_friendlyname(PKCS12_SAFEBAG *bag, unsigned char *name, int namelen)
1020 Add a local key id or a friendlyname to a safebag.
1022 1.2 Authsafe functions.
1024 PKCS7 *PKCS12_pack_p7data(STACK *sk)
1025 Take a stack of safebags and convert them into an unencrypted authsafe. The
1026 stack of safebags can be freed up after calling this function.
1028 PKCS7 *PKCS12_pack_p7encdata(int pbe_nid, unsigned char *pass, int passlen, unsigned char *salt, int saltlen, int iter, STACK *bags);
1030 As above but encrypted.
1032 1.3 PKCS12 functions.
1034 PKCS12 *PKCS12_init(int mode)
1036 Initialise a PKCS12 structure (currently mode should be NID_pkcs7_data).
1038 M_PKCS12_pack_authsafes(p12, safes)
1040 This macro takes a STACK of authsafes and adds them to a PKCS#12 structure.
1042 int PKCS12_set_mac(PKCS12 *p12, unsigned char *pass, int passlen, unsigned char *salt, int saltlen, int iter, EVP_MD *md_type);
1044 Add a MAC to a PKCS12 structure. If EVP_MD is NULL use SHA-1, the spec suggests
1045 that SHA-1 should be used.
1047 2. Extraction Functions.
1051 M_PKCS12_bag_type(bag)
1053 Return the type of "bag". Returns one of the following
1056 NID_pkcs8ShroudedKeyBag 7
1060 NID_safeContentsBag 11
1062 M_PKCS12_cert_bag_type(bag)
1064 Returns type of certificate bag, following are understood.
1066 NID_x509Certificate 14
1067 NID_sdsiCertificate 15
1069 M_PKCS12_crl_bag_type(bag)
1071 Returns crl bag type, currently only NID_crlBag is recognised.
1073 M_PKCS12_certbag2x509(bag)
1075 This macro extracts an X509 certificate from a certificate bag.
1077 M_PKCS12_certbag2x509crl(bag)
1079 As above but for a CRL.
1081 EVP_PKEY * PKCS82PKEY(PKCS8_PRIV_KEY_INFO *p8)
1083 Extract a private key from a PKCS8 private key info structure.
1085 M_PKCS12_decrypt_skey(bag, pass, passlen)
1087 Decrypt a shrouded key bag and return a PKCS8 private key info structure.
1088 Works with both RSA and DSA keys
1090 char *PKCS12_get_friendlyname(bag)
1092 Returns the friendlyName of a bag if present or NULL if none. The returned
1093 string is a null terminated ASCII string allocated with Malloc(). It should
1094 thus be freed up with Free() after use.
1096 2.2 AuthSafe functions.
1098 M_PKCS12_unpack_p7data(p7)
1100 Extract a STACK of safe bags from a PKCS#7 data ContentInfo.
1102 #define M_PKCS12_unpack_p7encdata(p7, pass, passlen)
1104 As above but for an encrypted content info.
1106 2.3 PKCS12 functions.
1108 M_PKCS12_unpack_authsafes(p12)
1110 Extract a STACK of authsafes from a PKCS12 structure.
1112 M_PKCS12_mac_present(p12)
1114 Check to see if a MAC is present.
1116 int PKCS12_verify_mac(PKCS12 *p12, unsigned char *pass, int passlen)
1118 Verify a MAC on a PKCS12 structure. Returns an error if MAC not present.
1123 1. All the function return 0 or NULL on error.
1124 2. Encryption based functions take a common set of parameters. These are
1128 ASCII password and length. The password on the MAC is called the "integrity
1129 password" the encryption password is called the "privacy password" in the
1130 PKCS#12 documentation. The passwords do not have to be the same. If -1 is
1131 passed for the length it is worked out by the function itself (currently
1132 this is sometimes done whatever is passed as the length but that may change).
1135 A 'salt' if salt is NULL a random salt is used. If saltlen is also zero a
1136 default length is used.
1139 Iteration count. This is a measure of how many times an internal function is
1140 called to encrypt the data. The larger this value is the longer it takes, it
1141 makes dictionary attacks on passwords harder. NOTE: Some implementations do
1142 not support an iteration count on the MAC. If the password for the MAC and
1143 encryption is the same then there is no point in having a high iteration
1144 count for encryption if the MAC has no count. The MAC could be attacked
1145 and the password used for the main decryption.
1148 This is the NID of the password based encryption method used. The following are
1150 NID_pbe_WithSHA1And128BitRC4
1151 NID_pbe_WithSHA1And40BitRC4
1152 NID_pbe_WithSHA1And3_Key_TripleDES_CBC
1153 NID_pbe_WithSHA1And2_Key_TripleDES_CBC
1154 NID_pbe_WithSHA1And128BitRC2_CBC
1155 NID_pbe_WithSHA1And40BitRC2_CBC
1157 Which you use depends on the implementation you are exporting to. "Export
1158 grade" (i.e. cryptographically challenged) products cannot support all
1159 algorithms. Typically you may be able to use any encryption on shrouded key
1160 bags but they must then be placed in an unencrypted authsafe. Other authsafes
1161 may only support 40bit encryption. Of course if you are using SSLeay
1162 throughout you can strongly encrypt everything and have high iteration counts
1165 3. For decryption routines only the password and length are needed.
1167 4. Unlike the external version the nid's of objects are the values of the
1168 constants: that is NID_certBag is the real nid, therefore there is no
1169 PKCS12_obj_offset() function. Note the object constants are not the same as
1170 those of the external version. If you use these constants then you will need
1171 to recompile your code.
1173 5. With the exception of PKCS12_MAKE_KEYBAG(), after calling any function or
1174 macro of the form PKCS12_MAKE_SOMETHING(other) the "other" structure can be
1175 reused or freed up safely.