2 This is some preliminary documentation for OpenSSL.
4 ==============================================================================
6 ==============================================================================
8 The buffer library handles simple character arrays. Buffers are used for
9 various purposes in the library, most notably memory BIOs.
11 The library uses the BUF_MEM structure defined in buffer.h:
13 typedef struct buf_mem_st
15 int length; /* current number of bytes */
17 int max; /* size of buffer */
20 'length' is the current size of the buffer in bytes, 'max' is the amount of
21 memory allocated to the buffer. There are three functions which handle these
22 and one "miscellaneous" function.
24 BUF_MEM *BUF_MEM_new()
26 This allocates a new buffer of zero size. Returns the buffer or NULL on error.
28 void BUF_MEM_free(BUF_MEM *a)
30 This frees up an already existing buffer. The data is zeroed before freeing
31 up in case the buffer contains sensitive data.
33 int BUF_MEM_grow(BUF_MEM *str, int len)
35 This changes the size of an already existing buffer. It returns zero on error
36 or the new size (i.e. 'len'). Any data already in the buffer is preserved if
39 char * BUF_strdup(char *str)
41 This is the previously mentioned strdup function: like the standard library
42 strdup() it copies a null terminated string into a block of allocated memory
43 and returns a pointer to the allocated block.
45 Unlike the standard C library strdup() this function uses Malloc() and so
46 should be used in preference to the standard library strdup() because it can
47 be used for memory leak checking or replacing the malloc() function.
49 The memory allocated from BUF_strdup() should be freed up using the Free()
52 ==============================================================================
53 OpenSSL X509V3 extension configuration
54 ==============================================================================
56 OpenSSL X509V3 extension configuration: preliminary documentation.
60 For OpenSSL 0.9.2 the extension code has be considerably enhanced. It is now
61 possible to add and print out common X509 V3 certificate and CRL extensions.
65 For most simple applications you don't need to know too much about extensions:
66 the default openssl.cnf values will usually do sensible things.
68 If you want to know more you can initially quickly look through the sections
69 describing how the standard OpenSSL utilities display and add extensions and
70 then the list of supported extensions.
72 For more technical information about the meaning of extensions see:
74 http://www.imc.org/ietf-pkix/
75 http://home.netscape.com/eng/security/certs.html
79 Extension values are automatically printed out for supported extensions.
81 openssl x509 -in cert.pem -text
82 openssl crl -in crl.pem -text
84 will give information in the extension printout, for example:
87 X509v3 Basic Constraints:
89 X509v3 Subject Key Identifier:
90 73:FE:F7:59:A7:E1:26:84:44:D6:44:36:EE:79:1A:95:7C:B1:4B:15
91 X509v3 Authority Key Identifier:
92 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
94 Certificate Sign, CRL Sign
95 X509v3 Subject Alternative Name:
96 email:email@1.address, email:email@2.address
100 The OpenSSL utilities 'ca' and 'req' can now have extension sections listing
101 which certificate extensions to include. In each case a line:
103 x509_extensions = extension_section
105 indicates which section contains the extensions. In the case of 'req' the
106 extension section is used when the -x509 option is present to create a
107 self signed root certificate.
109 The 'x509' utility also supports extensions when it signs a certificate.
110 The -extfile option is used to set the configuration file containing the
111 extensions. In this case a line with:
113 extensions = extension_section
115 in the nameless (default) section is used. If no such line is included then
116 it uses the default section.
118 You can also add extensions to CRLs: a line
120 crl_extensions = crl_extension_section
122 will include extensions when the -gencrl option is used with the 'ca' utility.
123 You can add any extension to a CRL but of the supported extensions only
124 issuerAltName and authorityKeyIdentifier make any real sense. Note: these are
125 CRL extensions NOT CRL *entry* extensions which cannot currently be generated.
126 CRL entry extensions can be displayed.
128 NB. At this time Netscape Communicator rejects V2 CRLs: to get an old V1 CRL
129 you should not include a crl_extensions line in the configuration file.
131 As with all configuration files you can use the inbuilt environment expansion
132 to allow the values to be passed in the environment. Therefore if you have
133 several extension sections used for different purposes you can have a line:
135 x509_extensions = $ENV::ENV_EXT
137 and set the ENV_EXT environment variable before calling the relevant utility.
141 Extensions have the basic form:
143 extension_name=[critical,] extension_options
145 the use of the critical option makes the extension critical. Extreme caution
146 should be made when using the critical flag. If an extension is marked
147 as critical then any client that does not understand the extension should
148 reject it as invalid. Some broken software will reject certificates which
149 have *any* critical extensions (these violates PKIX but we have to live
152 There are three main types of extension: string extensions, multi-valued
153 extensions, and raw extensions.
155 String extensions simply have a string which contains either the value itself
156 or how it is obtained.
160 nsComment="This is a Comment"
162 Multi-valued extensions have a short form and a long form. The short form
163 is a list of names and values:
165 basicConstraints=critical,CA:true,pathlen:1
167 The long form allows the values to be placed in a separate section:
169 basicConstraints=critical,@bs_section
176 Both forms are equivalent. However it should be noted that in some cases the
177 same name can appear multiple times, for example,
179 subjectAltName=email:steve@here,email:steve@there
181 in this case an equivalent long form is:
183 subjectAltName=@alt_section
190 This is because the configuration file code cannot handle the same name
191 occurring twice in the same section.
193 The syntax of raw extensions is governed by the extension code: it can
194 for example contain data in multiple sections. The correct syntax to
195 use is defined by the extension code itself: check out the certificate
196 policies extension for an example.
198 In addition it is also possible to use the word DER to include arbitrary
199 data in any extension.
201 1.2.3.4=critical,DER:01:02:03:04
204 The value following DER is a hex dump of the DER encoding of the extension
205 Any extension can be placed in this form to override the default behaviour.
208 basicConstraints=critical,DER:00:01:02:03
210 WARNING: DER should be used with caution. It is possible to create totally
211 invalid extensions unless care is taken.
213 CURRENTLY SUPPORTED EXTENSIONS.
215 If you aren't sure about extensions then they can be largely ignored: its only
216 when you want to do things like restrict certificate usage when you need to
219 The only extension that a beginner might want to look at is Basic Constraints.
220 If in addition you want to try Netscape object signing the you should also
221 look at Netscape Certificate Type.
223 Literal String extensions.
225 In each case the 'value' of the extension is placed directly in the
226 extension. Currently supported extensions in this category are: nsBaseUrl,
227 nsRevocationUrl, nsCaRevocationUrl, nsRenewalUrl, nsCaPolicyUrl,
228 nsSslServerName and nsComment.
232 nsComment="This is a test comment"
236 Bit string extensions just consist of a list of supported bits, currently
237 two extensions are in this category: PKIX keyUsage and the Netscape specific
240 nsCertType (netscape certificate type) takes the flags: client, server, email,
241 objsign, reserved, sslCA, emailCA, objCA.
243 keyUsage (PKIX key usage) takes the flags: digitalSignature, nonRepudiation,
244 keyEncipherment, dataEncipherment, keyAgreement, keyCertSign, cRLSign,
245 encipherOnly, decipherOnly.
251 keyUsage=digitalSignature, nonRepudiation
253 Hints on Netscape Certificate Type.
255 Other than Basic Constraints this is the only extension a beginner might
256 want to use, if you want to try Netscape object signing, otherwise it can
259 If you want a certificate that can be used just for object signing then:
263 will do the job. If you want to use it as a normal end user and server
264 certificate as well then
266 nsCertType=objsign,email,server
268 is more appropriate. You cannot use a self signed certificate for object
269 signing (well Netscape signtool can but it cheats!) so you need to create
270 a CA certificate and sign an end user certificate with it.
272 Side note: If you want to conform to the Netscape specifications then you
273 should really also set:
277 in the *CA* certificate for just an object signing CA and
279 nsCertType=objCA,emailCA,sslCA
281 for everything. Current Netscape software doesn't enforce this so it can
286 This is generally the only extension you need to worry about for simple
287 applications. If you want your certificate to be usable as a CA certificate
288 (in addition to an end user certificate) then you set this to:
290 basicConstraints=CA:TRUE
292 if you want to be certain the certificate cannot be used as a CA then do:
294 basicConstraints=CA:FALSE
296 The rest of this section describes more advanced usage.
298 Basic constraints is a multi-valued extension that supports a CA and an
299 optional pathlen option. The CA option takes the values true and false and
300 pathlen takes an integer. Note if the CA option is false the pathlen option
303 The pathlen parameter indicates the maximum number of CAs that can appear
304 below this one in a chain. So if you have a CA with a pathlen of zero it can
305 only be used to sign end user certificates and not further CAs. This all
306 assumes that the software correctly interprets this extension of course.
310 basicConstraints=CA:TRUE
311 basicConstraints=critical,CA:TRUE, pathlen:0
313 NOTE: for a CA to be considered valid it must have the CA option set to
314 TRUE. An end user certificate MUST NOT have the CA value set to true.
315 According to PKIX recommendations it should exclude the extension entirely,
316 however some software may require CA set to FALSE for end entity certificates.
320 This extensions consists of a list of usages.
322 These can either be object short names of the dotted numerical form of OIDs.
323 While any OID can be used only certain values make sense. In partiular the
324 following PKIX, NS and MS values are meaningful:
328 serverAuth SSL/TLS Web Server Authentication.
329 clientAuth SSL/TLS Web Client Authentication.
330 codeSigning Code signing.
331 emailProtection E-mail Protection (S/MIME).
332 timeStamping Trusted Timestamping
333 msCodeInd Microsoft Individual Code Signing (authenticode)
334 msCodeCom Microsoft Commercial Code Signing (authenticode)
335 msCTLSign Microsoft Trust List Signing
336 msSGC Microsoft Server Gated Crypto
337 msEFS Microsoft Encrypted File System
338 nsSGC Netscape Server Gated Crypto
340 For example, under IE5 a CA can be used for any purpose: by including a list
341 of the above usages the CA can be restricted to only authorised uses.
343 Note: software packages may place additional interpretations on certificate
344 use, in particular some usages may only work for selected CAs. Don't for example
345 expect just including msSGC or nsSGC will automatically mean that a certificate
346 can be used for SGC ("step up" encryption) otherwise anyone could use it.
348 Subject Key Identifier.
350 This is really a string extension and can take two possible values. Either
351 a hex string giving details of the extension value to include or the word
352 'hash' which then automatically follow PKIX guidelines in selecting and
353 appropriate key identifier. The use of the hex string is strongly discouraged.
355 Example: subjectKeyIdentifier=hash
357 Authority Key Identifier.
359 The authority key identifier extension permits two options. keyid and issuer:
360 both can take the optional value "always".
362 If the keyid option is present an attempt is made to copy the subject key
363 identifier from the parent certificate. If the value "always" is present
364 then an error is returned if the option fails.
366 The issuer option copies the issuer and serial number from the issuer
367 certificate. Normally this will only be done if the keyid option fails or
368 is not included: the "always" flag will always include the value.
370 Subject Alternative Name.
372 The subject alternative name extension allows various literal values to be
373 included in the configuration file. These include "email" (an email address)
374 "URI" a uniform resource indicator, "DNS" (a DNS domain name), RID (a
375 registered ID: OBJECT IDENTIFIER) and IP (and IP address).
377 Also the email option include a special 'copy' value. This will automatically
378 include and email addresses contained in the certificate subject name in
383 subjectAltName=email:copy,email:my@other.address,URL:http://my.url.here/
384 subjectAltName=email:my@other.address,RID:1.2.3.4
386 Issuer Alternative Name.
388 The issuer alternative name option supports all the literal options of
389 subject alternative name. It does *not* support the email:copy option because
390 that would not make sense. It does support an additional issuer:copy option
391 that will copy all the subject alternative name values from the issuer
392 certificate (if possible).
394 CRL distribution points.
396 This is a multi-valued extension that supports all the literal options of
397 subject alternative name. Of the few software packages that currently interpret
398 this extension most only interpret the URI option.
400 Currently each option will set a new DistributionPoint with the fullName
401 field set to the given value.
403 Other fields like cRLissuer and reasons cannot currently be set or displayed:
404 at this time no examples were available that used these fields.
406 If you see this extension with <UNSUPPORTED> when you attempt to print it out
407 or it doesn't appear to display correctly then let me know, including the
408 certificate (mail me at steve@openssl.org) .
412 crlDistributionPoints=URI:http://www.myhost.com/myca.crl
413 crlDistributionPoints=URI:http://www.my.com/my.crl,URI:http://www.oth.com/my.crl
415 Certificate Policies.
417 This is a RAW extension. It attempts to display the contents of this extension:
418 unfortunately this extension is often improperly encoded.
420 The certificate policies extension will rarely be used in practice: few
421 software packages interpret it correctly or at all. IE5 does partially
422 support this extension: but it needs the 'ia5org' option because it will
423 only correctly support a broken encoding. Of the options below only the
424 policy OID, explicitText and CPS options are displayed with IE5.
426 All the fields of this extension can be set by using the appropriate syntax.
428 If you follow the PKIX recommendations of not including any qualifiers and just
429 using only one OID then you just include the value of that OID. Multiple OIDs
430 can be set separated by commas, for example:
432 certificatePolicies= 1.2.4.5, 1.1.3.4
434 If you wish to include qualifiers then the policy OID and qualifiers need to
435 be specified in a separate section: this is done by using the @section syntax
436 instead of a literal OID value.
438 The section referred to must include the policy OID using the name
439 policyIdentifier, cPSuri qualifiers can be included using the syntax:
443 userNotice qualifiers can be set using the syntax:
445 userNotice.nnn=@notice
447 The value of the userNotice qualifier is specified in the relevant section.
448 This section can include explicitText, organization and noticeNumbers
449 options. explicitText and organization are text strings, noticeNumbers is a
450 comma separated list of numbers. The organization and noticeNumbers options
451 (if included) must BOTH be present. If you use the userNotice option with IE5
452 then you need the 'ia5org' option at the top level to modify the encoding:
453 otherwise it will not be interpreted properly.
457 certificatePolicies=ia5org,1.2.3.4,1.5.6.7.8,@polsect
461 policyIdentifier = 1.3.5.8
462 CPS.1="http://my.host.name/"
463 CPS.2="http://my.your.name/"
468 explicitText="Explicit Text Here"
469 organization="Organisation Name"
470 noticeNumbers=1,2,3,4
472 TECHNICAL NOTE: the ia5org option changes the type of the 'organization' field,
473 according to PKIX it should be of type DisplayText but Verisign uses an
474 IA5STRING and IE5 needs this too.
476 Display only extensions.
478 Some extensions are only partially supported and currently are only displayed
479 but cannot be set. These include private key usage period, CRL number, and
482 ==============================================================================
483 X509V3 Extension code: programmers guide
484 ==============================================================================
486 The purpose of the extension code is twofold. It allows an extension to be
487 created from a string or structure describing its contents and it prints out an
488 extension in a human or machine readable form.
490 1. Initialisation and cleanup.
492 X509V3_add_standard_extensions();
494 This function should be called before any other extension code. It adds support
495 for some common PKIX and Netscape extensions. Additional custom extensions can
496 be added as well (see later).
498 void X509V3_EXT_cleanup(void);
500 This function should be called last to cleanup the extension code. After this
501 call no other extension calls should be made.
503 2. Printing and parsing extensions.
505 The simplest way to print out extensions is via the standard X509 printing
506 routines: if you use the standard X509_print() function, the supported
507 extensions will be printed out automatically.
509 The following functions allow finer control over extension display:
511 int X509V3_EXT_print(BIO *out, X509_EXTENSION *ext, int flag, int indent);
512 int X509V3_EXT_print_fp(FILE *out, X509_EXTENSION *ext, int flag, int indent);
514 These two functions print out an individual extension to a BIO or FILE pointer.
515 Currently the flag argument is unused and should be set to 0. The 'indent'
516 argument is the number of spaces to indent each line.
518 void *X509V3_EXT_d2i(X509_EXTENSION *ext);
520 This function parses an extension and returns its internal structure. The
521 precise structure you get back depends on the extension being parsed. If the
522 extension if basicConstraints you will get back a pointer to a
523 BASIC_CONSTRAINTS structure. Check out the source in crypto/x509v3 for more
524 details about the structures returned. The returned structure should be freed
525 after use using the relevant free function, BASIC_CONSTRAINTS_free() for
528 3. Generating extensions.
530 An extension will typically be generated from a configuration file, or some
531 other kind of configuration database.
533 int X509V3_EXT_add_conf(LHASH *conf, X509V3_CTX *ctx, char *section,
535 int X509V3_EXT_CRL_add_conf(LHASH *conf, X509V3_CTX *ctx, char *section,
538 These functions add all the extensions in the given section to the given
539 certificate or CRL. They will normally be called just before the certificate
540 or CRL is due to be signed. Both return 0 on error on non zero for success.
542 In each case 'conf' is the LHASH pointer of the configuration file to use
543 and 'section' is the section containing the extension details.
545 See the 'context functions' section for a description of the ctx paramater.
548 X509_EXTENSION *X509V3_EXT_conf(LHASH *conf, X509V3_CTX *ctx, char *name,
551 This function returns an extension based on a name and value pair, if the
552 pair will not need to access other sections in a config file (or there is no
553 config file) then the 'conf' parameter can be set to NULL.
555 X509_EXTENSION *X509V3_EXT_conf_nid(char *conf, X509V3_CTX *ctx, int nid,
558 This function creates an extension in the same way as X509V3_EXT_conf() but
559 takes the NID of the extension rather than its name.
561 For example to produce basicConstraints with the CA flag and a path length of
564 x = X509V3_EXT_conf_nid(NULL, NULL, NID_basic_constraints,"CA:TRUE,pathlen:10");
567 X509_EXTENSION *X509V3_EXT_i2d(int ext_nid, int crit, void *ext_struc);
569 This function sets up an extension from its internal structure. The ext_nid
570 parameter is the NID of the extension and 'crit' is the critical flag.
572 4. Context functions.
574 The following functions set and manipulate an extension context structure.
575 The purpose of the extension context is to allow the extension code to
576 access various structures relating to the "environment" of the certificate:
577 for example the issuers certificate or the certificate request.
579 void X509V3_set_ctx(X509V3_CTX *ctx, X509 *issuer, X509 *subject,
580 X509_REQ *req, X509_CRL *crl, int flags);
582 This function sets up an X509V3_CTX structure with details of the certificate
583 environment: specifically the issuers certificate, the subject certificate,
584 the certificate request and the CRL: if these are not relevant or not
585 available then they can be set to NULL. The 'flags' parameter should be set
588 X509V3_set_ctx_test(ctx)
590 This macro is used to set the 'ctx' structure to a 'test' value: this is to
591 allow the syntax of an extension (or configuration file) to be tested.
593 X509V3_set_ctx_nodb(ctx)
595 This macro is used when no configuration database is present.
597 void X509V3_set_conf_lhash(X509V3_CTX *ctx, LHASH *lhash);
599 This function is used to set the configuration database when it is an LHASH
600 structure: typically a configuration file.
602 The following functions are used to access a configuration database: they
603 should only be used in RAW extensions.
605 char * X509V3_get_string(X509V3_CTX *ctx, char *name, char *section);
607 This function returns the value of the parameter "name" in "section", or NULL
608 if there has been an error.
610 void X509V3_string_free(X509V3_CTX *ctx, char *str);
612 This function frees up the string returned by the above function.
614 STACK_OF(CONF_VALUE) * X509V3_get_section(X509V3_CTX *ctx, char *section);
616 This function returns a whole section as a STACK_OF(CONF_VALUE) .
618 void X509V3_section_free( X509V3_CTX *ctx, STACK_OF(CONF_VALUE) *section);
620 This function frees up the STACK returned by the above function.
622 Note: it is possible to use the extension code with a custom configuration
623 database. To do this the "db_meth" element of the X509V3_CTX structure should
624 be set to an X509V3_CTX_METHOD structure. This structure contains the following
627 char * (*get_string)(void *db, char *section, char *value);
628 STACK_OF(CONF_VALUE) * (*get_section)(void *db, char *section);
629 void (*free_string)(void *db, char * string);
630 void (*free_section)(void *db, STACK_OF(CONF_VALUE) *section);
632 these will be called and passed the 'db' element in the X509V3_CTX structure
633 to access the database. If a given function is not implemented or not required
634 it can be set to NULL.
636 5. String helper functions.
638 There are several "i2s" and "s2i" functions that convert structures to and
639 from ASCII strings. In all the "i2s" cases the returned string should be
640 freed using Free() after use. Since some of these are part of other extension
641 code they may take a 'method' parameter. Unless otherwise stated it can be
644 char *i2s_ASN1_OCTET_STRING(X509V3_EXT_METHOD *method, ASN1_OCTET_STRING *oct);
646 This returns a hex string from an ASN1_OCTET_STRING.
648 char * i2s_ASN1_INTEGER(X509V3_EXT_METHOD *meth, ASN1_INTEGER *aint);
649 char * i2s_ASN1_ENUMERATED(X509V3_EXT_METHOD *meth, ASN1_ENUMERATED *aint);
651 These return a string decimal representations of an ASN1_INTEGER and an
652 ASN1_ENUMERATED type, respectively.
654 ASN1_OCTET_STRING *s2i_ASN1_OCTET_STRING(X509V3_EXT_METHOD *method,
655 X509V3_CTX *ctx, char *str);
657 This converts an ASCII hex string to an ASN1_OCTET_STRING.
659 ASN1_INTEGER * s2i_ASN1_INTEGER(X509V3_EXT_METHOD *meth, char *value);
661 This converts a decimal ASCII string into an ASN1_INTEGER.
663 6. Multi valued extension helper functions.
665 The following functions can be used to manipulate STACKs of CONF_VALUE
666 structures, as used by multi valued extensions.
668 int X509V3_get_value_bool(CONF_VALUE *value, int *asn1_bool);
670 This function expects a boolean value in 'value' and sets 'asn1_bool' to
671 it. That is it sets it to 0 for FALSE or 0xff for TRUE. The following
672 strings are acceptable: "TRUE", "true", "Y", "y", "YES", "yes", "FALSE"
673 "false", "N", "n", "NO" or "no".
675 int X509V3_get_value_int(CONF_VALUE *value, ASN1_INTEGER **aint);
677 This accepts a decimal integer of arbitrary length and sets an ASN1_INTEGER.
679 int X509V3_add_value(const char *name, const char *value,
680 STACK_OF(CONF_VALUE) **extlist);
682 This simply adds a string name and value pair.
684 int X509V3_add_value_uchar(const char *name, const unsigned char *value,
685 STACK_OF(CONF_VALUE) **extlist);
687 The same as above but for an unsigned character value.
689 int X509V3_add_value_bool(const char *name, int asn1_bool,
690 STACK_OF(CONF_VALUE) **extlist);
692 This adds either "TRUE" or "FALSE" depending on the value of 'ans1_bool'
694 int X509V3_add_value_bool_nf(char *name, int asn1_bool,
695 STACK_OF(CONF_VALUE) **extlist);
697 This is the same as above except it adds nothing if asn1_bool is FALSE.
699 int X509V3_add_value_int(const char *name, ASN1_INTEGER *aint,
700 STACK_OF(CONF_VALUE) **extlist);
702 This function adds the value of the ASN1_INTEGER in decimal form.
704 7. Other helper functions.
708 ADDING CUSTOM EXTENSIONS.
710 Currently there are three types of supported extensions.
712 String extensions are simple strings where the value is placed directly in the
713 extensions, and the string returned is printed out.
715 Multi value extensions are passed a STACK_OF(CONF_VALUE) name and value pairs
716 or return a STACK_OF(CONF_VALUE).
718 Raw extensions are just passed a BIO or a value and it is the extensions
719 responsiblity to handle all the necessary printing.
721 There are two ways to add an extension. One is simply as an alias to an already
722 existing extension. An alias is an extension that is identical in ASN1 structure
723 to an existing extension but has a different OBJECT IDENTIFIER. This can be
726 int X509V3_EXT_add_alias(int nid_to, int nid_from);
728 'nid_to' is the new extension NID and 'nid_from' is the already existing
731 Alternatively an extension can be written from scratch. This involves writing
732 the ASN1 code to encode and decode the extension and functions to print out and
733 generate the extension from strings. The relevant functions are then placed in
734 a X509V3_EXT_METHOD structure and int X509V3_EXT_add(X509V3_EXT_METHOD *ext);
737 The X509V3_EXT_METHOD structure is described below.
742 X509V3_EXT_NEW ext_new;
743 X509V3_EXT_FREE ext_free;
756 The elements have the following meanings.
758 ext_nid is the NID of the object identifier of the extension.
760 ext_flags is set of flags. Currently the only external flag is
761 X509V3_EXT_MULTILINE which means a multi valued extensions
762 should be printed on separate lines.
764 usr_data is an extension specific pointer to any relevant data. This
765 allows extensions to share identical code but have different
766 uses. An example of this is the bit string extension which uses
767 usr_data to contain a list of the bit names.
769 All the remaining elements are function pointers.
771 ext_new is a pointer to a function that allocates memory for the
772 extension ASN1 structure: for example ASN1_OBJECT_new().
774 ext_free is a pointer to a function that free up memory of the extension
775 ASN1 structure: for example ASN1_OBJECT_free().
777 d2i is the standard ASN1 function that converts a DER buffer into
778 the internal ASN1 structure: for example d2i_ASN1_IA5STRING().
780 i2d is the standard ASN1 function that converts the internal
781 structure into the DER representation: for example
782 i2d_ASN1_IA5STRING().
784 The remaining functions are depend on the type of extension. One i2X and
785 one X2i should be set and the rest set to NULL. The types set do not need
786 to match up, for example the extension could be set using the multi valued
787 v2i function and printed out using the raw i2r.
789 All functions have the X509V3_EXT_METHOD passed to them in the 'method'
790 parameter and an X509V3_CTX structure. Extension code can then access the
791 parent structure via the 'method' parameter to for example make use of the value
792 of usr_data. If the code needs to use detail relating to the request it can
793 use the 'ctx' parameter.
795 A note should be given here about the 'flags' member of the 'ctx' parameter.
796 If it has the value CTX_TEST then the configuration syntax is being checked
797 and no actual certificate or CRL exists. Therefore any attempt in the config
798 file to access such information should silently succeed. If the syntax is OK
799 then it should simply return a (possibly bogus) extension, otherwise it
802 char *i2s(struct v3_ext_method *method, void *ext);
804 This function takes the internal structure in the ext parameter and returns
805 a Malloc'ed string representing its value.
807 void * s2i(struct v3_ext_method *method, struct v3_ext_ctx *ctx, char *str);
809 This function takes the string representation in the ext parameter and returns
810 an allocated internal structure: ext_free() will be used on this internal
813 i2v and v2i handle a STACK_OF(CONF_VALUE):
822 Only the name and value members are currently used.
824 STACK_OF(CONF_VALUE) * i2v(struct v3_ext_method *method, void *ext);
826 This function is passed the internal structure in the ext parameter and
827 returns a STACK of CONF_VALUE structures. The values of name, value,
828 section and the structure itself will be freed up with Free after use.
829 Several helper functions are available to add values to this STACK.
831 void * v2i(struct v3_ext_method *method, struct v3_ext_ctx *ctx,
832 STACK_OF(CONF_VALUE) *values);
834 This function takes a STACK_OF(CONF_VALUE) structures and should set the
835 values of the external structure. This typically uses the name element to
836 determine which structure element to set and the value element to determine
837 what to set it to. Several helper functions are available for this
840 int i2r(struct v3_ext_method *method, void *ext, BIO *out, int indent);
842 This function is passed the internal extension structure in the ext parameter
843 and sends out a human readable version of the extension to out. The 'indent'
844 paremeter should be noted to determine the necessary amount of indentation
845 needed on the output.
847 void * r2i(struct v3_ext_method *method, struct v3_ext_ctx *ctx, char *str);
849 This is just passed the string representation of the extension. It is intended
850 to be used for more elaborate extensions where the standard single and multi
851 valued options are insufficient. They can use the 'ctx' parameter to parse the
852 configuration database themselves. See the context functions section for details
855 Note: although this type takes the same parameters as the "r2s" function there
856 is a subtle difference. Whereas an "r2i" function can access a configuration
857 database an "s2i" function MUST NOT. This is so the internal code can safely
858 assume that an "s2i" function will work without a configuration database.
860 ==============================================================================
862 ==============================================================================
864 This section describes the internal PKCS#12 support. There are very few
865 differences between the old external library and the new internal code at
866 present. This may well change because the external library will not be updated
869 This version now includes a couple of high level PKCS#12 functions which
870 generally "do the right thing" and should make it much easier to handle PKCS#12
873 HIGH LEVEL FUNCTIONS.
875 For most applications you only need concern yourself with the high level
876 functions. They can parse and generate simple PKCS#12 files as produced by
877 Netscape and MSIE or indeed any compliant PKCS#12 file containing a single
878 private key and certificate pair.
880 1. Initialisation and cleanup.
882 No special initialisation is needed for the internal PKCS#12 library: the
883 standard SSLeay_add_all_algorithms() is sufficient. If you do not wish to
884 add all algorithms (you should at least add SHA1 though) then you can manually
885 initialise the PKCS#12 library with:
889 The memory allocated by the PKCS#12 library is freed up when EVP_cleanup() is
890 called or it can be directly freed with:
894 after this call (or EVP_cleanup() ) no more PKCS#12 library functions should
899 i2d_PKCS12_bio(bp, p12)
901 This writes out a PKCS12 structure to a BIO.
903 i2d_PKCS12_fp(fp, p12)
905 This is the same but for a FILE pointer.
907 d2i_PKCS12_bio(bp, p12)
909 This reads in a PKCS12 structure from a BIO.
911 d2i_PKCS12_fp(fp, p12)
913 This is the same but for a FILE pointer.
915 3. Parsing and creation functions.
917 3.1 Parsing with PKCS12_parse().
919 int PKCS12_parse(PKCS12 *p12, char *pass, EVP_PKEY **pkey, X509 **cert,
922 This function takes a PKCS12 structure and a password (ASCII, null terminated)
923 and returns the private key, the corresponding certificate and any CA
924 certificates. If any of these is not required it can be passed as a NULL.
925 The 'ca' parameter should be either NULL, a pointer to NULL or a valid STACK
926 structure. Typically to read in a PKCS#12 file you might do:
928 p12 = d2i_PKCS12_fp(fp, NULL);
929 PKCS12_parse(p12, password, &pkey, &cert, NULL); /* CAs not wanted */
932 3.2 PKCS#12 creation with PKCS12_create().
934 PKCS12 *PKCS12_create(char *pass, char *name, EVP_PKEY *pkey, X509 *cert,
935 STACK *ca, int nid_key, int nid_cert, int iter,
936 int mac_iter, int keytype);
938 This function will create a PKCS12 structure from a given password, name,
939 private key, certificate and optional STACK of CA certificates. The remaining
940 5 parameters can be set to 0 and sensible defaults will be used.
942 The parameters nid_key and nid_cert are the key and certificate encryption
943 algorithms, iter is the encryption iteration count, mac_iter is the MAC
944 iteration count and keytype is the type of private key. If you really want
945 to know what these last 5 parameters do then read the low level section.
947 Typically to create a PKCS#12 file the following could be used:
949 p12 = PKCS12_create(pass, "My Certificate", pkey, cert, NULL, 0,0,0,0,0);
950 i2d_PKCS12_fp(fp, p12);
955 In some cases the high level functions do not provide the necessary
956 functionality. For example if you want to generate or parse more complex
957 PKCS#12 files. The sample pkcs12 application uses the low level functions
958 to display details about the internal structure of a PKCS#12 file.
962 This is a brief description of how a PKCS#12 file is represented internally:
963 some knowledge of PKCS#12 is assumed.
965 A PKCS#12 object contains several levels.
967 At the lowest level is a PKCS12_SAFEBAG. This can contain a certificate, a
968 CRL, a private key, encrypted or unencrypted, a set of safebags (so the
969 structure can be nested) or other secrets (not documented at present).
970 A safebag can optionally have attributes, currently these are: a unicode
971 friendlyName (a Unicode string) or a localKeyID (a string of bytes).
973 At the next level is an authSafe which is a set of safebags collected into
974 a PKCS#7 ContentInfo. This can be just plain data, or encrypted itself.
976 At the top level is the PKCS12 structure itself which contains a set of
977 authSafes in an embedded PKCS#7 Contentinfo of type data. In addition it
978 contains a MAC which is a kind of password protected digest to preserve
979 integrity (so any unencrypted stuff below can't be tampered with).
981 The reason for these levels is so various objects can be encrypted in various
982 ways. For example you might want to encrypt a set of private keys with
983 triple-DES and then include the related certificates either unencrypted or
984 with lower encryption. Yes it's the dreaded crypto laws at work again which
985 allow strong encryption on private keys and only weak encryption on other
988 To build one of these things you turn all certificates and keys into safebags
989 (with optional attributes). You collect the safebags into (one or more) STACKS
990 and convert these into authsafes (encrypted or unencrypted). The authsafes
991 are collected into a STACK and added to a PKCS12 structure. Finally a MAC
994 Pulling one apart is basically the reverse process. The MAC is verified against
995 the given password. The authsafes are extracted and each authsafe split into
996 a set of safebags (possibly involving decryption). Finally the safebags are
997 decomposed into the original keys and certificates and the attributes used to
998 match up private key and certificate pairs.
1000 Anyway here are the functions that do the dirty work.
1002 1. Construction functions.
1004 1.1 Safebag functions.
1006 M_PKCS12_x5092certbag(x509)
1008 This macro takes an X509 structure and returns a certificate bag. The
1009 X509 structure can be freed up after calling this function.
1011 M_PKCS12_x509crl2certbag(crl)
1013 As above but for a CRL.
1015 PKCS8_PRIV_KEY_INFO *PKEY2PKCS8(EVP_PKEY *pkey)
1017 Take a private key and convert it into a PKCS#8 PrivateKeyInfo structure.
1018 Works for both RSA and DSA private keys. NB since the PKCS#8 PrivateKeyInfo
1019 structure contains a private key data in plain text form it should be free'd
1020 up as soon as it has been encrypted for security reasons (freeing up the
1021 structure zeros out the sensitive data). This can be done with
1022 PKCS8_PRIV_KEY_INFO_free().
1024 PKCS8_add_keyusage(PKCS8_PRIV_KEY_INFO *p8, int usage)
1026 This sets the key type when a key is imported into MSIE or Outlook 98. Two
1027 values are currently supported: KEY_EX and KEY_SIG. KEY_EX is an exchange type
1028 key that can also be used for signing but its size is limited in the export
1029 versions of MS software to 512 bits, it is also the default. KEY_SIG is a
1030 signing only key but the keysize is unlimited (well 16K is supposed to work).
1031 If you are using the domestic version of MSIE then you can ignore this because
1032 KEY_EX is not limited and can be used for both.
1034 PKCS12_SAFEBAG *PKCS12_MAKE_KEYBAG(PKCS8_PRIV_KEY_INFO *p8)
1036 Convert a PKCS8 private key structure into a keybag. This routine embeds the
1037 p8 structure in the keybag so p8 should not be freed up or used after it is
1038 called. The p8 structure will be freed up when the safebag is freed.
1040 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)
1042 Convert a PKCS#8 structure into a shrouded key bag (encrypted). p8 is not
1043 embedded and can be freed up after use.
1045 int PKCS12_add_localkeyid(PKCS12_SAFEBAG *bag, unsigned char *name, int namelen)
1046 int PKCS12_add_friendlyname(PKCS12_SAFEBAG *bag, unsigned char *name, int namelen)
1048 Add a local key id or a friendlyname to a safebag.
1050 1.2 Authsafe functions.
1052 PKCS7 *PKCS12_pack_p7data(STACK *sk)
1053 Take a stack of safebags and convert them into an unencrypted authsafe. The
1054 stack of safebags can be freed up after calling this function.
1056 PKCS7 *PKCS12_pack_p7encdata(int pbe_nid, unsigned char *pass, int passlen, unsigned char *salt, int saltlen, int iter, STACK *bags);
1058 As above but encrypted.
1060 1.3 PKCS12 functions.
1062 PKCS12 *PKCS12_init(int mode)
1064 Initialise a PKCS12 structure (currently mode should be NID_pkcs7_data).
1066 M_PKCS12_pack_authsafes(p12, safes)
1068 This macro takes a STACK of authsafes and adds them to a PKCS#12 structure.
1070 int PKCS12_set_mac(PKCS12 *p12, unsigned char *pass, int passlen, unsigned char *salt, int saltlen, int iter, EVP_MD *md_type);
1072 Add a MAC to a PKCS12 structure. If EVP_MD is NULL use SHA-1, the spec suggests
1073 that SHA-1 should be used.
1075 2. Extraction Functions.
1079 M_PKCS12_bag_type(bag)
1081 Return the type of "bag". Returns one of the following
1084 NID_pkcs8ShroudedKeyBag 7
1088 NID_safeContentsBag 11
1090 M_PKCS12_cert_bag_type(bag)
1092 Returns type of certificate bag, following are understood.
1094 NID_x509Certificate 14
1095 NID_sdsiCertificate 15
1097 M_PKCS12_crl_bag_type(bag)
1099 Returns crl bag type, currently only NID_crlBag is recognised.
1101 M_PKCS12_certbag2x509(bag)
1103 This macro extracts an X509 certificate from a certificate bag.
1105 M_PKCS12_certbag2x509crl(bag)
1107 As above but for a CRL.
1109 EVP_PKEY * PKCS82PKEY(PKCS8_PRIV_KEY_INFO *p8)
1111 Extract a private key from a PKCS8 private key info structure.
1113 M_PKCS12_decrypt_skey(bag, pass, passlen)
1115 Decrypt a shrouded key bag and return a PKCS8 private key info structure.
1116 Works with both RSA and DSA keys
1118 char *PKCS12_get_friendlyname(bag)
1120 Returns the friendlyName of a bag if present or NULL if none. The returned
1121 string is a null terminated ASCII string allocated with Malloc(). It should
1122 thus be freed up with Free() after use.
1124 2.2 AuthSafe functions.
1126 M_PKCS12_unpack_p7data(p7)
1128 Extract a STACK of safe bags from a PKCS#7 data ContentInfo.
1130 #define M_PKCS12_unpack_p7encdata(p7, pass, passlen)
1132 As above but for an encrypted content info.
1134 2.3 PKCS12 functions.
1136 M_PKCS12_unpack_authsafes(p12)
1138 Extract a STACK of authsafes from a PKCS12 structure.
1140 M_PKCS12_mac_present(p12)
1142 Check to see if a MAC is present.
1144 int PKCS12_verify_mac(PKCS12 *p12, unsigned char *pass, int passlen)
1146 Verify a MAC on a PKCS12 structure. Returns an error if MAC not present.
1151 1. All the function return 0 or NULL on error.
1152 2. Encryption based functions take a common set of parameters. These are
1156 ASCII password and length. The password on the MAC is called the "integrity
1157 password" the encryption password is called the "privacy password" in the
1158 PKCS#12 documentation. The passwords do not have to be the same. If -1 is
1159 passed for the length it is worked out by the function itself (currently
1160 this is sometimes done whatever is passed as the length but that may change).
1163 A 'salt' if salt is NULL a random salt is used. If saltlen is also zero a
1164 default length is used.
1167 Iteration count. This is a measure of how many times an internal function is
1168 called to encrypt the data. The larger this value is the longer it takes, it
1169 makes dictionary attacks on passwords harder. NOTE: Some implementations do
1170 not support an iteration count on the MAC. If the password for the MAC and
1171 encryption is the same then there is no point in having a high iteration
1172 count for encryption if the MAC has no count. The MAC could be attacked
1173 and the password used for the main decryption.
1176 This is the NID of the password based encryption method used. The following are
1178 NID_pbe_WithSHA1And128BitRC4
1179 NID_pbe_WithSHA1And40BitRC4
1180 NID_pbe_WithSHA1And3_Key_TripleDES_CBC
1181 NID_pbe_WithSHA1And2_Key_TripleDES_CBC
1182 NID_pbe_WithSHA1And128BitRC2_CBC
1183 NID_pbe_WithSHA1And40BitRC2_CBC
1185 Which you use depends on the implementation you are exporting to. "Export
1186 grade" (i.e. cryptographically challenged) products cannot support all
1187 algorithms. Typically you may be able to use any encryption on shrouded key
1188 bags but they must then be placed in an unencrypted authsafe. Other authsafes
1189 may only support 40bit encryption. Of course if you are using SSLeay
1190 throughout you can strongly encrypt everything and have high iteration counts
1193 3. For decryption routines only the password and length are needed.
1195 4. Unlike the external version the nid's of objects are the values of the
1196 constants: that is NID_certBag is the real nid, therefore there is no
1197 PKCS12_obj_offset() function. Note the object constants are not the same as
1198 those of the external version. If you use these constants then you will need
1199 to recompile your code.
1201 5. With the exception of PKCS12_MAKE_KEYBAG(), after calling any function or
1202 macro of the form PKCS12_MAKE_SOMETHING(other) the "other" structure can be
1203 reused or freed up safely.