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.
350 extendedKeyUsage=critical,codeSigning,1.2.3.4
351 extendedKeyUsage=nsSGC,msSGC
353 Subject Key Identifier.
355 This is really a string extension and can take two possible values. Either
356 a hex string giving details of the extension value to include or the word
357 'hash' which then automatically follow PKIX guidelines in selecting and
358 appropriate key identifier. The use of the hex string is strongly discouraged.
360 Example: subjectKeyIdentifier=hash
362 Authority Key Identifier.
364 The authority key identifier extension permits two options. keyid and issuer:
365 both can take the optional value "always".
367 If the keyid option is present an attempt is made to copy the subject key
368 identifier from the parent certificate. If the value "always" is present
369 then an error is returned if the option fails.
371 The issuer option copies the issuer and serial number from the issuer
372 certificate. Normally this will only be done if the keyid option fails or
373 is not included: the "always" flag will always include the value.
375 Subject Alternative Name.
377 The subject alternative name extension allows various literal values to be
378 included in the configuration file. These include "email" (an email address)
379 "URI" a uniform resource indicator, "DNS" (a DNS domain name), RID (a
380 registered ID: OBJECT IDENTIFIER) and IP (and IP address).
382 Also the email option include a special 'copy' value. This will automatically
383 include and email addresses contained in the certificate subject name in
388 subjectAltName=email:copy,email:my@other.address,URL:http://my.url.here/
389 subjectAltName=email:my@other.address,RID:1.2.3.4
391 Issuer Alternative Name.
393 The issuer alternative name option supports all the literal options of
394 subject alternative name. It does *not* support the email:copy option because
395 that would not make sense. It does support an additional issuer:copy option
396 that will copy all the subject alternative name values from the issuer
397 certificate (if possible).
399 CRL distribution points.
401 This is a multi-valued extension that supports all the literal options of
402 subject alternative name. Of the few software packages that currently interpret
403 this extension most only interpret the URI option.
405 Currently each option will set a new DistributionPoint with the fullName
406 field set to the given value.
408 Other fields like cRLissuer and reasons cannot currently be set or displayed:
409 at this time no examples were available that used these fields.
411 If you see this extension with <UNSUPPORTED> when you attempt to print it out
412 or it doesn't appear to display correctly then let me know, including the
413 certificate (mail me at steve@openssl.org) .
417 crlDistributionPoints=URI:http://www.myhost.com/myca.crl
418 crlDistributionPoints=URI:http://www.my.com/my.crl,URI:http://www.oth.com/my.crl
420 Certificate Policies.
422 This is a RAW extension. It attempts to display the contents of this extension:
423 unfortunately this extension is often improperly encoded.
425 The certificate policies extension will rarely be used in practice: few
426 software packages interpret it correctly or at all. IE5 does partially
427 support this extension: but it needs the 'ia5org' option because it will
428 only correctly support a broken encoding. Of the options below only the
429 policy OID, explicitText and CPS options are displayed with IE5.
431 All the fields of this extension can be set by using the appropriate syntax.
433 If you follow the PKIX recommendations of not including any qualifiers and just
434 using only one OID then you just include the value of that OID. Multiple OIDs
435 can be set separated by commas, for example:
437 certificatePolicies= 1.2.4.5, 1.1.3.4
439 If you wish to include qualifiers then the policy OID and qualifiers need to
440 be specified in a separate section: this is done by using the @section syntax
441 instead of a literal OID value.
443 The section referred to must include the policy OID using the name
444 policyIdentifier, cPSuri qualifiers can be included using the syntax:
448 userNotice qualifiers can be set using the syntax:
450 userNotice.nnn=@notice
452 The value of the userNotice qualifier is specified in the relevant section.
453 This section can include explicitText, organization and noticeNumbers
454 options. explicitText and organization are text strings, noticeNumbers is a
455 comma separated list of numbers. The organization and noticeNumbers options
456 (if included) must BOTH be present. If you use the userNotice option with IE5
457 then you need the 'ia5org' option at the top level to modify the encoding:
458 otherwise it will not be interpreted properly.
462 certificatePolicies=ia5org,1.2.3.4,1.5.6.7.8,@polsect
466 policyIdentifier = 1.3.5.8
467 CPS.1="http://my.host.name/"
468 CPS.2="http://my.your.name/"
473 explicitText="Explicit Text Here"
474 organization="Organisation Name"
475 noticeNumbers=1,2,3,4
477 TECHNICAL NOTE: the ia5org option changes the type of the 'organization' field,
478 according to PKIX it should be of type DisplayText but Verisign uses an
479 IA5STRING and IE5 needs this too.
481 Display only extensions.
483 Some extensions are only partially supported and currently are only displayed
484 but cannot be set. These include private key usage period, CRL number, and
487 ==============================================================================
488 X509V3 Extension code: programmers guide
489 ==============================================================================
491 The purpose of the extension code is twofold. It allows an extension to be
492 created from a string or structure describing its contents and it prints out an
493 extension in a human or machine readable form.
495 1. Initialisation and cleanup.
497 X509V3_add_standard_extensions();
499 This function should be called before any other extension code. It adds support
500 for some common PKIX and Netscape extensions. Additional custom extensions can
501 be added as well (see later).
503 void X509V3_EXT_cleanup(void);
505 This function should be called last to cleanup the extension code. After this
506 call no other extension calls should be made.
508 2. Printing and parsing extensions.
510 The simplest way to print out extensions is via the standard X509 printing
511 routines: if you use the standard X509_print() function, the supported
512 extensions will be printed out automatically.
514 The following functions allow finer control over extension display:
516 int X509V3_EXT_print(BIO *out, X509_EXTENSION *ext, int flag, int indent);
517 int X509V3_EXT_print_fp(FILE *out, X509_EXTENSION *ext, int flag, int indent);
519 These two functions print out an individual extension to a BIO or FILE pointer.
520 Currently the flag argument is unused and should be set to 0. The 'indent'
521 argument is the number of spaces to indent each line.
523 void *X509V3_EXT_d2i(X509_EXTENSION *ext);
525 This function parses an extension and returns its internal structure. The
526 precise structure you get back depends on the extension being parsed. If the
527 extension if basicConstraints you will get back a pointer to a
528 BASIC_CONSTRAINTS structure. Check out the source in crypto/x509v3 for more
529 details about the structures returned. The returned structure should be freed
530 after use using the relevant free function, BASIC_CONSTRAINTS_free() for
533 3. Generating extensions.
535 An extension will typically be generated from a configuration file, or some
536 other kind of configuration database.
538 int X509V3_EXT_add_conf(LHASH *conf, X509V3_CTX *ctx, char *section,
540 int X509V3_EXT_CRL_add_conf(LHASH *conf, X509V3_CTX *ctx, char *section,
543 These functions add all the extensions in the given section to the given
544 certificate or CRL. They will normally be called just before the certificate
545 or CRL is due to be signed. Both return 0 on error on non zero for success.
547 In each case 'conf' is the LHASH pointer of the configuration file to use
548 and 'section' is the section containing the extension details.
550 See the 'context functions' section for a description of the ctx paramater.
553 X509_EXTENSION *X509V3_EXT_conf(LHASH *conf, X509V3_CTX *ctx, char *name,
556 This function returns an extension based on a name and value pair, if the
557 pair will not need to access other sections in a config file (or there is no
558 config file) then the 'conf' parameter can be set to NULL.
560 X509_EXTENSION *X509V3_EXT_conf_nid(char *conf, X509V3_CTX *ctx, int nid,
563 This function creates an extension in the same way as X509V3_EXT_conf() but
564 takes the NID of the extension rather than its name.
566 For example to produce basicConstraints with the CA flag and a path length of
569 x = X509V3_EXT_conf_nid(NULL, NULL, NID_basic_constraints,"CA:TRUE,pathlen:10");
572 X509_EXTENSION *X509V3_EXT_i2d(int ext_nid, int crit, void *ext_struc);
574 This function sets up an extension from its internal structure. The ext_nid
575 parameter is the NID of the extension and 'crit' is the critical flag.
577 4. Context functions.
579 The following functions set and manipulate an extension context structure.
580 The purpose of the extension context is to allow the extension code to
581 access various structures relating to the "environment" of the certificate:
582 for example the issuers certificate or the certificate request.
584 void X509V3_set_ctx(X509V3_CTX *ctx, X509 *issuer, X509 *subject,
585 X509_REQ *req, X509_CRL *crl, int flags);
587 This function sets up an X509V3_CTX structure with details of the certificate
588 environment: specifically the issuers certificate, the subject certificate,
589 the certificate request and the CRL: if these are not relevant or not
590 available then they can be set to NULL. The 'flags' parameter should be set
593 X509V3_set_ctx_test(ctx)
595 This macro is used to set the 'ctx' structure to a 'test' value: this is to
596 allow the syntax of an extension (or configuration file) to be tested.
598 X509V3_set_ctx_nodb(ctx)
600 This macro is used when no configuration database is present.
602 void X509V3_set_conf_lhash(X509V3_CTX *ctx, LHASH *lhash);
604 This function is used to set the configuration database when it is an LHASH
605 structure: typically a configuration file.
607 The following functions are used to access a configuration database: they
608 should only be used in RAW extensions.
610 char * X509V3_get_string(X509V3_CTX *ctx, char *name, char *section);
612 This function returns the value of the parameter "name" in "section", or NULL
613 if there has been an error.
615 void X509V3_string_free(X509V3_CTX *ctx, char *str);
617 This function frees up the string returned by the above function.
619 STACK_OF(CONF_VALUE) * X509V3_get_section(X509V3_CTX *ctx, char *section);
621 This function returns a whole section as a STACK_OF(CONF_VALUE) .
623 void X509V3_section_free( X509V3_CTX *ctx, STACK_OF(CONF_VALUE) *section);
625 This function frees up the STACK returned by the above function.
627 Note: it is possible to use the extension code with a custom configuration
628 database. To do this the "db_meth" element of the X509V3_CTX structure should
629 be set to an X509V3_CTX_METHOD structure. This structure contains the following
632 char * (*get_string)(void *db, char *section, char *value);
633 STACK_OF(CONF_VALUE) * (*get_section)(void *db, char *section);
634 void (*free_string)(void *db, char * string);
635 void (*free_section)(void *db, STACK_OF(CONF_VALUE) *section);
637 these will be called and passed the 'db' element in the X509V3_CTX structure
638 to access the database. If a given function is not implemented or not required
639 it can be set to NULL.
641 5. String helper functions.
643 There are several "i2s" and "s2i" functions that convert structures to and
644 from ASCII strings. In all the "i2s" cases the returned string should be
645 freed using Free() after use. Since some of these are part of other extension
646 code they may take a 'method' parameter. Unless otherwise stated it can be
649 char *i2s_ASN1_OCTET_STRING(X509V3_EXT_METHOD *method, ASN1_OCTET_STRING *oct);
651 This returns a hex string from an ASN1_OCTET_STRING.
653 char * i2s_ASN1_INTEGER(X509V3_EXT_METHOD *meth, ASN1_INTEGER *aint);
654 char * i2s_ASN1_ENUMERATED(X509V3_EXT_METHOD *meth, ASN1_ENUMERATED *aint);
656 These return a string decimal representations of an ASN1_INTEGER and an
657 ASN1_ENUMERATED type, respectively.
659 ASN1_OCTET_STRING *s2i_ASN1_OCTET_STRING(X509V3_EXT_METHOD *method,
660 X509V3_CTX *ctx, char *str);
662 This converts an ASCII hex string to an ASN1_OCTET_STRING.
664 ASN1_INTEGER * s2i_ASN1_INTEGER(X509V3_EXT_METHOD *meth, char *value);
666 This converts a decimal ASCII string into an ASN1_INTEGER.
668 6. Multi valued extension helper functions.
670 The following functions can be used to manipulate STACKs of CONF_VALUE
671 structures, as used by multi valued extensions.
673 int X509V3_get_value_bool(CONF_VALUE *value, int *asn1_bool);
675 This function expects a boolean value in 'value' and sets 'asn1_bool' to
676 it. That is it sets it to 0 for FALSE or 0xff for TRUE. The following
677 strings are acceptable: "TRUE", "true", "Y", "y", "YES", "yes", "FALSE"
678 "false", "N", "n", "NO" or "no".
680 int X509V3_get_value_int(CONF_VALUE *value, ASN1_INTEGER **aint);
682 This accepts a decimal integer of arbitrary length and sets an ASN1_INTEGER.
684 int X509V3_add_value(const char *name, const char *value,
685 STACK_OF(CONF_VALUE) **extlist);
687 This simply adds a string name and value pair.
689 int X509V3_add_value_uchar(const char *name, const unsigned char *value,
690 STACK_OF(CONF_VALUE) **extlist);
692 The same as above but for an unsigned character value.
694 int X509V3_add_value_bool(const char *name, int asn1_bool,
695 STACK_OF(CONF_VALUE) **extlist);
697 This adds either "TRUE" or "FALSE" depending on the value of 'ans1_bool'
699 int X509V3_add_value_bool_nf(char *name, int asn1_bool,
700 STACK_OF(CONF_VALUE) **extlist);
702 This is the same as above except it adds nothing if asn1_bool is FALSE.
704 int X509V3_add_value_int(const char *name, ASN1_INTEGER *aint,
705 STACK_OF(CONF_VALUE) **extlist);
707 This function adds the value of the ASN1_INTEGER in decimal form.
709 7. Other helper functions.
713 ADDING CUSTOM EXTENSIONS.
715 Currently there are three types of supported extensions.
717 String extensions are simple strings where the value is placed directly in the
718 extensions, and the string returned is printed out.
720 Multi value extensions are passed a STACK_OF(CONF_VALUE) name and value pairs
721 or return a STACK_OF(CONF_VALUE).
723 Raw extensions are just passed a BIO or a value and it is the extensions
724 responsiblity to handle all the necessary printing.
726 There are two ways to add an extension. One is simply as an alias to an already
727 existing extension. An alias is an extension that is identical in ASN1 structure
728 to an existing extension but has a different OBJECT IDENTIFIER. This can be
731 int X509V3_EXT_add_alias(int nid_to, int nid_from);
733 'nid_to' is the new extension NID and 'nid_from' is the already existing
736 Alternatively an extension can be written from scratch. This involves writing
737 the ASN1 code to encode and decode the extension and functions to print out and
738 generate the extension from strings. The relevant functions are then placed in
739 a X509V3_EXT_METHOD structure and int X509V3_EXT_add(X509V3_EXT_METHOD *ext);
742 The X509V3_EXT_METHOD structure is described below.
747 X509V3_EXT_NEW ext_new;
748 X509V3_EXT_FREE ext_free;
761 The elements have the following meanings.
763 ext_nid is the NID of the object identifier of the extension.
765 ext_flags is set of flags. Currently the only external flag is
766 X509V3_EXT_MULTILINE which means a multi valued extensions
767 should be printed on separate lines.
769 usr_data is an extension specific pointer to any relevant data. This
770 allows extensions to share identical code but have different
771 uses. An example of this is the bit string extension which uses
772 usr_data to contain a list of the bit names.
774 All the remaining elements are function pointers.
776 ext_new is a pointer to a function that allocates memory for the
777 extension ASN1 structure: for example ASN1_OBJECT_new().
779 ext_free is a pointer to a function that free up memory of the extension
780 ASN1 structure: for example ASN1_OBJECT_free().
782 d2i is the standard ASN1 function that converts a DER buffer into
783 the internal ASN1 structure: for example d2i_ASN1_IA5STRING().
785 i2d is the standard ASN1 function that converts the internal
786 structure into the DER representation: for example
787 i2d_ASN1_IA5STRING().
789 The remaining functions are depend on the type of extension. One i2X and
790 one X2i should be set and the rest set to NULL. The types set do not need
791 to match up, for example the extension could be set using the multi valued
792 v2i function and printed out using the raw i2r.
794 All functions have the X509V3_EXT_METHOD passed to them in the 'method'
795 parameter and an X509V3_CTX structure. Extension code can then access the
796 parent structure via the 'method' parameter to for example make use of the value
797 of usr_data. If the code needs to use detail relating to the request it can
798 use the 'ctx' parameter.
800 A note should be given here about the 'flags' member of the 'ctx' parameter.
801 If it has the value CTX_TEST then the configuration syntax is being checked
802 and no actual certificate or CRL exists. Therefore any attempt in the config
803 file to access such information should silently succeed. If the syntax is OK
804 then it should simply return a (possibly bogus) extension, otherwise it
807 char *i2s(struct v3_ext_method *method, void *ext);
809 This function takes the internal structure in the ext parameter and returns
810 a Malloc'ed string representing its value.
812 void * s2i(struct v3_ext_method *method, struct v3_ext_ctx *ctx, char *str);
814 This function takes the string representation in the ext parameter and returns
815 an allocated internal structure: ext_free() will be used on this internal
818 i2v and v2i handle a STACK_OF(CONF_VALUE):
827 Only the name and value members are currently used.
829 STACK_OF(CONF_VALUE) * i2v(struct v3_ext_method *method, void *ext);
831 This function is passed the internal structure in the ext parameter and
832 returns a STACK of CONF_VALUE structures. The values of name, value,
833 section and the structure itself will be freed up with Free after use.
834 Several helper functions are available to add values to this STACK.
836 void * v2i(struct v3_ext_method *method, struct v3_ext_ctx *ctx,
837 STACK_OF(CONF_VALUE) *values);
839 This function takes a STACK_OF(CONF_VALUE) structures and should set the
840 values of the external structure. This typically uses the name element to
841 determine which structure element to set and the value element to determine
842 what to set it to. Several helper functions are available for this
845 int i2r(struct v3_ext_method *method, void *ext, BIO *out, int indent);
847 This function is passed the internal extension structure in the ext parameter
848 and sends out a human readable version of the extension to out. The 'indent'
849 paremeter should be noted to determine the necessary amount of indentation
850 needed on the output.
852 void * r2i(struct v3_ext_method *method, struct v3_ext_ctx *ctx, char *str);
854 This is just passed the string representation of the extension. It is intended
855 to be used for more elaborate extensions where the standard single and multi
856 valued options are insufficient. They can use the 'ctx' parameter to parse the
857 configuration database themselves. See the context functions section for details
860 Note: although this type takes the same parameters as the "r2s" function there
861 is a subtle difference. Whereas an "r2i" function can access a configuration
862 database an "s2i" function MUST NOT. This is so the internal code can safely
863 assume that an "s2i" function will work without a configuration database.
865 ==============================================================================
867 ==============================================================================
869 This section describes the internal PKCS#12 support. There are very few
870 differences between the old external library and the new internal code at
871 present. This may well change because the external library will not be updated
874 This version now includes a couple of high level PKCS#12 functions which
875 generally "do the right thing" and should make it much easier to handle PKCS#12
878 HIGH LEVEL FUNCTIONS.
880 For most applications you only need concern yourself with the high level
881 functions. They can parse and generate simple PKCS#12 files as produced by
882 Netscape and MSIE or indeed any compliant PKCS#12 file containing a single
883 private key and certificate pair.
885 1. Initialisation and cleanup.
887 No special initialisation is needed for the internal PKCS#12 library: the
888 standard SSLeay_add_all_algorithms() is sufficient. If you do not wish to
889 add all algorithms (you should at least add SHA1 though) then you can manually
890 initialise the PKCS#12 library with:
894 The memory allocated by the PKCS#12 library is freed up when EVP_cleanup() is
895 called or it can be directly freed with:
899 after this call (or EVP_cleanup() ) no more PKCS#12 library functions should
904 i2d_PKCS12_bio(bp, p12)
906 This writes out a PKCS12 structure to a BIO.
908 i2d_PKCS12_fp(fp, p12)
910 This is the same but for a FILE pointer.
912 d2i_PKCS12_bio(bp, p12)
914 This reads in a PKCS12 structure from a BIO.
916 d2i_PKCS12_fp(fp, p12)
918 This is the same but for a FILE pointer.
920 3. Parsing and creation functions.
922 3.1 Parsing with PKCS12_parse().
924 int PKCS12_parse(PKCS12 *p12, char *pass, EVP_PKEY **pkey, X509 **cert,
927 This function takes a PKCS12 structure and a password (ASCII, null terminated)
928 and returns the private key, the corresponding certificate and any CA
929 certificates. If any of these is not required it can be passed as a NULL.
930 The 'ca' parameter should be either NULL, a pointer to NULL or a valid STACK
931 structure. Typically to read in a PKCS#12 file you might do:
933 p12 = d2i_PKCS12_fp(fp, NULL);
934 PKCS12_parse(p12, password, &pkey, &cert, NULL); /* CAs not wanted */
937 3.2 PKCS#12 creation with PKCS12_create().
939 PKCS12 *PKCS12_create(char *pass, char *name, EVP_PKEY *pkey, X509 *cert,
940 STACK *ca, int nid_key, int nid_cert, int iter,
941 int mac_iter, int keytype);
943 This function will create a PKCS12 structure from a given password, name,
944 private key, certificate and optional STACK of CA certificates. The remaining
945 5 parameters can be set to 0 and sensible defaults will be used.
947 The parameters nid_key and nid_cert are the key and certificate encryption
948 algorithms, iter is the encryption iteration count, mac_iter is the MAC
949 iteration count and keytype is the type of private key. If you really want
950 to know what these last 5 parameters do then read the low level section.
952 Typically to create a PKCS#12 file the following could be used:
954 p12 = PKCS12_create(pass, "My Certificate", pkey, cert, NULL, 0,0,0,0,0);
955 i2d_PKCS12_fp(fp, p12);
960 In some cases the high level functions do not provide the necessary
961 functionality. For example if you want to generate or parse more complex
962 PKCS#12 files. The sample pkcs12 application uses the low level functions
963 to display details about the internal structure of a PKCS#12 file.
967 This is a brief description of how a PKCS#12 file is represented internally:
968 some knowledge of PKCS#12 is assumed.
970 A PKCS#12 object contains several levels.
972 At the lowest level is a PKCS12_SAFEBAG. This can contain a certificate, a
973 CRL, a private key, encrypted or unencrypted, a set of safebags (so the
974 structure can be nested) or other secrets (not documented at present).
975 A safebag can optionally have attributes, currently these are: a unicode
976 friendlyName (a Unicode string) or a localKeyID (a string of bytes).
978 At the next level is an authSafe which is a set of safebags collected into
979 a PKCS#7 ContentInfo. This can be just plain data, or encrypted itself.
981 At the top level is the PKCS12 structure itself which contains a set of
982 authSafes in an embedded PKCS#7 Contentinfo of type data. In addition it
983 contains a MAC which is a kind of password protected digest to preserve
984 integrity (so any unencrypted stuff below can't be tampered with).
986 The reason for these levels is so various objects can be encrypted in various
987 ways. For example you might want to encrypt a set of private keys with
988 triple-DES and then include the related certificates either unencrypted or
989 with lower encryption. Yes it's the dreaded crypto laws at work again which
990 allow strong encryption on private keys and only weak encryption on other
993 To build one of these things you turn all certificates and keys into safebags
994 (with optional attributes). You collect the safebags into (one or more) STACKS
995 and convert these into authsafes (encrypted or unencrypted). The authsafes
996 are collected into a STACK and added to a PKCS12 structure. Finally a MAC
999 Pulling one apart is basically the reverse process. The MAC is verified against
1000 the given password. The authsafes are extracted and each authsafe split into
1001 a set of safebags (possibly involving decryption). Finally the safebags are
1002 decomposed into the original keys and certificates and the attributes used to
1003 match up private key and certificate pairs.
1005 Anyway here are the functions that do the dirty work.
1007 1. Construction functions.
1009 1.1 Safebag functions.
1011 M_PKCS12_x5092certbag(x509)
1013 This macro takes an X509 structure and returns a certificate bag. The
1014 X509 structure can be freed up after calling this function.
1016 M_PKCS12_x509crl2certbag(crl)
1018 As above but for a CRL.
1020 PKCS8_PRIV_KEY_INFO *PKEY2PKCS8(EVP_PKEY *pkey)
1022 Take a private key and convert it into a PKCS#8 PrivateKeyInfo structure.
1023 Works for both RSA and DSA private keys. NB since the PKCS#8 PrivateKeyInfo
1024 structure contains a private key data in plain text form it should be free'd
1025 up as soon as it has been encrypted for security reasons (freeing up the
1026 structure zeros out the sensitive data). This can be done with
1027 PKCS8_PRIV_KEY_INFO_free().
1029 PKCS8_add_keyusage(PKCS8_PRIV_KEY_INFO *p8, int usage)
1031 This sets the key type when a key is imported into MSIE or Outlook 98. Two
1032 values are currently supported: KEY_EX and KEY_SIG. KEY_EX is an exchange type
1033 key that can also be used for signing but its size is limited in the export
1034 versions of MS software to 512 bits, it is also the default. KEY_SIG is a
1035 signing only key but the keysize is unlimited (well 16K is supposed to work).
1036 If you are using the domestic version of MSIE then you can ignore this because
1037 KEY_EX is not limited and can be used for both.
1039 PKCS12_SAFEBAG *PKCS12_MAKE_KEYBAG(PKCS8_PRIV_KEY_INFO *p8)
1041 Convert a PKCS8 private key structure into a keybag. This routine embeds the
1042 p8 structure in the keybag so p8 should not be freed up or used after it is
1043 called. The p8 structure will be freed up when the safebag is freed.
1045 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)
1047 Convert a PKCS#8 structure into a shrouded key bag (encrypted). p8 is not
1048 embedded and can be freed up after use.
1050 int PKCS12_add_localkeyid(PKCS12_SAFEBAG *bag, unsigned char *name, int namelen)
1051 int PKCS12_add_friendlyname(PKCS12_SAFEBAG *bag, unsigned char *name, int namelen)
1053 Add a local key id or a friendlyname to a safebag.
1055 1.2 Authsafe functions.
1057 PKCS7 *PKCS12_pack_p7data(STACK *sk)
1058 Take a stack of safebags and convert them into an unencrypted authsafe. The
1059 stack of safebags can be freed up after calling this function.
1061 PKCS7 *PKCS12_pack_p7encdata(int pbe_nid, unsigned char *pass, int passlen, unsigned char *salt, int saltlen, int iter, STACK *bags);
1063 As above but encrypted.
1065 1.3 PKCS12 functions.
1067 PKCS12 *PKCS12_init(int mode)
1069 Initialise a PKCS12 structure (currently mode should be NID_pkcs7_data).
1071 M_PKCS12_pack_authsafes(p12, safes)
1073 This macro takes a STACK of authsafes and adds them to a PKCS#12 structure.
1075 int PKCS12_set_mac(PKCS12 *p12, unsigned char *pass, int passlen, unsigned char *salt, int saltlen, int iter, EVP_MD *md_type);
1077 Add a MAC to a PKCS12 structure. If EVP_MD is NULL use SHA-1, the spec suggests
1078 that SHA-1 should be used.
1080 2. Extraction Functions.
1084 M_PKCS12_bag_type(bag)
1086 Return the type of "bag". Returns one of the following
1089 NID_pkcs8ShroudedKeyBag 7
1093 NID_safeContentsBag 11
1095 M_PKCS12_cert_bag_type(bag)
1097 Returns type of certificate bag, following are understood.
1099 NID_x509Certificate 14
1100 NID_sdsiCertificate 15
1102 M_PKCS12_crl_bag_type(bag)
1104 Returns crl bag type, currently only NID_crlBag is recognised.
1106 M_PKCS12_certbag2x509(bag)
1108 This macro extracts an X509 certificate from a certificate bag.
1110 M_PKCS12_certbag2x509crl(bag)
1112 As above but for a CRL.
1114 EVP_PKEY * PKCS82PKEY(PKCS8_PRIV_KEY_INFO *p8)
1116 Extract a private key from a PKCS8 private key info structure.
1118 M_PKCS12_decrypt_skey(bag, pass, passlen)
1120 Decrypt a shrouded key bag and return a PKCS8 private key info structure.
1121 Works with both RSA and DSA keys
1123 char *PKCS12_get_friendlyname(bag)
1125 Returns the friendlyName of a bag if present or NULL if none. The returned
1126 string is a null terminated ASCII string allocated with Malloc(). It should
1127 thus be freed up with Free() after use.
1129 2.2 AuthSafe functions.
1131 M_PKCS12_unpack_p7data(p7)
1133 Extract a STACK of safe bags from a PKCS#7 data ContentInfo.
1135 #define M_PKCS12_unpack_p7encdata(p7, pass, passlen)
1137 As above but for an encrypted content info.
1139 2.3 PKCS12 functions.
1141 M_PKCS12_unpack_authsafes(p12)
1143 Extract a STACK of authsafes from a PKCS12 structure.
1145 M_PKCS12_mac_present(p12)
1147 Check to see if a MAC is present.
1149 int PKCS12_verify_mac(PKCS12 *p12, unsigned char *pass, int passlen)
1151 Verify a MAC on a PKCS12 structure. Returns an error if MAC not present.
1156 1. All the function return 0 or NULL on error.
1157 2. Encryption based functions take a common set of parameters. These are
1161 ASCII password and length. The password on the MAC is called the "integrity
1162 password" the encryption password is called the "privacy password" in the
1163 PKCS#12 documentation. The passwords do not have to be the same. If -1 is
1164 passed for the length it is worked out by the function itself (currently
1165 this is sometimes done whatever is passed as the length but that may change).
1168 A 'salt' if salt is NULL a random salt is used. If saltlen is also zero a
1169 default length is used.
1172 Iteration count. This is a measure of how many times an internal function is
1173 called to encrypt the data. The larger this value is the longer it takes, it
1174 makes dictionary attacks on passwords harder. NOTE: Some implementations do
1175 not support an iteration count on the MAC. If the password for the MAC and
1176 encryption is the same then there is no point in having a high iteration
1177 count for encryption if the MAC has no count. The MAC could be attacked
1178 and the password used for the main decryption.
1181 This is the NID of the password based encryption method used. The following are
1183 NID_pbe_WithSHA1And128BitRC4
1184 NID_pbe_WithSHA1And40BitRC4
1185 NID_pbe_WithSHA1And3_Key_TripleDES_CBC
1186 NID_pbe_WithSHA1And2_Key_TripleDES_CBC
1187 NID_pbe_WithSHA1And128BitRC2_CBC
1188 NID_pbe_WithSHA1And40BitRC2_CBC
1190 Which you use depends on the implementation you are exporting to. "Export
1191 grade" (i.e. cryptographically challenged) products cannot support all
1192 algorithms. Typically you may be able to use any encryption on shrouded key
1193 bags but they must then be placed in an unencrypted authsafe. Other authsafes
1194 may only support 40bit encryption. Of course if you are using SSLeay
1195 throughout you can strongly encrypt everything and have high iteration counts
1198 3. For decryption routines only the password and length are needed.
1200 4. Unlike the external version the nid's of objects are the values of the
1201 constants: that is NID_certBag is the real nid, therefore there is no
1202 PKCS12_obj_offset() function. Note the object constants are not the same as
1203 those of the external version. If you use these constants then you will need
1204 to recompile your code.
1206 5. With the exception of PKCS12_MAKE_KEYBAG(), after calling any function or
1207 macro of the form PKCS12_MAKE_SOMETHING(other) the "other" structure can be
1208 reused or freed up safely.