This is some preliminary documentation for OpenSSL. ============================================================================== BUFFER Library ============================================================================== The buffer library handles simple character arrays. Buffers are used for various purposes in the library, most notably memory BIOs. The library uses the BUF_MEM structure defined in buffer.h: typedef struct buf_mem_st { int length; /* current number of bytes */ char *data; int max; /* size of buffer */ } BUF_MEM; 'length' is the current size of the buffer in bytes, 'max' is the amount of memory allocated to the buffer. There are three functions which handle these and one "miscelanous" function. BUF_MEM *BUF_MEM_new() This allocates a new buffer of zero size. Returns the buffer or NULL on error. void BUF_MEM_free(BUF_MEM *a) This frees up an already existing buffer. The data is zeroed before freeing up in case the buffer contains sensitive data. int BUF_MEM_grow(BUF_MEM *str, int len) This changes the size of an already existing buffer. It returns zero on error or the new size (i.e. 'len'). Any data already in the buffer is preserved if it increases in size. char * BUF_strdup(char *str) This is the previously mentioned strdup function: like the standard library strdup() it copies a null terminated string into a block of allocated memory and returns a pointer to the allocated block. Unlike the standard C library strdup() this function uses Malloc() and so should be used in preference to the standard library strdup() because it can be used for memory leak checking or replacing the malloc() function. The memory allocated from BUF_strdup() should be freed up using the Free() function. ============================================================================== OpenSSL X509V3 extension configuration ============================================================================== OpenSSL X509V3 extension configuration: preliminary documentation. INTRODUCTION. For OpenSSL 0.9.2 the extension code has be considerably enhanced. It is now possible to add and print out common X509 V3 certificate and CRL extensions. For more information about the meaning of extensions see: http://www.imc.org/ietf-pkix/ http://home.netscape.com/eng/security/certs.html PRINTING EXTENSIONS. Extension values are automatically printed out for supported extensions. openssl x509 -in cert.pem -text openssl crl -in crl.pem -text will give information in the extension printout, for example: X509v3 extensions: X509v3 Basic Constraints: CA:TRUE X509v3 Subject Key Identifier: 73:FE:F7:59:A7:E1:26:84:44:D6:44:36:EE:79:1A:95:7C:B1:4B:15 X509v3 Authority Key Identifier: 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 X509v3 Key Usage: Certificate Sign, CRL Sign X509v3 Subject Alternative Name: email:email@1.address, email:email@2.address CONFIGURATION FILES. The OpenSSL utilities 'ca' and 'req' can now have extension sections listing which certificate extensions to include. In each case a line: x509_extensions = extension_section indicates which section contains the extensions. In the case of 'req' the extension section is used when the -x509 option is present to create a self signed root certificate. The 'x509' utility also supports extensions when it signs a certificate. The -config option is used to set the configuration file containing the extensions. In this case a line with: extensions = extension_section in the nameless (default) section is used. If no such line is include then it uses the default section. You can also add extensions to CRLs: a line crl_extensions = crl_extension_section will include extensions when the -gencrl option is used with the 'ca' utility. You can add any extension to a CRL but of the supported extensions only issuerAltName and authorityKeyIdentifier make any real sense. Note: these are CRL extensions NOT CRL *entry* extensions which cannot currently be generated. CRL entry extensions can be displayed. NB. At this time Netscape Communicator rejects V2 CRLs: to get an old V1 CRL you should comment out the crl_extensions line in the configuration file. As with all configuration files you can use the inbuilt environment expansion to allow the values to be passed in the environment. Therefore if you have several extension sections used for different purposes you can have a line: x509_extensions = $ENV::ENV_EXT and set the ENV_EXT environment variable before calling the relevant utility. EXTENSION SYNTAX. Extensions have the basic form: extension_name=[critical,] extension_options the use of the critical option makes the extension critical. Extreme caution should be made when using the critical flag. If an extension is marked as critical then any client that does not understand the extension should reject it as invalid. Some broken software will reject certificates which have *any* critical extensions (these violates PKIX but we have to live with it). There are three main types of extension, string extensions, multi valued extensions, and raw extensions. String extensions simply have a string which defines the value of the or how it is obtained. For example: nsComment="This is a Comment" Multi valued extensions have a short form and a long form. The short form is a list of names and values: basicConstraints=critical,CA:true,pathlen:1 The long form allows the values to be placed in a separate section: basicConstraints=critical,@bs_section [bs_section] CA=true pathlen=1 Both forms are equivalent. However it should be noted that in some cases the same name can appear multiple times, for example, subjectAltName=email:steve@here,email:steve@there in this case an equivalent long form is: subjectAltName=@alt_section [alt_section] email.1=steve@here email.2=steve@there This is because the configuration file code cannot handle the same name occurring twice in the same extension. Raw extensions allow arbitrary data to be placed in an extension. For example 1.2.3.4=critical,RAW:01:02:03:04 1.2.3.4=RAW:01020304 The value following RAW is a hex dump of the extension contents. Any extension can be placed in this form to override the default behaviour. For example: basicConstraints=critical,RAW:00:01:02:03 WARNING: raw extensions should be used with caution. It is possible to create totally invalid extensions unless care is taken. CURRENTLY SUPPORTED EXTENSIONS. Literal String extensions. In each case the 'value' of the extension is placed directly in the extension. Currently supported extensions in this category are: nsBaseUrl, nsRevocationUrl nsCaRevocationUrl, nsRenewalUrl, nsCaPolicyUrl, nsSslServerName and nsComment. For example: nsComment="This is a test comment" Bit Strings. Bit string extensions just consist of a list of suppported bits, currently two extensions are in this category: PKIX keyUsage and the Netscape specific nsCertType. nsCertType (netscape certificate type) takes the flags: client, server, email, objsign, reserved, sslCA, emailCA, objCA. keyUsage (PKIX key usage) takes the flags: digitalSignature, nonRepudiation, keyEncipherment, dataEncipherment, keyAgreement, keyCertSign, cRLSign, encipherOnly, decipherOnly. For example: nsCertType=server keyUsage=critical, digitalSignature, nonRepudiation Basic Constraints. Basic constraints is a multi valued extension that supports a CA and an optional pathlen option. The CA option takes the values true and false and pathlen takes an integer. Note if the CA option is false the pathlen option should be omitted. Examples: basicConstraints=CA:TRUE basicConstraints=critical,CA:TRUE, pathlen:10 NOTE: for a CA to be considered valid it must have the CA option set to TRUE. An end user certificate MUST NOT have the CA value set to true. According to PKIX recommendations it should exclude the extension entirely, however some software may require CA set to FALSE for end entity certificates. Subject Key Identifier. This is really a string extension and can take two possible values. Either a hex string giving details of the extension value to include or the word 'hash' which then automatically follow PKIX guidelines in selecting and appropriate key identifier. The use of the hex string is strongly discouraged. Example: subjectKeyIdentifier=hash Authority Key Identifier. The authority key identifier extension permits two options. keyid and issuer: both can take the optional value "always". If the keyid option is present an attempt is made to copy the subject key identifier from the parent certificate. If the value "always" is present then an error is returned if the option fails. The issuer option copies the issuer and serial number from the issuer certificate. Normally this will only be done if the keyid option fails or is not included: the "always" flag will always include the value. Subject Alternative Name. The subject alternative name extension allows various literal values to be included in the configuration file. These include "email" (an email address) "URI" a uniform resource indicator, "DNS" (a DNS domain name), RID (a registered ID: OBJECT IDENTIFIER) and IP (and IP address). Also the email option include a special 'copy' value. This will automatically include and email addresses contained in the certificate subject name in the extension. Examples: subjectAltName=email:copy,email:my@other.address,URL:http://my.url.here/ subjectAltName=email:my@other.address,RID:1.2.3.4 Issuer Alternative Name. The issuer alternative name option supports all the literal options of subject alternative name. It does *not* support the email:copy option because that would not make sense. It does support an additional issuer:copy option that will copy all the subject alternative name values from the issuer certificate (if possible). CRL distribution points. This is a multivalued extension that supports all the literal options of subject alternative name. Of the few software packages that currently interpret this extension most only interpret the URI option. Currently each option will set a new DistributionPoint with the fullName field set to the given value. Other fields like cRLissuer and reasons cannot currently be set or displayed: at this time no examples were available that used these fields. If you see this extension with when you attempt to print it out or it doesn't appear to display correctly then let me know, including the certificate (mail me at steve@openssl.org) . Examples: crlDistributionPoints=URI:http://www.myhost.com/myca.crl crlDistributionPoints=URI:http://www.my.com/my.crl,URI:http://www.oth.com/my.crl Certificate Policies. This is a RAW extension. It attempts to display the contents of this extension: unfortuntately this extension is often improperly encoded. The certificate policies extension will rarely be used in practice: few software packages interpret it correctly or at all. IE5 does partially support this extension: but it needs the 'ia5org' option because it will only correctly support a broken encoding. Of the options below only the policy OID, explicitText and CPS options are displayed with IE5. All the fields of this extension can be set by using the appropriate syntax. If you follow the PKIX recommendations of not including any qualifiers and just using only one OID then you just include the value of that OID. Multiple OIDs can be set separated by commas, for example: certificatePolicies= 1.2.4.5, 1.1.3.4 If you wish to include qualifiers then the policy OID and qualifiers need to be specified in a separate section: this is done by using the @section syntax instead of a literal OID value. The section referred to must include the policy OID using the name policyIdentifier, cPSuri qualifiers can be included using the syntax: CPS.nnn=value userNotice qualifiers can be set using the syntax: userNotice.nnn=@notice The value of the userNotice qualifier is specified in the relevant section. This section can include explicitText, organization and noticeNumbers options. explicitText and organization are text strings, noticeNumbers is a comma separated list of numbers. The organization and noticeNumbers options (if included) must BOTH be present. If you use the userNotice option with IE5 then you need the 'ia5org' option at the top level to modify the encoding: otherwise it will not be interpreted properly. Example: certificatePolicies=ia5org,1.2.3.4,1.5.6.7.8,@polsect [polsect] policyIdentifier = 1.3.5.8 CPS.1="http://my.host.name/" CPS.2="http://my.your.name/" userNotice.1=@notice [notice] explicitText="Explicit Text Here" organization="Organisation Name" noticeNumbers=1,2,3,4 TECHNICAL NOTE: the ia5org option changes the type of the 'organization' field, according to PKIX it should be of type DisplayText but Verisign uses an IA5STRING and IE5 needs this too. Display only extensions. Some extensions are only partially supported and currently are only displayed but cannot be set. These include private key usage period, CRL number, and CRL reason. ============================================================================== PKCS#12 Library ============================================================================== This section describes the internal PKCS#12 support. There are very few differences between the old external library and the new internal code at present. This may well change because the external library will not be updated much in future. This version now includes a couple of high level PKCS#12 functions which generally "do the right thing" and should make it much easier to handle PKCS#12 structures. HIGH LEVEL FUNCTIONS. For most applications you only need concern yourself with the high level functions. They can parse and generate simple PKCS#12 files as produced by Netscape and MSIE or indeed any compliant PKCS#12 file containing a single private key and certificate pair. 1. Initialisation and cleanup. No special initialisation is needed for the internal PKCS#12 library: the standard SSLeay_add_all_algorithms() is sufficient. If you do not wish to add all algorithms (you should at least add SHA1 though) then you can manually initialise the PKCS#12 library with: PKSC12_PBE_add(); The memory allocated by the PKCS#12 libray is freed up when EVP_cleanup() is called or it can be directly freed with: EVP_PBE_cleanup(); after this call (or EVP_cleanup() ) no more PKCS#12 library functions should be called. 2. I/O functions. i2d_PKCS12_bio(bp, p12) This writes out a PKCS12 structure to a BIO. i2d_PKCS12_fp(fp, p12) This is the same but for a FILE pointer. d2i_PKCS12_bio(bp, p12) This reads in a PKCS12 structure from a BIO. d2i_PKCS12_fp(fp, p12) This is the same but for a FILE pointer. 3. Parsing and creation functions. 3.1 Parsing with PKCS12_parse(). int PKCS12_parse(PKCS12 *p12, char *pass, EVP_PKEY **pkey, X509 **cert, STACK **ca); This function takes a PKCS12 structure and a password (ASCII, null terminated) and returns the private key, the corresponding certificate and any CA certificates. If any of these is not required it can be passed as a NULL. The 'ca' parameter should be either NULL, a pointer to NULL or a valid STACK structure. Typically to read in a PKCS#12 file you might do: p12 = d2i_PKCS12_fp(fp, NULL); PKCS12_parse(p12, password, &pkey, &cert, NULL); /* CAs not wanted */ PKCS12_free(p12); 3.2 PKCS#12 creation with PKCS12_create(). PKCS12 *PKCS12_create(char *pass, char *name, EVP_PKEY *pkey, X509 *cert, STACK *ca, int nid_key, int nid_cert, int iter, int mac_iter, int keytype); This function will create a PKCS12 structure from a given password, name, private key, certificate and optional STACK of CA certificates. The remaining 5 parameters can be set to 0 and sensible defaults will be used. The parameters nid_key and nid_cert are the key and certificate encryption algorithms, iter is the encryption iteration count, mac_iter is the MAC iteration count and keytype is the type of private key. If you really want to know what these last 5 parameters do then read the low level section. Typically to create a PKCS#12 file the following could be used: p12 = PKCS12_create(pass, "My Certificate", pkey, cert, NULL, 0,0,0,0,0); i2d_PKCS12_fp(fp, p12); PKCS12_free(p12); LOW LEVEL FUNCTIONS. In some cases the high level functions do not provide the necessary functionality. For example if you want to generate or parse more complex PKCS#12 files. The sample pkcs12 application uses the low level functions to display details about the internal structure of a PKCS#12 file. Introduction. This is a brief description of how a PKCS#12 file is represented internally: some knowledge of PKCS#12 is assumed. A PKCS#12 object contains several levels. At the lowest level is a PKCS12_SAFEBAG. This can contain a certificate, a CRL, a private key, encrypted or unencrypted, a set of safebags (so the structure can be nested) or other secrets (not documented at present). A safebag can optionally have attributes, currently these are: a unicode friendlyName (a Unicode string) or a localKeyID (a string of bytes). At the next level is an authSafe which is a set of safebags collected into a PKCS#7 ContentInfo. This can be just plain data, or encrypted itself. At the top level is the PKCS12 structure itself which contains a set of authSafes in an embedded PKCS#7 Contentinfo of type data. In addition it contains a MAC which is a kind of password protected digest to preserve integrity (so any unencrypted stuff below can't be tampered with). The reason for these levels is so various objects can be encrypted in various ways. For example you might want to encrypt a set of private keys with triple-DES and then include the related certificates either unencrypted or with lower encryption. Yes it's the dreaded crypto laws at work again which allow strong encryption on private keys and only weak encryption on other stuff. To build one of these things you turn all certificates and keys into safebags (with optional attributes). You collect the safebags into (one or more) STACKS and convert these into authsafes (encrypted or unencrypted). The authsafes are collected into a STACK and added to a PKCS12 structure. Finally a MAC inserted. Pulling one apart is basically the reverse process. The MAC is verified against the given password. The authsafes are extracted and each authsafe split into a set of safebags (possibly involving decryption). Finally the safebags are decomposed into the original keys and certificates and the attributes used to match up private key and certificate pairs. Anyway here are the functions that do the dirty work. 1. Construction functions. 1.1 Safebag functions. M_PKCS12_x5092certbag(x509) This macro takes an X509 structure and returns a certificate bag. The X509 structure can be freed up after calling this function. M_PKCS12_x509crl2certbag(crl) As above but for a CRL. PKCS8_PRIV_KEY_INFO *PKEY2PKCS8(EVP_PKEY *pkey) Take a private key and convert it into a PKCS#8 PrivateKeyInfo structure. Works for both RSA and DSA private keys. NB since the PKCS#8 PrivateKeyInfo structure contains a private key data in plain text form it should be free'd up as soon as it has been encrypted for security reasons (freeing up the structure zeros out the sensitive data). This can be done with PKCS8_PRIV_KEY_INFO_free(). PKCS8_add_keyusage(PKCS8_PRIV_KEY_INFO *p8, int usage) This sets the key type when a key is imported into MSIE or Outlook 98. Two values are currently supported: KEY_EX and KEY_SIG. KEY_EX is an exchange type key that can also be used for signing but its size is limited in the export versions of MS software to 512 bits, it is also the default. KEY_SIG is a signing only key but the keysize is unlimited (well 16K is supposed to work). If you are using the domestic version of MSIE then you can ignore this because KEY_EX is not limited and can be used for both. PKCS12_SAFEBAG *PKCS12_MAKE_KEYBAG(PKCS8_PRIV_KEY_INFO *p8) Convert a PKCS8 private key structure into a keybag. This routine embeds the p8 structure in the keybag so p8 should not be freed up or used after it is called. The p8 structure will be freed up when the safebag is freed. 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) Convert a PKCS#8 structure into a shrouded key bag (encrypted). p8 is not embedded and can be freed up after use. int PKCS12_add_localkeyid(PKCS12_SAFEBAG *bag, unsigned char *name, int namelen) int PKCS12_add_friendlyname(PKCS12_SAFEBAG *bag, unsigned char *name, int namelen) Add a local key id or a friendlyname to a safebag. 1.2 Authsafe functions. PKCS7 *PKCS12_pack_p7data(STACK *sk) Take a stack of safebags and convert them into an unencrypted authsafe. The stack of safebags can be freed up after calling this function. PKCS7 *PKCS12_pack_p7encdata(int pbe_nid, unsigned char *pass, int passlen, unsigned char *salt, int saltlen, int iter, STACK *bags); As above but encrypted. 1.3 PKCS12 functions. PKCS12 *PKCS12_init(int mode) Initialise a PKCS12 structure (currently mode should be NID_pkcs7_data). M_PKCS12_pack_authsafes(p12, safes) This macro takes a STACK of authsafes and adds them to a PKCS#12 structure. int PKCS12_set_mac(PKCS12 *p12, unsigned char *pass, int passlen, unsigned char *salt, int saltlen, int iter, EVP_MD *md_type); Add a MAC to a PKCS12 structure. If EVP_MD is NULL use SHA-1, the spec suggests that SHA-1 should be used. 2. Extraction Functions. 2.1 Safebags. M_PKCS12_bag_type(bag) Return the type of "bag". Returns one of the following NID_keyBag NID_pkcs8ShroudedKeyBag 7 NID_certBag 8 NID_crlBag 9 NID_secretBag 10 NID_safeContentsBag 11 M_PKCS12_cert_bag_type(bag) Returns type of certificate bag, following are understood. NID_x509Certificate 14 NID_sdsiCertificate 15 M_PKCS12_crl_bag_type(bag) Returns crl bag type, currently only NID_crlBag is recognised. M_PKCS12_certbag2x509(bag) This macro extracts an X509 certificate from a certificate bag. M_PKCS12_certbag2x509crl(bag) As above but for a CRL. EVP_PKEY * PKCS82PKEY(PKCS8_PRIV_KEY_INFO *p8) Extract a private key from a PKCS8 private key info structure. M_PKCS12_decrypt_skey(bag, pass, passlen) Decrypt a shrouded key bag and return a PKCS8 private key info structure. Works with both RSA and DSA keys char *PKCS12_get_friendlyname(bag) Returns the friendlyName of a bag if present or NULL if none. The returned string is a null terminated ASCII string allocated with Malloc(). It should thus be freed up with Free() after use. 2.2 AuthSafe functions. M_PKCS12_unpack_p7data(p7) Extract a STACK of safe bags from a PKCS#7 data ContentInfo. #define M_PKCS12_unpack_p7encdata(p7, pass, passlen) As above but for an encrypted content info. 2.3 PKCS12 functions. M_PKCS12_unpack_authsafes(p12) Extract a STACK of authsafes from a PKCS12 structure. M_PKCS12_mac_present(p12) Check to see if a MAC is present. int PKCS12_verify_mac(PKCS12 *p12, unsigned char *pass, int passlen) Verify a MAC on a PKCS12 structure. Returns an error if MAC not present. Notes. 1. All the function return 0 or NULL on error. 2. Encryption based functions take a common set of parameters. These are described below. pass, passlen ASCII password and length. The password on the MAC is called the "integrity password" the encryption password is called the "privacy password" in the PKCS#12 documentation. The passwords do not have to be the same. If -1 is passed for the length it is worked out by the function itself (currently this is sometimes done whatever is passed as the length but that may change). salt, saltlen A 'salt' if salt is NULL a random salt is used. If saltlen is also zero a default length is used. iter Iteration count. This is a measure of how many times an internal function is called to encrypt the data. The larger this value is the longer it takes, it makes dictionary attacks on passwords harder. NOTE: Some implementations do not support an iteration count on the MAC. If the password for the MAC and encryption is the same then there is no point in having a high iteration count for encryption if the MAC has no count. The MAC could be attacked and the password used for the main decryption. pbe_nid This is the NID of the password based encryption method used. The following are supported. NID_pbe_WithSHA1And128BitRC4 NID_pbe_WithSHA1And40BitRC4 NID_pbe_WithSHA1And3_Key_TripleDES_CBC NID_pbe_WithSHA1And2_Key_TripleDES_CBC NID_pbe_WithSHA1And128BitRC2_CBC NID_pbe_WithSHA1And40BitRC2_CBC Which you use depends on the implementation you are exporting to. "Export grade"(i.e. cryptograhically challenged) products cannot support all algorithms. Typically you may be able to use any encryption on shrouded key bags but they must then be placed in an unencrypted authsafe. Other authsafes may only support 40bit encryption. Of course if you are using SSLeay throughout you can strongly encrypt everything and have high iteration counts on everything. 3. For decryption routines only the password and length are needed. 4. Unlike the external version the nid's of objects are the values of the constants: that is NID_certBag is the real nid, therefore there is no PKCS12_obj_offset() function. Note the object constants are not the same as those of the external version. If you use these constants then you will need to recompile your code. 5. With the exception of PKCS12_MAKE_KEYBAG(), after calling any function or macro of the form PKCS12_MAKE_SOMETHING(other) the "other" structure can be reused or freed up safely.