This is some preliminary documentation for OpenSSL. ============================================================================== BUFFER Library ============================================================================== [Note: I wrote this when I saw a Malloc version of strdup() in there which I'd written myself anyway. I was so annoyed at not noticing this I decided to document it :-) Steve.] 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. 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. 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 and additional issuer:copy option that will copy all the subject alternative name values from the issuer certificate (if possible). 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.