ASN1_generate_v3 (3)

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NAME

ASN1_generate_nconf, ASN1_generate_v3 - ASN1 generation functions

SYNOPSIS

 #include <openssl/asn1.h>

 ASN1_TYPE *ASN1_generate_nconf(char *str, CONF *nconf);
 ASN1_TYPE *ASN1_generate_v3(char *str, X509V3_CTX *cnf);

DESCRIPTION

These functions generate the encoding of a string in an structure.

str contains the string to encode nconf or cnf contains the optional configuration information where additional strings will be read from. nconf will typically come from a config file wherease cnf is obtained from an X509V3_CTX structure which will typically be used by X509 v3 certificate extension functions. cnf or nconf can be set to

if no additional configuration will be used.

GENERATION STRING FORMAT

The actual data encoded is determined by the string str and the configuration information. The general format of the string is:

[modifier,]type[:value]

That is zero or more comma separated modifiers followed by a type followed by an optional colon and a value. The formats of type, value and modifier are explained below.

SUPPORTED TYPES

The supported types are listed below. Unless otherwise specified only the format is permissible.

BOOLEAN

,

BOOL

This encodes a boolean type. The value string is mandatory and should be

TRUE

or

FALSE

. Additionally

TRUE

, true, Y, y,

YES

, yes,

FALSE

, false, N, n,

NO

and no are acceptable.

NULL

Encode the

NULL

type, the value string must not be present.

INTEGER

,

INT

Encodes an

ASN1

INTEGER

type. The value string represents the value of the integer, it can be prefaced by a minus sign and is normally interpreted as a decimal value unless the prefix 0x is included.

ENUMERATED

,

ENUM

Encodes the

ASN1

ENUMERATED

type, it is otherwise identical to

INTEGER

.

OBJECT

,

OID

Encodes an

ASN1

OBJECT IDENTIFIER

, the value string can be a short name, a long name or numerical format.

UTCTIME

,

UTC

Encodes an

ASN1

UTCTime structure, the value should be in the format

YYMMDDHHMMSSZ

.

GENERALIZEDTIME

,

GENTIME

Encodes an

ASN1

GeneralizedTime structure, the value should be in the format

YYYYMMDDHHMMSSZ

.

OCTETSTRING

,

OCT

Encodes an

ASN1

OCTET STRING

. value represents the contents of this structure, the format strings

ASCII

and

HEX

can be used to specify the format of value.

BITSTRING

,

BITSTR

Encodes an

ASN1

BIT STRING

. value represents the contents of this structure, the format strings

ASCII

,

HEX

and

BITLIST

can be used to specify the format of value.

If the format is anything other than

BITLIST

the number of unused bits is set to zero.

UNIVERSALSTRING

,

UNIV

,

IA5

,

IA5STRING

,

UTF8

, UTF8String,

BMP

,

BMPSTRING

,

VISIBLESTRING

,

VISIBLE

,

PRINTABLESTRING

,

PRINTABLE

, T61, T61STRING,

TELETEXSTRING

, GeneralString,

NUMERICSTRING

,

NUMERIC

These encode the corresponding string types. value represents the contents of this structure. The format can be

ASCII

or

UTF8

.

SEQUENCE

,

SEQ

,

SET

Formats the result as an

ASN1

SEQUENCE

or

SET

type. value should be a section name which will contain the contents. The field names in the section are ignored and the values are in the generated string format. If value is absent then an empty

SEQUENCE

will be encoded.

MODIFIERS

Modifiers affect the following structure, they can be used to add or tagging, add wrappers or to change the string format of the final type and value. The supported formats are documented below.

EXPLICIT

,

EXP

Add an explicit tag to the following structure. This string should be followed by a colon and the tag value to use as a decimal value.

By following the number with U, A, P or C

UNIVERSAL, APPLICATION, PRIVATE

or

CONTEXT SPECIFIC

tagging can be used, the default is

CONTEXT SPECIFIC.

IMPLICIT

,

IMP

This is the same as

EXPLICIT

except

IMPLICIT

tagging is used instead.

OCTWRAP

,

SEQWRAP

,

SETWRAP

,

BITWRAP

The following structure is surrounded by an

OCTET STRING,

a

SEQUENCE,

a

SET

or a

BIT STRING

respectively. For a

BIT STRING

the number of unused bits is set to zero.

FORMAT

This specifies the format of the ultimate value. It should be followed by a colon and one of the strings

ASCII

,

UTF8

,

HEX

or

BITLIST

.

If no format specifier is included then

ASCII

is used. If

UTF8

is specified then the value string must be a valid

UTF8

string. For

HEX

the output must be a set of hex digits.

BITLIST

(which is only valid for a

BIT STRING

) is a comma separated list of the indices of the set bits, all other bits are zero.

EXAMPLES

A simple IA5String:

 IA5STRING:Hello World

An IA5String explicitly tagged:

 EXPLICIT:0,IA5STRING:Hello World

An IA5String explicitly tagged using

tagging:

 EXPLICIT:0A,IA5STRING:Hello World

A

with bits 1 and 5 set and all others zero:

 FORMAT:BITLIST,BITSTRING:1,5

A more complex example using a config file to produce a

consiting of a an and a UTF8String:

 asn1 = SEQUENCE:seq_section

 [seq_section]

 field1 = BOOLEAN:TRUE
 field2 = OID:commonName
 field3 = UTF8:Third field

This example produces an RSAPrivateKey structure, this is the key contained in the file client.pem in all OpenSSL distributions (note: the field names such as 'coeff' are ignored and are present just for clarity):

 asn1=SEQUENCE:private_key
 [private_key]
 version=INTEGER:0

 n=INTEGER:0xBB6FE79432CC6EA2D8F970675A5A87BFBE1AFF0BE63E879F2AFFB93644\
 D4D2C6D000430DEC66ABF47829E74B8C5108623A1C0EE8BE217B3AD8D36D5EB4FCA1D9

 e=INTEGER:0x010001

 d=INTEGER:0x6F05EAD2F27FFAEC84BEC360C4B928FD5F3A9865D0FCAAD291E2A52F4A\
 F810DC6373278C006A0ABBA27DC8C63BF97F7E666E27C5284D7D3B1FFFE16B7A87B51D

 p=INTEGER:0xF3929B9435608F8A22C208D86795271D54EBDFB09DDEF539AB083DA912\
 D4BD57

 q=INTEGER:0xC50016F89DFF2561347ED1186A46E150E28BF2D0F539A1594BBD7FE467\
 46EC4F

 exp1=INTEGER:0x9E7D4326C924AFC1DEA40B45650134966D6F9DFA3A7F9D698CD4ABEA\
 9C0A39B9

 exp2=INTEGER:0xBA84003BB95355AFB7C50DF140C60513D0BA51D637272E355E397779\
 E7B2458F

 coeff=INTEGER:0x30B9E4F2AFA5AC679F920FC83F1F2DF1BAF1779CF989447FABC2F5\
 628657053A

This example is the corresponding public key in a SubjectPublicKeyInfo structure:

 # Start with a SEQUENCE
 asn1=SEQUENCE:pubkeyinfo

 # pubkeyinfo contains an algorithm identifier and the public key wrapped
 # in a BIT STRING
 [pubkeyinfo]
 algorithm=SEQUENCE:rsa_alg
 pubkey=BITWRAP,SEQUENCE:rsapubkey

 # algorithm ID for RSA is just an OID and a NULL
 [rsa_alg]
 algorithm=OID:rsaEncryption
 parameter=NULL

 # Actual public key: modulus and exponent
 [rsapubkey]
 n=INTEGER:0xBB6FE79432CC6EA2D8F970675A5A87BFBE1AFF0BE63E879F2AFFB93644\
 D4D2C6D000430DEC66ABF47829E74B8C5108623A1C0EE8BE217B3AD8D36D5EB4FCA1D9

 e=INTEGER:0x010001

RETURN VALUES

ASN1_generate_nconf() and ASN1_generate_v3() return the encoded data as an structure or if an error occurred.

The error codes that can be obtained by ERR_get_error(3).

SEE ALSO

ERR_get_error(3)

HISTORY

ASN1_generate_nconf() and ASN1_generate_v3() were added to OpenSSL 0.9.8