ASN1_generate_nconf.3

.\"	$OpenBSD: ASN1_generate_nconf.3,v 1.13 2019/06/10 14:58:48 schwarze Exp $
.\"	OpenSSL 05ea606a Fri May 20 20:52:46 2016 -0400
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.\" This file was written by Dr. Stephen Henson.
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.Dd $Mdocdate: June 10 2019 $
.Dt ASN1_GENERATE_NCONF 3
.Os
.Sh NAME
.Nm ASN1_generate_nconf ,
.Nm ASN1_generate_v3
.Nd ASN.1 generation functions
.Sh SYNOPSIS
.In openssl/asn1.h
.Ft ASN1_TYPE *
.Fo ASN1_generate_nconf
.Fa "const char *str"
.Fa "CONF *nconf"
.Fc
.Ft ASN1_TYPE *
.Fo ASN1_generate_v3
.Fa "const char *str"
.Fa "X509V3_CTX *cnf"
.Fc
.Sh DESCRIPTION
These functions generate the ASN.1 encoding of a string in an
.Vt ASN1_TYPE
structure.
.Pp
.Fa str
contains the string to encode
.Fa nconf
or
.Fa cnf
contains the optional configuration information
where additional strings will be read from.
.Fa nconf
will typically come from a config file whereas
.Fa cnf
is obtained from an
.Vt X509V3_CTX
structure which will typically be used
by X509 v3 certificate extension functions.
.Fa cnf
or
.Fa nconf
can be set to
.Dv NULL
if no additional configuration will be used.
.Sh GENERATION STRING FORMAT
The actual data encoded is determined by the string
.Fa str
and the configuration information.
The general format of the string is:
.Pp
.D1 Oo Ar modifier , Oc Ns Ar type Ns Op : Ns Ar value
.Pp
That is zero or more comma separated modifiers followed by a type
followed by an optional colon and a value.
The formats of
.Ar type ,
.Ar value
and
.Ar modifier
are explained below.
.Ss Supported types
The supported types are listed below.
Unless otherwise specified, only the
.Cm ASCII
format is permissible.
.Bl -tag -width Ds
.It Cm BOOLEAN , BOOL
This encodes a boolean type.
The
.Ar value
string is mandatory and should be
.Cm TRUE
or
.Cm FALSE .
Additionally
.Cm true ,
.Cm Y ,
.Cm y ,
.Cm YES ,
.Cm yes ,
.Cm false ,
.Cm N ,
.Cm n ,
.Cm NO
and
.Cm no
are acceptable.
.It Cm NULL
Encode the NULL type.
The
.Ar value
string must not be present.
.It Cm INTEGER , INT
Encodes an ASN.1 INTEGER type.
The
.Ar 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
.Cm 0x
is included.
.It Cm ENUMERATED , ENUM
Encodes the ASN.1 ENUMERATED type.
It is otherwise identical to
.Cm INTEGER .
.It Cm OBJECT , OID
Encodes an ASN.1 OBJECT IDENTIFIER.
The
.Ar value
string can be a short name, a long name, or numerical format.
.It Cm UTCTIME , UTC
Encodes an ASN.1 UTCTime structure.
The value should be in the format
.Ar YYMMDDHHMMSSZ .
.It Cm GENERALIZEDTIME , GENTIME
Encodes an ASN.1 GeneralizedTime structure.
The value should be in the format
.Ar YYYYMMDDHHMMSSZ .
.It Cm OCTETSTRING , OCT
Encodes an ASN.1 OCTET STRING.
.Ar value
represents the contents of this structure.
The format strings
.Cm ASCII
and
.Cm HEX
can be used to specify the format of
.Ar value .
.It Cm BITSTRING , BITSTR
Encodes an ASN.1 BIT STRING.
.Ar value
represents the contents of this structure.
The format strings
.Cm ASCII ,
.Cm HEX ,
and
.Cm BITLIST
can be used to specify the format of
.Ar value .
.Pp
If the format is anything other than
.Cm BITLIST ,
the number of unused bits is set to zero.
.It Xo
.Cm BMPSTRING , BMP ,
.Cm GeneralString ,
.Cm IA5STRING , IA5 ,
.Cm NUMERICSTRING , NUMERIC ,
.Cm PRINTABLESTRING , PRINTABLE ,
.Cm T61STRING , T61 ,
.Cm TELETEXSTRING ,
.Cm UNIVERSALSTRING , UNIV ,
.Cm UTF8String , UTF8 ,
.Cm VISIBLESTRING , VISIBLE
.Xc
These encode the corresponding string types.
.Ar value
represents the contents of this structure.
The format can be
.Cm ASCII
or
.Cm UTF8 .
.It Cm SEQUENCE , SEQ , SET
Formats the result as an ASN.1 SEQUENCE or SET type.
.Ar 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
.Ar value
is absent, then an empty SEQUENCE will be encoded.
.El
.Ss Modifiers
Modifiers affect the following structure.
They can be used to add EXPLICIT or IMPLICIT tagging, add wrappers,
or to change the string format of the final type and value.
The supported formats are:
.Bl -tag -width Ds
.It Cm 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.
.Pp
By following the number with
.Cm U ,
.Cm A ,
.Cm P
or
.Cm C ,
UNIVERSAL, APPLICATION, PRIVATE or CONTEXT SPECIFIC tagging can be used.
The default is CONTEXT SPECIFIC.
.It Cm IMPLICIT , IMP
This is the same as
.Cm EXPLICIT
except IMPLICIT tagging is used instead.
.It Cm 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.
.It Cm FORMAT
This specifies the format of the ultimate value.
It should be followed by a colon and one of the strings
.Cm ASCII ,
.Cm UTF8 ,
.Cm HEX ,
or
.Cm BITLIST .
.Pp
If no format specifier is included, then
.Cm ASCII
is used.
If
.Cm UTF8
is specified, then the
.Ar value
string must be a valid UTF-8 string.
For
.Cm HEX ,
the output must be a set of hex digits.
.Cm 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.
.El
.Sh RETURN VALUES
.Fn ASN1_generate_nconf
and
.Fn ASN1_generate_v3
return the encoded data as an
.Vt ASN1_TYPE
structure or
.Dv NULL
if an error occurred.
.Pp
The error codes can be obtained by
.Xr ERR_get_error 3 .
.Sh EXAMPLES
A simple
.Vt IA5String :
.Pp
.Dl IA5STRING:Hello World
.Pp
An
.Vt IA5String
explicitly tagged:
.Pp
.Dl EXPLICIT:0,IA5STRING:Hello World
.Pp
An
.Vt IA5String
explicitly tagged using APPLICATION tagging:
.Pp
.Dl EXPLICIT:0A,IA5STRING:Hello World
.Pp
A BITSTRING with bits 1 and 5 set and all others zero:
.Pp
.Dl FORMAT:BITLIST,BITSTRING:1,5
.Pp
A more complex example using a config file to produce a
SEQUENCE consisting of a BOOL an OID and a
.Vt UTF8String :
.Bd -literal -offset indent
asn1 = SEQUENCE:seq_section

[seq_section]

field1 = BOOLEAN:TRUE
field2 = OID:commonName
field3 = UTF8:Third field
.Ed
.Pp
This example produces an
.Vt RSAPrivateKey
structure.
This is the key contained in the file
.Pa client.pem
in all OpenSSL distributions.
Note that the field names such as
.Qq coeff
are ignored and are present just for clarity.
.Bd -literal -offset 2n
asn1=SEQUENCE:private_key
[private_key]
version=INTEGER:0

n=INTEGER:0xBB6FE79432CC6EA2D8F970675A5A87BFBE1AFF0BE63E879F2AFFB93644\e
D4D2C6D000430DEC66ABF47829E74B8C5108623A1C0EE8BE217B3AD8D36D5EB4FCA1D9

e=INTEGER:0x010001

d=INTEGER:0x6F05EAD2F27FFAEC84BEC360C4B928FD5F3A9865D0FCAAD291E2A52F4A\e
F810DC6373278C006A0ABBA27DC8C63BF97F7E666E27C5284D7D3B1FFFE16B7A87B51D

p=INTEGER:0xF3929B9435608F8A22C208D86795271D54EBDFB09DDEF539AB083DA912\e
D4BD57

q=INTEGER:0xC50016F89DFF2561347ED1186A46E150E28BF2D0F539A1594BBD7FE467\e
46EC4F

exp1=INTEGER:0x9E7D4326C924AFC1DEA40B45650134966D6F9DFA3A7F9D698CD4ABEA\e
9C0A39B9

exp2=INTEGER:0xBA84003BB95355AFB7C50DF140C60513D0BA51D637272E355E397779\e
E7B2458F

coeff=INTEGER:0x30B9E4F2AFA5AC679F920FC83F1F2DF1BAF1779CF989447FABC2F5\e
628657053A
.Ed
.Pp
This example is the corresponding public key in an ASN.1
.Vt SubjectPublicKeyInfo
structure:
.Bd -literal -offset 2n
# 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\e
D4D2C6D000430DEC66ABF47829E74B8C5108623A1C0EE8BE217B3AD8D36D5EB4FCA1D9

e=INTEGER:0x010001
.Ed
.Sh SEE ALSO
.Xr ASN1_TYPE_get 3 ,
.Xr d2i_ASN1_TYPE 3 ,
.Xr x509v3.cnf 5
.Sh HISTORY
.Fn ASN1_generate_nconf
and
.Fn ASN1_generate_v3
first appeared in OpenSSL 0.9.8 and have been available since
.Ox 4.5 .