ASN1_generate_nconf,
ASN1_generate_v3 —
ASN.1 generation functions
#include
<openssl/asn1.h>
ASN1_TYPE *
ASN1_generate_nconf(
const
char *str,
CONF *nconf);
ASN1_TYPE *
ASN1_generate_v3(
const
char *str,
X509V3_CTX *cnf);
These functions generate the ASN.1 encoding of a string in an
ASN1_TYPE 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 whereas
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
NULL if no additional
configuration will be used.
The actual data encoded is determined by the string
str and the configuration information. The
general format of the string is:
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.
The supported types are listed below. Unless otherwise specified, only the
ASCII format is permissible.
-
-
BOOLEAN,
BOOL- This encodes a boolean type. The value
string is mandatory and should be
TRUE
or FALSE. Additionally
true,
Y,
y,
YES,
yes,
false,
N,
n,
NO and
no are acceptable.
-
-
NULL- Encode the NULL type. The value string
must not be present.
-
-
INTEGER,
INT- Encodes an ASN.1 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 ASN.1 ENUMERATED type. It is otherwise identical to
INTEGER.
-
-
OBJECT,
OID- Encodes an ASN.1 OBJECT IDENTIFIER. The
value string can be a short name, a long
name, or numerical format.
-
-
UTCTIME,
UTC- Encodes an ASN.1 UTCTime structure. The value should be in the format
YYMMDDHHMMSSZ.
-
-
GENERALIZEDTIME,
GENTIME- Encodes an ASN.1 GeneralizedTime structure. The value should be in the
format YYYYMMDDHHMMSSZ.
-
-
OCTETSTRING,
OCT- Encodes an ASN.1 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 ASN.1 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.
-
-
BMPSTRING,
BMP,
GeneralString,
IA5STRING,
IA5,
NUMERICSTRING,
NUMERIC,
PRINTABLESTRING,
PRINTABLE,
T61STRING,
T61,
TELETEXSTRING,
UNIVERSALSTRING,
UNIV,
UTF8String,
UTF8,
VISIBLESTRING,
VISIBLE- 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 ASN.1 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 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:
-
-
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 UTF-8
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.
ASN1_generate_nconf() and
ASN1_generate_v3() return the encoded data
as an
ASN1_TYPE structure or
NULL if an error occurred.
The error codes can be obtained by
ERR_get_error(3).
A simple
IA5String:
IA5STRING:Hello World
An
IA5String explicitly tagged:
EXPLICIT:0,IA5STRING:Hello
World
An
IA5String explicitly tagged using
APPLICATION tagging:
EXPLICIT:0A,IA5STRING:Hello
World
A BITSTRING 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 SEQUENCE consisting of a
BOOL an OID 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 that 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 an ASN.1
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
ERR_get_error(3),
x509v3.cnf(5)
ASN1_generate_nconf() and
ASN1_generate_v3() first appeared in
OpenSSL 0.9.8 and have been available since
OpenBSD
4.5.
![[OpenBSD]](/openbsd.gif){kind=small}