ASN1_GENERATE_NCONF(3) BSD Library Functions Manual ASN1_GENERATE_NCONF(3)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 ASN1 encoding of a string in an ASN1_TYPE
structure.
str contains the string to encode nconf or cnf contains the optional con‐
figuration 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.
GENERATION STRING FORMAT
The actual data encoded is determined by the string str and the configu‐
ration information. The general format of the string is:
[modifier,]type[:value]
That is zero or more comma separated modifiers followed by a type fol‐
lowed 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 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 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.
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 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 gener‐
ated 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
EXPLICIT or IMPLICIT tagging, add wrappers, or to change the string for‐
mat 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 deci‐
mal value.
By following the number with U, A, P or C, UNIVERSAL, APPLICA‐
TION, 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.
RETURN VALUESASN1_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).
EXAMPLES
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 consit‐
ing 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 con‐
tained 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 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
SEE ALSOERR_get_error(3)HISTORYASN1_generate_nconf() and ASN1_generate_v3() were added to OpenSSL 0.9.8.
BSD July 17, 2014 BSD
