NAME

ASN1_generate_nconf, ASN1_generate_v3 — ASN.1 generation functions

SYNOPSIS

#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);

DESCRIPTION

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.

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.

RETURN VALUES

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).

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 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

SEE ALSO

ASN1_TYPE_get(3), d2i_ASN1_TYPE(3), x509v3.cnf(5)

HISTORY

ASN1_generate_nconf() and ASN1_generate_v3() first appeared in OpenSSL 0.9.8 and have been available since OpenBSD 4.5.