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ASN1_PUT_OBJECT(3) Library Functions Manual ASN1_PUT_OBJECT(3)

ASN1_put_object, ASN1_put_eocstart and end the BER encoding of an arbitrary ASN.1 data element

#include <openssl/asn1.h>

ASN1_put_object(unsigned char **ber_out, int constructed, int length, int tag, int class);

ASN1_put_eoc(unsigned char **ber_out);

ASN1_put_object() begins writing the BER encoding of an arbitrary ASN.1 data element to the buffer *ber_out by writing the identifier and the length bytes. Making sure that there is sufficient space in the buffer is the responsibility of the caller. This function does not write any content bytes nor any end-of-content bytes.

The tag class can be V_ASN1_UNIVERSAL, V_ASN1_APPLICATION, V_ASN1_CONTEXT_SPECIFIC, or V_ASN1_PRIVATE and is written to the two most significant bits of the first byte written.

The constructed argument can have the following values:

Start a primitive value by setting the third most significant bit of the first byte written to 0. Always use the definite form.
Start a constructed value by setting the third most significant bit of the first byte written to 1, and use the definite form.
Start a constructed value and use the indefinite form,

If the tag is less than 0x1f, it is written to the five least significant bits of the only identifier byte written. Otherwise, these five bits are all set to 1, and the tag is encoded in one or more following identifier bytes as needed.

After completing the identifier byte(s), when using the definite form, the given length is encoded in one or more bytes as needed. Otherwise, the special byte 0x80 is written instead and the length argument is ignored.

At the end, *ber_out is set to the byte following the last byte written. The calling code can then start writing content bytes.

If the indefinite form was selected, the calling code is also responsible for calling ASN1_put_eoc() which writes an end-of-content marker to *ber_out, consisting of two NUL bytes, and advances *ber_out by two bytes.

ASN1_put_eoc() returns the number of bytes written, which is always 2.

ASN1_item_i2d(3), ASN1_TYPE_get(3), i2d_ASN1_NULL(3), i2d_ASN1_OBJECT(3), i2d_ASN1_OCTET_STRING(3), i2d_ASN1_SEQUENCE_ANY(3)

ASN1_put_object() first appeared in SSLeay 0.5.1 and has been available since OpenBSD 2.4.

ASN1_put_eoc() first appeared in OpenSSL 0.9.8 and has been available since OpenBSD 4.5.

Neither ASN1_put_object() nor ASN1_put_eoc() do any sanity checking. When called in inconsistent ways, invalid content may result in *ber_out, for example

If the calling code wants to find out how many bytes were written, it needs to save a copy of the pointer *ber_out before calling ASN1_put_object().

August 26, 2019 OpenBSD-current