tlv.cpp File Reference

#include "mod_gpg/openpgp/tlv.h"
#include <string.h>

Go to the source code of this file.

Functions
size_t	tlv_tag_size (uint16_t tag)
	BER-TLV codec implementation (see tlv.h).
size_t	tlv_len_size (size_t value_len)
	Compute the BER definite-length encoded size for a length value.
tlv_status_t	tlv_write_tag (uint8_t *buf, size_t buf_max, uint16_t tag, size_t *written)
	Encode a tag. Writes either one or two bytes depending on the magnitude of tag.
tlv_status_t	tlv_write_len (uint8_t *buf, size_t buf_max, size_t value_len, size_t *written)
	Encode a BER definite length field.
tlv_status_t	tlv_build (uint8_t *buf, size_t buf_max, uint16_t tag, const uint8_t *value, size_t value_len, size_t *written)
	Build a complete TLV: tag, length, and value (which may be NULL when value_len == 0).
tlv_status_t	tlv_read_tag (const uint8_t *buf, size_t buf_len, size_t *pos, uint16_t *tag_out)
	Read a tag from the input buffer at pos.
tlv_status_t	tlv_read_len (const uint8_t *buf, size_t buf_len, size_t *pos, size_t *length_out)
	Read a BER definite length field starting at pos.
tlv_status_t	tlv_parse (const uint8_t *buf, size_t buf_len, size_t *pos, tlv_t *out)
	Parse a single TLV starting at pos. On success pos advances past the entire field and out is filled.

Function Documentation

tlv_build()

tlv_status_t tlv_build	(	uint8_t *	buf,
		size_t	buf_max,
		uint16_t	tag,
		const uint8_t *	value,
		size_t	value_len,
		size_t *	written )

Build a complete TLV: tag, length, and value (which may be NULL when value_len == 0).

Parameters

buf	Output buffer.
buf_max	Buffer capacity.
tag	Tag value.
value	Optional value bytes.
value_len	Value length.
written	Receives the total number of bytes written.

Definition at line 54 of file tlv.cpp.

References TLV_ERR_BUF_TOO_SMALL, TLV_ERR_NULL, TLV_OK, tlv_write_len(), and tlv_write_tag().

tlv_len_size()

size_t tlv_len_size

(

size_t

value_len

)

Compute the BER definite-length encoded size for a length value.

Parameters

value_len

Value length.

Returns

Encoded length-field width (1, 2 or 3 bytes).

Definition at line 13 of file tlv.cpp.

Referenced by tlv_write_len().

tlv_parse()

tlv_status_t tlv_parse	(	const uint8_t *	buf,
		size_t	buf_len,
		size_t *	pos,
		tlv_t *	out )

Parse a single TLV starting at pos. On success pos advances past the entire field and out is filled.

The function rejects truncated values (length field claims more bytes than the buffer holds). It is safe to chain calls in a loop to walk a sequence of TLVs.

Definition at line 122 of file tlv.cpp.

References tlv_t::length, tlv_t::tag, TLV_ERR_BUF_TOO_SMALL, TLV_ERR_NULL, TLV_OK, tlv_read_len(), tlv_read_tag(), tlv_t::total_size, and tlv_t::value.

tlv_read_len()

tlv_status_t tlv_read_len	(	const uint8_t *	buf,
		size_t	buf_len,
		size_t *	pos,
		size_t *	length_out )

Read a BER definite length field starting at pos.

Accepts the short form (first_byte < 128) and the 0x81 / 0x82 long forms.

Parameters

buf	Input buffer.
buf_len	Available bytes in the buffer.
pos	In/out byte index.
length_out	Receives the parsed length value.

Definition at line 98 of file tlv.cpp.

References TLV_ERR_BAD_LENGTH, TLV_ERR_BUF_TOO_SMALL, TLV_ERR_NULL, and TLV_OK.

Referenced by tlv_parse().

tlv_read_tag()

tlv_status_t tlv_read_tag	(	const uint8_t *	buf,
		size_t	buf_len,
		size_t *	pos,
		uint16_t *	tag_out )

Read a tag from the input buffer at pos.

Advances pos past the tag. Two-byte tags are required to follow the ISO 7816-4 continuation rule (low five bits of the first byte = 0x1F).

Parameters

buf	Input buffer.
buf_len	Available bytes in the buffer.
pos	In/out byte index.
tag_out	Receives the parsed tag value.

Definition at line 76 of file tlv.cpp.

References TLV_ERR_BAD_TAG, TLV_ERR_BUF_TOO_SMALL, TLV_ERR_NULL, and TLV_OK.

Referenced by tlv_parse().

tlv_tag_size()

size_t tlv_tag_size

(

uint16_t

tag

)

BER-TLV codec implementation (see tlv.h).

Compute the encoded size of a tag.

Definition at line 9 of file tlv.cpp.

Referenced by tlv_write_tag().

tlv_write_len()

tlv_status_t tlv_write_len	(	uint8_t *	buf,
		size_t	buf_max,
		size_t	value_len,
		size_t *	written )

Encode a BER definite length field.

Supports value lengths 0..65535 (≤ 64 KiB minus 1). Lengths beyond that are rejected with TLV_ERR_BAD_LENGTH because OpenPGP 3.4.1 never asks for more, and ESP32 buffers are far below that.

Parameters

buf	Output buffer.
buf_max	Buffer capacity.
value_len	Value length to encode.
written	Receives the number of bytes written.

Definition at line 34 of file tlv.cpp.

References TLV_ERR_BAD_LENGTH, TLV_ERR_BUF_TOO_SMALL, TLV_ERR_NULL, tlv_len_size(), and TLV_OK.

Referenced by tlv_build().

tlv_write_tag()

tlv_status_t tlv_write_tag	(	uint8_t *	buf,
		size_t	buf_max,
		uint16_t	tag,
		size_t *	written )

Encode a tag. Writes either one or two bytes depending on the magnitude of tag.

Parameters

buf	Output buffer.
buf_max	Buffer capacity.
tag	Tag value.
written	Receives the number of bytes written.

Definition at line 19 of file tlv.cpp.

References TLV_ERR_BUF_TOO_SMALL, TLV_ERR_NULL, TLV_OK, and tlv_tag_size().

Referenced by tlv_build().