Generic ASN.1 parsing. More...

#include "mbedtls/private_access.h"
#include "mbedtls/build_info.h"
#include <stddef.h>
#include "mbedtls/bignum.h"

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Data Structures
struct	mbedtls_asn1_buf

struct	mbedtls_asn1_bitstring

struct	mbedtls_asn1_sequence

struct	mbedtls_asn1_named_data

Macros
#define	MBEDTLS_OID_SIZE(x) (sizeof(x) - 1)

#define	MBEDTLS_OID_CMP(oid_str, oid_buf)

#define	MBEDTLS_OID_CMP_RAW(oid_str, oid_buf, oid_buf_len)

ASN1 Error codes
These error codes are OR'ed to X509 error codes for higher error granularity. ASN1 is a standard to specify data structures.
#define	MBEDTLS_ERR_ASN1_OUT_OF_DATA -0x0060

#define	MBEDTLS_ERR_ASN1_UNEXPECTED_TAG -0x0062

#define	MBEDTLS_ERR_ASN1_INVALID_LENGTH -0x0064

#define	MBEDTLS_ERR_ASN1_LENGTH_MISMATCH -0x0066

#define	MBEDTLS_ERR_ASN1_INVALID_DATA -0x0068

#define	MBEDTLS_ERR_ASN1_ALLOC_FAILED -0x006A

#define	MBEDTLS_ERR_ASN1_BUF_TOO_SMALL -0x006C

DER constants
These constants comply with the DER encoded ASN.1 type tags. DER encoding uses hexadecimal representation. An example DER sequence is: 0x02 – tag indicating INTEGER 0x01 – length in octets 0x05 – value Such sequences are typically read into `mbedtls_x509_buf`.
#define	MBEDTLS_ASN1_BOOLEAN 0x01

#define	MBEDTLS_ASN1_INTEGER 0x02

#define	MBEDTLS_ASN1_BIT_STRING 0x03

#define	MBEDTLS_ASN1_OCTET_STRING 0x04

#define	MBEDTLS_ASN1_NULL 0x05

#define	MBEDTLS_ASN1_OID 0x06

#define	MBEDTLS_ASN1_ENUMERATED 0x0A

#define	MBEDTLS_ASN1_UTF8_STRING 0x0C

#define	MBEDTLS_ASN1_SEQUENCE 0x10

#define	MBEDTLS_ASN1_SET 0x11

#define	MBEDTLS_ASN1_PRINTABLE_STRING 0x13

#define	MBEDTLS_ASN1_T61_STRING 0x14

#define	MBEDTLS_ASN1_IA5_STRING 0x16

#define	MBEDTLS_ASN1_UTC_TIME 0x17

#define	MBEDTLS_ASN1_GENERALIZED_TIME 0x18

#define	MBEDTLS_ASN1_UNIVERSAL_STRING 0x1C

#define	MBEDTLS_ASN1_BMP_STRING 0x1E

#define	MBEDTLS_ASN1_PRIMITIVE 0x00

#define	MBEDTLS_ASN1_CONSTRUCTED 0x20

#define	MBEDTLS_ASN1_CONTEXT_SPECIFIC 0x80

#define	MBEDTLS_ASN1_IS_STRING_TAG(tag)

#define	MBEDTLS_ASN1_TAG_CLASS_MASK 0xC0

#define	MBEDTLS_ASN1_TAG_PC_MASK 0x20

#define	MBEDTLS_ASN1_TAG_VALUE_MASK 0x1F

Functions to parse ASN.1 data structures
typedef struct mbedtls_asn1_buf	mbedtls_asn1_buf

typedef struct mbedtls_asn1_bitstring	mbedtls_asn1_bitstring

typedef struct mbedtls_asn1_sequence	mbedtls_asn1_sequence

typedef struct mbedtls_asn1_named_data	mbedtls_asn1_named_data

int	mbedtls_asn1_get_len (unsigned char *p, const unsigned char end, size_t *len)
	Get the length of an ASN.1 element. Updates the pointer to immediately behind the length. More...

int	mbedtls_asn1_get_tag (unsigned char *p, const unsigned char end, size_t *len, int tag)
	Get the tag and length of the element. Check for the requested tag. Updates the pointer to immediately behind the tag and length. More...

int	mbedtls_asn1_get_bool (unsigned char *p, const unsigned char end, int *val)
	Retrieve a boolean ASN.1 tag and its value. Updates the pointer to immediately behind the full tag. More...

int	mbedtls_asn1_get_int (unsigned char *p, const unsigned char end, int *val)
	Retrieve an integer ASN.1 tag and its value. Updates the pointer to immediately behind the full tag. More...

int	mbedtls_asn1_get_enum (unsigned char *p, const unsigned char end, int *val)
	Retrieve an enumerated ASN.1 tag and its value. Updates the pointer to immediately behind the full tag. More...

int	mbedtls_asn1_get_bitstring (unsigned char *p, const unsigned char end, mbedtls_asn1_bitstring *bs)
	Retrieve a bitstring ASN.1 tag and its value. Updates the pointer to immediately behind the full tag. More...

int	mbedtls_asn1_get_bitstring_null (unsigned char *p, const unsigned char end, size_t *len)
	Retrieve a bitstring ASN.1 tag without unused bits and its value. Updates the pointer to the beginning of the bit/octet string. More...

int	mbedtls_asn1_get_sequence_of (unsigned char *p, const unsigned char end, mbedtls_asn1_sequence *cur, int tag)
	Parses and splits an ASN.1 "SEQUENCE OF <tag>". Updates the pointer to immediately behind the full sequence tag. More...

void	mbedtls_asn1_sequence_free (mbedtls_asn1_sequence *seq)
	Free a heap-allocated linked list presentation of an ASN.1 sequence, including the first element. More...

int	mbedtls_asn1_traverse_sequence_of (unsigned char *p, const unsigned char end, unsigned char tag_must_mask, unsigned char tag_must_val, unsigned char tag_may_mask, unsigned char tag_may_val, int(cb)(void ctx, int tag, unsigned char start, size_t len), void ctx)
	Traverse an ASN.1 SEQUENCE container and call a callback for each entry. More...

int	mbedtls_asn1_get_mpi (unsigned char *p, const unsigned char end, mbedtls_mpi *X)
	Retrieve an integer ASN.1 tag and its value. Updates the pointer to immediately behind the full tag. More...

int	mbedtls_asn1_get_alg (unsigned char *p, const unsigned char end, mbedtls_asn1_buf alg, mbedtls_asn1_buf params)
	Retrieve an AlgorithmIdentifier ASN.1 sequence. Updates the pointer to immediately behind the full AlgorithmIdentifier. More...

int	mbedtls_asn1_get_alg_null (unsigned char *p, const unsigned char end, mbedtls_asn1_buf *alg)
	Retrieve an AlgorithmIdentifier ASN.1 sequence with NULL or no params. Updates the pointer to immediately behind the full AlgorithmIdentifier. More...

const mbedtls_asn1_named_data *	mbedtls_asn1_find_named_data (const mbedtls_asn1_named_data list, const char oid, size_t len)
	Find a specific named_data entry in a sequence or list based on the OID. More...

void	mbedtls_asn1_free_named_data (mbedtls_asn1_named_data *entry)
	Free a mbedtls_asn1_named_data entry. More...

void	mbedtls_asn1_free_named_data_list (mbedtls_asn1_named_data **head)
	Free all entries in a mbedtls_asn1_named_data list. More...

Detailed Description

Generic ASN.1 parsing.

Definition in file asn1.h.

Macro Definition Documentation

#define MBEDTLS_OID_CMP	(	oid_str,
		oid_buf
	)

Value:

( ( MBEDTLS_OID_SIZE(oid_str) != (oid_buf)->len ) || \

memcmp( (oid_str), (oid_buf)->p, (oid_buf)->len) != 0 )

MBEDTLS_OID_SIZE

#define MBEDTLS_OID_SIZE(x)

Definition: asn1.h:125

Compares an mbedtls_asn1_buf structure to a reference OID.

Only works for 'defined' oid_str values (MBEDTLS_OID_HMAC_SHA1), you cannot use a 'unsigned char *oid' here!

Definition at line 133 of file asn1.h.

#define MBEDTLS_OID_CMP_RAW	(	oid_str,
		oid_buf,
		oid_buf_len
	)

Value:

( ( MBEDTLS_OID_SIZE(oid_str) != (oid_buf_len) ) || \

memcmp( (oid_str), (oid_buf), (oid_buf_len) ) != 0 )

MBEDTLS_OID_SIZE

#define MBEDTLS_OID_SIZE(x)

Definition: asn1.h:125

Definition at line 137 of file asn1.h.

#define MBEDTLS_OID_SIZE ( x ) (sizeof(x) - 1)

Returns the size of the binary string, without the trailing \0

Definition at line 125 of file asn1.h.

Referenced by mbedtls_psa_get_ecc_oid_from_id().

Typedef Documentation

typedef struct mbedtls_asn1_bitstring mbedtls_asn1_bitstring

Container for ASN1 bit strings.

typedef struct mbedtls_asn1_buf mbedtls_asn1_buf

Type-length-value structure that allows for ASN1 using DER.

typedef struct mbedtls_asn1_named_data mbedtls_asn1_named_data

Container for a sequence or list of 'named' ASN.1 data items

typedef struct mbedtls_asn1_sequence mbedtls_asn1_sequence

Container for a sequence of ASN.1 items

Function Documentation

const mbedtls_asn1_named_data* mbedtls_asn1_find_named_data	(	const mbedtls_asn1_named_data *	list,
		const char *	oid,
		size_t	len
	)

Find a specific named_data entry in a sequence or list based on the OID.

Parameters

list	The list to seek through
oid	The OID to look for
len	Size of the OID

Returns: NULL if not found, or a pointer to the existing entry.

void mbedtls_asn1_free_named_data ( mbedtls_asn1_named_data * entry )

Free a mbedtls_asn1_named_data entry.

Parameters

entry The named data entry to free. This function calls mbedtls_free() on entry->oid.p and entry->val.p.

void mbedtls_asn1_free_named_data_list ( mbedtls_asn1_named_data ** head )

Free all entries in a mbedtls_asn1_named_data list.

Parameters

head	Pointer to the head of the list of named data entries to free. This function calls mbedtls_asn1_free_named_data() and mbedtls_free() on each list element and sets `*head` to `NULL`.

int mbedtls_asn1_get_alg	(	unsigned char **	p,
		const unsigned char *	end,
		mbedtls_asn1_buf *	alg,
		mbedtls_asn1_buf *	params
	)

Retrieve an AlgorithmIdentifier ASN.1 sequence. Updates the pointer to immediately behind the full AlgorithmIdentifier.

Parameters

p	On entry, `p` points to the start of the ASN.1 element. On successful completion, `p` points to the first byte beyond the AlgorithmIdentifier element. On error, the value of `*p` is undefined.
end	End of data.
alg	The buffer to receive the OID.
params	The buffer to receive the parameters. This is zeroized if there are no parameters.

Returns: 0 if successful or a specific ASN.1 or MPI error code.

int mbedtls_asn1_get_alg_null	(	unsigned char **	p,
		const unsigned char *	end,
		mbedtls_asn1_buf *	alg
	)

Retrieve an AlgorithmIdentifier ASN.1 sequence with NULL or no params. Updates the pointer to immediately behind the full AlgorithmIdentifier.

Parameters

p	On entry, `p` points to the start of the ASN.1 element. On successful completion, `p` points to the first byte beyond the AlgorithmIdentifier element. On error, the value of `*p` is undefined.
end	End of data.
alg	The buffer to receive the OID.

Returns: 0 if successful or a specific ASN.1 or MPI error code.

int mbedtls_asn1_get_bitstring	(	unsigned char **	p,
		const unsigned char *	end,
		mbedtls_asn1_bitstring *	bs
	)

Retrieve a bitstring ASN.1 tag and its value. Updates the pointer to immediately behind the full tag.

Parameters

p	On entry, `p` points to the start of the ASN.1 element. On successful completion, `p` is equal to `end`. On error, the value of `*p` is undefined.
end	End of data.
bs	On success, mbedtls_asn1_bitstring information about the parsed value.

Returns: 0 if successful.; MBEDTLS_ERR_ASN1_LENGTH_MISMATCH if the input contains extra data after a valid BIT STRING.; An ASN.1 error code if the input does not start with a valid ASN.1 BIT STRING.

int mbedtls_asn1_get_bitstring_null	(	unsigned char **	p,
		const unsigned char *	end,
		size_t *	len
	)

Retrieve a bitstring ASN.1 tag without unused bits and its value. Updates the pointer to the beginning of the bit/octet string.

Parameters

p	On entry, `p` points to the start of the ASN.1 element. On successful completion, `p` points to the first byte of the content of the BIT STRING. On error, the value of `*p` is undefined.
end	End of data.
len	On success, `*len` is the length of the content in bytes.

Returns: 0 if successful.; MBEDTLS_ERR_ASN1_INVALID_DATA if the input starts with a valid BIT STRING with a nonzero number of unused bits.; An ASN.1 error code if the input does not start with a valid ASN.1 BIT STRING.

int mbedtls_asn1_get_bool	(	unsigned char **	p,
		const unsigned char *	end,
		int *	val
	)

Retrieve a boolean ASN.1 tag and its value. Updates the pointer to immediately behind the full tag.

Parameters

p	On entry, `p` points to the start of the ASN.1 element. On successful completion, `p` points to the first byte beyond the ASN.1 element. On error, the value of `*p` is undefined.
end	End of data.
val	On success, the parsed value (`0` or `1`).

Returns: 0 if successful.; An ASN.1 error code if the input does not start with a valid ASN.1 BOOLEAN.

int mbedtls_asn1_get_enum	(	unsigned char **	p,
		const unsigned char *	end,
		int *	val
	)

Retrieve an enumerated ASN.1 tag and its value. Updates the pointer to immediately behind the full tag.

Parameters

p	On entry, `p` points to the start of the ASN.1 element. On successful completion, `p` points to the first byte beyond the ASN.1 element. On error, the value of `*p` is undefined.
end	End of data.
val	On success, the parsed value.

Returns: 0 if successful.; An ASN.1 error code if the input does not start with a valid ASN.1 ENUMERATED.; MBEDTLS_ERR_ASN1_INVALID_LENGTH if the parsed value does not fit in an int.

int mbedtls_asn1_get_int	(	unsigned char **	p,
		const unsigned char *	end,
		int *	val
	)

Retrieve an integer ASN.1 tag and its value. Updates the pointer to immediately behind the full tag.

Parameters

p	On entry, `p` points to the start of the ASN.1 element. On successful completion, `p` points to the first byte beyond the ASN.1 element. On error, the value of `*p` is undefined.
end	End of data.
val	On success, the parsed value.

Returns: 0 if successful.; An ASN.1 error code if the input does not start with a valid ASN.1 INTEGER.; MBEDTLS_ERR_ASN1_INVALID_LENGTH if the parsed value does not fit in an int.

int mbedtls_asn1_get_len	(	unsigned char **	p,
		const unsigned char *	end,
		size_t *	len
	)

Get the length of an ASN.1 element. Updates the pointer to immediately behind the length.

Parameters

p	On entry, `p` points to the first byte of the length, i.e. immediately after the tag. On successful completion, `p` points to the first byte after the length, i.e. the first byte of the content. On error, the value of `*p` is undefined.
end	End of data.
len	On successful completion, `*len` contains the length read from the ASN.1 input.

Returns: 0 if successful.; MBEDTLS_ERR_ASN1_OUT_OF_DATA if the ASN.1 element would end beyond end.; MBEDTLS_ERR_ASN1_INVALID_LENGTH if the length is unparseable.

int mbedtls_asn1_get_mpi	(	unsigned char **	p,
		const unsigned char *	end,
		mbedtls_mpi *	X
	)

Retrieve an integer ASN.1 tag and its value. Updates the pointer to immediately behind the full tag.

Parameters

p	On entry, `p` points to the start of the ASN.1 element. On successful completion, `p` points to the first byte beyond the ASN.1 element. On error, the value of `*p` is undefined.
end	End of data.
X	On success, the parsed value.

Returns: 0 if successful.; An ASN.1 error code if the input does not start with a valid ASN.1 INTEGER.; MBEDTLS_ERR_ASN1_INVALID_LENGTH if the parsed value does not fit in an int.; An MPI error code if the parsed value is too large.

int mbedtls_asn1_get_sequence_of	(	unsigned char **	p,
		const unsigned char *	end,
		mbedtls_asn1_sequence *	cur,
		int	tag
	)

Parses and splits an ASN.1 "SEQUENCE OF <tag>". Updates the pointer to immediately behind the full sequence tag.

This function allocates memory for the sequence elements. You can free the allocated memory with mbedtls_asn1_sequence_free().

Note: On error, this function may return a partial list in cur. You must set cur->next = NULL before calling this function! Otherwise it is impossible to distinguish a previously non-null pointer from a pointer to an object allocated by this function.; If the sequence is empty, this function does not modify *cur. If the sequence is valid and non-empty, this function sets cur->buf.tag to tag. This allows callers to distinguish between an empty sequence and a one-element sequence.

Parameters

p	On entry, `p` points to the start of the ASN.1 element. On successful completion, `p` is equal to `end`. On error, the value of `*p` is undefined.
end	End of data.
cur	A mbedtls_asn1_sequence which this function fills. When this function returns, `cur` is the head of a linked list. Each node in this list is allocated with mbedtls_calloc() apart from `cur` itself, and should therefore be freed with mbedtls_free(). The list describes the content of the sequence. The head of the list (i.e. `cur` itself) describes the first element, `*cur->next` describes the second element, etc. For each element, `buf.tag == tag`, `buf.len` is the length of the content of the content of the element, and `buf.p` points to the first byte of the content (i.e. immediately past the length of the element). Note that list elements may be allocated even on error.
tag	Each element of the sequence must have this tag.

Returns: 0 if successful.; MBEDTLS_ERR_ASN1_LENGTH_MISMATCH if the input contains extra data after a valid SEQUENCE OF tag.; MBEDTLS_ERR_ASN1_UNEXPECTED_TAG if the input starts with an ASN.1 SEQUENCE in which an element has a tag that is different from tag.; MBEDTLS_ERR_ASN1_ALLOC_FAILED if a memory allocation failed.; An ASN.1 error code if the input does not start with a valid ASN.1 SEQUENCE.

int mbedtls_asn1_get_tag	(	unsigned char **	p,
		const unsigned char *	end,
		size_t *	len,
		int	tag
	)

Get the tag and length of the element. Check for the requested tag. Updates the pointer to immediately behind the tag and length.

Parameters

p	On entry, `p` points to the start of the ASN.1 element. On successful completion, `p` points to the first byte after the length, i.e. the first byte of the content. On error, the value of `*p` is undefined.
end	End of data.
len	On successful completion, `*len` contains the length read from the ASN.1 input.
tag	The expected tag.

Returns: 0 if successful.; MBEDTLS_ERR_ASN1_UNEXPECTED_TAG if the data does not start with the requested tag.; MBEDTLS_ERR_ASN1_OUT_OF_DATA if the ASN.1 element would end beyond end.; MBEDTLS_ERR_ASN1_INVALID_LENGTH if the length is unparseable.

void mbedtls_asn1_sequence_free ( mbedtls_asn1_sequence * seq )

Free a heap-allocated linked list presentation of an ASN.1 sequence, including the first element.

There are two common ways to manage the memory used for the representation of a parsed ASN.1 sequence:

Allocate a head node mbedtls_asn1_sequence *head with mbedtls_calloc(). Pass this node as the cur argument to mbedtls_asn1_get_sequence_of(). When you have finished processing the sequence, call mbedtls_asn1_sequence_free() on head.
Allocate a head node mbedtls_asn1_sequence *head in any manner, for example on the stack. Make sure that head->next == NULL. Pass head as the cur argument to mbedtls_asn1_get_sequence_of(). When you have finished processing the sequence, call mbedtls_asn1_sequence_free() on head->cur, then free head itself in the appropriate manner.

Parameters

seq	The address of the first sequence component. This may be `NULL`, in which case this functions returns immediately.

int mbedtls_asn1_traverse_sequence_of	(	unsigned char **	p,
		const unsigned char *	end,
		unsigned char	tag_must_mask,
		unsigned char	tag_must_val,
		unsigned char	tag_may_mask,
		unsigned char	tag_may_val,
		int()(void ctx, int tag, unsigned char *start, size_t len)	cb,
		void *	ctx
	)

Traverse an ASN.1 SEQUENCE container and call a callback for each entry.

This function checks that the input is a SEQUENCE of elements that each have a "must" tag, and calls a callback function on the elements that have a "may" tag.

For example, to validate that the input is a SEQUENCE of tag1 and call cb on each element, use ``` mbedtls_asn1_traverse_sequence_of(&p, end, 0xff, tag1, 0, 0, cb, ctx); ```

To validate that the input is a SEQUENCE of ANY and call cb on each element, use ``` mbedtls_asn1_traverse_sequence_of(&p, end, 0, 0, 0, 0, cb, ctx); ```

To validate that the input is a SEQUENCE of CHOICE {NULL, OCTET STRING} and call cb on each element that is an OCTET STRING, use ``` mbedtls_asn1_traverse_sequence_of(&p, end, 0xfe, 0x04, 0xff, 0x04, cb, ctx); ```

The callback is called on the elements with a "may" tag from left to right. If the input is not a valid SEQUENCE of elements with a "must" tag, the callback is called on the elements up to the leftmost point where the input is invalid.

Warning: This function is still experimental and may change at any time.

Parameters

p	The address of the pointer to the beginning of the ASN.1 SEQUENCE header. This is updated to point to the end of the ASN.1 SEQUENCE container on a successful invocation.
end	The end of the ASN.1 SEQUENCE container.
tag_must_mask	A mask to be applied to the ASN.1 tags found within the SEQUENCE before comparing to `tag_must_value`.
tag_must_val	The required value of each ASN.1 tag found in the SEQUENCE, after masking with `tag_must_mask`. Mismatching tags lead to an error. For example, a value of `0` for both `tag_must_mask` and `tag_must_val` means that every tag is allowed, while a value of `0xFF` for `tag_must_mask` means that `tag_must_val` is the only allowed tag.
tag_may_mask	A mask to be applied to the ASN.1 tags found within the SEQUENCE before comparing to `tag_may_value`.
tag_may_val	The desired value of each ASN.1 tag found in the SEQUENCE, after masking with `tag_may_mask`. Mismatching tags will be silently ignored. For example, a value of `0` for `tag_may_mask` and `tag_may_val` means that any tag will be considered, while a value of `0xFF` for `tag_may_mask` means that all tags with value different from `tag_may_val` will be ignored.
cb	The callback to trigger for each component in the ASN.1 SEQUENCE that matches `tag_may_val`. The callback function is called with the following parameters: `ctx`. The tag of the current element. A pointer to the start of the current element's content inside the input. The length of the content of the current element. If the callback returns a non-zero value, the function stops immediately, forwarding the callback's return value.
ctx	The context to be passed to the callback `cb`.

Returns: 0 if successful the entire ASN.1 SEQUENCE was traversed without parsing or callback errors.; MBEDTLS_ERR_ASN1_LENGTH_MISMATCH if the input contains extra data after a valid SEQUENCE of elements with an accepted tag.; MBEDTLS_ERR_ASN1_UNEXPECTED_TAG if the input starts with an ASN.1 SEQUENCE in which an element has a tag that is not accepted.; An ASN.1 error code if the input does not start with a valid ASN.1 SEQUENCE.; A non-zero error code forwarded from the callback cb in case the latter returns a non-zero value.

Data Structures

Macros

Functions to parse ASN.1 data structures

Detailed Description

Macro Definition Documentation

Typedef Documentation

Function Documentation