Improve the documentation of ASN.1 parsing functions
Document preconditions on parameters, values changed through pointers, and error codes. This commit leaves some issues regarding integers (especially negative integers) open, because we don't have a policy decision on how to handle them yet.
This commit is contained in:
Gilles Peskine
parent
5605591cc1
commit
bcbe1dfb23
@ -176,119 +176,203 @@ mbedtls_asn1_named_data;
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* \brief Get the length of an ASN.1 element.
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* Updates the pointer to immediately behind the length.
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*
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* \param p The position in the ASN.1 data
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* \param end End of data
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* \param len The variable that will receive the value
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* \param p On entry, \c *p points to the first byte of the length,
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* i.e. immediately after the tag.
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* On successful completion, \c *p points to the first byte
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* after the length, i.e. the first byte of the content.
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* On error, the value of \c *p is undefined.
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* \param end End of data.
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* \param len On successful completion, \c *len contains the lengtth
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* read from the ASN.1 input.
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*
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* \return 0 if successful, MBEDTLS_ERR_ASN1_OUT_OF_DATA on reaching
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* end of data, MBEDTLS_ERR_ASN1_INVALID_LENGTH if length is
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* unparseable.
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* \return 0 if successful.
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* \return #MBEDTLS_ERR_ASN1_OUT_OF_DATA if the ASN.1 element
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* would end beyond \p end.
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* \return #MBEDTLS_ERR_ASN1_INVALID_LENGTH if the length is unparseable.
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*/
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int mbedtls_asn1_get_len( unsigned char **p,
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const unsigned char *end,
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size_t *len );
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const unsigned char *end,
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size_t *len );
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/**
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* \brief Get the tag and length of the tag. Check for the requested tag.
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* \brief Get the tag and length of the element.
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* Check for the requested tag.
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* Updates the pointer to immediately behind the tag and length.
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*
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* \param p The position in the ASN.1 data
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* \param end End of data
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* \param len The variable that will receive the length
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* \param tag The expected tag
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* \param p On entry, \c *p points to the start of the ASN.1 element.
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* On successful completion, \c *p points to the first byte
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* after the length, i.e. the first byte of the content.
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* On error, the value of \c *p is undefined.
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* \param end End of data.
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* \param len On successful completion, \c *len contains the lengtth
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* read from the ASN.1 input.
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* \param tag The expected tag.
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*
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* \return 0 if successful, MBEDTLS_ERR_ASN1_UNEXPECTED_TAG if tag did
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* not match requested tag, or another specific ASN.1 error code.
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* \return 0 if successful.
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* \return #MBEDTLS_ERR_ASN1_UNEXPECTED_TAG if the data does not start
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* with the requested tag.
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* \return #MBEDTLS_ERR_ASN1_OUT_OF_DATA if the ASN.1 element
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* would end beyond \p end.
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* \return #MBEDTLS_ERR_ASN1_INVALID_LENGTH if the length is unparseable.
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*/
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int mbedtls_asn1_get_tag( unsigned char **p,
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const unsigned char *end,
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size_t *len, int tag );
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const unsigned char *end,
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size_t *len, int tag );
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/**
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* \brief Retrieve a boolean ASN.1 tag and its value.
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* Updates the pointer to immediately behind the full tag.
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*
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* \param p The position in the ASN.1 data
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* \param end End of data
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* \param val The variable that will receive the value
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* \param p On entry, \c *p points to the start of the ASN.1 element.
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* On successful completion, \c *p points to the first byte
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* beyond the ASN.1 element.
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* On error, the value of \c *p is undefined.
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* \param end End of data.
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* \param val On success, the parsed value (\c 0 or \c 1).
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*
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* \return 0 if successful or a specific ASN.1 error code.
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* \return 0 if successful.
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* \return An ASN.1 error code if the input does not start with
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* a valid ASN.1 BOOLEAN.
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*/
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int mbedtls_asn1_get_bool( unsigned char **p,
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const unsigned char *end,
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int *val );
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const unsigned char *end,
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int *val );
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/**
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* \brief Retrieve an integer ASN.1 tag and its value.
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* Updates the pointer to immediately behind the full tag.
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*
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* \param p The position in the ASN.1 data
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* \param end End of data
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* \param val The variable that will receive the value
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* \param p On entry, \c *p points to the start of the ASN.1 element.
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* On successful completion, \c *p points to the first byte
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* beyond the ASN.1 element.
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* On error, the value of \c *p is undefined.
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* \param end End of data.
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* \param val On success, the parsed value.
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*
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* \return 0 if successful or a specific ASN.1 error code.
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* \return 0 if successful.
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* \return An ASN.1 error code if the input does not start with
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* a valid ASN.1 INTEGER.
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* \return #MBEDTLS_ERR_ASN1_INVALID_LENGTH if the parsed value does
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* not fit in an \c int.
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* \return An ASN.1 error code if the input does not start with
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* a valid ASN.1 INTEGER.
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*/
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int mbedtls_asn1_get_int( unsigned char **p,
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const unsigned char *end,
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int *val );
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const unsigned char *end,
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int *val );
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/**
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* \brief Retrieve a bitstring ASN.1 tag and its value.
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* Updates the pointer to immediately behind the full tag.
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*
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* \param p The position in the ASN.1 data
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* \param end End of data
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* \param bs The variable that will receive the value
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* \param p On entry, \c *p points to the start of the ASN.1 element.
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* On successful completion, \c *p is equal to \p end.
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* On error, the value of \c *p is undefined.
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* \param end End of data.
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* \param bs On success, ::mbedtls_asn1_bitstring information about
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* the parsed value.
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*
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* \return 0 if successful or a specific ASN.1 error code.
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* \return 0 if successful.
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* \return #MBEDTLS_ERR_ASN1_LENGTH_MISMATCH if the input contains
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* extra data after a valid BIT STRING.
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* \return An ASN.1 error code if the input does not start with
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* a valid ASN.1 BIT STRING.
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*/
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int mbedtls_asn1_get_bitstring( unsigned char **p, const unsigned char *end,
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mbedtls_asn1_bitstring *bs);
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mbedtls_asn1_bitstring *bs );
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/**
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* \brief Retrieve a bitstring ASN.1 tag without unused bits and its
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* value.
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* Updates the pointer to the beginning of the bit/octet string.
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*
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* \param p The position in the ASN.1 data
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* \param end End of data
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* \param len Length of the actual bit/octect string in bytes
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* \param p On entry, \c *p points to the start of the ASN.1 element.
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* On successful completion, \c *p points to the first byte
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* of the content of the BIT STRING.
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* On error, the value of \c *p is undefined.
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* \param end End of data.
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* \param len On success, \c *len is the length of the content in bytes.
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*
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* \return 0 if successful or a specific ASN.1 error code.
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* \return 0 if successful.
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* \return #MBEDTLS_ERR_ASN1_INVALID_DATA if the input starts with
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* a valid BIT STRING with a nonzero number of unused bits.
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* \return An ASN.1 error code if the input does not start with
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* a valid ASN.1 BIT STRING.
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*/
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int mbedtls_asn1_get_bitstring_null( unsigned char **p, const unsigned char *end,
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size_t *len );
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int mbedtls_asn1_get_bitstring_null( unsigned char **p,
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const unsigned char *end,
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size_t *len );
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/**
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* \brief Parses and splits an ASN.1 "SEQUENCE OF <tag>"
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* Updated the pointer to immediately behind the full sequence tag.
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*
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* \param p The position in the ASN.1 data
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* \param end End of data
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* \param cur First variable in the chain to fill
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* \param tag Type of sequence
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* \note On error, this function may return a partial list in \p cur.
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* You must set `cur->next = NULL` before calling this function!
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* Otherwise it is impossible to distinguish a previously non-null
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* pointer from a pointer to an object allocated by this function.
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*
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* \return 0 if successful or a specific ASN.1 error code.
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* \note If the sequence is empty, this function does not modify
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* \c *cur. If the sequence is valid and non-empty, this
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* function sets `cur->buf.tag` to \p tag. This allows
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* callers to distinguish between an empty sequence and
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* a one-element sequence.
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*
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* \param p On entry, \c *p points to the start of the ASN.1 element.
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* On successful completion, \c *p is equal to \p end.
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* On error, the value of \c *p is undefined.
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* \param end End of data.
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* \param cur A ::mbedtls_asn1_sequence which this function fills.
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* When this function returns, \c *cur is the head of a linked
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* list. Each node in this list is allocated with
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* mbedtls_calloc() apart from \p cur itself, and should
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* therefore be freed with mbedtls_free().
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* The list describes the content of the sequence.
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* The head of the list (i.e. \c *cur itself) describes the
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* first element, `*cur->next` describes the second element, etc.
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* For each element, `buf.tag == tag`, `buf.len` is the length
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* of the content of the content of the element, and `buf.p`
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* points to the first byte of the content (i.e. immediately
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* past the length of the element).
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* Note that list elements may be allocated even on error.
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* \param tag Each element of the sequence must have this tag.
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*
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* \return 0 if successful.
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* \return #MBEDTLS_ERR_ASN1_LENGTH_MISMATCH if the input contains
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* extra data after a valid SEQUENCE OF \p tag.
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* \return #MBEDTLS_ERR_ASN1_ALLOC_FAILED if a memory allocation failed.
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* \return An ASN.1 error code if the input does not start with
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* a valid ASN.1 BIT STRING.
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*/
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int mbedtls_asn1_get_sequence_of( unsigned char **p,
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const unsigned char *end,
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mbedtls_asn1_sequence *cur,
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int tag);
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const unsigned char *end,
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mbedtls_asn1_sequence *cur,
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int tag );
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#if defined(MBEDTLS_BIGNUM_C)
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/**
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* \brief Retrieve a MPI value from an integer ASN.1 tag.
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* \brief Retrieve an integer ASN.1 tag and its value.
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* Updates the pointer to immediately behind the full tag.
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*
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* \param p The position in the ASN.1 data
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* \param end End of data
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* \param X The MPI that will receive the value
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* \param p On entry, \c *p points to the start of the ASN.1 element.
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* On successful completion, \c *p points to the first byte
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* beyond the ASN.1 element.
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* On error, the value of \c *p is undefined.
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* \param end End of data.
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* \param X On success, the parsed value.
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*
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* \return 0 if successful or a specific ASN.1 or MPI error code.
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* \return 0 if successful.
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* \return An ASN.1 error code if the input does not start with
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* a valid ASN.1 INTEGER.
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* \return #MBEDTLS_ERR_ASN1_INVALID_LENGTH if the parsed value does
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* not fit in an \c int.
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* \return An MPI error code if the parsed value is too large.
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* \return An ASN.1 error code if the input does not start with
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* a valid ASN.1 INTEGER.
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*/
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int mbedtls_asn1_get_mpi( unsigned char **p,
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const unsigned char *end,
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mbedtls_mpi *X );
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const unsigned char *end,
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mbedtls_mpi *X );
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#endif /* MBEDTLS_BIGNUM_C */
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/**
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@ -296,10 +380,14 @@ int mbedtls_asn1_get_mpi( unsigned char **p,
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* Updates the pointer to immediately behind the full
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* AlgorithmIdentifier.
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*
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* \param p The position in the ASN.1 data
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* \param end End of data
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* \param alg The buffer to receive the OID
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* \param params The buffer to receive the params (if any)
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* \param p On entry, \c *p points to the start of the ASN.1 element.
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* On successful completion, \c *p points to the first byte
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* beyond the AlgorithmIdentifier element.
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* On error, the value of \c *p is undefined.
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* \param end End of data.
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* \param alg The buffer to receive the OID.
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* \param params The buffer to receive the parameters.
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* This is zeroized if there are no parameters.
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*
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* \return 0 if successful or a specific ASN.1 or MPI error code.
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*/
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@ -313,9 +401,12 @@ int mbedtls_asn1_get_alg( unsigned char **p,
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* Updates the pointer to immediately behind the full
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* AlgorithmIdentifier.
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*
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* \param p The position in the ASN.1 data
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* \param end End of data
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* \param alg The buffer to receive the OID
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* \param p On entry, \c *p points to the start of the ASN.1 element.
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* On successful completion, \c *p points to the first byte
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* beyond the AlgorithmIdentifier element.
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* On error, the value of \c *p is undefined.
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* \param end End of data.
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* \param alg The buffer to receive the OID.
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*
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* \return 0 if successful or a specific ASN.1 or MPI error code.
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*/
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@ -339,15 +430,19 @@ mbedtls_asn1_named_data *mbedtls_asn1_find_named_data( mbedtls_asn1_named_data *
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/**
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* \brief Free a mbedtls_asn1_named_data entry
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*
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* \param entry The named data entry to free
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* \param entry The named data entry to free.
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* This function calls mbedtls_free() on
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* `entry->oid.p` and `entry->val.p`.
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*/
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void mbedtls_asn1_free_named_data( mbedtls_asn1_named_data *entry );
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/**
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* \brief Free all entries in a mbedtls_asn1_named_data list
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* Head will be set to NULL
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* \brief Free all entries in a mbedtls_asn1_named_data list.
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*
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* \param head Pointer to the head of the list of named data entries to free
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* \param head Pointer to the head of the list of named data entries to free.
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* This function calls mbedtls_asn1_free_named_data() and
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* mbedtls_free() on each list element and
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* sets \c *head to \c NULL.
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*/
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void mbedtls_asn1_free_named_data_list( mbedtls_asn1_named_data **head );
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