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Feb 25, 2018
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ECC-step1: ASN.1 changes required for future ECC enhancements #309

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f155d3c
ASN.1 changes required fo future ECC enhancements
karel-m Oct 11, 2017
fd7c2b8
no need for der_decode_subject_public_key_info_ex
karel-m Oct 19, 2017
54dd6ce
fix naming of SubjectPublicKeyInfo de-&encoder
sjaeckel Nov 20, 2017
2a78ed3
add CRYPT_PK_ASN1_ERROR
sjaeckel Nov 20, 2017
64875d3
add ASN.1-length functions
sjaeckel Nov 20, 2017
509ad52
add maps for ASN.1 en-/decoding
sjaeckel Nov 22, 2017
1b3a757
add ASN.1-identifier functions
sjaeckel Nov 22, 2017
0d02137
add required ASN.1 custom-types functions
sjaeckel Nov 22, 2017
5230977
implement the Custom-type de-/encoders
sjaeckel Nov 22, 2017
799e147
Update makefiles
sjaeckel Nov 22, 2017
b75c3ce
remove LTC_ASN1_CONSTRUCTED and LTC_ASN1_CONTEXT_SPECIFIC
sjaeckel Nov 22, 2017
3431763
update/add more DER tests
sjaeckel Nov 22, 2017
756bc7f
use new ASN.1 functionality
sjaeckel Nov 23, 2017
7e2d163
add testvectors from [1]
sjaeckel Dec 19, 2017
3044b22
improve style of length-checks
karel-m Dec 31, 2017
9d03c38
add flags to `der_decode_sequence()`
sjaeckel Jan 16, 2018
e4efd70
add der_decode_custom_type_ex()
sjaeckel Jan 16, 2018
d89326b
update doc
sjaeckel Jan 21, 2018
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108 changes: 83 additions & 25 deletions doc/crypt.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -5563,6 +5563,10 @@ \chapter{Standards Support}
void *data;
unsigned long size;
int used;
int optional;
ltc_asn1_class class;
ltc_asn1_pc pc;
ulong64 tag;
struct ltc_asn1_list_ *prev, *next,
*child, *parent;
} ltc_asn1_list;
Expand Down Expand Up @@ -5625,9 +5629,8 @@ \chapter{Standards Support}
\hline LTC\_ASN1\_SETOF & SET OF \\
\hline LTC\_ASN1\_RAW\_BIT\_STRING & BIT STRING (one octet per char) \\
\hline LTC\_ASN1\_TELETEX\_STRING & TELETEX STRING (one octet per char) \\
\hline LTC\_ASN1\_CONSTRUCTED & A constructed type that is not SEQUENCE or SET \\
\hline LTC\_ASN1\_CONTEXT\_SPECIFIC & A context-specific type \\
\hline LTC\_ASN1\_GENERALIZEDTIME & GeneralizedTime (see ltc\_generalizedtime structure) \\
\hline LTC\_ASN1\_CUSTOM\_TYPE & A custom type (see LTC\_SET\_ASN1\_CUSTOM\_XXX macros) \\
\hline
\end{tabular}
\caption{List of ASN.1 Supported Types}
Expand All @@ -5636,6 +5639,36 @@ \chapter{Standards Support}
\end{center}
\end{figure}

\index{LTC\_ASN1\_CUSTOM\_TYPE}
\index{LTC\_SET\_ASN1\_CUSTOM\_CONSTRUCTED macro}
\index{LTC\_SET\_ASN1\_CUSTOM\_PRIMITIVE macro}

To be able to encode and decode all other valid ASN.1 Identifiers, such as Context-Specific types the macros
\textit{LTC\_SET\_ASN1\_CUSTOM\_CONSTRUCTED(list, index, Class, Tag, Data)} resp.
\textit{LTC\_SET\_ASN1\_CUSTOM\_PRIMITIVE(list, index, Class, Tag, Type, Data, Size)} have been provided.

They will assign to the \textit{index}th position in the \textit{list} the Identifier-triplet (Class, CONSTRUCTED resp. PRIMITIVE, Tag).
An example usage would be:

\begin{small}
\begin{verbatim}
...
ltc_asn1_list sequence[4], custom[1];
unsigned long three=3;
unsigned char buf[128];

LTC_SET_ASN1(sequence, 0, LTC_ASN1_IA5_STRING, "hello", 5);
LTC_SET_ASN1(sequence, 1, LTC_ASN1_SHORT_INTEGER, &three, 1);
LTC_SET_ASN1(sequence, 2, LTC_ASN1_NULL, NULL, 0);
LTC_SET_ASN1_CUSTOM_PRIMITIVE(sequence, 3, LTC_ASN1_CL_CONTEXT_SPECIFIC, 23, \
LTC_ASN1_OCTET_STRING, buf, sizeof(buf));

LTC_SET_ASN1_CUSTOM_CONSTRUCTED(custom, 0, LTC_ASN1_CL_CONTEXT_SPECIFIC, 0, sequence);
\end{verbatim}
\end{small}

This would allow (un)pack'ing the given \textit{sequence} from/in the context-specific tag \textit{[0]}.

\subsection{SEQUENCE Type}
The SEQUENCE data type is a collection of other ASN.1 data types encapsulated with a small header which is a useful way of sending multiple data types in one packet.

Expand All @@ -5660,6 +5693,7 @@ \subsubsection{SEQUENCE Encoding}
\subsubsection{SEQUENCE Decoding}

\index{der\_decode\_sequence()}
\index{der\_decode\_sequence\_strict()}

Decoding a SEQUENCE is similar to encoding. You set up an array of \textbf{ltc\_asn1\_list} where in this case the \textit{size} member is the maximum size
(in certain cases). For types such as IA5 STRING, BIT STRING, OCTET STRING (etc) the \textit{size} field is updated after successful decoding to reflect how many
Expand All @@ -5670,18 +5704,27 @@ \subsubsection{SEQUENCE Decoding}
unsigned long inlen,
ltc_asn1_list *list,
unsigned long outlen);

int der_decode_sequence_strict(const unsigned char *in,
unsigned long inlen,
ltc_asn1_list *list,
unsigned long outlen);
\end{verbatim}

This will decode upto \textit{outlen} items from the input buffer \textit{in} of length \textit{inlen} octets. The function will stop (gracefully) when it runs out of items to decode.
It will fail (for among other reasons) when it runs out of input bytes to read, a data type is invalid or a heap failure occurred.
The regular variant will return \textbf{CRYPT\_INPUT\_TOO\_LONG} in cases where there was more data to be decoded given through \textit{inlen} than the ASN.1 length-tag specified.
The strict variant \textit{der\_decode\_sequence\_strict()} returns an error in this case.

For the following types the \textit{size} field will be updated to reflect the number of units read of the given type.
\begin{enumerate}
\item BIT STRING
\item (RAW) BIT STRING
\item OCTET STRING
\item OBJECT IDENTIFIER
\item IA5 STRING
\item PRINTABLE STRING
\item TELETEX STRING
\item UTF8 STRING
\end{enumerate}

\subsubsection{SEQUENCE Length}
Expand Down Expand Up @@ -6139,32 +6182,53 @@ \subsection{ASN.1 CHOICE}
\textit{outlen} elements. The \textit{inlen} field will be updated with the length of the decoded data type, as well as the respective entry in the \textit{list} field
will have the \textit{used} flag set to non--zero to reflect it was the data type decoded.

\subsection{ASN.1 Custom Types}

To be able to represent all other valid types besides the primitive types having their own decoder, the \textit{custom\_type} de- and encoders are provided.

\index{der\_encode\_custom\_type()} \index{der\_decode\_custom\_type()} \index{der\_length\_custom\_type()} \index{LTC\_ASN1\_CUSTOM\_TYPE}
\begin{verbatim}
int der_encode_custom_type(const ltc_asn1_list *root,
unsigned char *out, unsigned long *outlen);

int der_decode_custom_type(const unsigned char *in, unsigned long inlen,
ltc_asn1_list *root);

int der_length_custom_type(const ltc_asn1_list *root,
unsigned long *outlen,
unsigned long *payloadlen);
\end{verbatim}

The usage of this de- and encoder is a bit different than the others since the type to be encoded has to be passed to the function.
Therefore the \textit{root} parameter identifies the type that should be encoded which has been set by the \textit{LTC\_SET\_ASN1}
and \textit{LTC\_SET\_ASN1\_IDENTIFIER}, resp. \textit{LTC\_SET\_ASN1\_CUSTOM} macros.
The value to de-/encode has to be linked through the \textit{data} argument of the \textit{LTC\_SET\_ASN1} macro, as done for sequences.
The value that should be de-/encoded can either be a primitive or a constructed type.

\subsection{ASN.1 Flexi Decoder}
The ASN.1 \textit{flexi} decoder allows the developer to decode arbitrary ASN.1 DER packets (provided they use data types LibTomCrypt supports) without first knowing
the structure of the data. Where der\_decode\_sequence() requires the developer to specify the data types to decode in advance the flexi decoder is entirely
free form.

The ASN.1 \textit{flexi} decoder allows the developer to decode arbitrary ASN.1 DER packets without first knowing the structure of the data.
Where der\_decode\_sequence() requires the developer to specify the data types to decode in advance the flexi decoder is entirely free form.

The flexi decoder uses the same \textit{ltc\_asn1\_list} but instead of being stored in an array it uses the linked list pointers \textit{prev}, \textit{next}, \textit{parent}
and \textit{child}. The list works as a \textit{doubly-linked list} structure where decoded items at the same level are siblings (using next and prev) and items
encoded in a SEQUENCE are stored as a child element.
and \textit{child}. The list works as a \textit{doubly-linked list} structure where decoded items at the same level are siblings (using \textit{next} and \textit{prev}) and items
encoded in a SEQUENCE are stored as a \textit{child} element.

When a SEQUENCE or SET has been encountered a SEQUENCE (or SET resp.) item will be added as a sibling (e.g. list.type == LTC\_ASN1\_SEQUENCE) and the child
When a SEQUENCE or SET has been encountered a SEQUENCE (or SET resp.) item will be added as a sibling (e.g. list.type == LTC\_ASN1\_SEQUENCE) and the \textit{child}
pointer points to a new list of items contained within the object.

\index{der\_decode\_sequence\_flexi()}
\index{LTC\_ASN1\_CONSTRUCTED}
\index{LTC\_ASN1\_CONTEXT\_SPECIFIC}
\begin{verbatim}
int der_decode_sequence_flexi(const unsigned char *in,
unsigned long *inlen,
ltc_asn1_list **out);
ltc_asn1_list **out);
\end{verbatim}

This will decode items in the \textit{in} buffer of max input length \textit{inlen} and store the newly created pointer to the list in \textit{out}. This function allocates
all required memory for the decoding. It stores the number of octets read back into \textit{inlen}.

The function will terminate when either it hits an invalid ASN.1 tag, or it reads \textit{inlen} octets. An early termination is a soft error, and returns
normally. The decoded list \textit{out} will point to the very first element of the list (e.g. both parent and prev pointers will be \textbf{NULL}).
normally. The decoded list \textit{out} will point to the very first element of the list (i.e. both parent and prev pointers will be \textbf{NULL}).

An invalid decoding will terminate the process, and free the allocated memory automatically.

Expand All @@ -6175,18 +6239,12 @@ \subsection{ASN.1 Flexi Decoder}
This can be detected by checking for \textit{child} elements with
type \textbf{LTC\_ASN1\_EOL} after decoding.

As of v1.18.0 the flexi decoder will also decode arbitrary constructed types
other than SEQUENCE and SET. The \textit{type} field will be set to
\textbf{LTC\_ASN1\_CONSTRUCTED} and the plain identifier that was indicated in the ASN.1
encoding is stored in the \textit{used} field. Further decoding is done in the
same way as if it were a SEQUENCE or SET.

Also as of v1.18.0 the flexi decoder is capable to handle
\textit{context-specific} encodings. The \textit{type} field will be set to
\textbf{LTC\_ASN1\_CONTEXT\_SPECIFIC} and the plain identifier that was indicated
in the ASN.1 encoding is stored in the \textit{used} field. Encapsulated data
in the \textit{context-specific} encoding is copied to newly allocated memory
and is accessible through the \textit{data} field.
The v1.18.0 of the library had support for decoding two new types, \textbf{LTC\_ASN1\_CONSTRUCTED} and \textbf{LTC\_ASN1\_CONTEXT\_SPECIFIC},
which has been replaced in FIXME-version-next by a more complete approach.

As of FIXME-version-next all ASN.1 Identifiers which don't have a decoder implemented (and thereby their own type) will be marked as
\textbf{LTC\_ASN1\_CUSTOM\_TYPE}.


\textbf{Note:} the list decoded by this function is \textbf{NOT} in the correct form for der\_encode\_sequence() to use directly. You will first
have to convert the list by first storing all of the siblings in an array then storing all the children as sub-lists of a sequence using the \textit{.data}
Expand Down
68 changes: 60 additions & 8 deletions libtomcrypt_VS2008.vcproj
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Expand Up @@ -1849,6 +1849,54 @@
>
</File>
</Filter>
<Filter
Name="custom_type"
>
<File
RelativePath="src\pk\asn1\der\custom_type\der_decode_custom_type.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\custom_type\der_encode_custom_type.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\custom_type\der_length_custom_type.c"
>
</File>
</Filter>
<Filter
Name="general"
>
<File
RelativePath="src\pk\asn1\der\general\der_asn1_maps.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\general\der_decode_asn1_identifier.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\general\der_decode_asn1_length.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\general\der_encode_asn1_identifier.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\general\der_encode_asn1_length.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\general\der_length_asn1_identifier.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\general\der_length_asn1_length.c"
>
</File>
</Filter>
<Filter
Name="generalizedtime"
>
Expand Down Expand Up @@ -1960,10 +2008,6 @@
RelativePath="src\pk\asn1\der\sequence\der_decode_sequence_multi.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\sequence\der_decode_subject_public_key_info.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\sequence\der_encode_sequence_ex.c"
>
Expand All @@ -1972,10 +2016,6 @@
RelativePath="src\pk\asn1\der\sequence\der_encode_sequence_multi.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\sequence\der_encode_subject_public_key_info.c"
>
</File>
<File
RelativePath="src\pk\asn1\der\sequence\der_length_sequence.c"
>
Expand Down Expand Up @@ -2062,6 +2102,18 @@
</File>
</Filter>
</Filter>
<Filter
Name="x509"
>
<File
RelativePath="src\pk\asn1\x509\x509_decode_subject_public_key_info.c"
>
</File>
<File
RelativePath="src\pk\asn1\x509\x509_encode_subject_public_key_info.c"
>
</File>
</Filter>
</Filter>
<Filter
Name="dh"
Expand Down
25 changes: 15 additions & 10 deletions makefile.mingw
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Original file line number Diff line number Diff line change
Expand Up @@ -130,6 +130,12 @@ src/pk/asn1/der/bit/der_decode_raw_bit_string.o src/pk/asn1/der/bit/der_encode_b
src/pk/asn1/der/bit/der_encode_raw_bit_string.o src/pk/asn1/der/bit/der_length_bit_string.o \
src/pk/asn1/der/boolean/der_decode_boolean.o src/pk/asn1/der/boolean/der_encode_boolean.o \
src/pk/asn1/der/boolean/der_length_boolean.o src/pk/asn1/der/choice/der_decode_choice.o \
src/pk/asn1/der/custom_type/der_decode_custom_type.o \
src/pk/asn1/der/custom_type/der_encode_custom_type.o \
src/pk/asn1/der/custom_type/der_length_custom_type.o src/pk/asn1/der/general/der_asn1_maps.o \
src/pk/asn1/der/general/der_decode_asn1_identifier.o src/pk/asn1/der/general/der_decode_asn1_length.o \
src/pk/asn1/der/general/der_encode_asn1_identifier.o src/pk/asn1/der/general/der_encode_asn1_length.o \
src/pk/asn1/der/general/der_length_asn1_identifier.o src/pk/asn1/der/general/der_length_asn1_length.o \
src/pk/asn1/der/generalizedtime/der_decode_generalizedtime.o \
src/pk/asn1/der/generalizedtime/der_encode_generalizedtime.o \
src/pk/asn1/der/generalizedtime/der_length_generalizedtime.o \
Expand All @@ -147,24 +153,23 @@ src/pk/asn1/der/printable_string/der_length_printable_string.o \
src/pk/asn1/der/sequence/der_decode_sequence_ex.o \
src/pk/asn1/der/sequence/der_decode_sequence_flexi.o \
src/pk/asn1/der/sequence/der_decode_sequence_multi.o \
src/pk/asn1/der/sequence/der_decode_subject_public_key_info.o \
src/pk/asn1/der/sequence/der_encode_sequence_ex.o \
src/pk/asn1/der/sequence/der_encode_sequence_multi.o \
src/pk/asn1/der/sequence/der_encode_subject_public_key_info.o \
src/pk/asn1/der/sequence/der_length_sequence.o src/pk/asn1/der/sequence/der_sequence_free.o \
src/pk/asn1/der/sequence/der_sequence_shrink.o src/pk/asn1/der/set/der_encode_set.o \
src/pk/asn1/der/set/der_encode_setof.o src/pk/asn1/der/short_integer/der_decode_short_integer.o \
src/pk/asn1/der/sequence/der_encode_sequence_multi.o src/pk/asn1/der/sequence/der_length_sequence.o \
src/pk/asn1/der/sequence/der_sequence_free.o src/pk/asn1/der/sequence/der_sequence_shrink.o \
src/pk/asn1/der/set/der_encode_set.o src/pk/asn1/der/set/der_encode_setof.o \
src/pk/asn1/der/short_integer/der_decode_short_integer.o \
src/pk/asn1/der/short_integer/der_encode_short_integer.o \
src/pk/asn1/der/short_integer/der_length_short_integer.o \
src/pk/asn1/der/teletex_string/der_decode_teletex_string.o \
src/pk/asn1/der/teletex_string/der_length_teletex_string.o \
src/pk/asn1/der/utctime/der_decode_utctime.o src/pk/asn1/der/utctime/der_encode_utctime.o \
src/pk/asn1/der/utctime/der_length_utctime.o src/pk/asn1/der/utf8/der_decode_utf8_string.o \
src/pk/asn1/der/utf8/der_encode_utf8_string.o src/pk/asn1/der/utf8/der_length_utf8_string.o \
src/pk/dh/dh.o src/pk/dh/dh_check_pubkey.o src/pk/dh/dh_export.o src/pk/dh/dh_export_key.o \
src/pk/dh/dh_free.o src/pk/dh/dh_generate_key.o src/pk/dh/dh_import.o src/pk/dh/dh_set.o \
src/pk/dh/dh_set_pg_dhparam.o src/pk/dh/dh_shared_secret.o src/pk/dsa/dsa_decrypt_key.o \
src/pk/dsa/dsa_encrypt_key.o src/pk/dsa/dsa_export.o src/pk/dsa/dsa_free.o \
src/pk/asn1/x509/x509_decode_subject_public_key_info.o \
src/pk/asn1/x509/x509_encode_subject_public_key_info.o src/pk/dh/dh.o src/pk/dh/dh_check_pubkey.o \
src/pk/dh/dh_export.o src/pk/dh/dh_export_key.o src/pk/dh/dh_free.o src/pk/dh/dh_generate_key.o \
src/pk/dh/dh_import.o src/pk/dh/dh_set.o src/pk/dh/dh_set_pg_dhparam.o src/pk/dh/dh_shared_secret.o \
src/pk/dsa/dsa_decrypt_key.o src/pk/dsa/dsa_encrypt_key.o src/pk/dsa/dsa_export.o src/pk/dsa/dsa_free.o \
src/pk/dsa/dsa_generate_key.o src/pk/dsa/dsa_generate_pqg.o src/pk/dsa/dsa_import.o \
src/pk/dsa/dsa_make_key.o src/pk/dsa/dsa_set.o src/pk/dsa/dsa_set_pqg_dsaparam.o \
src/pk/dsa/dsa_shared_secret.o src/pk/dsa/dsa_sign_hash.o src/pk/dsa/dsa_verify_hash.o \
Expand Down
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