Heimdal's ASN.1 Compiler
This is a new README, and it's not very rich in contents yet. Be sure to check out the README on the template backend and the README on automatic open type decoding via X.681/X.682/X.683 annotations.
Table of Contents
- Introduction
- ASN.1 Support in Heimdal
- News
- Features
- Limitations
- Compiler Usage
- asn1_print Usage
- Implementation
- Moving From C
Introduction
ASN.1 is a... some would say baroque, perhaps obsolete, archaic even, "syntax" for expressing data type schemas, and also a set of "encoding rules" (ERs) that specify many ways to encode values of those types for interchange.
Some ERs are binary, others are textual. Some binary ERs are tag-length-value (TLV), others have no need for tagging. Some of the ERs are roundly and rightly disliked, but then there are XER (XML Encoding Rules) and JER (JSON Encoding Rules) that really illustrate how the syntax and the encoding rules really are separate and distinct things.
ASN.1 is a wheel that everyone loves to reinvent, and often badly. It's worth knowing a bit about it before reinventing this wheel badly yet again.
It's also worth pondering that there appears to be ways to map most data exchange metaschemas and schemas onto others, and therefore too, transliterate most encodings onto others.
First, an example of the syntax:
-- This is what a certificate looks like (as in TLS server certificates, or
-- "SSL certs):
Certificate ::= SEQUENCE {
tbsCertificate TBSCertificate,
signatureAlgorithm AlgorithmIdentifier,
signatureValue BIT STRING
}
-- The main body of a certificate is here though:
TBSCertificate ::= SEQUENCE {
version [0] Version DEFAULT 1,
serialNumber CertificateSerialNumber,
signature AlgorithmIdentifier,
issuer Name,
validity Validity,
subject Name,
subjectPublicKeyInfo SubjectPublicKeyInfo,
issuerUniqueID [1] IMPLICIT BIT STRING OPTIONAL,
subjectUniqueID [2] IMPLICIT BIT STRING OPTIONAL,
extensions [3] EXPLICIT Extensions OPTIONAL
}
Here we see something akin to a "structure" or "record" with various named fields of various types. Some of these are optional, which means they can have no value given in encodings. One is defaulted, which means that if no values is given in encodings then the default value is intended.
Those [0] things are called tags and are decidedly obsolete, along with all
"tag-length-value" (TLV) or "self-describing" encoding rules. Tags appear as
lexical tokens in ASN.1 only because a) in the early 80s TLV encodings were
thought fantastic, and b) automatic tagging wasn't invented and implemented
until it was too late. New ASN.1 modules should never need to have those tags
appear in the syntax.
ASN.1 has a lot of competition, and may even be obsolete. Obsolete technologies take decades to die out because of the need to interoperate with the installed base. So even if ASN.1 is obsolete, we find ourselves needing to implement a large subset of it in order to implement certain important network protocols.
Encoding rules? There are many:
-
JSON Encoding Rules (JER) (X.697)
Use JSON instead of some binary scheme like DER (see below).
-
XML Encoding Rules (XER) (X.693)
-
Generic String Encoding Rules (GSER) (RFC2641)
-
Basic, Distinguished, and Canonical Encoding Rules (BER, DER, CER) (X.690
These are the dreaded tag-length-value encoding rules. They are redundant, wasteful, and inefficient in spite of being non-textual (i.e., binary)!
The descriptor "tag-length-value" is due to all values being encoded as some bytes for a "tag", then some bytes for the length of the encoded value, then the encoded value itself. The body of a structured type (e.g.,
Certificate) is itself a concatenation of the TLV encodings of the fields of that structured type, in order.DER and CER are alternative canonical forms of BER.
-
Packed Encoding Rules (PER) (X.691) and Octet Encoding Rules (OER) (X.696)
These are a lot like eXternal Data Representation (XDR), but with 1-octet alignment instead of 4-octet alignment.
There is also a meta encoding rule system, the Encoding Control Notation (ECN) (X.692) intended to be able to express all sorts of kinds of encodings.
Heimdal currently only supports DER for encoding, and DER and BER for decoding, but soon may support JER as well, and can print values as JSON, though not compliant with JER.
The syntax itself is specified by X.680, with extensions via X.681, X.682, and X.683,.
ASN.1 Support in Heimdal
Heimdal contains an implementation of:
-
ASN.1
-
PKIX
-
Kerberos
-
misc. Heimdal-specific protocols related to PKIX and Kerberos, such as:
- Online certification authority protocols
- Kerberos KDC replication protocols
- Kerberos administration protocols
PKIX and Kerberos both require ASN.1 and DER support.
For historical reasons many ASN.1-using projects have used hand-rolled codecs that have proven difficult to implement, maintain, and extend, and, of course, buggy. Heimdal has its own ASN.1 module compiler and library in order to avoid the pitfalls of hand-rolled codecs, and to satisfy Heimdal's internal needs.
There are other ASN.1 compilers and libraries out there, of course, but it would prove difficult to switch compilers as generally ASN.1 compilers lack sufficient control over generated types and APIs for programming languages.
Heimdal's ASN.1 compiler supports a large subset of X.680, X.681, X.682, and X.683, as well as a large subset of X.690, with an architecture that should make it easy to add support for encoding rules other than X.690.
News
In recent times the following features have been added:
-
Feature parity for the "template" backend, even superiority, as the codegen backend does not yet support automatic open type decoding/encoding.
-
IMPLICIT tagging support is finally complete.
-
Automatic open type traversal, using a subset of X.681/X.682/X.683 for expressing the requisite metadata.
Futures
-
JER support?
-
XDR/OER support?
-
Generate comparators? (lib/hx509 has a half-baked Certificate comparator)
Features
-
Most of X.680 is supported.
-
Most of X.690 is supported for decoding, with only DER supported for encoding.
-
We have an
asn1_printprogram that can decode DER from any exported types from any ASN.1 modules committed in Heimdal:$ ./asn1_print ek.crt Certificate | jq '.tbsCertificate.extensions[3]._extnValue[]._values'[ { "_type": "TPMSpecification", "family": "2.0", "level": 0, "revision": 138 } ] [ { "_type": "TPMSecurityAssertions", "version": 0, "fieldUpgradable": true, "ekGenerationType": "ekgt-injected", "ekGenerationLocation": "tpmManufacturer", "ekCertificateGenerationLocation": "tpmManufacturer", "ccInfo": { "_type": "CommonCriteriaMeasures", "version": "3.1", "assurancelevel": "ealevel4", "evaluationStatus": "evaluationCompleted", "plus": true, "strengthOfFunction": null, "profileOid": null, "profileUri": null, "targetOid": null, "targetUri": null }, "fipsLevel": { "_type": "FIPSLevel", "version": "140-2", "level": "sllevel2", "plus": false }, "iso9000Certified": false, "iso9000Uri": null } ]A complete dump of such a certificate:
$ ./asn1_print ek.crt Certificate | jq .{ "_type": "Certificate", "tbsCertificate": { "_type": "TBSCertificate", "_save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version": "rfc3280_version_3", "serialNumber": "6A0597BA71D7E6D3AC0EDC9EDC95A15B998DE40A", "signature": { "_type": "AlgorithmIdentifier", "algorithm": { "_type": "OBJECT IDENTIFIER", "oid": "1.2.840.113549.1.1.11", "components": [ 1, 2, 840, 113549, 1, 1, 11 ], "name": "id-pkcs1-sha256WithRSAEncryption" }, "parameters": "0500" }, "issuer": { "_choice": "rdnSequence", "value": [ [ { "_type": "AttributeTypeAndValue", "type": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.4.6", "components": [ 2, 5, 4, 6 ], "name": "id-at-countryName" }, "value": { "_choice": "printableString", "value": "CH" } } ], [ { "_type": "AttributeTypeAndValue", "type": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.4.10", "components": [ 2, 5, 4, 10 ], "name": "id-at-organizationName" }, "value": { "_choice": "printableString", "value": "STMicroelectronics NV" } } ], [ { "_type": "AttributeTypeAndValue", "type": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.4.3", "components": [ 2, 5, 4, 3 ], "name": "id-at-commonName" }, "value": { "_choice": "printableString", "value": "STM TPM EK Intermediate CA 05" } } ] ] }, "validity": { "_type": "Validity", "notBefore": { "_choice": "utcTime", "value": "2018-12-14T00:00:00Z" }, "notAfter": { "_choice": "utcTime", "value": "2028-12-14T00:00:00Z" } }, "subject": { "_choice": "rdnSequence", "value": [] }, "subjectPublicKeyInfo": { "_type": "SubjectPublicKeyInfo", "algorithm": { "_type": "AlgorithmIdentifier", "algorithm": { "_type": "OBJECT IDENTIFIER", "oid": "1.2.840.113549.1.1.1", "components": [ 1, 2, 840, 113549, 1, 1, 1 ], "name": "id-pkcs1-rsaEncryption" }, "parameters": "0500" }, "subjectPublicKey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}, "issuerUniqueID": null, "subjectUniqueID": null, "extensions": [ { "_type": "Extension", "extnID": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.29.35", "components": [ 2, 5, 29, 35 ], "name": "id-x509-ce-authorityKeyIdentifier" }, "critical": false, "extnValue": "301680141ADB994AB58BE57A0CC9B900E7851E1A43C08660", "_extnValue_choice": "", "_extnValue": { "_type": "AuthorityKeyIdentifier", "keyIdentifier": "1ADB994AB58BE57A0CC9B900E7851E1A43C08660", "authorityCertIssuer": null, "authorityCertSerialNumber": null } }, { "_type": "Extension", "extnID": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.29.32", "components": [ 2, 5, 29, 32 ], "name": "id-x509-ce-certificatePolicies" }, "critical": false, "extnValue": "303930370604551D2000302F302D06082B060105050702011621687474703A2F2F7777772E73742E636F6D2F54504D2F7265706F7369746F72792F", "_extnValue_choice": "", "_extnValue": [ { "_type": "PolicyInformation", "policyIdentifier": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.29.32.0", "components": [ 2, 5, 29, 32, 0 ], "name": "id-x509-ce-certificatePolicies-anyPolicy" }, "policyQualifiers": [ { "_type": "PolicyQualifierInfo", "policyQualifierId": { "_type": "OBJECT IDENTIFIER", "oid": "1.3.6.1.5.5.7.2.1", "components": [ 1, 3, 6, 1, 5, 5, 7, 2, 1 ], "name": "id-pkix-qt-cps" }, "qualifier": "1621687474703A2F2F7777772E73742E636F6D2F54504D2F7265706F7369746F72792F" } ] } ] }, { "_type": "Extension", "extnID": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.29.17", "components": [ 2, 5, 29, 17 ], "name": "id-x509-ce-subjectAltName" }, "critical": true, "extnValue": "304DA44B304931163014060567810502010C0B69643A353335343444323031173015060567810502020C0C53543333485450484148433031163014060567810502030C0B69643A3030343930303038", "_extnValue_choice": "", "_extnValue": [ { "_choice": "directoryName", "value": { "_choice": "rdnSequence", "value": [ [ { "_type": "AttributeTypeAndValue", "type": { "_type": "OBJECT IDENTIFIER", "oid": "2.23.133.2.1", "components": [ 2, 23, 133, 2, 1 ], "name": "tcg-at-tpmManufacturer" }, "value": { "_choice": "utf8String", "value": "id:53544D20" } } ], [ { "_type": "AttributeTypeAndValue", "type": { "_type": "OBJECT IDENTIFIER", "oid": "2.23.133.2.2", "components": [ 2, 23, 133, 2, 2 ], "name": "tcg-at-tpmModel" }, "value": { "_choice": "utf8String", "value": "ST33HTPHAHC0" } } ], [ { "_type": "AttributeTypeAndValue", "type": { "_type": "OBJECT IDENTIFIER", "oid": "2.23.133.2.3", "components": [ 2, 23, 133, 2, 3 ], "name": "tcg-at-tpmVersion" }, "value": { "_choice": "utf8String", "value": "id:00490008" } } ] ] } } ] }, { "_type": "Extension", "extnID": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.29.9", "components": [ 2, 5, 29, 9 ], "name": "id-x509-ce-subjectDirectoryAttributes" }, "critical": false, "extnValue": "305E301706056781050210310E300C0C03322E300201000202008A304306056781050212313A30380201000101FFA0030A0101A1030A0100A2030A0100A310300E1603332E310A01040A01020101FFA40F300D16053134302D320A0102010100", "_extnValue_choice": "", "_extnValue": [ { "_type": "AttributeSet", "type": { "_type": "OBJECT IDENTIFIER", "oid": "2.23.133.2.16", "components": [ 2, 23, 133, 2, 16 ], "name": "tcg-at-tpmSpecification" }, "values": [ "300C0C03322E300201000202008A" ], "_values_choice": "", "_values": [ { "_type": "TPMSpecification", "family": "2.0", "level": 0, "revision": 138 } ] }, { "_type": "AttributeSet", "type": { "_type": "OBJECT IDENTIFIER", "oid": "2.23.133.2.18", "components": [ 2, 23, 133, 2, 18 ], "name": "tcg-at-tpmSecurityAssertions" }, "values": [ "30380201000101FFA0030A0101A1030A0100A2030A0100A310300E1603332E310A01040A01020101FFA40F300D16053134302D320A0102010100" ], "_values_choice": "", "_values": [ { "_type": "TPMSecurityAssertions", "version": 0, "fieldUpgradable": true, "ekGenerationType": "ekgt-injected", "ekGenerationLocation": "tpmManufacturer", "ekCertificateGenerationLocation": "tpmManufacturer", "ccInfo": { "_type": "CommonCriteriaMeasures", "version": "3.1", "assurancelevel": "ealevel4", "evaluationStatus": "evaluationCompleted", "plus": true, "strengthOfFunction": null, "profileOid": null, "profileUri": null, "targetOid": null, "targetUri": null }, "fipsLevel": { "_type": "FIPSLevel", "version": "140-2", "level": "sllevel2", "plus": false }, "iso9000Certified": false, "iso9000Uri": null } ] } ] }, { "_type": "Extension", "extnID": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.29.15", "components": [ 2, 5, 29, 15 ], "name": "id-x509-ce-keyUsage" }, "critical": true, "extnValue": "03020520", "_extnValue_choice": "", "_extnValue": [ "keyEncipherment" ] }, { "_type": "Extension", "extnID": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.29.19", "components": [ 2, 5, 29, 19 ], "name": "id-x509-ce-basicConstraints" }, "critical": true, "extnValue": "3000", "_extnValue_choice": "", "_extnValue": { "_type": "BasicConstraints", "cA": false, "pathLenConstraint": null } }, { "_type": "Extension", "extnID": { "_type": "OBJECT IDENTIFIER", "oid": "2.5.29.37", "components": [ 2, 5, 29, 37 ], "name": "id-x509-ce-extKeyUsage" }, "critical": false, "extnValue": "300706056781050801", "_extnValue_choice": "", "_extnValue": [ { "_type": "OBJECT IDENTIFIER", "oid": "2.23.133.8.1", "components": [ 2, 23, 133, 8, 1 ], "name": "tcg-kp-EKCertificate" } ] }, { "_type": "Extension", "extnID": { "_type": "OBJECT IDENTIFIER", "oid": "1.3.6.1.5.5.7.1.1", "components": [ 1, 3, 6, 1, 5, 5, 7, 1, 1 ], "name": "id-pkix-pe-authorityInfoAccess" }, "critical": false, "extnValue": "303C303A06082B06010505073002862E687474703A2F2F7365637572652E676C6F62616C7369676E2E636F6D2F73746D74706D656B696E7430352E637274", "_extnValue_choice": "", "_extnValue": [ { "_type": "AccessDescription", "accessMethod": { "_type": "OBJECT IDENTIFIER", "oid": "1.3.6.1.5.5.7.48.2", "components": [ 1, 3, 6, 1, 5, 5, 7, 48, 2 ], "name": "id-pkix-ad-caIssuers" }, "accessLocation": { "_choice": "uniformResourceIdentifier", "value": "http://secure.globalsign.com/stmtpmekint05.crt" } } ] } ] }, "signatureAlgorithm": { "_type": "AlgorithmIdentifier", "algorithm": { "_type": "OBJECT IDENTIFIER", "oid": "1.2.840.113549.1.1.11", "components": [ 1, 2, 840, 113549, 1, 1, 11 ], "name": "id-pkcs1-sha256WithRSAEncryption" }, "parameters": "0500" }, "signatureValue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}(Notice that OID names look a bit weird. For reasons that may have been lost to time and may no longer be relevant, these OIDs are defined with slightly different names in the ASN.1 modules in Heimdal's source tree. We'll fix this eventually.)
-
Unconstrained integer types have a large integer representation in C that is not terribly useful in common cases. Range constraints on integer types cause the compiler to use
int32_t,int64_t,uint32_t, and/oruint64_t. -
The Heimdal ASN.1 compiler currently handles a large subset of X.680, and (in a branch) a small subset of X.681, X.682, and X.683, which manifests as automatic handling of all open types contained in
SET/SEQUENCEtypes that are parameterized with information object sets. This allows all open types in PKIX certificates, for example, to get decoded automatically no matter how deeply nested. We use a TCG EK certificate that has eight certificate extensions, including subject alternative names and subject directory attributes where the attribute values are not string types, and all of these things get decoded automatically. -
The template backend dedups templates to save space. This is an O(N^2) kind of feature that we need to make optional, but it works. (When we implement JER this will have the side-effect of printing the wrong type names in some cases because two or more types have the same templates and get deduped.)
...
Limitations
-
asn1_print's JSON support is not X.697 (JER) compatible. -
Control over C types generated is very limited, mainly only for integer types.
-
When using the template backend,
SET { .. }types are currently not sorted by tag as they should be, but if the module author sorts them by hand then DER will be produced. -
BMPStringis not supported. -
IA5String is not properly supported -- it's essentially treated as a
UTF8Stringwith a different tag. This is true of all the string types. -
Only types can be imported at this time. Without some rototilling we likely will not be able to import anything other than types, values, and object sets.
-
Only simple value syntax is supported. Structured value syntax is not supported.
-
...
Compiler Usage
See the manual page asn1_compile.1:
ASN1_COMPILE(1) HEIMDAL General Commands Manual ASN1_COMPILE(1)
NAME
asn1_compile — compile ASN.1 modules
SYNOPSIS
asn1_compile [--template] [--prefix-enum] [--enum-prefix=PREFIX]
[--encode-rfc1510-bit-string] [--decode-dce-ber]
[--support-ber] [--preserve-binary=TYPE-NAME]
[--sequence=TYPE-NAME] [--one-code-file] [--gen-name=NAME]
[--option-file=FILE] [--original-order] [--no-parse-units]
[--type-file=C-HEADER-FILE] [--version] [--help]
[FILE.asn1 [NAME]]
DESCRIPTION
asn1_compile Compiles an ASN.1 module into C source code and header
files.
Options supported:
--template
Use the “template” backend instead of the “codegen” backend
(which is the default backend). The template backend generates
“templates” which are akin to bytecode, and which are interpreted
at run-time. The codegen backend generates C code for all func‐
tions directly, with no template interpretation. The template
backend scales better than the codegen backend because as we add
support for more encoding rules the templates stay mostly the
same, thus scaling linearly with size of module. Whereas the
codegen backend scales linear with the product of module size and
number of encoding rules supported. More importantly, currently
only the template backend supports automatic decoding of open
types via X.681/X.682/X.683 annotations.
--prefix-enum
This option should be removed because ENUMERATED types should
always have their labels prefixed.
--enum-prefix=PREFIX
This option should be removed because ENUMERATED types should
always have their labels prefixed.
--encode-rfc1510-bit-string
Use RFC1510, non-standard handling of “BIT STRING” types.
--decode-dce-ber
--support-ber
--preserve-binary=TYPE-NAME
Generate ‘_save’ fields in structs to preserve the original
encoding of some sub-value. This is useful for cryptographic
applications to avoid having to re-encode values to check signa‐
tures, etc.
--sequence=TYPE-NAME
Generate add/remove functions for ‘SET OF’ and ‘SEQUENCE OF’
types.
--one-code-file
Generate a single source code file. Otherwise a separate code
file will be generated for every type.
--gen-name=NAME
Use NAME to form the names of the files generated.
--option-file=FILE
Take additional command-line options from FILE.
--original-order
Attempt to preserve the original order of type definition in the
ASN.1 module. By default the compiler generates types in a topo‐
logical sort order.
--no-parse-units
Do not generate to-int / from-int functions for enumeration
types.
--type-file=C-HEADER-FILE
Generate an include of the named header file that might be needed
for common type defintions.
--version
--help
HEIMDAL February 22, 2021 HEIMDAL
asn1_print Usage
ASN1_PRINT(1) BSD General Commands Manual ASN1_PRINT(1)
NAME
asn1_print — dump ASN.1 DER encoded values
SYNOPSIS
asn1_print [-i | --no-indent] [-I | --inner] [-l | --list-types]
[-l -v | --version] [-l -h | --help] [FILE [TypeName]]
DESCRIPTION
asn1_print Dumps ASN.1 DER-encoded values. If a TypeName is given, then
asn1_print will print the value in a JSON-like format using its knowledge
of the ASN.1 module defining that type. If a TypeName is given, it must
be the name of an ASN.1 type exported by an ASN.1 module that is compiled
into asn1_print. Use the --list-types option to list ASN.1 types known
to asn1_print.
Options supported:
-i, --no-indent
Do not indent dump.
-I, --inner
Try to parse inner structures of OCTET STRING and constructed
values.
-l, --list-types
Try to parse inner structures of OCTET STRING and constructed
values.
-v, --version
-h, --help
HEIMDAL February 22, 2021 HEIMDAL
Implementation
...
Futures
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Add JER support so we can convert between JER and DER?
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Add XDR support?
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Add OER support?
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Add NDR support?
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Perhaps third parties will contribute more control over generate types?
Moving From C
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Generate and output a JSON representation of the compiled ASN.1 module.
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Code codegen/templategen backends in jq or Haskell or whatever.
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Code template interpreters in some host language.
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Eventually rewrite the compiler itself in Rust or whatever.