Plugins – Lua Programming Reference

Last Updated: July 26, 2023 17:10

Language

Lua plugins are run using the standard Lua 5.3 interpreter.

Plugins may use the following standard Lua 5.3 symbols:

assert
bit32
collectgarbage
coroutine
error
getmetatable
ipairs
load
math
next
pairs
rawequal
rawget
rawlen
rawset
select
setmetatable
string
table
tonumber
tostring
type
utf8
xpcall
_VERSION
_G

The following will be supported soon:

print
require

Support is not planned for the following:

loadfile
arg
debug
dofile
package
os
io

The following DSM-defined symbols are also in scope, detailed below:

cbor
json
Error
Blob
EntityId
Sobject
App
User
Plugin
Group
AuditLog
principal
this_plugin
digest
null
BigNum
Time
EcGroup
EcPoint
require_approval_for

Invoking plugins

The `run` function

A plugin must define a function run.

When the plugin is invoked, run will be called with the following parameters:

input: The JSON data with which the plugin was invoked, decoded into a Lua object as in json.decode, or nil if no input data was supplied.
url: The URL that was used to invoke the plugin, represented as a Lua table:
- url.path: A Lua array of path components, for example, ['sys', 'v1', 'plugins', '08ce8c3e-50fc-4c95-a633-ca417e6f2828'].
  Users and apps may append arbitrary custom path components when invoking a plugin.
- url.query: The query string (the part of the URL after ?), or nil if the URL does not include a query string.
method: The method used to invoke the plugin, either 'POST' or 'GET'.

The function run may accept any prefix of these arguments, for example:

function run() ... end
function run(input) ... end
function run(input, url, method) ... end

The function run may return the following:

nil: the plugin invocation returns successfully with no content.
an encodable Lua object: the object is encoded to JSON as in json.encode and returned.
nil and an Error: the plugin invocation errors as described in the Error section below.

The `check` function

A plugin can optionally define a function check.

If this function is defined, it will be called before function run and with the same input parameters that will be passed to function run, for example:function check(input, url, method) ... end.

If the check function returns an error or throws an exception, the plugin
invocation is aborted and the error will be returned to the caller.

You can use function check for access checks, input validation logic, and so on.
You can also call require_approval_for in function check to require the caller to submit an approval request to invoke the plugin subject to the approval policy defined on the object you pass to require_approval_for. For example:

function check(input)
   -- Validate input fields
   if not input.signing_key_id then return nil, 'missing field `signing_key_id`' end
   if not input.hash then return nil, 'missing field `hash`' end
   -- Look up the signing key
   local signing_key = assert(Sobject { kid = input.signing_key_id })
   -- If the signing key is subject to an approval policy, then the following
   -- call will ensure that this plugin can only be invoked by creating an
   -- approval request. Otherwise the call has no effect.
   require_approval_for(signing_key)
end

function run(input)
  local signing_key = assert(Sobject >{ kid = input.signing_key_id })
  local signature =assert(signing_key:sign { hash = input.hash, hash_alg = 'SHA256' })
  return signature
end

Note that even though you can call require_approval_for in function run, it will not have any effect. You should only use it in function check.

The `Blob` class

A Blob represents arbitrary binary data.

DSM REST APIs use JSON and distinguish between

UTF-8 strings (e.g. key name), which use JSON strings, and
binary data (e.g. key material), which use base64-encoded JSON strings.

JSON strings must be valid UTF-8, so in general raw binary data is not a valid JSON string.

Lua plugin APIs use Lua strings for UTF-8 strings and Blobs for binary data.

For interoperability with the JSON REST APIs, a base64-encoded Lua string may be used instead of a Blob where binary data is expected.

Constructors

Blob.from_bytes(string)

Constructs a Blob from a Lua string with raw binary data.

Note that Lua strings do not need to be valid UTF-8.

For example: local blob = Blob.from_bytes('\1\2\255').
Blob.from_base64(string)

Constructs a Blob from base64-encoded data in a Lua string.

For example: local blob = Blob.from_base64('AQL/').
Blob.from_hex(string)

Constructs a Blob from hex-encoded data in a Lua string.

For example: local blob = Blob.from_hex('0102FF').
Blob.from_base58(string)

Constructs a Blob from base58-encoded data in a Lua string.

For example: local blob = Blob.from_base58('LiA').
Blob.from_base58_check(string)

Constructs a Blob from base58-encoded data in a Lua string. Unlike plain base58, this also includes a SHA-256d checksum.

For example: local blob = Blob.from_base58_check('3DyWSpcNi').
Blob.random(num_bytes)

Constructs a random Blob with the given number of bytes.

The bytes will be generated using DSM's cryptographically secure random number generator.

Blob.random { bytes = num_bytes } and Blob.random { bits = num_bits } are also supported.

num_bytes must be a whole number; num_bits must be a multiple of 8.
Blob.pack(fmt, ...)

This is equivalent to Blob.from_bytes(string.pack(fmt, ...)).

See the documentation for string.pack.

For example: assert(Blob.pack('>i8', 0xDEADBEEF):hex() == '00000000DEADBEEF')

Methods

blob:unpack(fmt)

This is equivalent to string.unpack(fmt, blob:bytes()).

See the documentation for string.unpack.

For example: assert(Blob.from_hex('00000000DEADBEEF'):unpack('>i8') == 0xDEADBEEF)
blob:bytes()

Returns a Lua string with the raw binary data.

For example: assert(blob:bytes() == '\1\2\255')
blob:base64()

Returns a Lua string with the base64-encoded binary data.

For example: assert(blob:base64() == 'AQL/')
blob:hex()

Returns a Lua string with the hex-encoded binary data.

For example: assert(blob:hex() == '0102FF')
blob:base58()

Returns a Lua string with the base58-encoded binary data.

E.g.: assert(blob:base58() == 'LiA')
blob:base58_check()

Returns a Lua string with the base58-encoding (including SHA-256d checksum) of the binary data.

For example: assert(blob:base58_check() == '3DyWSpcNi')
blob:slice(lo_byte, hi_byte)

Returns a blob consisting of the bytes between lo_byte and hi_byte, 1-indexed and inclusive.

For example, Blob.from_bytes('\1\2\3\4'):slice(2, 3) == Blob.from_bytes('\2\3').
blob .. blob2

.. may be used to concatenate two blobs, e.g. Blob.from_bytes('\1') .. Blob.from_bytes('\2') == Blob.from_bytes('\1\2').
#blob

# may be used to get the number of bytes in the blob, e.g. assert(#Blob.from_bytes('\1\1\1') == 3).
blob & blob2, blob | blob2, blob ~ blob2

&, |, and ~ may be used to take the bitwise and, the bitwise or, and the bitwise xor of two blobs. The blobs must be the same size, or else these operations will throw an exception.
~blob

~ may be used to take the bitwise not of a blob.

The `cbor` module

cbor.encode(object)

cbor.encode encodes (serializes) a Lua object into a Blob containing binary data in the CBOR format.

Encodable Lua objects include:
- nil, which encodes to null.
- Lua numbers and booleans, which encode to CBOR numbers and booleans.
- Blobs, which encode to CBOR byte strings.
- Lua strings, which encode to CBOR text strings.
  - CBOR text string should be valid UTF-8, while Lua strings may contain arbitrary binary data. To encode a Lua string representing potentially non-UTF-8 binary data, use Blob.from_bytes(string).
- Lua tables, which encode to CBOR maps or CBOR array.
  - A table is encoded as an array if the set of keys is {1, 2, .., n} for some n.
A Lua object may use a custom encoder by adding an encoder function __tocbor to the metatable.

There is no corresponding way to use a custom decoder.

For example,
```
null = setmetatable({}, { __tocbor = function(self) return cbor.encode(nil) end })
```
cbor.decode(data)

cbor.decode decodes (deserializes) a blob containing CBOR binary data, returning a Lua object that encodes to the given CBOR as defined in cbor.encode.

CBOR byte strings decode to Blobs and CBOR nil decodes to null.

The other CBOR types decode to primitive strings, numbers, booleans, and tables.

The `json` module

json.encode(object)

json.encode encodes (serializes) a Lua object into Lua string containing JSON data.

json.encode(object) returns the JSON corresponding to cbor.encode(object).

CBOR byte strings (Blobs) become base64-encoded JSON strings.
json.decode(data)

json.decode decodes (deserializes) a Lua string containing JSON data, returning a Lua object that encodes to the given JSON, as defined in json.encode.

JSON nil decodes to null. The other JSON types decode to primitive strings, numbers, booleans, and tables.

JSON strings always decode to Lua strings, including base64-encoded JSON strings.

For example, encoding a Blob to JSON and then decoding the JSON will produce a base64-encoded Lua string. To get the original Blob, apply Blob.from_base64 to the decoded string.

The `null` object

This is an object that encodes to CBOR or JSON null.

This is returned on success in methods like sobject:delete() that return no data.

We do not return nil here so that assert(sobject:delete()) works.

The `Array` class

An Array is a table that always serializes to an JSON/CBOR array, not a map.

Non-numeric keys in an Array (more precisely, keys not included in ipairs) are ignored during serialization.

Motivation

The empty map {} and the empty array [] in JSON both deserialize to the empty Lua table {}.

The empty Lua table serializes to the empty map. Array() serializes to the empty array.

Constructors

Array() or Array {} is the empty array.

Array(table) returns setmetatable(table, Array).

E.g. assert(json.encode(Array { 1, 2, a = 3 }) == '[1,2]').

The `Error` class

This class is used for errors from the plugin APIs.

If an error occurs, a function will return two values: nil and the error (this is a standard Lua idiom).

An error has two properties: an HTTP status code number status and message string.

Custom errors may be constructed using Error.new { status = <code>, message = "<message>" }.

For example,

function run()
   local result, error = Sobject { name = "nonexistent key" }
   assert(result == nil)
   assert(error.status == 404)

  // return a custom 401 Unauthorized error to the plugin invoker
  return nil, Error.new { status = 401, message = "custom error" }
end

The function `principal`

principal() returns the EntityId of the entity that invoked the plugin.

For example,

function run()
  if principal():type() ~= 'user'
    return nil, Error.new { = 401, message = "Plugin may only be invoked by users" }
  end
end

The function `this_plugin`

this_plugin() returns a Plugin object corresponding to the plugin being invoked.

For example,

function run()
  return "the name of this plugin is " .. this_plugin().name
end

The `AuditLog` module

AuditLog.log { message = message, severity = severity }
Write an audit log entry associated with this plugin with the given message and severity.

severity may be one of 'INFO', 'WARNING', 'ERROR', or 'CRITICAL'.
AuditLog.get_all { ... }

Get audit log entries matching the requested filters. This corresponds to GET /sys/v1/logs in the REST API.

Returns an array of audit log entries, or nil and an Error if the logs could not be fetched.

The `Sobject` class

This represents a security object, transient or persisted.

The properties of this object are described in the REST API docs (it is named KeyObject there). sobject.value and sobject.pub_key are Blobs (unless they are nil).

sobject.creator is an EntityId object.

Like apps, plugin may create transient keys by adding transient = true to the create, import, unwrap, derive, or agree request.

These transient keys only exist during the invocation of the plugin. As soon as the plugin's function run returns, they become invalid.

Constructors

Sobject { id = '<uuid>' } or Sobject { kid = '<uuid>' }

This return the persisted security object with the given UUID, or nil and an Error if no such object exists.
For example,
```
local sobject = assert(Sobject { id = '123e4567-e89b-12d3-a456-426655440000' })
```
Sobject { name = 'key name' }

This returns the persisted security object with the given name, or nil and an Error if no such object exists.
Sobject.create { ... }

Create a security object. This corresponds to POST /crypto/v1/keys in the REST API.

The arguments to this function are described in the REST API documentation for SobjectRequest.

This returns the created Sobject, or nil and an Error if the object could not be created.
For example,
```
local sobject = assert(Sobject.create { name = "my key", obj_type = "AES", key_size = 128 })
```
Sobject.import { ... }

Import a security object. This corresponds to PUT /crypto/v1/keys in the REST API.

The arguments to this function are described in the REST API documentation for SobjectRequest.

This returns the import Sobject, or nil and an Error if the object could not be imported.

For example,

local sobject = assert(Sobject.import { name = "my key", obj_type = "AES", value = Blob.random { bits = 128 } })

Sobject.get_all { ... }

Get detailed information on all security objects. This corresponds to GET /crypto/v1/keys in the REST API.

This returns Sobject, or nil and an Error.
For example,
```
local sobject, error = Sobject.get_all { }
```
Sobject.get_by_names { ... }

Get detailed information on security objects that match names.

This returns Sobject, or nil and an Error.
For example,
```
local sobject, error = Sobject.get_by_names { "My key", "Another key", "Unavailable key" }
```

Methods

sobject:update { ... }

Update the properties of sobject. This corresponds to PATCH /crypto/v1/keys/<uuid> in the REST API.

The arguments to this method are described in the REST API documentation for SobjectRequest.

This method may not be called on a transient sobject.

Returns null on success, or nil and an Error if the object could not be updated.
For example,
```
assert(sobject:update { name = "new key name" }) -- throw an exception if update fails
```
sobject:delete()

Delete the sobject. This corresponds to DELETE /crypto/v1/keys/<uuid> in the REST API.

This method may not be called on a transient sobject.

Returns null on success, or nil and an Error if the object could not be deleted.
For example,
```
assert(sobject:delete()) -- throw an exception if update fails
```
sobject:export()

Retrieve the value of sobject. This corresponds to GET /crypto/v1/keys/export in the REST API.

This returns a Sobject which has a value property on success, or returns nil and an Error if the object could not be exported.
For example,
```
local exported_value = assert(Sobject { name = 'my key' }):export().value
```
sobject:descriptor()

Returns { kid = "<uuid>" } if sobject is persisted, or { transient_key = blob } if sobject is transient.
sobject:encrypt { ... }

Encrypt data using sobject. This corresponds to POST /crypto/v1/encrypt in the REST API.

The arguments to this method are described in the REST API docs for EncryptRequest.

Returns an object corresponding to EncryptResponse in the REST API on success, or nil and an Error if the data could not be encrypted.

In the returned object, cipher and iv are Blobs.
For example,
```
local sobject = assert(Sobject { name = "my aes key" })
local encrypt_response = assert(sobject:encrypt { plain = Blob.from_bytes("hello world"), mode = 'CBC' })
return encrypt_response.cipher:base64() .. ':' .. encrypt_response.iv:base64()
```
sobject:decrypt { ... }

Decrypt data using sobject. This corresponds to POST /crypto/v1/decrypt in the REST API.

The arguments to this method are described in the REST API docs for DecryptRequest.

Returns an object corresponding to DecryptResponse in the REST API on success, or nil and an Error if the data could not be decrypted.

In the retuned object, plain is a Blob.
For example,
```
function encrypt(blob)
   local sobject = assert(Sobject { name = "my rsa key" })
   return assert(sobject:decrypt { cipher = blob }).plain
end
```
sobject:sign { ... }

Sign data using sobject. This corresponds to POST /crypto/v1/sign in the REST API.

The arguments to this method are described in the REST API docs for SignRequest.

Returns a object corresponding to SignResponse in the REST API on success, or nil and an Error if the data could not be signed.

In the returned object, signature is a Blob.
For example,
```
local sobject = assert(Sobject { name = "my rsa key" })
local sign_response = assert(sobject:sign { data = Blob.from_bytes("hello world"), hash_alg = 'SHA256' })
return sign_response.signature
```
sobject:verify { ... }

Verify data signed by sobject. This corresponds to POST /crypto/v1/verify in the REST API.

The arguments to this method are described in the REST API docs for VerifyRequest.

Returns a object corresponding to VerifyResponse in the REST API on success, or nil and an Error if the validity of the signature could not be established.

Note that if the signature is determined to be invalid, the call will successfully return { result = false }.
For example,
```
local sobject = assert(Sobject { name = "my rsa key" })
local verify_response = assert(sobject:verify { data = Blob.from_bytes("hello world"), signature = signature, hash_alg = 'SHA256' })
assert(verify_response.result == true)
```
sobject:wrap { ... }

Use sobject to wrap another security object. This corresponds to POST /crypto/v1/wrapkey in the REST API.

The arguments to this method are described in the REST API docs for WrapKeyRequestEx.

The subject argument may be a descriptor (as described in the REST API) or a Sobject.

Returns an object corresponding to WrapKeyResponse in the REST API on success, or nil and an Error if the sobject key could not be wrapped.
For example,
```
local wrapping_key = assert(Sobject { name = "AES wrapping key" })
local generated_key = assert(Sobject.create { obj_type = 'AES', key_size = 128, transient = true })
local wrap_response = assert(wrapping_key:wrap { subject = generated_key, mode = 'CBC' })
local result = wrap_response.wrapped_key:base64() .. ':' .. wrap_response.iv:base64()
```

sobject:unwrap { ... }

Use sobject to unwrap and import a wrapped key. This corresponds to POST /crypto/v1/unwrapkey in the REST API.

The arguments to this method are described in the REST API docs for UnwrapKeyRequest.

Returns the unwrapped Sobject, or nil and an Error if the wrapped key could not be unwrapped.

For example,

function run(input)
  local wrapping_key = assert(Sobject { name = "RSA wrapping key" })
  local unwrapped_key =
    assert(wrapping_key:unwrap { wrapped_key = input.wrapped_key, obj_type = 'AES', transient = true })
  return unwrapped_key:encrypt(input.encrypt_request)
end

sobject:agree { ... }

Perform a key agreement algorithm using the private key sobject and the public key from another party. This corresponds to POST /crypto/v1/agree in the REST API.

The arguments to this method are described in the REST API for AgreeKeyRequest.

The public_key argument may be a descriptor (as described in the REST API) or a Sobject.

Returns the agreed Sobject, or nil and an Error if the key agreement could not be completed.
sobject:mac { ... }
Use sobject to compute a cryptographic Message Authentication Code on a message. sobject must be a symmetric key. This corresponds to POST /crypto/v1/mac in the REST API.

The arguments to this method are described in the REST API docs for MacGenerateRequest.

Returns an object corresponding to MacGenerateResponse from the REST API on success, or nil and an Error if the MAC could not be generated.
sobject:mac_verify { ... }

Use sobject to verify a cryptographic Message Authentication Code on a message. sobject must be a symmetric key. This corresponds to POST /crypto/v1/macverify in the REST API.

The arguments to this method are described in the REST API docs for MacVerifyRequest.

Returns an object corresponding to MacVerifyResponse from the REST API on success, or nil and an Error if the validity of the MAC could not be established.

Note that if the MAC is determined to be invalid, the call will successfully return { result = false }.

sobject:derive { ... }

Use sobject to derive another key. This corresponds to POST /crypto/v1/derivein the REST API.

The arguments to this method are described in the REST API docs for DeriveKeyRequest.

Returns a newly created Sobject, or nil and an Error if the key could not be derived.

For example,

function run(input)
    local sobject = assert(Sobject.create { name = "test_key_20230314", obj_type = "AES", key_size = 256 })
    local derive_response = assert(sobject:derive { name = "derived_key_20230314", 
                                                    key_size = 256, key_type = "AES", 
                                                    mechanism = { encrypt_data = { alg = "AES", mode = "CBC", iv = "6pduXJMk351eaTbb0XLozw==",
                                                                  plain = "OjKlKPBH89/K8QfdxiutVyD/yAMg0k+NH7xeFEsR0hxkUwOaen+Uv/uXCvPUNj53"}}})
     return derive_response
 end

sobject:agree { ... }
Sobject:issuer_dn()

If the object is a certificate, then returns an X509Name representing the certificate issuer.
Sobject:subject_dn()

If the object is a certificate, then returns an X509Name representing the certificate subject.
Sobject:get_extension(oid)

If the object is a certificate, then returns the value of the extension specified by the OID argument.

For example: let extn = sobject.get_extension(Oid.from_str('subjectKeyIdentifier'))
Sobject:extension_oids()

If the object is a certificate, returns a list of OIDs which are used in the certificate.

For example: let extn_oids = sobject.extension_oids()
Sobject:verify_certificate(issuing_cert)

If the object is a certificate, then verifies the signature on the cert using the issuing certificate which is provided as an argument.

The `EntityId` class

This identifies an app, user, or plugin. It corresponds to CreatorType in the REST API docs.

Methods

entity_id:id()

Returns the UUID of the app, user, or plugin.
entity_id:type()

Returns "app", "user", or "plugin".

entity_id:entity()

Returns the appropriate App, User, or Plugin object, or nil and an Error if no such object exists.

For example,

local key = assert(Sobject { name = "my key" })
local creator = key.creator
return "Created by a " .. creator:type() .. " named " .. creator:entity().name

The `App` class

This represents an app.

The properties of this object are described in the REST API docs.

app.creator is an EntityId object.

Constructors

App { id = "<uuid>" }

This returns the app with the given UUID, or nil and an Error if no such app exists.

The `Plugin` class

This represents a Plugin.

The properties of this object are described in the REST API docs.

plugin.creator is an EntityId object.

Constructors

Plugin { id = "<uuid>" }

This returns the plugin with the given UUID, or nil and an Error if no such object exists.

The `User` class

This represents a User.

The properties of this object are described in the REST API docs.

Constructors

User { id = "<uuid>" }
This returns the user with the given UUID, or nil and an Error if no such user exists.

The `Group` class

This represents a Group.

The properties of this object are described in the REST API docs.

Constructors

Group { id = "<uuid>" }

This returns the group with the given UUID, or nil and an Error if no such group exists.

The function `digest`

Compute the digest (hash) of the given data using the given algorithm. This corresponds to POST /crypto/v1/digest from the REST API.

digest returns an object corresponding to DigestResponse from the REST API on success, or nil and an Error if the digest could not be computed. The returned digest is a Blob.

For example,

local sha256_hash = assert(digest { data = Blob.from_bytes('Hello world'), alg = 'SHA256' }).digest
return sha256_hash:hex()

The `BigNum` class

A BigNum represents an arbitrary-precision integer.

Constructors

BigNum.from_bytes_be(string)

Constructs a BigNum from a Lua string with big endian binary data.

For example: local bignum = BigNum.from_bytes_be('\x01\x00\x01').
BigNum.from_bytes_be(blob)

Constructs a BigNum from a Blob with big endian binary data.

E.g.: local bignum = BigNum.from_bytes_be(Blob.from_bytes('\x01\x00\x01')).

Methods

bignum:to_bytes_be()

Returns a Blob with unsigned binary data, big endian..

For example: local bytes = bignum:to_bytes_be().
bignum:to_bytes_be_zero_pad(n)

Returns a Blob with unsigned binary data, big endian, zero padding to n bytes.

For example: local bytes = bignum:to_bytes_be_zero_pad(16).
bignum:copy()

Returns a copy of bignum.

For example: `local copy = bignum:copy().
bignum == bignum

Compare two bignums for equality

For example: local same = bignum1 == bignum2
bignum < bignum
Test if one bignum is less than another

For example: local less = bignum1 < bignum2
bignum <= bignum

Test if one bignum is less than or equal to another

For example: local lte = bignum1 <= bignum2
bignum > bignum

Test if one bignum is greater than another

For example: local greater = bignum1 > bignum2
bignum >= bignum

Test if one bignum is greater than or equal to another

For example: local gte = bignum1 >= bignum2
bignum:add(bignum2)

Performs a signed addition of bignum2 to bignum and updates bignum to result.

For example: bignum:add(bignum2).
bignum + bignum2

Performs a signed addition of bignum2 to bignum and returns result.

For example: local result = bignum + bignum2.
bignum:sub(bignum2)

Performs a signed subtraction of bignum2 from bignum and updates bignum to result.

For example: bignum:sub(bignum2).
bignum - bignum2

Performs a signed subtraction of bignum2 from bignum and returns result.

For example: local result = bignum - bignum2.
bignum:mul(bignum2)

Performs a multiplication of bignum by bignum2 and updates bignum to result.

For example: bignum:mul(bignum2).
bignum * bignum2

Performs a multiplication of bignum by bignum2 and returns result.

For example: local result = bignum * bignum2.
bignum:div()

Performs a division of bignum by bignum2 and updates bignum to result.

For example: bignum:div().
bignum / bignum2

Performs a division of bignum by bignum2 and returns result.

For example: local result = bignum / bignum2.
bignum:mod()

Performs a modular reduction of bignum for the base bignum2 and updates bignum to result.

For example: bignum:mod().
bignum % bignum2

Performs a modular reduction of bignum for the base bignum2 and returns result.

For example: local result = bignum % bignum2.

The `Time` class

A Time represents current system time.

Constructors

Time.now_insecure()

Constructs a Time.

For example: local time = Time.now_insecure().
Time.from_iso8601(date_time)

Constructs a Time representing the provided date/time which must be in ISO-8601 format. Returns an error if the provided input does not have the correct format or is outside the range supported by Time. Note that Time does not support date/times before Jan 1, 1970 00:00:00 UTC or after Apr 11, 2262 23:47:16 UTC.

For example: local time = assert(Time.from_iso8601('20060102T150405Z')).

Methods

time:unix_epoch_seconds()

Returns a Lua number representing time as seconds since Jan 1, 1970 00:00:00 UTC.

For example: local secs = time:unix_epoch_seconds().
time:unix_epoch_nanoseconds()

Returns a Lua number representing time as nanoseconds since Jan 1, 1970 00:00:00 UTC.

For example: local nanosecs = time:unix_epoch_nanoseconds().

time:to_iso8601()

Returns a Lua string representing time in ISO-8601 format.

For example.:

local now = Time.now_insecure()
 return now:to_iso8601() -- for example: "20210914T193810Z"

time:add_seconds(seconds)

Returns a new Time instance representing seconds after time. Note that time is not modified.

For example:

local t0 = assert(Time.from_iso8601('20060102T150405Z'))
 local t1 = t0:add_seconds(30)
 assert(t1:to_iso8601() == '20060102T150435Z')

The `OID` class

An OID represents an ASN.1 object identifier.

Constructors

Oid.from_str(str)

Load an OID from a string which can be either the usual dotted decimal notation or a name (for some well known and commonly used OIDs).

For example: local cn = Oid.from_str('CN') E.g.: local email = Oid.from_str('1.2.840.113549.1.9.1')

Methods

Oid:to_str()

If the OID has a known value, return the string associated with it. Otherwise returns the dotted decimal value.

For example: assert(email:to_str() == 'emailAddress')

The `DerEncoder` class

A DerEncoder allows creating DER encodings of arbitrary objects. This is useful when creating X.509 certificate extensions, or when the plugin wants to return an ASN.1 structure such as a CAdES signature.

Constructors

DerEncoder:new()

Return a new DerEncoder object

Methods

DerEncoder:value()

This returns the binary blob of the DER encoding so far. It is possible to call value more than once, and it is also possible to add more data to a DerEncoder after calling value. The sequences (calls to start_seq/end_seq) must be matched.
DerEncoder:start_seq()

Being a new DER SEQUENCE structure. This can be nested.
DerEncoder:end_seq()

End the currently active SEQUENCE
DerEncoder:implicit_context(tag)

Tag the following datum with an implicit context-specific tag. For example DerEncoder.new():implicit_context(1):start_seq():implicit_context(2):add_int(2):end_seq() will tag the SEQUENCE with a context specific tag of 1 and the INTEGER with a context specific tag of 2. The tag should be given as a non-negative integer.
DerEncoder:explicit_context(tag)

Similar to implicit_context expect using explicit DER tagging.
DerEncoder:add_bool(b)

Add a boolean value to the current DER encoding.
DerEncoder:add_int(i)

Add an integer value to the current DER encoding. This can be either a Lua integer or a BigNum object.
DerEncoder:add_oid(oid)

Add an Oid to the encoding.
DerEncoder:add_enum(en)

Add an enum to the encoding; the enum should be specified as a Lua integer.
DerEncoder:add_string(str, encoding)

Add a string to the encoding. The encoding parameter specifies what ASN.1 string type to use; 'utf8', 'printable', 'numeric' or 'ia5'. If the encoding paramter is not given or is nil, default to 'utf8'.

Be aware that when using 'printable' or 'numeric', the encoder does not check that the string satisfies the content requirements; it is possible to insert arbitrary data with 'numeric' or 'printable' types, which is an invalid DER encoding and is likely to be rejected by at least some parsers.
DerEncoder:add_octets(input)

Add an OCTET STRING. The argument can be either a Blob or a Lua string. If the argument is a string it is assumed to be a hexadecimal input.
DerEncoder:add_raw(input)

Insert arbitrary values into the DER encoding stream. The argument is directly inserted into the stream as-is with no inspection. This allows encoding values that are not expressible using the current API.

The `X509Name` class

An X509Name represents an X.509 distinguished name, as used in certificates and signing requests.

Constructors

X509Name.from_der(der)

Load a DN from the binary DER encoding.

For example: local name = X509Name.from_der(der)
X509Name.new()

Create a new (empty) DN.

For example: local name = X509Name.new()

Methods

X509Name.to_str()

Return a readable string encoding for the DN.
X509Name.oids()

Return an array of OIDs specifying the values it contains
X509Name.get(oid)

If the specified OID is set in the DN, return the value. Otherwise returns nil.
X509Name.set(oid, value, string_type)

Set the OID to the provided value. The string_type field specifies how the string is encoded; for best interop use "utf8". Other accepted encodings are "printable", "numeric", and "ia5".

For example: name.set(oids.from_str('CN'), 'localhost', 'utf8')

The `Pkcs10Csr` class

A Pkcs10Csr represents a certificate signing request as specified in PKCS 10.

Constructors

Pkcs10Csr.new(key_id, subject)
Pkcs10Csr.from_der(der)

Load a PKCS10 CSR from the binary DER value

Methods

csr:verify_signature()

Verify the self-signature on a CSR, returning true on success. This simply verifies that whoever generated the CSR does have access to the private key corresponding to the public key in the CSR. This does not authenticate the CSR in any way. However, this prevents certain forgery attacks that are otherwise possible.
csr:subject_dn()

Return an X509Name of the subject set in the CSR.
csr:sign(ca_cert, ca_key_name, cert_lifetime, digest, serial_bits, copy_extensions)

Sign a CSR, creating a new certificate object. The ca_cert should be a CA certificate Sobject. The ca_key_name should be the name of a key stored in DSM which is associated with the issuing CA certificate. The certificate lifetime is given in seconds from the current time.

The digest parameter specifies what hash function to use when signing the certificate. If not specified (or nil), then SHA-256 is used by default.

The copy_extensions parameter's default value is false if not provided. This parameter determines if the extensions from CSR should be copied into a signed certificate or not.

The `TbsCertificate` class

A TbsCertificate represents the body of a certificate without an associated signature. It allows creating a custom certificate without first creating a CSR.

Constructors

TbsCertificate.new(key_id, subject, skid, lifetime)

Methods

TbsCertificate:add_extension(oid, critical, value)

Add an extension to the TbsCertificate.

Each certificate extension is identified by an OID and is marked either critical or non-critical. During validation, any implementation that encounters a critical extension it cannot identify is required to reject the certificate. So ordinarily critical extensions are only used when the certificate cannot be safely validated without understanding the extension. If the extension is just for informative purposes it is usually non-critical.

The value must be the complete DER encoding of the extension. This can be creating using DerEncoder, for example to insert a critical basicConstraints extension,
```
local bc = DerEncoder.new():start_seq():add_bool(false):end_seq():value()
 tbs:add_extension(Oid.from_str('basicConstraints'), true, bc)
```
TbsCertificate:to_der()

Encode the TbsCertificate as a DER value
TbsCertificate:sign(ca_cert, ca_key_name, serial_bits, digest)

Sign the TbsCertificate and return a new certificate object. The issuing certificate should be an Sobject and the ca_key_name gives the name of the signing key which must be stored in Fortanix DSM.

If serial_bits is set to a positive integer, then a new serial number is created of the specified bit size. If it is set to true, then a new serial of some default size (currently 160 bits) is used. If it is set to 0 or false, then the serial number set in the original TbsCertificate structure is used in the final signed certificate.

The digest parameter specifies what hash function to use when signing the certificate. If not specified (or nil), then SHA-256 is used by default.
TbsCertificate:self_sign(signing_key, digest)

Self-sign a TbsCertificate, creating a new self-signed certificate, that is, with the issuer DN set the same as the subject DN that was provided when the new constructor was invoked.

The signing_key must be a reference to the private key which will be used to generate the signature.

The digest parameter specifies what hash function to use when signing the certificate. If not specified (or nil), then SHA-256 is used by default.

The `EcGroup` class

An EcGroup represents some elliptic curve group supported in Fortanix DSM.

Constructors

EcGroup.SecP256R1, EcGroup.SecP256K1, ...

EcGroup supports construction using a enum-style syntax. Possible values are "Bp256R1", "Bp384R1", "Bp512R1", "Curve25519", "SecP192K1", "SecP192R1", "SecP224K1", "SecP224R1", "SecP256K1", "SecP256R1", "SecP384R1", and "SecP521R1".
EcGroup.from_name

This function constructs an EC group from a string (values matching the above named enums). This is useful when the desired group is provided as a parameter by the invoker of a plugin.

Methods

EcGroup:name()

This function returns the name of the group.
EcGroup:generator()

This function returns an EcPoint which is the generator of this group.
EcGroup:point_from_components(x, y)

This function returns a new EcPoint taking BigNum components x and y.
EcGroup:point_from_binary(v)

This function decodes an encoded EC point using the standard OS2ECP convention. Both compressed and uncompressed points are supported.

The `EcPoint` class

An EcPoint represents a particular point on an elliptic curve. It is constructed using the functions on EcGroup.

Methods

EcPoint:group()

This function returns the EcGroup that this point belongs to.
EcPoint:add(other)

This function performs point addition, adding two points and returning the resulting point.
EcPoint:mul(scalar)

This function performs point multiplication, multiplying a point by a scalar BigNum and returning the resulting point.
EcPoint:x()

This function returns the affine x coordinate of the point as a BigNum.
EcPoint:y()

This function returns the affine y coordinate of the point as a BigNum.
EcPoint:to_binary(compress)

This function returns the binary encoding of a point. If compress is false then uncompressed encoding is used. If compress is nil or true then point compression is used.

The function `require_approval_for`

You can call this function in your function check to require the caller to submit an approval request to invoke the plugin. For example:

function check(input)
  local key = assert(Sobject { name = 'my key' })
  require_approval_for(key)
end

In the above example, if my key is subject to an approval policy then the caller needs to submit an approval request to invoke the plugin and the plugin is invoked once enough reviewers approve that request.

Language

Invoking plugins

The run function

The check function

The Blob class

The cbor module

The json module

The null object

The Array class

The Error class

The function principal

The function this_plugin

The AuditLog module

The Sobject class

The EntityId class

The App class

The Plugin class

The User class

The Group class

The function digest

The BigNum class

The Time class

The OID class

The DerEncoder class

The X509Name class

The Pkcs10Csr class

The TbsCertificate class

The EcGroup class

The EcPoint class

The function require_approval_for

Related articles

Comments

The `run` function

The `check` function

The `Blob` class

The `cbor` module

The `json` module

The `null` object

The `Array` class

The `Error` class

The function `principal`

The function `this_plugin`

The `AuditLog` module

The `Sobject` class

The `EntityId` class

The `App` class

The `Plugin` class

The `User` class

The `Group` class

The function `digest`

The `BigNum` class

The `Time` class

The `OID` class

The `DerEncoder` class

The `X509Name` class

The `Pkcs10Csr` class

The `TbsCertificate` class

The `EcGroup` class

The `EcPoint` class

The function `require_approval_for`