Previously the behavior of the type-checking functions was arguably
underdescribed in the docs when the type-check failed.
This change specifies that the result is undefined.
Signed-off-by: Tim Hinrichs <tim@styra.com>
This document is the authoritative specification of the Rego policy language
(V1). All policies in OPA are written in Rego.
Built-in Functions
The built-in functions for the language provide basic operations to manipulate
scalar values (e.g. numbers and strings), and aggregate functions that summarize
complex types.
Comparison
Built-in
Description
x == y
x is equal to y
x != y
x is not equal to y
x < y
x is less than y
x <= y
x is less than or equal to y
x > y
x is greater than y
x >= y
x is greater than or equal to y
Numbers
Built-in
Description
z := x + y
z is the sum of x and y
z := x - y
z is the difference of x and y
z := x * y
z is the product of x and y
z := x / y
z is the quotient of x and y
z := x % y
z is the remainder from the division of x and y
output := round(x)
output is x rounded to the nearest integer
output := abs(x)
output is the absolute value of x
Aggregates
Built-in
Description
output := count(collection_or_string)
output is the length of the object, array, set, or string provided as input
output := sum(array_or_set)
output is the sum of the numbers in array_or_set
output := product(array_or_set)
output is the product of the numbers in array_or_set
output := max(array_or_set)
output is the maximum value in array_or_set
output := min(array_or_set)
output is the minimum value in array_or_set
output := sort(array_or_set)
output is the sorted array containing elements from array_or_set.
output := all(array_or_set)
output is true if all of the values in array_or_set are true. A collection of length 0 returns true.
output := any(array_or_set)
output is true if any of the values in array_or_set is true. A collection of length 0 returns false.
Arrays
Built-in
Description
output := array.concat(array, array)
output is the result of concatenating the two input arrays together.
output is the part of the array from startIndex to stopIndex including the first but excluding the last. If startIndex >= stopIndex then output == []. If both startIndex and stopIndex are less than zero, output == []. Otherwise, startIndex and stopIndex are clamped to 0 and count(array) respectively.
Sets
Built-in
Description
s3 := s1 & s2
s3 is the intersection of s1 and s2.
s3 := s1 | s2
s3 is the union of s1 and s2.
s3 := s1 - s2
s3 is the difference between s1 and s2, i.e., the elements in s1 that are not in s2
output := intersection(set[set])
output is the intersection of the sets in the input set
output := union(set[set])
output is the union of the sets in the input set
Strings
Built-in
Description
output := concat(delimiter, array_or_set)
output is the result of joining together the elements of array_or_set with the string delimiter
contains(string, search)
true if string contains search
endswith(string, search)
true if string ends with search
output := format_int(number, base)
output is string representation of number in the given base
output := indexof(string, search)
output is the index inside string where search first occurs, or -1 if search does not exist
output := lower(string)
output is string after converting to lower case
output := replace(string, old, new)
output is a string representing string with all instances of old replaced by new
output := split(string, delimiter)
output is array[string] representing elements of string separated by delimiter
output := sprintf(string, values)
output is a string representing string formatted by the values in the arrayvalues.
startswith(string, search)
true if string begins with search
output := substring(string, start, length)
output is the portion of string from index start and having a length of length. If length is less than zero, length is the remainder of the string. If start is greater than the length of the string, output is empty. It is invalid to pass a negative offset to this function.
output := trim(string, cutset)
output is a string representing string with all leading and trailing instances of the characters in cutset removed.
output := upper(string)
output is string after converting to upper case
Regex
Built-in
Description
re_match(pattern, value)
true if the value matches the regex pattern
output := regex.split(pattern, string)
output is array[string] representing elements of string separated by pattern
regex.globs_match(glob1, glob2)
true if the intersection of regex-style globs glob1 and glob2 matches a non-empty set of non-empty strings. The set of regex symbols is limited for this builtin: only ., *, +, [, -, ] and \ are treated as special symbols.
output is true if string matches pattern. pattern is a string containing 0..n regular expressions delimited by delimiter_start and delimiter_end. Example regex.template_match("urn:foo:{.*}", "urn:foo:bar:baz", "{", "}", x) returns true for x.
output := regex.find_n(pattern, string, number)
output is an array[string] with the number of values matching the pattern. A number of -1 means all matches.
Glob
Built-in
Description
output := glob.match(pattern, delimiters, match)
output is true if match can be found in pattern which is separated by delimiters. For valid patterns, check the table below. Argument delimiters is an array of single-characters (e.g. [".", ":"]). If delimiters is empty, it defaults to ["."].
output := glob.quote_meta(pattern)
output is the escaped string of pattern. Calling glob.quote_meta("*.github.com", output) returns \\*.github.com as output.
The following table shows examples of how glob.match works:
output is x converted to a number. null is converted to zero, true and false are converted to one and zero (respectively), string values are interpreted as base 10, and numbers are a no-op. Other types are not supported.
Units
Built-in
Description
output := units.parse_bytes(x)
output is x converted to a number with support for standard byte units (e.g., KB, KiB, etc.) KB, MB, GB, and TB are treated as decimal units and KiB, MiB, GiB, and TiB are treated as binary units.
Types
Built-in
Description
output := is_number(x)
output is true if x is a number; otherwise undefined
output := is_string(x)
output is true if x is a string; otherwise undefined
output := is_boolean(x)
output is true if x is a boolean; otherwise undefined
output := is_array(x)
output is true if x is an array; otherwise undefined
output := is_set(x)
output is true if x is a set; otherwise undefined
output := is_object(x)
output is true if x is an object; otherwise undefined
output := is_null(x)
output is true if x is null; otherwise undefined
output := type_name(x)
output is the type of x
Encoding
Built-in
Description
output := base64.encode(x)
output is x serialized to a base64 encoded string
output := base64.decode(string)
output is x deserialized from a base64 encoding string
output := base64url.encode(x)
output is x serialized to a base64url encoded string
output := base64url.decode(string)
output is string deserialized from a base64url encoding string
output := urlquery.encode(string)
output is string serialized to a URL query parameter encoded string
output := urlquery.encode_object(object)
output is object serialized to a URL query parameter encoded string
output := urlquery.decode(string)
output is string deserialized from a URL query parameter encoded string
output := json.marshal(x)
output is x serialized to a JSON string
output := json.unmarshal(string)
output is string deserialized to a term from a JSON encoded string
output := yaml.marshal(x)
output is x serialized to a YAML string
output := yaml.unmarshal(string)
output is string deserialized to a term from YAML encoded string
Token Signing
OPA provides two builtins that implement JSON Web Signature RFC7515 functionality.
io.jwt.encode_sign_raw() takes three JSON Objects (strings) as parameters and returns their JWS Compact Serialization. This builtin should be used by those that want maximum control over the signing and serialization procedure. It is important to remember that StringOrURI values are compared as case-sensitive strings with no transformations or canonicalizations applied. Therefore, line breaks and whitespaces are significant.
io.jwt.encode_sign() takes three Rego Objects as parameters and returns their JWS Compact Serialization. This builtin should be used by those that want to use rego objects for signing during policy evaluation. Notice that since these are objects canonicalization is applied and all whitespace is removed.
The following algorithms are supported:
ES256 "ES256" // ECDSA using P-256 and SHA-256
ES384 "ES384" // ECDSA using P-384 and SHA-384
ES512 "ES512" // ECDSA using P-521 and SHA-512
HS256 "HS256" // HMAC using SHA-256
HS384 "HS384" // HMAC using SHA-384
HS512 "HS512" // HMAC using SHA-512
NoSignature "none"
PS256 "PS256" // RSASSA-PSS using SHA256 and MGF1-SHA256
PS384 "PS384" // RSASSA-PSS using SHA384 and MGF1-SHA384
PS512 "PS512" // RSASSA-PSS using SHA512 and MGF1-SHA512
RS256 "RS256" // RSASSA-PKCS-v1.5 using SHA-256
RS384 "RS384" // RSASSA-PKCS-v1.5 using SHA-384
RS512 "RS512" // RSASSA-PKCS-v1.5 using SHA-512
If you need to generate the signature for a serialized token you an use the
io.jwt.encode_sign_raw built-in function which accepts JSON serialized string
parameters.
output is true if the RS256 signature of the input token is valid. certificate is the PEM encoded certificate or the JWK key (set) used to verify the RS256 signature
output is true if the PS256 signature of the input token is valid. certificate is the PEM encoded certificate or the JWK key (set) used to verify the PS256 signature
output is true if the ES256 signature of the input token is valid. certificate is the PEM encoded certificate or the JWK key (set) used to verify the ES256 signature
output := io.jwt.verify_hs256(string, secret)
output is true if the Secret signature of the input token is valid. secret is a plain text secret used to verify the HS256 signature
output := io.jwt.decode(string)
output is of the form [header, payload, sig]. header and payload are object. sig is the hexadecimal representation of the signature on the token.
output is of the form [valid, header, payload]. If the input token verifies and meets the requirements of constraints then valid is true and header and payload are objects containing the JOSE header and the JWT claim set. Otherwise, valid is false and header and payload are {}.
The input string is a JSON Web Token encoded with JWS Compact Serialization. JWE and JWS JSON Serialization are not supported. If nested signing was used, the header, payload and signature will represent the most deeply nested token.
For io.jwt.decode_verify, constraints is an object with the following members:
Name
Meaning
Required
cert
A PEM encoded certificate or a JWK key (set) containing an RSA or ECDSA public key.
See below
secret
The secret key for HS256, HS384 and HS512 verification.
See below
alg
The JWA algorithm name to use. If it is absent then any algorithm that is compatible with the key is accepted.
Optional
iss
The issuer string. If it is present the only tokens with this issuer are accepted. If it is absent then any issuer is accepted.
Optional
time
The time in nanoseconds to verify the token at. If this is present then the exp and nbf claims are compared against this value. If it is absent then they are compared against the current time.
Optional
aud
The audience that the verifier identifies with. If this is present then the aud claim is checked against it. If it is absent then the aud claim must be absent too.
Optional
Exactly one of cert and secret must be present.
If there are any unrecognized constraints then the token is considered invalid.
Time
Built-in
Description
output := time.now_ns()
output is number representing the current time since epoch in nanoseconds.
output := time.parse_ns(layout, value)
output is number representing the time value in nanoseconds since epoch. See the Go time package documentation for more details on layout.
output := time.parse_rfc3339_ns(value)
output is number representing the time value in nanoseconds since epoch.
output := time.parse_duration_ns(duration)
output is number representing the duration duration in nanoseconds. See the Go time package documentation for more details on duration.
output is of the form [year, month, day], which includes the year, month (0-12), and day (0-31) as numbers representing the date from the nanoseconds since epoch (ns) in the timezone (tz), if supplied, or as UTC.
output is of the form [hour, minute, second], which outputs the hour, minute (0-59), and second (0-59) as numbers representing the time of day for the nanoseconds since epoch (ns) in the timezone (tz), if supplied, or as UTC.
day := time.weekday(ns) day := time.weekday([ns, tz])
outputs the day as string representing the day of the week for the nanoseconds since epoch (ns) in the timezone (tz), if supplied, or as UTC.
Multiple calls to the time.now_ns built-in function within a single policy
evaluation query will always return the same value.
"UTC" or "", which are equivalent to not passing a timezone (i.e. will return as UTC)
"Local", which will use the local timezone.
Note that the opa executable will need access to the timezone files in the environment it is running in (see the Go time.LoadLocation() documentation for more information).
Cryptography
Built-in
Description
output := crypto.x509.parse_certificates(string)
output is an array of X.509 certificates represented as JSON objects.
Graphs
Built-in
Description
walk(x, [path, value])
walk is a relation that produces path and value pairs for documents under x. path is array representing a pointer to value in x. Queries can use walk to traverse documents nested under x (recursively).
HTTP
Built-in
Description
http.send(request, output)
http.send executes a HTTP request and returns the response.request is an object containing keys method, url and optionally body, enable_redirect, force_json_decode, headers, tls_use_system_certs, tls_ca_cert_file, tls_ca_cert_env_variable, tls_client_cert_env_variable, tls_client_key_env_variable or tls_client_cert_file, tls_client_key_file . For example, http.send({"method": "get", "url": "http://www.openpolicyagent.org/", "headers": {"X-Foo":"bar", "X-Opa": "rules"}}, output). output is an object containing keys status, status_code, body and raw_body which represent the HTTP status, status code, JSON value from the response body and response body as string respectively. Sample output, {"status": "200 OK", "status_code": 200, "body": {"hello": "world"}, "raw_body": "{\"hello\": \"world\"}"}. By default, HTTP redirects are not enabled. To enable, set enable_redirect to true. Also force_json_decode is set to false by default. This means if the HTTP server response does not specify the Content-type as application/json, the response body will not be JSON decoded ie. output's body field will be null. To change this behaviour, set force_json_decode to true.
HTTPs Usage
The following table explains the HTTPs objects
Object
Definition
Value
tls_use_system_certs
Use system certificate pool
true or false
tls_ca_cert_file
Path to file containing a root certificate in PEM encoded format
double-quoted string
tls_ca_cert_env_variable
Environment variable containing a root certificate in PEM encoded format
double-quoted string
tls_client_cert_env_variable
Environment variable containing a client certificate in PEM encoded format
double-quoted string
tls_client_key_env_variable
Environment variable containing a client key in PEM encoded format
double-quoted string
tls_client_cert_file
Path to file containing a client certificate in PEM encoded format
double-quoted string
tls_client_key_file
Path to file containing a key in PEM encoded format
double-quoted string
In order to trigger the use of HTTPs the user must provide one of the following combinations:
The user must also provide a trusted root CA through tls_ca_cert_file or tls_ca_cert_env_variable. Alternatively the user could set tls_use_system_certs to true and the system certificate pool will be used.
output is true if cidr_or_ip (e.g. 127.0.0.64/26 or 127.0.0.1) is contained within cidr (e.g. 127.0.0.1/24) and false otherwise. Supports both IPv4 and IPv6 notations.
net.cidr_intersects(cidr1, cidr2)
output is true if cidr1 (e.g. 192.168.0.0/16) overlaps with cidr2 (e.g. 192.168.1.0/24) and false otherwise. Supports both IPv4 and IPv6 notations.
Rego
Built-in
Description
output := rego.parse_module(filename, string)
rego.parse_module parses the input string as a Rego module and returns the AST as a JSON object output.
OPA
Built-in
Description
output := opa.runtime()
opa.runtime returns a JSON object output that describes the runtime environment where OPA is deployed. Caution: Policies that depend on the output of opa.runtime may return different answers depending on how OPA was started. If possible, prefer using an explicit input or data value instead of opa.runtime. The output of opa.runtime will include a "config" key if OPA was started with a configuration file. The output of opa.runtime will include a "env" key containing the environment variables that the OPA process was started with. The output of opa.runtime will include "version" and "commit" keys containing the semantic version and build commit of OPA.
Debugging
Built-in
Description
trace(string)
trace outputs the debug message string as a Note event in the query explanation. For example, trace("Hello There!") includes Note "Hello There!" in the query explanation. To print variables, use sprintf. For example, person := "Bob"; trace(sprintf("Hello There! %v", [person])) will emit Note "Hello There! Bob".
Reserved Names
The following words are reserved and cannot be used as variable names, rule
names, or dot-access style reference arguments:
as
default
else
false
import
package
not
null
true
with
Grammar
Rego’s syntax is defined by the following grammar:
module = package { import } policy
package = "package" ref
import = "import" package [ "as" var ]
policy = { rule }
rule = [ "default" ] rule-head { rule-body }
rule-head = var [ "(" rule-args ")" ] [ "[" term "]" ] [ ( ":=" / "=" ) term ]
rule-args = term { "," term }
rule-body = [ else [ = term ] ] "{" query "}"
query = literal { ";" | [\r\n] literal }
literal = ( some-decl | expr | "not" expr ) { with-modifier }
with-modifier = "with" term "as" term
some-decl = "some" var { "," var }
expr = term | expr-built-in | expr-infix
expr-built-in = var [ "." var ] "(" [ term { , term } ] ")"
expr-infix = [ term "=" ] term infix-operator term
term = ref | var | scalar | array | object | set | array-compr | object-compr | set-compr
array-compr = "[" term "|" rule-body "]"
set-compr = "{" term "|" rule-body "}"
object-compr = "{" object-item "|" rule-body "}"
infix-operator = bool-operator | arith-operator | bin-operator
bool-operator = "==" | "!=" | "<" | ">" | ">=" | "<="
arith-operator = "+" | "-" | "*" | "/"
bin-operator = "&" | "|"
ref = var { ref-arg }
ref-arg = ref-arg-dot | ref-arg-brack
ref-arg-brack = "[" ( scalar | var | array | object | set | "_" ) "]"
ref-arg-dot = "." var
var = ( ALPHA | "_" ) { ALPHA | DIGIT | "_" }
scalar = string | NUMBER | TRUE | FALSE | NULL
string = STRING | raw-string
raw-string = "`" { CHAR-"`" } "`"
array = "[" term { "," term } "]"
object = "{" object-item { "," object-item } "}"
object-item = ( scalar | ref | var ) ":" term
set = empty-set | non-empty-set
non-empty-set = "{" term { "," term } "}"
empty-set = "set(" ")"
The grammar defined above makes use of the following syntax. See the Wikipedia page on EBNF for more details:
[] optional (zero or one instances)
{} repetition (zero or more instances)
| alternation (one of the instances)
() grouping (order of expansion)
STRING JSON string
NUMBER JSON number
TRUE JSON true
FALSE JSON false
NULL JSON null
CHAR Unicode character
ALPHA ASCII characters A-Z and a-z
DIGIT ASCII characters 0-9
Tim Hinrichs
1aae0a4b2d