The related_resources annotation is a list of related-resource entries, where each links to some related external resource; such as RFCs and other reading material. Refer to playground link for applications. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? OPA will attempt to parse the YAML document in comments following the what does this error really mean - why would my rule be "unsafe", any idea why this would work in the playground but not when running through the OPA binary. Canadian of Polish descent travel to Poland with Canadian passport. it fails, complaining that the every expression wasn't safe because of __local21__3. a reference to another (possibly custom) built-in function: a reference to a rule that will be used as the. From a developer's perspective, there are two general categories of "safe" HTML in Angular. If it still doesn't work out, I'll happily have a look at your policies. It is not safe because the comprehension on line 4 comes after the object.get call of line 1. the opa run sub-command. collections of unique values. npm err! Rego will assign variables to values that make the comparison true. When a comprehension refers to a variable in an outer body, OPA will reorder expressions in the outer body so that variables referred to in the comprehension are bound by the time the comprehension is evaluated. Like other applications which support declarative query languages, OPA is able to optimize queries to improve performance. variable to be bound, i.e., an equality expression or the target position of References written this way are used to select a value from every element in a collection. If the body is omitted, it defaults to true. Schemas can also be provided for policy and data files loaded via opa eval --bundle, Samples provided at: https://github.com/aavarghese/opa-schema-examples/. See the docs on future keywords for more information. E.g., input["foo~bar"]. Overriding is a schema transformation feature and combines existing schemas. assign that set to a variable. Hopefully, it will benefit a lot of people. // Construct a Rego object that can be prepared or evaluated. that generate a set of servers that are in violation. Starting from the capabilities.json of your OPA version (which can be found in the Explicitly trusted HTML is safe Sanitized HTML is safe Let's look at #2 first. A single expression is rego_unsafe_var_error: expression is unsafe . Since you're using Gatekeeper, you'll have to refer to the data.inventory document. Similarly, if you edit the queries or rules in the examples below the output Most REPLs let you define variables that you can reference later on. query inputs, your policies can generate arbitrary structured data as output. and closely resembles dictionary lookup in a language such as Python: Both forms are valid, however, the dot-access style is typically more readable. The error only appears when I run "opa test test_myrule.rego" locally. We can generalize the example above with a rule that defines a set document instead of a boolean document: We can re-write the rule r from above to make use of q. We can manipulate this traversal information in various ways and make deductions. defined in terms of scalars, variables, references, and other composite values. We can refactor the raw input received before using it. Generating sets: Head declares only keys whose value is defined and returned from the body. We can pass this schema to the evaluator as follows: With the erroneous Rego code, we now obtain the following type error: This indicates the error to the Rego developer right away, without having the need to observe the results of runs on actual data, thereby improving productivity. Second, the sites[_].servers[_].hostname fragment selects the hostname attribute from all of the objects in the servers collection. For example, we can write a rule that defines a document containing names of apps not deployed on the "prod" site: Rego allows for several ways to express universal quantification. We add a negative rule for each rule we add which will execute when the corresponding positive rule fails to execute. The Rego compiler supports strict mode, where additional constraints and safety checks are enforced during compilation. Already on GitHub? using Comprehensions. evaluates to true. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. OPA was originally created by Styra and is proud to be Rego queries are assertions on data stored in OPA. Eigenvalues of position operator in higher dimensions is vector, not scalar? OPA as a library is to import the github.com/open-policy-agent/opa/rego The organizations annotation is a list of string values representing the organizations associated with the annotation target. Object Comprehensions have the form: We can use Object Comprehensions to write the rule from above as a comprehension instead: Object comprehensions are not allowed to have conflicting entries, similar to rules: Set Comprehensions build set values out of sub-queries. When comparing sets, the order of elements does not matter: Because sets are unordered, variables inside sets must be unified with a ground Documents can be defined solely in terms of scalar values. (none of which are public): Partial rules are if-then statements that generate a set of values and In the example below, the second expression is false: You can store values in intermediate variables using the := (assignment) The data that your service and its users publish can be inspected and transformed using OPA's native query language Rego. Attempting to add a validating capability with OPA Gatekeeper with a constraint template. set of values just like any other value: Iteration over the set of values can be done with the some in expression: With a literal, or a bound variable, you can check if the value exists in the set cannot refer to the index of an element within a set. The idea is that I want to look for annotations in the metadata which have the key of value either "apparmor" or "seccomp", Anything else you would like to add: Jinja2 filters let you transform the value of a variable within a template expression. The following reference will select the hostnames of all the servers in our To express FOR ALL in Rego, complement the logic in the ruling body (e.g., != becomes ==) and then, complement the check using negation (e.g. This keyword allows more expressive rule heads: This keyword allows more expressive rule heads for partial set rules: The some keyword allows queries to explicitly declare local variables. If OPA cannot enumerate the values of a variable in any expression, OPA will Use the obtain the same result. I am finding that I can examine some variables and not others when I used the key binding OPA: Evaluate Selection. though the input matches the second rule as well. 566), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Read more, A description of the annotation target. arguments, parentheses are required to use the form with two left-hand side Unlike many programming languages, where a variable is either an input or an output, in Rego a variable is simultaneously an input and an output. Rego is declarative so policy authors can focus on what queries should return rather than how queries should be executed. Overriding affects the type of the longest prefix that already has a type. produced by rules with Complete Definitions. Rego is declarative so policy authors can focus on what queries should return rather than how queries should be executed. The schemas field specifies an array associating schemas to data values. to optimize queries to improve performance. With a regular string, the regex is "[a-zA-Z_]\\w*", but with raw strings, it becomes `[a-zA-Z_]\w*`. I think that's missing __local21__3. It's saying that there is no report-uri directive. The path can be either a directory or file, directories are loaded recursively. Unification (=) combines assignment and comparison. They can also be run locally on your machine using the opa eval command, here are setup instructions. In the example below, evaluation stops immediately after the first rule even ", "https://kubernetesjsonschema.dev/v1.14.0/_definitions.json#/definitions/io.k8s.apimachinery.pkg.apis.meta.v1.ObjectMeta", "Standard object's metadata. error: You can restart OPA and configure to use any decision as the default decision: OPA can be embedded inside Go programs as a library. Expressive universal quantification keyword: There is no need to also import future.keywords.in, that is implied by importing future.keywords.every. found. Imports can include an optional as keyword to handle namespacing issues: To ensure backwards-compatibility, new keywords (like every) are introduced slowly. Third, the name := sites[_].servers[_].hostname expression binds the value of the hostname attribute to the variable name, which is also declared in the head of the rule. quantified. This is the list of all future keywords known to OPA: More expressive membership and existential quantification keyword: in was introduced in v0.34.0. Unification lets you ask for values for variables that make an expression true. Alternatively, we can implement the same kind of logic inside a single rule Language documentation. When you execute queries without providing a path, you do not have to wrap the for base data documents, they are only valid for references into virtual documents. OPA is purpose-built for reasoning around information represented in structured documents. The path of a rule is always: References can include Composite Values as keys if the key is being used to refer into a set. Rego allows authors to omit the body of rules. By importing a document, the identifiers exported by that document can be referenced within the current module. I'm not sure about the location and all that, but __local16__ is definitely unsafe there. opa eval supports a large number of options for controlling evaluation. as strings (because JSON does not support non-string object keys). There are just two important points: Using a different key on the same array or object provides the equivalent of self-join in SQL. policies and data. Commonly used flags include: Flag Short Description In that case, the equi starts with a specific prefix. If the output term is omitted, it is equivalent to having the output term *Rego.Eval and *Rego.PartialResult behave the same on same rego files. The reference above can be rewritten as: The underscore is special because it cannot be referred to by other parts of the rule, e.g., the other side of the expression, another expression, etc. include a public network then any_public_networks will be undefined (which is variables or references. defined. Consider the following Rego code which checks if an operation is allowed by a user, given an ACL data document: Consider a directory named mySchemasDir with the following structure, provided via opa eval --schema opa-schema-examples/mySchemasDir. Here's my constraint template. Here are examples of unsafe expressions: # 'x' is unsafe because it does not appear as an output of a non-negated expression not p [x]; not q [x] # 'y' is unsafe because it only appears as a built-in function input count (y) Safety errors can also occur with variables that appear in the head of the rule: when called in non-collection arguments: Using the some variant, it can be used to introduce new variables based on a collections items: Furthermore, passing a second argument allows you to work with object keys and array indices: Any argument to the some variant can be a composite, non-ground value: Rego supports three kinds of equality: assignment (:=), comparison (==), and unification =. Rules provide a complete definition by omitting the key in the head. Rego (pronounced "ray-go") is purpose-built for expressing policies over complex hierarchical data structures. receives a JSON representation of the system as input: Earlier in the day your boss told you about a new security policy that has to be The first is likely to be the most familiar: characters surrounded by double quotes. Which times of day the system can be accessed at. While Rego itself obviously looks entirely different from JSON, one of the commands accepted by the OPA program could help us with this: opa parse. The document scope annotation can be applied to any rule in the set (i.e., ordering does not matter.). The some keyword is not required but its recommended to avoid situations like For example: These documents can be queried like any other: Rego supports two different types of syntax for declaring strings. It is designed to work with the nested structure of JSON and YAML documents. to your account. Comprehensions are similar to the same constructs found in other languages like Python. for them using the subpackages scope. code: rego_unsafe_var_error, Code causing the error: sum(a,b) = x { a + b} Cause: this happens because x is not assigned. The examples in this section try to represent the best practices. Steps to Reproduce the Problem policies/test.rego (might be a bit too verbose, but I am still new to rego) Using some, we can express the rules introduced above in different ways: For details on some in , see the documentation of the in operator. Issue with Constraint Template - rego_unsafe_var_error: expression is unsafe. How to use parameters in Rego rules? Angular will only render "safe" HTML into the DOM. Merging of the JSON subSchemas essentially combines the passed in subSchemas based on what types they contain. We can use with to iterate over the resources in input and written output as a list. In simple cases, composite values can be treated as constants like Scalar Values: Composite values can also be defined in terms of Variables or References. Notice that this code has a typo in it: input.request.kind.kinds is undefined and should have been input.request.kind.kind. And its failing with the ingest error rego_unsafe_var_error: expression is unsafe. For a concise reference, see the Policy The exception to this rule is when multiple I can share the exact policies privately if necessary. above would have changed the result of tuples because the i symbol in the evaluated: The rego.Rego supports several options that let you customize evaluation. Please refer to the playground link to check the exact use-case. the one above where introduction of a rule inside a package could change When you use logical OR with partial rules, each rule definition contributes Similarly, assigning a schema to a package name is not a good idea and can cause problems. Find centralized, trusted content and collaborate around the technologies you use most. If you edit the input data above containing servers, networks, and ports, the output will change below. undefined. a graduated project in the Cloud Native Computing Foundation Deprecated built-in functions: String keys containing characters other than. In the unusual case that it is critical to use the same name, the function could be made to take the list of parameters as a single array. Note that we use the relative path inside the mySchemasDir directory to identify a schema, omit the .json suffix, and use the global variable schema to stand for the top-level of the directory. be safe, i.e., it must be assigned elsewhere in the query. (Importing every means also importing in without an extra import statement.). The simplest use of negation involves only scalar values or variables and is equivalent to complementing the operator: Negation is required to check whether some value does not exist in a collection. I made sure the error is the exact same after trimming it down and anonymizing it, but I'm not sure if that could have changed something unintentionally--there are several rules in actual usage that aren't in the policies above. Well occasionally send you account related emails. It introduces new bindings to the evaluation of the rest of the rule body. arguments compare: Combined with not, the operator can be handy when asserting that an element is not For example, we can write a rule that abstracts over our servers and When the default keyword is used, the rule syntax is restricted to: The term may be any scalar, composite, or comprehension value but it may not be I tried this rego policy on the playground and it worked just fine. pairs (aka objects). Furthermore, if can be used to write shorter definitions. order-sensitive system like IPTables. document itself) or data document, or references to functions (built-in or not). Examples: # Unsafe: x in head does not appear in body. When OPA evaluates policies it binds data provided in the query to a global the other rules with the same name are undefined. These documents are referenced in other sections above. When OPA evaluates expressions, it finds values for the variables that make all The policy decision is contained in the results returned by the Eval() call. For safety, a variable appearing in a negated expression must also appear in another non-negated equality expression in the rule. A schema for Admission Review has a generic type object for that field that has no further specification. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. update their policies, so that the new keyword will not cause clashes with existing We only know that it refers to a collections of values. Once this is fixed, the second typo is highlighted, informing the user that versions should be one of accessNum or version. Under the hood, OPA translates the _ character to a unique variable name that does not conflict with variables and rules that are in scope. The else keyword may be used repeatedly on the same rule and there is no in the rules path ancestry. of the expressions true. For example, the following reference returns the hostname of the second server in the first site document from our example data: References are typically written using the dot-access style. can use OPA to enforce policies in microservices, Kubernetes, CI/CD pipelines, Another rule thats enforced by OPA is that a variable appearing in a negated expression must also appear in another non-negated equality expression in the rule else it will throw an error. Metaschemas for different JSON Schema draft versions are not subject to this I'm writing a test for a rule but am hitting the error below in the test; Each of the "as" variables/function are defined in the same file as the test. Why does OPA generate a safety error in the original example? for those bindings. a built-in function. Call Eval() to supports so-called complete definitions of any type of document. I've just opened a second PR, #4801, to address the second bug we've cornered here. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. First, the rule defines a set document where the contents are defined by the variable name. commonly used for constants: Documents produced by rules with complete definitions can only have one value at every was introduced in v0.38.0. Rego is declarative so policy authors can focus on what queries should return By clicking Sign up for GitHub, you agree to our terms of service and If so, you need to import the rule under test into the test module: It's also possible to split the same package over multiple modules/files by declaring the same package in them, which might be what you actually want to do. What is this brick with a round back and a stud on the side used for? Debugging in playground/styra is simple but in live environments, its challenging to analyse and figure out which rule is executed. To learn more, see our tips on writing great answers. I don't understand why I get the var is unsafe message. Rego provides a feature to load static data and use that information to author and derive outcomes from the policy. If future keywords are not available to you, you can define the same rule as follows: When we query for the content of hostnames we see the same data as we would if we queried using the sites[_].servers[_].hostname reference directly: This example introduces a few important aspects of Rego. outside the set, OPA will complain: Because sets share curly-brace syntax with objects, and an empty object is construct using a helper rule: Negating every is forbidden. JSON object: Create a copy the input file for sending via curl: Execute a few curl requests and inspect the output: By default data.system.main is used to serve policy queries without a path. The other type of string declaration is a raw string declaration. body would capture the global value. Asking for help, clarification, or responding to other answers. For example, imagine you want to express a policy that says (in English): The most expressive way to state this in Rego is using the every keyword: Variables in Rego are existentially quantified by default: when you write. If no such prefix exists, the new path and type are added to the type environment for the scope of the rule. The every keyword takes an (optional) key argument, a value argument, a domain, and a