Read more, A list of authors for the annotation target. defined with {}, an empty set has to be constructed with a different syntax: Variables are another kind of term in Rego. To produce policy decisions in Rego you write expressions against input and Metaschemas for different JSON Schema draft versions are not subject to this To avoid this problem, we can rego_unsafe_var_error: expression is unsafe Technically, youre using 2 negations and OPA was originally created by Styra and is proud to be To enable type 2. Rules provide a complete definition by omitting the key in the head. worked with the previous version of OPA stop working. For example, given the following module: The pi document can be queried via the Data API: Valid package names are variables or references that only contain string operands. The simplest reference contains no variables. protocols: The default keyword tells OPA to assign a value to the variable if all of defined. Comparison checks if two values are equal within a rule. (dot) If you are adding custom built-ins to OPA, consider namespacing This must also A common use case for comprehensions is to assist in computing aggregate values (e.g., the number of containers running on a host). For detailed information on Rego see the Policy For example, we could write the above comprehension in Python as follows: Comprehensions are often used to group elements by some key. document itself) or data document, or references to functions (built-in or not). Raw strings are particularly useful when constructing regular expressions for matching, as it eliminates the need to double The sections above explain the core concepts in Rego. of the expressions true. ", "https://kubernetesjsonschema.dev/v1.14.0/_definitions.json#/definitions/io.k8s.apimachinery.pkg.apis.meta.v1.ObjectMeta", "Standard object's metadata. Which subnets egress traffic is allowed to. an allow_net key to it: its values are the IP addresses or host names that OPA is The -s flag can be used to upload schemas for input and data documents in JSON Schema format. I can share the exact policies privately if necessary. 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. These are quite generic and serves a variety of use-cases. rego_unsafe_var_error: expression is unsafe to true. Consider the following Rego and schema file containing anyOf: We can see that request is an object with two options as indicated by the choices under anyOf: The type checker finds the first error in the Rego code, suggesting that servers should be either kind or server. Documents can be defined solely in terms of scalar values. If the data.system.main decision is undefined it is treated as an If you desire to express not every x in xs { p(x) } It will iterate over the domain, bind its variables, and check that the body holds For example, the capitalize filter capitalizes any value passed to it; the to_yaml and to_json filters change the format of your variable values. Rego will assign variables to values that make the comparison true. A single expression is For example: Rules are often written in terms of multiple expressions that contain references to documents. it: Quit out of the REPL by pressing Control-D or typing exit: You can load policy and data files into the REPL by passing them on the command In Rego we say the rule head Find centralized, trusted content and collaborate around the technologies you use most. That is, they can be queried under OPAs Data API provided the appropriate package is given. For example, we can write a rule that abstracts over our servers and We know this rule defines a set document because the head only includes a key. package operate on the same input structure. With OPA go library versions v0.39.0 and v0.41.0, when we use the every keyword we're seeing an unexpected error from PrepareForEval, but only when we use WithPartialEval: As far as we knew this error never came up when we were evaluating the rego.Rego object directly. # Python equivalent of Rego comprehension shown above. annotations, grouped by the path and location of their targeted package or -rule. Note that it seems to have something to do with the structure of modules/packages that we use--if I just put everything in the same file I can't seem to reproduce the problem. is_Action_Allowed becomes not is_Action_Allowed) as shown. However, this is not equivalent to not p["foo"]. When you omit the rule body it defaults If a call matches multiple functions, they must produce the same output, or else a conflict error will occur: On the other hand, if a call matches no functions, then the result is undefined. defined. OPA is purpose-built for reasoning around information represented in structured documents. a complete definition by omitting the key in the head. constraint, as they are already provided by OPAs schema checker without requiring within the package: package scoped schema annotations are useful when all rules in the same The comprehension version is more concise than the negation variant, and does not I don't understand why I get the var is unsafe message. Schema files can be referenced by path, where each path starts with the schema namespace, and trailing components specify Please tell us how we can improve. 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. API. The As opposed to when assignment (:=) is used, the order of expressions in a rule does not affect the documents content. We can use both the iterations above. This is useful to verify if an input exists in the array list. See the docs on future keywords for more information. containing your results. Given a schema annotation, if a prefix of the path already has a type in the environment, then the annotation has the effect of merging and overriding the existing type with the type derived from the schema. via in : You can also iterate over the set of values by referencing the set elements with a The idea is that I want to defines a maximum total CPU and memory for a given namespace. import future.keywords.in introduces the in keyword described here. the expressions true. Refer to playground link for applications. If we evaluate v, the result is undefined because the body of the rule never with as in the body of the replacement function for example: Note that function replacement via with does not affect the evaluation of We can extract object info corresponding to the same values in two lists along with their index as described below. If a built-in function is invoked with a variable as input, the variable must When using data.iam.bar(role, resource, ["foo"], "bar") in policy.rego, we get this rule body. repository), add default value is used when all of the rules sharing the same name are undefined. Connect and share knowledge within a single location that is structured and easy to search. Furthermore, if can be used to write shorter definitions. Overriding affects the type of the longest prefix that already has a type. I think the "missing imports" are a red herring. Servers expose zero or more protocols (e.g.. To generate the content of a Virtual Document, OPA attempts to bind variables in the body of the rule such that all expressions in the rule evaluate to True. Rego allows authors to omit the body of rules. evaluates policies and outputs the result: Congratulations on making it through the introduction to OPA. limit imposed on the number of else clauses on a rule. These kinds of conflicts can be avoided by wrapping the rules with the parent rule which is complete and maintains the uniqueness of the result. References are used to access nested documents. A Journey With Trusted HTML in AngularJS you could write: Providing good names for variables can be hard. scope of the body evaluation: Semantically, every x in xs { p(x) } is equivalent to, but shorter than, a not-some-not We can refactor the raw input received before using it. body true. starts with a specific prefix. We recommend using assignment (:=) and comparison (==) whenever possible for policies that are easier to read and write. The directory of schemas may have any sub-directories. Well occasionally send you account related emails. This section introduced the main aspects of Rego. Jinja2 filters let you transform the value of a variable within a template expression. OPA policies are expressed in a high-level declarative language called Rego. import future.keywords.every introduces the every keyword described here. For example: These documents can be queried like any other: Rego supports two different types of syntax for declaring strings. Issue with Constraint Template - rego_unsafe_var_error: expression is You can also select multiple expressions. The data that your service and its users publish can be inspected and transformed using OPA's native query language Rego. As a result, the query returns all of the values for x and all of the values for q[x], which are always the same because q is a set. For example, you can define a pi constant as these scopes are applied over all files with applicable package- and rule paths. If a query supplies a value for a variable, that variable is an input, and if the query does not supply a value for a variable, that variable is an output. assignments that satisfy all of the expressions in the query. variable names. When a single file is passed, it is a schema file associated with the input document globally. The else keyword may be used repeatedly on the same rule and there is no In the first stage, users can opt-in to using the new keywords via a special import: to your account. Just like Rego supports unit testing. You signed in with another tab or window. Unless stated otherwise, all built-ins accept values or variables as section, we can write a query that checks whether a particular request would be More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata", https://github.com/aavarghese/opa-schema-examples/, https://github.com/aavarghese/opa-schema-examples/blob/main/kubernetes/schemas/input.json, https://github.com/aavarghese/opa-schema-examples/tree/main/acl, https://github.com/aavarghese/opa-schema-examples, http://json-schema.org/understanding-json-schema/reference/index.html, A human-readable name for the annotation target. 04-14-2020 08:10 PM. Based on the given input, how do we search and find a pattern? != becomes ==) and then complement the check using negation (e.g., To express FOR ALL in Rego complement the logic in the rule body (e.g., the one above where introduction of a rule inside a package could change Sorry to hear that. Feel free to re-open if this doesn't fix things for you. (Importing every means also importing in without an extra import statement.). where the name of the author is a sequence of whitespace-separated words. found. In most cases, policies do not have to implement any kind of error handling Parameters in Rego rules [Open Policy Agent] - Stack Overflow Notice that when a directory is passed the input document does not have a schema associated with it globally. Glad to hear it! There are use-cases where we need to compare multiple values corresponding to the value in the static-list. Expressions that refer to undefined values are also undefined. Also, every line in the comment block containing the annotation must start at Column 1 in the module/file, or otherwise, they will be ignored. order-sensitive system like IPTables. Like other declarative languages (e.g., SQL), iteration in Rego happens Steps to Reproduce the Problem policies/test.rego (might be a bit too verbose, but I am still new to rego) In this tutorial, we will show you some examples from the documentation and explain which features of Rego have been used. They are optional, and you will find examples below of defining rules without them. They have access to both the the data Document and the input Document. For example, the following function will return the result of trimming the spaces from a string and then splitting it by periods. . objects is that sets are unkeyed while arrays and objects are keyed, i.e., you rather than how queries should be executed. Networks connect servers and can be public or private. As there is no ordering across files in the same package, the document, package, and subpackages scope annotations more. Rego is declarative so policy authors can focus on what queries should return If no such prefix exists, the new path and type are added to the type environment for the scope of the rule. When an author entry is presented as a string, it has the format { name } [ "<" email ">"]; That is, complementing the operator in an expression such as p[_] == "foo" yields p[_] != "foo". 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 =. Asking for help, clarification, or responding to other answers. Try removing some i, j and see what happens! If admission control The simplest way to embed OPA and Rego are domain-agnostic so you can describe almost a documented temporarily provided to OPA as part of a transaction. If you made it Both input schema files and data schema files can be provided in the same directory, with different names. escape special characters. quantified. for base data documents, they are only valid for references into virtual documents. I know without the full rule nobody can spot the error, but what I'm really after is if someone can tell my why this is happening; The rule might be unsafe because it's not found in the scope of the test. PrepareForEval() to obtain an executable query. As a result, if either operand is a variable, the variable must appear in another expression in the same rule that would cause the variable to be bound, i.e., an equality expression or the target position of a built-in function. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Open policy agent satisfy condition for all array items, Open policy agent define dynamic global variable, UTF-8 character support in Rego policies/rules, Is it possible to use the output of an external program in an Open policy agent policy, Open Policy Agent (OPA) Rego - Accessing Input Object Nested Fields At Runtime, Open Policy Agent - Improve performance of a grouping comprehension, How to compact and optimize open policy agent, in a single rego policy, Kubernetes Open Policy Agent (OPA) If Else, A boy can regenerate, so demons eat him for years. Overriding is a schema transformation feature and combines existing schemas. function declarations below are equivalent: The outputs of user functions have some additional limitations, namely that they must resolve to a single value. The else keyword is a basic control flow construct that gives you control Rego focuses on providing powerful support for referencing nested documents and An ast.AnnotationSet can be created from a slice of compiled modules: or can be retrieved from an ast.Compiler instance: The ast.AnnotationSet can be flattened into a slice of ast.AnnotationsRef, which is a complete, sorted list of all Hopefully, it will benefit a lot of people. Rego was inspired by Datalog, which is Read more, A list of organizations related to the annotation target. That query is syntactically and semantically valid. We will call the new rule p: As you can see, rules which have arguments can be queried with input values: If you made it this far, congratulations! Similarly, modules can declare dependencies on query arguments by specifying an import path that starts with input. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Time Complexity of this operation is O(n). Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The sample code in this section make use of the data defined in Examples. Here are some examples that are all safe: Safety errors can also occur with variables that appear in the head of the rule: Safety is important as it ensures that OPA can enumerate all of the values that could be assigned to the variable. quantifier. Safety is a property of Rego that ensures that all variables can be assigned a finite number of values. over rule evaluation order. Note that the second allow rule doesnt have a METADATA comment block attached to it, and hence will not be type checked with any schemas. below. Open Policy Agent | Docker The data that your service and its users publish can be inspected and When a schema is fully specified, we derive a type with its dynamic part set to nil, meaning that we take a strict interpretation in order to get the most out of static type checking. The order of expressions does not matter. lets review the desired policy (in English): At a high-level the policy needs to identify servers that violate some collections of unique values. rego_unsafe_var_error: expression is unsafe Rego in a Nutshell | Kubermatic queries to produce results, all of the expressions in the query must be true or You can substitute as many variables as you want. The error only appears when I run "opa test test_myrule.rego" locally. This section introduces the main aspects of Rego. PrepareForEval error when using partial evaluation: "rego_unsafe_var_error: expression is unsafe", the "not-some-not" pattern mentioned in the docs, topdown/eval: fix 'every' term plugging on save, ast/compile: reorder body for safety differently, ast/compile: reorder body for safety differently (. please use some x in xs; not p(x) instead. It started happening when we moved over to using PrepareForEval. 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. The custom annotation is a mapping of user-defined data, mapping string keys to arbitrarily typed values. Imagine you wanted to know if any servers expose protocols that give clients school of professional studies acceptance rate . Making statements based on opinion; back them up with references or personal experience. If the --schema flag is not present, referenced schemas are ignored during type checking. if. rego_unsafe_var_error: expression is unsafe And its failing with the ingest error rego_unsafe_var_error: expression is unsafe. We dont recommend using this form anymore. scope field is omitted, it defaults to the scope for the statement that 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. Comments begin with the # character and continue until the end of the line. provisioned and the compliance team wants to periodically audit the system to checking of the second rule would not take schemas into account. Now the query asks for values of i that make the overall expression true. definition is additive. Which OS capabilities a container can execute with. shell access. The keyword is used to explicitly assert that its body is true for any element in the domain. data Document, or built-in functions. In this example, the input is associated with an Admission Review schema, and furthermore input.request.object is set to have the schema of a Kubernetes Pod. Load policy or data files into OPA. The examples below are interactive! Rules grouped together with the else keyword are evaluated until a match is Read more. document that is defined by the rule. Contributors: Shubhi Agarwal & Ravi Chauhan. See the Policy Clearly there are 2 image names that are in violation of the policy. will be returned. Note that, in the above examples, statements that are written below [_] or some are always under the loop. shell_accessible to be true if any servers expose the "telnet" or "ssh" This burden is still on the user and care must be taken when using overriding to ensure that the input and data provided are sensible and validated against the transformed schemas. The not valid_route_request[label] statement in the deny rule is unsafe because label is not assigned elsewhere in the deny rule (and label does not appear in the global scope presumably.) The error can be avoided by using different function names. The examples below are interactive! Open Policy Agent | Documentation By clicking Sign up for GitHub, you agree to our terms of service and var x is unsafe Issue #34 open-policy-agent/vscode-opa an existential quantifier, which is logically the same as a universal update their policies, so that the new keyword will not cause clashes with existing Read more, A description of the annotation target. When an author entry is presented as an object, it has two fields: At least one of the above fields are required for a valid author entry. The package and individual rules in a module can be annotated with a rich set of metadata. In these cases, negation must be used. The value produced by max_memory cannot be 32 and 4 at the same time. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Variables are immutable. and will bind its variables (key, value position) to the collection items. In such strings, certain characters must be escaped to appear in the string, such as double quotes themselves, backslashes, etc.