Add lambda wrapper for cfn guard (#12)

* Add lambda wrapper for cfn guard - Add function to valdiate input json data and rules - Add function to return result in json format - Create cfn guard lib - Create directory for cfn-guard-lambda, call cfn guard lib from the lambda wrapper - Add test directory for functional tests
aws-cloudformation · Mar 8, 2021 · 3189828 · 3189828
1 parent b6fc6c9
commit 3189828
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diff --git a/Cargo.toml b/Cargo.toml
@@ -1,5 +1,6 @@
 [workspace]
 
 members = [
-    "cfn-guard"
+    "cfn-guard",
+    "cfn-guard-lambda"
 ]
diff --git a/cfn-guard-lambda/Cargo.toml b/cfn-guard-lambda/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "cfn-guard-lambda"
+version = "1.0.0"
+authors = ["Omkar Hegde <omkhegde@amazon.com>", "aws-cloudformation-developers <aws-cloudformation-developers@amazon.com>"]
+description = "Lambda version of cfn-guard. Checks AWS CloudFormation templates for policy compliance using a simple, policy-as-code, declarative syntax"
+license = "Apache-2.0"
+edition = "2018"
+
+[dependencies]
+lambda_runtime = "0.2.1"
+serde = "1.0.92"
+serde_derive = "1.0.92"
+simple-error = "0.2.0"
+simple_logger = "1.3.0"
+log = "0.4.6"
+cfn-guard = { version = "0.10.0", path = "../cfn-guard" }
diff --git a/cfn-guard-lambda/src/main.rs b/cfn-guard-lambda/src/main.rs
@@ -0,0 +1,44 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+use std::error::Error;
+
+use cfn_guard;
+use lambda_runtime::{error::HandlerError, lambda, Context};
+use log::{self, info};
+use serde_derive::{Deserialize, Serialize};
+use simple_logger;
+
+#[derive(Deserialize, Debug)]
+struct CustomEvent {
+    #[serde(rename = "data")]
+    data: String,
+    #[serde(rename = "rules")]
+    rules: String,
+}
+
+#[derive(Serialize)]
+struct CustomOutput {
+    message: String,
+}
+
+fn main() -> Result<(), Box<dyn Error>> {
+    simple_logger::init_with_level(log::Level::Info)?;
+    lambda!(call_cfn_guard);
+
+    Ok(())
+}
+
+fn call_cfn_guard(e: CustomEvent, _c: Context) -> Result<CustomOutput, HandlerError> {
+    info!("Template is [{}]", &e.data);
+    info!("Rule Set is [{}]", &e.rules);
+    let (result) = match cfn_guard::run_checks(&e.data, &e.rules)
+    {
+        Ok(t) => t,
+        Err(e) => (e.to_string()),
+    };
+
+    Ok(CustomOutput {
+        message: result,
+    })
+}
diff --git a/cfn-guard/Cargo.toml b/cfn-guard/Cargo.toml
@@ -5,6 +5,9 @@ authors = ["diwakar <diwakar@amazon.com>"]
 edition = "2018"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[lib]
+name = "cfn_guard"
+path = "src/lib.rs"
 
 [dependencies]
 nom = "5.1.2"

diff --git a/cfn-guard/src/commands/helper.rs b/cfn-guard/src/commands/helper.rs
@@ -0,0 +1,40 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::rules::errors::{Error, ErrorKind};
+use crate::rules::evaluate::RootScope;
+use crate::rules::path_value::PathAwareValue;
+use crate::commands::tracker::StackTracker;
+use crate::commands::validate::ConsoleReporter;
+use crate::rules::{Evaluate, Result};
+use std::convert::TryFrom;
+
+pub fn validate_and_return_json(
+    data: &str,
+    rules: &str,
+) -> Result<String> {
+    let mut input_data = match serde_json::from_str::<serde_json::Value>(&data) {
+       Ok(value) => PathAwareValue::try_from(value),
+       Err(e) => return Err(Error::new(ErrorKind::ParseError(e.to_string()))),
+    };
+
+    let span = crate::rules::parser::Span::new_extra(&rules, "lambda");
+
+    match crate::rules::parser::rules_file(span) {
+
+        Ok(rules) => {
+            match input_data {
+                Ok(root) => {
+                    let root_context = RootScope::new(&rules, &root);
+                    let stacker = StackTracker::new(&root_context);
+                    let reporter = ConsoleReporter::new(stacker, true, true);
+                    rules.evaluate(&root, &reporter)?;
+                    let json_result = reporter.get_result_json();
+                    return Ok((json_result));
+                }
+                Err(e) => return Err(e),
+            }
+        }
+        Err(e) =>  return Err(Error::new(ErrorKind::ParseError(e.to_string()))),
+    }
+}
diff --git a/cfn-guard/src/commands/mod.rs b/cfn-guard/src/commands/mod.rs
@@ -1,10 +1,10 @@
 pub(crate) mod files;
 pub(crate) mod validate;
 pub(crate) mod test;
+pub(crate) mod helper;
 pub(crate) mod parse_tree;
 
 mod tracker;
-mod helper;
 
 //
 // Constants for arguments

diff --git a/cfn-guard/src/commands/tracker.rs b/cfn-guard/src/commands/tracker.rs
@@ -28,7 +28,7 @@ impl StatusContext {
     }
 }
 
-pub(super) struct StackTracker<'r> {
+pub(crate) struct StackTracker<'r> {
     root_context: &'r dyn EvaluationContext,
     stack: std::cell::RefCell<Vec<StatusContext>>,
 }

diff --git a/cfn-guard/src/commands/validate.rs b/cfn-guard/src/commands/validate.rs
@@ -96,8 +96,38 @@ impl Command for Validate {
     }
 }
 
+pub fn validate_and_return_json(
+    data: &str,
+    rules: &str,
+) -> Result<String> {
+    let mut input_data = match serde_json::from_str::<serde_json::Value>(&data) {
+       Ok(value) => PathAwareValue::try_from(value),
+       Err(e) => return Err(Error::new(ErrorKind::ParseError(e.to_string()))),
+    };
+
+    let span = crate::rules::parser::Span::new_extra(&rules, "lambda");
+
+    match crate::rules::parser::rules_file(span) {
+
+        Ok(rules) => {
+            match input_data {
+                Ok(root) => {
+                    let root_context = RootScope::new(&rules, &root);
+                    let stacker = StackTracker::new(&root_context);
+                    let reporter = ConsoleReporter::new(stacker, true, true);
+                    rules.evaluate(&root, &reporter)?;
+                    let json_result = reporter.get_result_json();
+                    return Ok((json_result));
+                }
+                Err(e) => return Err(e),
+            }
+        }
+        Err(e) =>  return Err(Error::new(ErrorKind::ParseError(e.to_string()))),
+    }
+}
+
 #[derive(Debug)]
-struct ConsoleReporter<'r> {
+pub(crate) struct ConsoleReporter<'r> {
     root_context: StackTracker<'r>,
     verbose: bool,
     print_json: bool
@@ -159,14 +189,20 @@ pub(super) fn print_context(cxt: &StatusContext, depth: usize) {
 }
 
 impl<'r, 'loc> ConsoleReporter<'r> {
-    fn new(root: StackTracker<'r>, verbose: bool, print_json: bool) -> Self {
+    pub(crate) fn new(root: StackTracker<'r>, verbose: bool, print_json: bool) -> Self {
         ConsoleReporter {
             root_context: root,
             verbose,
             print_json,
         }
     }
 
+    pub fn get_result_json(self) -> String {
+        let stack = self.root_context.stack();
+        let top = stack.first().unwrap();
+        return format!("{}", serde_json::to_string_pretty(&top.children).unwrap());
+    }
+
     fn report(self) {
         let stack = self.root_context.stack();
         let top = stack.first().unwrap();

diff --git a/cfn-guard/src/lib.rs b/cfn-guard/src/lib.rs
@@ -0,0 +1,13 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+mod rules;
+mod commands;
+mod command;
+
+pub extern "C" fn run_checks(
+    data: &str,
+    rules: &str,
+) -> crate::rules::Result<String> {
+    return  crate::commands::helper::validate_and_return_json(&data, &rules);
+}
diff --git a/cfn-guard/tests/functional.rs b/cfn-guard/tests/functional.rs
@@ -0,0 +1,103 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+use cfn_guard;
+
+mod tests {
+    use super::*;
+     #[test]
+        fn test_run_check() {
+            let mut data = String::from(
+                r#"
+                    {
+                        "Resources": {
+                            "VPC" : {
+                                "Type" : "AWS::ApiGateway::Method",
+                                "Properties" : {
+                                    "AuthorizationType" : "10.0.0.0/24"
+                                }
+                            }
+                        }
+                    }
+                "#,
+            );
+            let rule = "AWS::ApiGateway::Method { Properties.AuthorizationType == \"NONE\"}";
+            let mut expected = String::from(
+                r#"
+                    [
+                      {
+                        "eval_type": "Rule",
+                        "context": "default",
+                        "from": null,
+                        "to": null,
+                        "status": "FAIL",
+                        "children": [
+                          {
+                            "eval_type": "Type",
+                            "context": "AWS::ApiGateway::Method",
+                            "from": null,
+                            "to": null,
+                            "status": "FAIL",
+                            "children": [
+                              {
+                                "eval_type": "Filter",
+                                "context": "Path=/Resources/VPC,Type=MapElement",
+                                "from": null,
+                                "to": null,
+                                "status": "PASS",
+                                "children": [
+                                  {
+                                    "eval_type": "Clause",
+                                    "context": "GuardAccessClause[ check = Type  EQUALS String(\"AWS::ApiGateway::Method\"), loc = Location[file=#1@14] ]",
+                                    "from": null,
+                                    "to": null,
+                                    "status": "PASS",
+                                    "children": []
+                                  }
+                                ]
+                              },
+                              {
+                                "eval_type": "Type",
+                                "context": "AWS::ApiGateway::Method#0(/Resources/VPC)",
+                                "from": null,
+                                "to": null,
+                                "status": "FAIL",
+                                "children": [
+                                  {
+                                    "eval_type": "Clause",
+                                    "context": "GuardAccessClause[ check = Properties.AuthorizationType  EQUALS String(\"NONE\"), loc = Location[file=lambda#1@27] ]",
+                                    "from": {
+                                      "String": [
+                                        "/Resources/VPC/Properties/AuthorizationType",
+                                        "10.0.0.0/24"
+                                      ]
+                                    },
+                                    "to": {
+                                      "String": [
+                                        "lambda/1/27/Clause/",
+                                        "NONE"
+                                      ]
+                                    },
+                                    "status": "FAIL",
+                                    "children": []
+                                  }
+                                ]
+                              }
+                            ]
+                          }
+                        ]
+                      }
+                    ]
+                "#,
+                );
+
+            // Remove white spaces from expected and calculated result for easy comparison.
+            expected.retain(|c| !c.is_whitespace());
+
+            let mut serialized =   cfn_guard::run_checks(&data, &rule).unwrap();
+            serialized.retain(|c| !c.is_whitespace());
+
+            assert_eq!(expected, serialized);
+        }
+
+}