docs(go): add 1.17 info (#765)
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Justin Perez
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@ -12,35 +12,268 @@ Go detection depends on the following to successfully run:
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- Go v1.11+.
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Full dependency graph generation is supported if Go v1.11+ is present on the build agent.
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If no Go v1.11+ is present, fallback detection strategy is performed.
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Full dependency graph generation is supported if Go v1.11+ is present
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on the build agent. If no Go v1.11+ is present, fallback detection
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strategy is performed.
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Go detection is performed by parsing output from executing [go list -m -json all](1). To generate the graph, the command [go mod graph](2) is executed, this only adds edges between the components that were already registered by `go list`.
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Go detection is performed by parsing output from executing [go list -m
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-json all](1). To generate the graph, the command [go mod graph](2) is
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executed, this only adds edges between the components that were
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already registered by `go list`.
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## Fallback Detection strategy
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Go detection is performed by parsing any `go.mod` or `go.sum` found under the scan directory.
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### `go.mod` before go 1.17
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Go detection is performed by parsing any `go.mod` or `go.sum` found
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under the scan directory.
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Only root dependency information is generated instead of full graph.
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I.e. tags the top level component or explicit dependency a given transitive dependency was brought by.
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Given a dependency tree A -> B -> C, C's root dependency is A.
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I.e. tags the top level component or explicit dependency a given
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transitive dependency was brought by. Given a dependency tree A -> B
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-> C, C's root dependency is A.
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**To force fallback detection strategy, create set environment variable `DisableGoCliScan=true`.**
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### `go.mod` after 1.17
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Go detection is performed by only scanning the `go.mod` files. This
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reduces over reporting dependencies. The `go.mod` file contains all
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dependencies, including transitive ones. [^3]
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Similarly, no graph is generated.
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**To force fallback detection strategy, create set environment
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variable `DisableGoCliScan=true`.**
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## Known limitations
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- If the default strategy is used and go modules are not present in the system before the detector is executed, the go cli will fetch all modules to generate the dependency graph. This will incur additional detector time execution.
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- If the default strategy is used and go modules are not present in
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the system before the detector is executed, the go cli will fetch all
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modules to generate the dependency graph. This will incur additional
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detector time execution.
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- Dev dependency tagging is not supported.
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- Go detection will fallback if no Go v1.11+ is present.
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- Due to the nature of `go.sum` containing references for all dependencies, including historical, no-longer-needed dependencies; the fallback strategy can result in over detection.
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Executing [go mod tidy](https://go.dev/ref/mod#go-mod-tidy) before detection via the fallback strategy is encouraged.
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- (Prior to Go 1.17) Due to the nature of `go.sum` containing
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references for all dependencies, including historical,
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no-longer-needed dependencies; the fallback strategy can result in
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over detection. Executing [go mod
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tidy](https://go.dev/ref/mod#go-mod-tidy) before detection via the
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fallback strategy is encouraged.
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- Some legacy dependencies may report stale transitive dependencies in their manifests, in this case you can remove them safely from your binaries by using [exclude directive](https://go.dev/doc/modules/gomod-ref#exclude).
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- Some legacy dependencies may report stale transitive dependencies in
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their manifests, in this case you can remove them safely from your
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binaries by using [exclude
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directive](https://go.dev/doc/modules/gomod-ref#exclude).
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## Environment Variables
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If the environment variable `DisableGoCliScan` is set to `true`, the Go detector parses `go.mod` and `go.sum` to discover dependencies. otherwise, it executes default strategy.
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If the environment variable `DisableGoCliScan` is set to `true`, the
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Go detector parses `go.mod` and `go.sum` to discover dependencies.
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otherwise, it executes default strategy.
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[1]: https://go.dev/ref/mod#go-list-m
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## Go Overview
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### `go.mod` and `go.sum` Files
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In the Go programming language, `go.mod` and `go.sum` files play a
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vital role in managing dependencies and ensuring the reproducibility
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and security of a Go project. These files are central to Go's module
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system, introduced in Go version 1.11, which revolutionized how Go
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manages external packages and dependencies.
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### `go.mod` File
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The `go.mod` file, short for "module file," is a fundamental component
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of Go's module system.[^4] It serves several crucial purposes:
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1. **Module Definition**: The `go.mod` file defines the module name,
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which uniquely identifies the project. The module name typically
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follows the format of a version control repository URL or a custom
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path, such as `example.com/myproject`.
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2. **Dependency Declaration**: Inside the `go.mod` file, you declare
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the specific versions of dependencies your project relies on.
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Dependencies are listed with their module paths and version
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constraints.
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```
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go module example.com/myproject
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go 1.17
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require (
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github.com/somepackage v1.2.3 golang.org/x/someotherpackage v0.4.0
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)
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```
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Here, `github.com/somepackage` and `golang.org/x/someotherpackage`
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are declared as project dependencies with specific version
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constraints.
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3. **Semantic Versioning**: Go uses Semantic Versioning (Semver) to
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specify version constraints for dependencies. You can specify
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constraints such as `v1.2.3` (exact version) or `>=1.2.0, <2.0.0`
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(range of versions).
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4. **Dependency Resolution**: When you build your project or import
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new dependencies, Go uses the `go.mod` file to resolve and download
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the exact versions of dependencies that satisfy the specified
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constraints.
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5. **Dependency Graph**: The `go.mod` file implicitly constructs a
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dependency graph of your project's dependencies, allowing Go to
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ensure that all dependencies are compatible and can be built together.
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### `go.sum` File
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The `go.sum` file, short for "checksum file," is used for ensuring the
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integrity and security of dependencies. It contains checksums
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(cryptographic hashes) of specific versions of packages listed in the
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`go.mod` file.[^5] The `go.sum` file serves the following purposes:
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1. **Cryptographic Verification**: When Go downloads a package
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specified in the `go.mod` file, it verifies the downloaded
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package's integrity by comparing its checksum with the checksum
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recorded in the `go.sum` file. If they don't match, it signals a
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potential security breach or data corruption.
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2. **Dependency Pinning**: The `go.sum` file pins the exact versions
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of dependencies used in the project. It ensures that the same
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package versions are consistently used across different builds and
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development environments, which aids in reproducibility.
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3. **Security**: By including checksums, the `go.sum` file helps
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protect against tampering with packages during transit or in case
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of compromised repositories. It adds a layer of trust in the packages
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being used.
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Here's a simplified example of entries in a `go.sum` file:
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```
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github.com/somepackage v1.2.3 h1:jh2u3r9z0wokljwesdczryhtnu1xf6wl4h7h2us9rj0=
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github.com/anotherpackage v0.4.0 h1:rn2iw0z7liy6d87dwygfawxqvx86jxd4m8hkw6yaj88=
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```
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Each line contains the package path, version, and a cryptographic hash
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of the package contents.
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#### Relevance in Dependency Scanning
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1. **Dependency Resolution**: Dependency scanners use the information
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in `go.mod` to understand which packages and versions a Go project
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depends on.
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2. **Security and Trust**: The `go.sum` file ensures that dependencies
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are downloaded securely and have not been tampered with during
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transit.
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3. **Build Reproducibility**: `go.mod` and `go.sum` files contribute
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to build reproducibility by pinning exact versions of dependencies,
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making it possible to recreate the same build environment
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consistently.
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### Detection Strategy
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The Go Component Detector follows a strategy that involves the
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following key steps:
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1. **File Discovery**: The detector searches for go.mod and go.sum files
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within the project directory.
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2. **Filtering go.sum Files**: The detector filters out go.sum files when
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there is no adjacent go.mod file or when the go.mod file specifies
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a Go version lower than 1.17. This filtering reduces the risk of
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over-reporting components. More on this later.
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3. **Go CLI Scanning (Optional)**: If the Go CLI (go) is available and not
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manually disabled, the detector attempts to use it to scan the
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project for dependencies and build a dependency graph. This step can
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significantly improve detection speed.
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4. **Fallback Detection**: If Go CLI scanning is not possible or not
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successful, the detector falls back to parsing go.mod and go.sum
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files directly to identify components.
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5. **Parsing go.mod File**: The detector parses the go.mod file to
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identify direct and transitive dependencies, recording their names
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and versions.
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6. **Parsing go.sum File**: The detector parses the go.sum file, recording
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information about dependencies, including their names, versions,
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and hashes.
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7. **Dependency Graph Construction**: If Go CLI scanning was successful,
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the detector constructs a dependency graph based on the information
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gathered. This graph helps identify relationships between components.
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8. **Recording Components**: Throughout the detection process, the
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detector records identified components and their relationships.
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9. **Environment Variable Check**: The detector checks for an environment
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variable (DisableGoCliScan) to determine whether Go CLI scanning
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should be disabled.
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The logic for checking if the Go version present in the `go.mod` file
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is greater than or equal to 1.17 is relevant because it determines
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whether the `go.sum` file should be processed for detection.
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This check is essential because Go introduced significant changes in
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how it handles dependencies and the `go.sum` file in Go version 1.17,
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which have implications for dependency scanning.
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### Go Module Changes in Go 1.17
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Prior to Go 1.17, the `go.mod` file primarily contained information
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about direct dependencies, but it didn't include information about
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transitive (indirect) dependencies. This made it challenging to
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accurately detect and manage all dependencies in a project.
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In Go 1.17 and later, Go introduced an important change: the `go.mod`
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file now includes information about both direct and transitive
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dependencies. This improvement enhances the clarity and completeness
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of dependency information within the `go.mod` file.
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#### Relevance of the Go Version Check
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1. **Accuracy of Dependency Detection**: Checking the Go version in
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the `go.mod` file allows the Go Component Detector to determine
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whether the project is using the enhanced module system introduced in
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Go 1.17. If the Go version is 1.17 or higher, it indicates that the
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`go.mod` file contains information about transitive dependencies.
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Processing this updated `go.mod` file provides a more accurate and
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comprehensive view of the project's dependencies.
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2. **Avoiding Over-Reporting**: In projects using Go 1.17 and later,
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transitive dependencies are already listed in the `go.mod` file,
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and processing the corresponding `go.sum` file could lead to
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over-reporting components. By not processing the `go.sum` file when
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it's not necessary (i.e., when the `go.mod` file includes transitive
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dependencies), the detector avoids redundant or incorrect component
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detection.
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3. **Minimizing Noise**: Over-reporting components can result in
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unnecessary noise in the scan results.
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## Detection Validation Strategy
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The changes in the Go detector were validated by:
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1. **Unit tests**: Sample `go.mod` and `go.sum` files were created
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and placed as unit tests. Other unit tests for go version less than
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1.17 were still maintained to ensure there were no regressions.
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2. **Local testing**: Real `go.mod` and `go.sum` from the go CLI
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were created from a real test codebase and verified manually.
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The main change for the go detector was not in the parsing of the
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go.mod files, but rather simply filtering `go.sum` files if an
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adjacent `go.mod` file specified a version higher than 1.17.
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[1]: https://go.dev/ref/mod#go-list-m
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[2]: https://go.dev/ref/mod#go-mod-graph
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[3]: https://go.dev/doc/modules/gomod-ref#go-notes
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[4]: https://go.dev/doc/modules/gomod-ref
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[5]: https://go.dev/ref/mod#go-sum-files
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