Gosec : Golang Security Checker To Inspects Source Code

Gosec is a inspects source code for security problems by scanning the Go AST. Licensed under the Apache License, Version 2.0 (the “License”). You may not use this file except in compliance with the License. You may obtain a copy of the License here.

Install

CI Installation

# binary will be $GOPATH/bin/gosec
curl -sfL https://raw.githubusercontent.com/securego/gosec/master/install.sh | sh -s — -b $GOPATH/bin vX.Y.Z

# or install it into ./bin/
curl -sfL https://raw.githubusercontent.com/securego/gosec/master/install.sh | sh -s vX.Y.Z

# In alpine linux (as it does not come with curl by default)
wget -O – -q https://raw.githubusercontent.com/securego/gosec/master/install.sh | sh -s vX.Y.Z

# If you want to use the checksums provided on the “Releases” page
#then you will have to download a tar.gz file for your operating system instead of a binary file
wget https://github.com/securego/gosec/releases/download/vX.Y.Z/gosec_vX.Y.Z_OS.tar.gz

#The file will be in the current folder where you run the command
#and you can check the checksum like this
echo ” gosec_vX.Y.Z_OS.tar.gz” | sha256sum -c –
gosec –help

Local Installation

go get github.com/securego/gosec/cmd/gosec

Usage

Gosec can be configured to only run a subset of rules, to exclude certain file paths, and produce reports in different formats. By default all rules will be run against the supplied input files. To recursively scan from the current directory you can supply ./... as the input argument.

Available Rules

• G101: Look for hard coded credentials
• G102: Bind to all interfaces
• G103: Audit the use of unsafe block
• G104: Audit errors not checked
• G106: Audit the use of ssh.InsecureIgnoreHostKey
• G107: Url provided to HTTP request as taint input
• G108: Profiling endpoint automatically exposed on /debug/pprof
• G201: SQL query construction using format string
• G202: SQL query construction using string concatenation
• G203: Use of unescaped data in HTML templates
• G204: Audit use of command execution
• G301: Poor file permissions used when creating a directory
• G302: Poor file permissions used with chmod
• G303: Creating tempfile using a predictable path
• G304: File path provided as taint input
• G305: File traversal when extracting zip archive
• G401: Detect the usage of DES, RC4, MD5 or SHA1
• G402: Look for bad TLS connection settings
• G403: Ensure minimum RSA key length of 2048 bits
• G404: Insecure random number source (rand)
• G501: Import blacklist: crypto/md5
• G502: Import blacklist: crypto/des
• G503: Import blacklist: crypto/rc4
• G504: Import blacklist: net/http/cgi
• G505: Import blacklist: crypto/sha1

Retired Rules

• G105: Audit the use of math/big.Int.Exp – CVE is fixed

Selecting Rules

By default, gosec will run all rules against the supplied file paths. It is however possible to select a subset of rules to run via the -include= flag, or to specify a set of rules to explicitly exclude using the -exclude= flag.

# Run a specific set of rules
$ gosec -include=G101,G203,G401 ./…

# Run everything except for rule G303
$ gosec -exclude=G303 ./…

CWE Mapping

Every issue detected by gosec is mapped to a CWE (Common Weakness Enumeration) which describes in more generic terms the vulnerability. The exact mapping can be found here.

Configuration

A number of global settings can be provided in a configuration file as follows:

{
“global”: {
“nosec”: “enabled”,
“audit”: “enabled”
}
}

• nosec: this setting will overwrite all #nosec directives defined throughout the code base
• audit: runs in audit mode which enables addition checks that for normal code analysis might be too nosy

# Run with a global configuration file
$ gosec -conf config.json .

Also some rules accept configuration. For instance on rule G104, it is possible to define packages along with a list of functions which will be skipped when auditing the not checked errors:

{
“G104”: {
“io/ioutil”: [“WriteFile”]
}
}

Dependencies

gosec will fetch automatically the dependencies of the code which is being analyzed when go module is turned on (e.g. GO111MODULE=on). If this is not the case, the dependencies need to be explicitly downloaded by running the go get -d command before the scan.

Excluding Test Files & Folders

gosec will ignore test files across all packages and any dependencies in your vendor directory.

The scanning of test files can be enabled with the following flag:

gosec -tests ./…

Also additional folders can be excluded as follows:

gosec -exclude-dir=rules -exclude-dir=cmd ./…

Annotating code

As with all automated detection tools, there will be cases of false positives. In cases where gosec reports a failure that has been manually verified as being safe, it is possible to annotate the code with a #nosec comment.

The annotation causes gosec to stop processing any further nodes within the AST so can apply to a whole block or more granularly to a single expression.

import “md5” // #nosec

func main(){
/* #nosec */
if x > y {
h := md5.New() // this will also be ignored
}
}

When a specific false positive has been identified and verified as safe, you may wish to suppress only that single rule (or a specific set of rules) within a section of code, while continuing to scan for other problems. To do this, you can list the rule(s) to be suppressed within the #nosec annotation, e.g: /* #nosec G401 */ or // #nosec G201 G202 G203

In some cases you may also want to revisit places where #nosec annotations have been used. To run the scanner and ignore any #nosec annotations you can do the following:

gosec -nosec=true ./…

Build Tags

gosec is able to pass your Go build tags to the analyzer. They can be provided as a comma separated list as follows:

gosec -tag debug,ignore ./…

Output Formats

gosec currently supports text, json, yaml, csv, sonarqube and JUnit XML output formats. By default results will be reported to stdout, but can also be written to an output file. The output format is controlled by the ‘-fmt’ flag, and the output file is controlled by the ‘-out’ flag as follows:

# Write output in json format to results.json
$ gosec -fmt=json -out=results.json *.go

Development

Build

make

Tests

make test

Release Build

Make sure you have installed the goreleaser tool and then you can release gosec as follows:

git tag v1.0.0
export GITHUB_TOKEN=<YOUR GITHUB TOKEN>
make release

The released version of the tool is available in the dist folder. The build information should be displayed in the usage text.

./dist/darwin_amd64/gosec -h
gosec – Golang security checker

gosec analyzes Go source code to look for common programming mistakes that

VERSION: 1.0.0
GIT TAG: v1.0.0
BUILD DATE: 2018-04-27T12:41:38Z

Note that all released archives are also uploaded to GitHub.

Docker Image

You can build the docker image as follows:

make image

You can run the gosec tool in a container against your local Go project. You just have to mount the project into a volume as follows:

docker run -it -v <YOUR PROJECT PATH>/<PROJECT>:/<PROJECT> securego/gosec /<PROJECT>/…

Generate TLS rule

The configuration of TLS rule can be generated from Mozilla’s TLS ciphers recommendation.

First you need to install the generator tool:

go get github.com/securego/gosec/cmd/tlsconfig/…

You can invoke now the go generate in the root of the project:

go generate ./…

This will generate the rules/tls_config.go file which will contain the current ciphers recommendation from Mozilla.