Validate base branches in DefaultCommandRunner

Fixes #1539

The branch matcher feature has been introduced in #1383, but the current
implementation was broken and doesn't work at all (#1539).

If my understanding is correct, there are two problems:

(1) The `GlobalCfg` has a default `Repo` instance which always matches
any repositries and branches. Therefore the branch matcher never be
functional.
(2) Validating base branches in
`DefaultPreWorkflowHooksCommandRunner.RunPreHooks()` implicitly assumed
that users customize `pre_workflow_hooks`, but the assumption isn't
always true because it defaults to empty.

For (1), I added a new method `MatchingRepo()` to `GlobalCfg` to check
`BranchMatches()` for a single `Repo` instance.

For (2), I moved validating branch to
`DefaultCommandRunner.validateCtxAndComment()`. Since the method has
already validated meta data of pull request, I think it's suitable place
to check base branches, but please let me know if there is anywhere more
suitable.

server/controllers/events/events_controller_e2e_test.go

@@ -883,6 +883,7 @@ func setupE2E(t *testing.T, repoDir string) (events_controllers.VCSEventsControl
 		GithubPullGetter:              e2eGithubGetter,
 		GitlabMergeRequestGetter:      e2eGitlabGetter,
 		Logger:                        logger,
+		GlobalCfg:                     globalCfg,
 		AllowForkPRs:                  allowForkPRs,
 		AllowForkPRsFlag:              "allow-fork-prs",
 		CommentCommandRunnerByCmd:     commentCommandRunnerByCmd,

server/events/command_runner.go

@@ -22,6 +22,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/runatlantis/atlantis/server/events/models"
 	"github.com/runatlantis/atlantis/server/events/vcs"
+	"github.com/runatlantis/atlantis/server/events/yaml/valid"
 	"github.com/runatlantis/atlantis/server/logging"
 	"github.com/runatlantis/atlantis/server/recovery"
 	gitlab "github.com/xanzy/go-gitlab"
@@ -95,6 +96,7 @@ type DefaultCommandRunner struct {
 	DisableAutoplan          bool
 	EventParser              EventParsing
 	Logger                   logging.SimpleLogging
+	GlobalCfg                valid.GlobalCfg
 	// AllowForkPRs controls whether we operate on pull requests from forks.
 	AllowForkPRs bool
 	// ParallelPoolSize controls the size of the wait group used to run
@@ -320,6 +322,13 @@ func (c *DefaultCommandRunner) validateCtxAndComment(ctx *CommandContext) bool {
 		}
 		return false
 	}
+
+	repo := c.GlobalCfg.MatchingRepo(ctx.Pull.BaseRepo.ID())
+	if !repo.BranchMatches(ctx.Pull.BaseBranch) {
+		ctx.Log.Info("command was run on a pull request which doesn't match base branches")
+		// just ignore it to allow us to use any git workflows without malicious intentions.
+		return false
+	}
 	return true
 }
 

server/events/command_runner_test.go

@@ -16,6 +16,7 @@ package events_test
 import (
 	"errors"
 	"fmt"
+	"regexp"
 	"strings"
 	"testing"
 
@@ -182,6 +183,8 @@ func setup(t *testing.T) *vcsmocks.MockClient {
 
 	When(preWorkflowHooksCommandRunner.RunPreHooks(matchers.AnyPtrToEventsCommandContext())).ThenReturn(nil)
 
+	globalCfg := valid.NewGlobalCfgFromArgs(valid.GlobalCfgArgs{})
+
 	ch = events.DefaultCommandRunner{
 		VCSClient:                     vcsClient,
 		CommentCommandRunnerByCmd:     commentCommandRunnerByCmd,
@@ -190,6 +193,7 @@ func setup(t *testing.T) *vcsmocks.MockClient {
 		GitlabMergeRequestGetter:      gitlabGetter,
 		AzureDevopsPullGetter:         azuredevopsGetter,
 		Logger:                        logger,
+		GlobalCfg:                     globalCfg,
 		AllowForkPRs:                  false,
 		AllowForkPRsFlag:              "allow-fork-prs-flag",
 		Drainer:                       drainer,
@@ -404,6 +408,40 @@ func TestRunCommentCommand_ClosedPull(t *testing.T) {
 	vcsClient.VerifyWasCalledOnce().CreateComment(fixtures.GithubRepo, modelPull.Num, "Atlantis commands can't be run on closed pull requests", "")
 }
 
+func TestRunCommentCommand_MatchedBranch(t *testing.T) {
+	t.Log("if a command is run on a pull request which matches base branches run plan successfully")
+	vcsClient := setup(t)
+
+	ch.GlobalCfg.Repos = append(ch.GlobalCfg.Repos, valid.Repo{
+		IDRegex:     regexp.MustCompile(".*"),
+		BranchRegex: regexp.MustCompile("^main$"),
+	})
+	var pull github.PullRequest
+	modelPull := models.PullRequest{BaseRepo: fixtures.GithubRepo, BaseBranch: "main"}
+	When(githubGetter.GetPullRequest(fixtures.GithubRepo, fixtures.Pull.Num)).ThenReturn(&pull, nil)
+	When(eventParsing.ParseGithubPull(&pull)).ThenReturn(modelPull, modelPull.BaseRepo, fixtures.GithubRepo, nil)
+
+	ch.RunCommentCommand(fixtures.GithubRepo, nil, nil, fixtures.User, fixtures.Pull.Num, &events.CommentCommand{Name: models.PlanCommand})
+	vcsClient.VerifyWasCalledOnce().CreateComment(fixtures.GithubRepo, modelPull.Num, "Ran Plan for 0 projects:\n\n\n\n", "plan")
+}
+
+func TestRunCommentCommand_UnmatchedBranch(t *testing.T) {
+	t.Log("if a command is run on a pull request which doesn't match base branches do not comment with error")
+	vcsClient := setup(t)
+
+	ch.GlobalCfg.Repos = append(ch.GlobalCfg.Repos, valid.Repo{
+		IDRegex:     regexp.MustCompile(".*"),
+		BranchRegex: regexp.MustCompile("^main$"),
+	})
+	var pull github.PullRequest
+	modelPull := models.PullRequest{BaseRepo: fixtures.GithubRepo, BaseBranch: "foo"}
+	When(githubGetter.GetPullRequest(fixtures.GithubRepo, fixtures.Pull.Num)).ThenReturn(&pull, nil)
+	When(eventParsing.ParseGithubPull(&pull)).ThenReturn(modelPull, modelPull.BaseRepo, fixtures.GithubRepo, nil)
+
+	ch.RunCommentCommand(fixtures.GithubRepo, nil, nil, fixtures.User, fixtures.Pull.Num, &events.CommentCommand{Name: models.PlanCommand})
+	vcsClient.VerifyWasCalled(Never()).CreateComment(matchers.AnyModelsRepo(), AnyInt(), AnyString(), AnyString())
+}
+
 func TestRunUnlockCommand_VCSComment(t *testing.T) {
 	t.Log("if unlock PR command is run, atlantis should" +
 		" invoke the delete command and comment on PR accordingly")

server/events/pre_workflow_hooks_command_runner.go

@@ -34,7 +34,7 @@ func (w *DefaultPreWorkflowHooksCommandRunner) RunPreHooks(
 
 	preWorkflowHooks := make([]*valid.PreWorkflowHook, 0)
 	for _, repo := range w.GlobalCfg.Repos {
-		if repo.IDMatches(baseRepo.ID()) && repo.BranchMatches(pull.BaseBranch) && len(repo.PreWorkflowHooks) > 0 {
+		if repo.IDMatches(baseRepo.ID()) && len(repo.PreWorkflowHooks) > 0 {
 			preWorkflowHooks = append(preWorkflowHooks, repo.PreWorkflowHooks...)
 		}
 	}

server/events/yaml/valid/global_cfg.go

@@ -467,3 +467,15 @@ func (g GlobalCfg) getMatchingCfg(log logging.SimpleLogging, repoID string) (app
 	}
 	return
 }
+
+// MatchingRepo returns an instance of Repo which matches a given repoID.
+// If multiple repos match, return the last one for consistency with getMatchingCfg.
+func (g GlobalCfg) MatchingRepo(repoID string) *Repo {
+	for i := len(g.Repos) - 1; i >= 0; i-- {
+		repo := g.Repos[i]
+		if repo.IDMatches(repoID) {
+			return &repo
+		}
+	}
+	return nil
+}

server/events/yaml/valid/global_cfg_test.go

@@ -892,6 +892,69 @@ func TestRepo_BranchMatches(t *testing.T) {
 	Equals(t, false, (valid.Repo{BranchRegex: regexp.MustCompile("release")}).BranchMatches("main"))
 }
 
+func TestGlobalCfg_MatchingRepo(t *testing.T) {
+	defaultRepo := valid.Repo{
+		IDRegex:           regexp.MustCompile(".*"),
+		BranchRegex:       regexp.MustCompile(".*"),
+		ApplyRequirements: []string{},
+	}
+	repo1 := valid.Repo{
+		IDRegex:           regexp.MustCompile(".*"),
+		BranchRegex:       regexp.MustCompile("^main$"),
+		ApplyRequirements: []string{"approved"},
+	}
+	repo2 := valid.Repo{
+		ID:                "github.com/owner/repo",
+		BranchRegex:       regexp.MustCompile("^master$"),
+		ApplyRequirements: []string{"approved", "mergeable"},
+	}
+
+	cases := map[string]struct {
+		gCfg   valid.GlobalCfg
+		repoID string
+		exp    *valid.Repo
+	}{
+		"matches to default": {
+			gCfg: valid.GlobalCfg{
+				Repos: []valid.Repo{
+					defaultRepo,
+					repo2,
+				},
+			},
+			repoID: "foo",
+			exp:    &defaultRepo,
+		},
+		"matches to IDRegex": {
+			gCfg: valid.GlobalCfg{
+				Repos: []valid.Repo{
+					defaultRepo,
+					repo1,
+					repo2,
+				},
+			},
+			repoID: "foo",
+			exp:    &repo1,
+		},
+		"matches to ID": {
+			gCfg: valid.GlobalCfg{
+				Repos: []valid.Repo{
+					defaultRepo,
+					repo1,
+					repo2,
+				},
+			},
+			repoID: "github.com/owner/repo",
+			exp:    &repo2,
+		},
+	}
+
+	for name, c := range cases {
+		t.Run(name, func(t *testing.T) {
+			Equals(t, c.exp, c.gCfg.MatchingRepo(c.repoID))
+		})
+	}
+}
+
 // String is a helper routine that allocates a new string value
 // to store v and returns a pointer to it.
 func String(v string) *string { return &v }

server/server.go

@@ -599,6 +599,7 @@ func NewServer(userConfig UserConfig, config Config) (*Server, error) {
 		CommentCommandRunnerByCmd:     commentCommandRunnerByCmd,
 		EventParser:                   eventParser,
 		Logger:                        logger,
+		GlobalCfg:                     globalCfg,
 		AllowForkPRs:                  userConfig.AllowForkPRs,
 		AllowForkPRsFlag:              config.AllowForkPRsFlag,
 		SilenceForkPRErrors:           userConfig.SilenceForkPRErrors,