Sign merges, CRUD, Wiki and Repository initialisation with gpg key (#7631)

This PR fixes #7598 by providing a configurable way of signing commits across the Gitea instance. Per repository configurability and import/generation of trusted secure keys is not provided by this PR - from a security PoV that's probably impossible to do properly. Similarly web-signing, that is asking the user to sign something, is not implemented - this could be done at a later stage however.

## Features
- [x] If commit.gpgsign is set in .gitconfig sign commits and files created through repofiles. (merges should already have been signed.)
- [x] Verify commits signed with the default gpg as valid
- [x] Signer, Committer and Author can all be different
    - [x] Allow signer to be arbitrarily different - We still require the key to have an activated email on Gitea. A more complete implementation would be to use a keyserver and mark external-or-unactivated with an "unknown" trust level icon.
- [x] Add a signing-key.gpg endpoint to get the default gpg pub key if available
    - Rather than add a fake web-flow user I've added this as an endpoint on /api/v1/signing-key.gpg
    - [x] Try to match the default key with a user on gitea - this is done at verification time
- [x] Make things configurable?
    - app.ini configuration done
    - [x] when checking commits are signed need to check if they're actually verifiable too
- [x] Add documentation

I have decided that adjusting the docker to create a default gpg key is not the correct thing to do and therefore have not implemented this.

1 files changed, 252 insertions, 0 deletions

diff --git a/integrations/gpg_git_test.go b/integrations/gpg_git_test.go
new file mode 100644
index 0000000000..12f0a138c7
--- /dev/null
+++ b/integrations/gpg_git_test.go
@@ -0,0 +1,252 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package integrations
+
+import (
+	"encoding/base64"
+	"fmt"
+	"io/ioutil"
+	"net/url"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/process"
+	"code.gitea.io/gitea/modules/setting"
+	api "code.gitea.io/gitea/modules/structs"
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/crypto/openpgp"
+	"golang.org/x/crypto/openpgp/armor"
+)
+
+func TestGPGGit(t *testing.T) {
+	onGiteaRun(t, testGPGGit)
+}
+
+func testGPGGit(t *testing.T, u *url.URL) {
+	username := "user2"
+	baseAPITestContext := NewAPITestContext(t, username, "repo1")
+
+	u.Path = baseAPITestContext.GitPath()
+
+	// OK Set a new GPG home
+	tmpDir, err := ioutil.TempDir("", "temp-gpg")
+	assert.NoError(t, err)
+	defer os.RemoveAll(tmpDir)
+
+	err = os.Chmod(tmpDir, 0700)
+	assert.NoError(t, err)
+
+	oldGNUPGHome := os.Getenv("GNUPGHOME")
+	err = os.Setenv("GNUPGHOME", tmpDir)
+	assert.NoError(t, err)
+	defer os.Setenv("GNUPGHOME", oldGNUPGHome)
+
+	// Need to create a root key
+	rootKeyPair, err := createGPGKey(tmpDir, "gitea", "gitea@fake.local")
+	assert.NoError(t, err)
+
+	rootKeyID := rootKeyPair.PrimaryKey.KeyIdShortString()
+
+	oldKeyID := setting.Repository.Signing.SigningKey
+	oldName := setting.Repository.Signing.SigningName
+	oldEmail := setting.Repository.Signing.SigningEmail
+	defer func() {
+		setting.Repository.Signing.SigningKey = oldKeyID
+		setting.Repository.Signing.SigningName = oldName
+		setting.Repository.Signing.SigningEmail = oldEmail
+	}()
+
+	setting.Repository.Signing.SigningKey = rootKeyID
+	setting.Repository.Signing.SigningName = "gitea"
+	setting.Repository.Signing.SigningEmail = "gitea@fake.local"
+	user := models.AssertExistsAndLoadBean(t, &models.User{Name: username}).(*models.User)
+
+	t.Run("Unsigned-Initial", func(t *testing.T) {
+		PrintCurrentTest(t)
+		setting.Repository.Signing.InitialCommit = []string{"never"}
+		testCtx := NewAPITestContext(t, username, "initial-unsigned")
+		t.Run("CreateRepository", doAPICreateRepository(testCtx, false))
+		t.Run("CheckMasterBranchUnsigned", doAPIGetBranch(testCtx, "master", func(t *testing.T, branch api.Branch) {
+			assert.NotNil(t, branch.Commit)
+			assert.NotNil(t, branch.Commit.Verification)
+			assert.False(t, branch.Commit.Verification.Verified)
+			assert.Empty(t, branch.Commit.Verification.Signature)
+		}))
+		setting.Repository.Signing.CRUDActions = []string{"never"}
+		t.Run("CreateCRUDFile-Never", crudActionCreateFile(
+			t, testCtx, user, "master", "never", "unsigned-never.txt", func(t *testing.T, response api.FileResponse) {
+				assert.False(t, response.Verification.Verified)
+			}))
+		t.Run("CreateCRUDFile-Never", crudActionCreateFile(
+			t, testCtx, user, "never", "never2", "unsigned-never2.txt", func(t *testing.T, response api.FileResponse) {
+				assert.False(t, response.Verification.Verified)
+			}))
+		setting.Repository.Signing.CRUDActions = []string{"parentsigned"}
+		t.Run("CreateCRUDFile-ParentSigned", crudActionCreateFile(
+			t, testCtx, user, "master", "parentsigned", "signed-parent.txt", func(t *testing.T, response api.FileResponse) {
+				assert.False(t, response.Verification.Verified)
+			}))
+		t.Run("CreateCRUDFile-ParentSigned", crudActionCreateFile(
+			t, testCtx, user, "parentsigned", "parentsigned2", "signed-parent2.txt", func(t *testing.T, response api.FileResponse) {
+				assert.False(t, response.Verification.Verified)
+			}))
+		setting.Repository.Signing.CRUDActions = []string{"never"}
+		t.Run("CreateCRUDFile-Never", crudActionCreateFile(
+			t, testCtx, user, "parentsigned", "parentsigned-never", "unsigned-never2.txt", func(t *testing.T, response api.FileResponse) {
+				assert.False(t, response.Verification.Verified)
+			}))
+		setting.Repository.Signing.CRUDActions = []string{"always"}
+		t.Run("CreateCRUDFile-Always", crudActionCreateFile(
+			t, testCtx, user, "master", "always", "signed-always.txt", func(t *testing.T, response api.FileResponse) {
+				assert.True(t, response.Verification.Verified)
+				assert.Equal(t, "gitea@fake.local", response.Verification.Signer.Email)
+			}))
+		t.Run("CreateCRUDFile-ParentSigned-always", crudActionCreateFile(
+			t, testCtx, user, "parentsigned", "parentsigned-always", "signed-parent2.txt", func(t *testing.T, response api.FileResponse) {
+				assert.True(t, response.Verification.Verified)
+				assert.Equal(t, "gitea@fake.local", response.Verification.Signer.Email)
+			}))
+		setting.Repository.Signing.CRUDActions = []string{"parentsigned"}
+		t.Run("CreateCRUDFile-Always-ParentSigned", crudActionCreateFile(
+			t, testCtx, user, "always", "always-parentsigned", "signed-always-parentsigned.txt", func(t *testing.T, response api.FileResponse) {
+				assert.True(t, response.Verification.Verified)
+				assert.Equal(t, "gitea@fake.local", response.Verification.Signer.Email)
+			}))
+	})
+	t.Run("AlwaysSign-Initial", func(t *testing.T) {
+		PrintCurrentTest(t)
+		setting.Repository.Signing.InitialCommit = []string{"always"}
+		testCtx := NewAPITestContext(t, username, "initial-always")
+		t.Run("CreateRepository", doAPICreateRepository(testCtx, false))
+		t.Run("CheckMasterBranchSigned", doAPIGetBranch(testCtx, "master", func(t *testing.T, branch api.Branch) {
+			assert.NotNil(t, branch.Commit)
+			assert.NotNil(t, branch.Commit.Verification)
+			assert.True(t, branch.Commit.Verification.Verified)
+			assert.Equal(t, "gitea@fake.local", branch.Commit.Verification.Signer.Email)
+		}))
+		setting.Repository.Signing.CRUDActions = []string{"never"}
+		t.Run("CreateCRUDFile-Never", crudActionCreateFile(
+			t, testCtx, user, "master", "never", "unsigned-never.txt", func(t *testing.T, response api.FileResponse) {
+				assert.False(t, response.Verification.Verified)
+			}))
+		setting.Repository.Signing.CRUDActions = []string{"parentsigned"}
+		t.Run("CreateCRUDFile-ParentSigned", crudActionCreateFile(
+			t, testCtx, user, "master", "parentsigned", "signed-parent.txt", func(t *testing.T, response api.FileResponse) {
+				assert.True(t, response.Verification.Verified)
+				assert.Equal(t, "gitea@fake.local", response.Verification.Signer.Email)
+			}))
+		setting.Repository.Signing.CRUDActions = []string{"always"}
+		t.Run("CreateCRUDFile-Always", crudActionCreateFile(
+			t, testCtx, user, "master", "always", "signed-always.txt", func(t *testing.T, response api.FileResponse) {
+				assert.True(t, response.Verification.Verified)
+				assert.Equal(t, "gitea@fake.local", response.Verification.Signer.Email)
+			}))
+
+	})
+	t.Run("UnsignedMerging", func(t *testing.T) {
+		PrintCurrentTest(t)
+		testCtx := NewAPITestContext(t, username, "initial-unsigned")
+		var pr api.PullRequest
+		var err error
+		t.Run("CreatePullRequest", func(t *testing.T) {
+			pr, err = doAPICreatePullRequest(testCtx, testCtx.Username, testCtx.Reponame, "master", "never2")(t)
+			assert.NoError(t, err)
+		})
+		setting.Repository.Signing.Merges = []string{"commitssigned"}
+		t.Run("MergePR", doAPIMergePullRequest(testCtx, testCtx.Username, testCtx.Reponame, pr.Index))
+		t.Run("CheckMasterBranchUnsigned", doAPIGetBranch(testCtx, "master", func(t *testing.T, branch api.Branch) {
+			assert.NotNil(t, branch.Commit)
+			assert.NotNil(t, branch.Commit.Verification)
+			assert.False(t, branch.Commit.Verification.Verified)
+			assert.Empty(t, branch.Commit.Verification.Signature)
+		}))
+		setting.Repository.Signing.Merges = []string{"basesigned"}
+		t.Run("CreatePullRequest", func(t *testing.T) {
+			pr, err = doAPICreatePullRequest(testCtx, testCtx.Username, testCtx.Reponame, "master", "parentsigned2")(t)
+			assert.NoError(t, err)
+		})
+		t.Run("MergePR", doAPIMergePullRequest(testCtx, testCtx.Username, testCtx.Reponame, pr.Index))
+		t.Run("CheckMasterBranchUnsigned", doAPIGetBranch(testCtx, "master", func(t *testing.T, branch api.Branch) {
+			assert.NotNil(t, branch.Commit)
+			assert.NotNil(t, branch.Commit.Verification)
+			assert.False(t, branch.Commit.Verification.Verified)
+			assert.Empty(t, branch.Commit.Verification.Signature)
+		}))
+		setting.Repository.Signing.Merges = []string{"commitssigned"}
+		t.Run("CreatePullRequest", func(t *testing.T) {
+			pr, err = doAPICreatePullRequest(testCtx, testCtx.Username, testCtx.Reponame, "master", "always-parentsigned")(t)
+			assert.NoError(t, err)
+		})
+		t.Run("MergePR", doAPIMergePullRequest(testCtx, testCtx.Username, testCtx.Reponame, pr.Index))
+		t.Run("CheckMasterBranchUnsigned", doAPIGetBranch(testCtx, "master", func(t *testing.T, branch api.Branch) {
+			assert.NotNil(t, branch.Commit)
+			assert.NotNil(t, branch.Commit.Verification)
+			assert.True(t, branch.Commit.Verification.Verified)
+		}))
+
+	})
+}
+
+func crudActionCreateFile(t *testing.T, ctx APITestContext, user *models.User, from, to, path string, callback ...func(*testing.T, api.FileResponse)) func(*testing.T) {
+	return doAPICreateFile(ctx, path, &api.CreateFileOptions{
+		FileOptions: api.FileOptions{
+			BranchName:    from,
+			NewBranchName: to,
+			Message:       fmt.Sprintf("from:%s to:%s path:%s", from, to, path),
+			Author: api.Identity{
+				Name:  user.FullName,
+				Email: user.Email,
+			},
+			Committer: api.Identity{
+				Name:  user.FullName,
+				Email: user.Email,
+			},
+		},
+		Content: base64.StdEncoding.EncodeToString([]byte("This is new text")),
+	}, callback...)
+}
+
+func createGPGKey(tmpDir, name, email string) (*openpgp.Entity, error) {
+	keyPair, err := openpgp.NewEntity(name, "test", email, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, id := range keyPair.Identities {
+		err := id.SelfSignature.SignUserId(id.UserId.Id, keyPair.PrimaryKey, keyPair.PrivateKey, nil)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	keyFile := filepath.Join(tmpDir, "temporary.key")
+	keyWriter, err := os.Create(keyFile)
+	if err != nil {
+		return nil, err
+	}
+	defer keyWriter.Close()
+	defer os.Remove(keyFile)
+
+	w, err := armor.Encode(keyWriter, openpgp.PrivateKeyType, nil)
+	if err != nil {
+		return nil, err
+	}
+	defer w.Close()
+
+	keyPair.SerializePrivate(w, nil)
+	if err := w.Close(); err != nil {
+		return nil, err
+	}
+	if err := keyWriter.Close(); err != nil {
+		return nil, err
+	}
+
+	if _, _, err := process.GetManager().Exec("gpg --import temporary.key", "gpg", "--import", keyFile); err != nil {
+		return nil, err
+	}
+	return keyPair, nil
+}