Sign protected branches (#8993)

* Move SignMerge to PullRequest

* Add approved signing mode

* As per @guillep2k comment

models/pull_sign.go

@@ -0,0 +1,121 @@
+// 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 models
+
+import (
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+)
+
+// SignMerge determines if we should sign a PR merge commit to the base repository
+func (pr *PullRequest) SignMerge(u *User, tmpBasePath, baseCommit, headCommit string) (bool, string) {
+	if err := pr.GetBaseRepo(); err != nil {
+		log.Error("Unable to get Base Repo for pull request")
+		return false, ""
+	}
+	repo := pr.BaseRepo
+
+	signingKey := signingKey(repo.RepoPath())
+	if signingKey == "" {
+		return false, ""
+	}
+	rules := signingModeFromStrings(setting.Repository.Signing.Merges)
+
+	var gitRepo *git.Repository
+	var err error
+
+	for _, rule := range rules {
+		switch rule {
+		case never:
+			return false, ""
+		case always:
+			break
+		case pubkey:
+			keys, err := ListGPGKeys(u.ID)
+			if err != nil || len(keys) == 0 {
+				return false, ""
+			}
+		case twofa:
+			twofa, err := GetTwoFactorByUID(u.ID)
+			if err != nil || twofa == nil {
+				return false, ""
+			}
+		case approved:
+			protectedBranch, err := GetProtectedBranchBy(repo.ID, pr.BaseBranch)
+			if err != nil || protectedBranch == nil {
+				return false, ""
+			}
+			if protectedBranch.GetGrantedApprovalsCount(pr) < 1 {
+				return false, ""
+			}
+		case baseSigned:
+			if gitRepo == nil {
+				gitRepo, err = git.OpenRepository(tmpBasePath)
+				if err != nil {
+					return false, ""
+				}
+				defer gitRepo.Close()
+			}
+			commit, err := gitRepo.GetCommit(baseCommit)
+			if err != nil {
+				return false, ""
+			}
+			verification := ParseCommitWithSignature(commit)
+			if !verification.Verified {
+				return false, ""
+			}
+		case headSigned:
+			if gitRepo == nil {
+				gitRepo, err = git.OpenRepository(tmpBasePath)
+				if err != nil {
+					return false, ""
+				}
+				defer gitRepo.Close()
+			}
+			commit, err := gitRepo.GetCommit(headCommit)
+			if err != nil {
+				return false, ""
+			}
+			verification := ParseCommitWithSignature(commit)
+			if !verification.Verified {
+				return false, ""
+			}
+		case commitsSigned:
+			if gitRepo == nil {
+				gitRepo, err = git.OpenRepository(tmpBasePath)
+				if err != nil {
+					return false, ""
+				}
+				defer gitRepo.Close()
+			}
+			commit, err := gitRepo.GetCommit(headCommit)
+			if err != nil {
+				return false, ""
+			}
+			verification := ParseCommitWithSignature(commit)
+			if !verification.Verified {
+				return false, ""
+			}
+			// need to work out merge-base
+			mergeBaseCommit, _, err := gitRepo.GetMergeBase("", baseCommit, headCommit)
+			if err != nil {
+				return false, ""
+			}
+			commitList, err := commit.CommitsBeforeUntil(mergeBaseCommit)
+			if err != nil {
+				return false, ""
+			}
+			for e := commitList.Front(); e != nil; e = e.Next() {
+				commit = e.Value.(*git.Commit)
+				verification := ParseCommitWithSignature(commit)
+				if !verification.Verified {
+					return false, ""
+				}
+			}
+		}
+	}
+	return true, signingKey
+}