1 files changed, 82 insertions, 0 deletions
diff --git a/services/migrations/common.go b/services/migrations/common.go
new file mode 100644
index 0000000000..305ae89b2d
--- /dev/null
+++ b/services/migrations/common.go
@@ -0,0 +1,82 @@
+// Copyright 2022 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 migrations
+
+import (
+	"fmt"
+	"strings"
+
+	admin_model "code.gitea.io/gitea/models/admin"
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/log"
+	base "code.gitea.io/gitea/modules/migration"
+)
+
+// WarnAndNotice will log the provided message and send a repository notice
+func WarnAndNotice(fmtStr string, args ...interface{}) {
+	log.Warn(fmtStr, args...)
+	if err := admin_model.CreateRepositoryNotice(fmt.Sprintf(fmtStr, args...)); err != nil {
+		log.Error("create repository notice failed: ", err)
+	}
+}
+
+func hasBaseURL(toCheck, baseURL string) bool {
+	if len(baseURL) > 0 && baseURL[len(baseURL)-1] != '/' {
+		baseURL += "/"
+	}
+	return strings.HasPrefix(toCheck, baseURL)
+}
+
+// CheckAndEnsureSafePR will check that a given PR is safe to download
+func CheckAndEnsureSafePR(pr *base.PullRequest, commonCloneBaseURL string, g base.Downloader) bool {
+	valid := true
+	// SECURITY: the patchURL must be checked to have the same baseURL as the current to prevent open redirect
+	if pr.PatchURL != "" && !hasBaseURL(pr.PatchURL, commonCloneBaseURL) {
+		// TODO: Should we check that this url has the expected format for a patch url?
+		WarnAndNotice("PR #%d in %s has invalid PatchURL: %s baseURL: %s", pr.Number, g, pr.PatchURL, commonCloneBaseURL)
+		pr.PatchURL = ""
+		valid = false
+	}
+
+	// SECURITY: the headCloneURL must be checked to have the same baseURL as the current to prevent open redirect
+	if pr.Head.CloneURL != "" && !hasBaseURL(pr.Head.CloneURL, commonCloneBaseURL) {
+		// TODO: Should we check that this url has the expected format for a patch url?
+		WarnAndNotice("PR #%d in %s has invalid HeadCloneURL: %s baseURL: %s", pr.Number, g, pr.Head.CloneURL, commonCloneBaseURL)
+		pr.Head.CloneURL = ""
+		valid = false
+	}
+
+	// SECURITY: SHAs Must be a SHA
+	if pr.MergeCommitSHA != "" && !git.IsValidSHAPattern(pr.MergeCommitSHA) {
+		WarnAndNotice("PR #%d in %s has invalid MergeCommitSHA: %s", pr.Number, g, pr.MergeCommitSHA)
+		pr.MergeCommitSHA = ""
+	}
+	if pr.Head.SHA != "" && !git.IsValidSHAPattern(pr.Head.SHA) {
+		WarnAndNotice("PR #%d in %s has invalid HeadSHA: %s", pr.Number, g, pr.Head.SHA)
+		pr.Head.SHA = ""
+		valid = false
+	}
+	if pr.Base.SHA != "" && !git.IsValidSHAPattern(pr.Base.SHA) {
+		WarnAndNotice("PR #%d in %s has invalid BaseSHA: %s", pr.Number, g, pr.Base.SHA)
+		pr.Base.SHA = ""
+		valid = false
+	}
+
+	// SECURITY: Refs must be valid refs or SHAs
+	if pr.Head.Ref != "" && !git.IsValidRefPattern(pr.Head.Ref) {
+		WarnAndNotice("PR #%d in %s has invalid HeadRef: %s", pr.Number, g, pr.Head.Ref)
+		pr.Head.Ref = ""
+		valid = false
+	}
+	if pr.Base.Ref != "" && !git.IsValidRefPattern(pr.Base.Ref) {
+		WarnAndNotice("PR #%d in %s has invalid BaseRef: %s", pr.Number, g, pr.Base.Ref)
+		pr.Base.Ref = ""
+		valid = false
+	}
+
+	pr.EnsuredSafe = true
+
+	return valid
+}