Gitea: Missing repository-unit authorization on issue-template API endpoints

Summary

Three Gitea API endpoints — GET /repos/{owner}/{repo}/issue_templates, GET /repos/{owner}/{repo}/issue_config and GET /repos/{owner}/{repo}/issue_config/validate — read files from the repository's Code default branch (.gitea/ISSUE_TEMPLATE/* and issue_config.yaml) and return their contents, but are registered without the reqRepoReader(unit.TypeCode) authorization middleware that every sibling Code-tree endpoint in the same route group carries.

A user who has access to a private repository through any single repository unit (for example an organization team granted only the Issues unit, with no Code access) can therefore read the issue-template and issue-config files of that repository's Code tree, which their permission set should not expose.

Root cause

The three endpoints lack the unit guard

routers/api/v1/api.go:1433-1437:

m.Get("/issue_templates", context.ReferencesGitRepo(), repo.GetIssueTemplates)
m.Get("/issue_config", context.ReferencesGitRepo(), repo.GetIssueConfig)
m.Get("/issue_config/validate", context.ReferencesGitRepo(), repo.ValidateIssueConfig)
m.Get("/languages", reqRepoReader(unit.TypeCode), repo.GetLanguages)
m.Get("/licenses", reqRepoReader(unit.TypeCode), repo.GetLicenses)

context.ReferencesGitRepo() only opens the git repository — it performs no permission check. Every other endpoint in this group that reads Code-tree content is guarded with reqRepoReader(unit.TypeCode): /languages, /licenses, /contents/*, /file-contents, and /{ball_type:tarball|zipball|bundle}/* (api.go:1418-1445). The three issue-template endpoints are the only Code-tree readers in the group missing that guard.

The enclosing group runs repoAssignment() (api.go:1446), whose access check is satisfied by HasAnyUnitAccessOrPublicAccess — i.e. access to any unit of the repository is sufficient to pass. Without a per-unit reqRepoReader, the handlers run for a caller who has no Code permission.

The handlers return Code-tree file contents

routers/api/v1/repo/repo.go:

func GetIssueTemplates(ctx *context.APIContext) {                       // :1179
    ret := issue.ParseTemplatesFromDefaultBranch(ctx.Repo.Repository, ctx.Repo.GitRepo)
    ...
    ctx.JSON(http.StatusOK, ret.IssueTemplates)
}

func GetIssueConfig(ctx *context.APIContext) {                          // :1209
    issueConfig, _ := issue.GetTemplateConfigFromDefaultBranch(ctx.Repo.Repository, ctx.Repo.GitRepo)
    ctx.JSON(http.StatusOK, issueConfig)
}

ParseTemplatesFromDefaultBranch / GetTemplateConfigFromDefaultBranch read .gitea/ISSUE_TEMPLATE/* and issue_config.yaml from the default (Code) branch and return them in the JSON response.

Proof of Concept

victim-org/private-repo is a private repository. The attacker is a member of an organization team granted access to that repository through a non-Code unit only (e.g. the Issues unit) — a supported Gitea permission configuration.

GET /api/v1/repos/victim-org/private-repo/issue_templates HTTP/1.1
Host: TARGET
Authorization: token <attacker token>

The response is 200 OK with the parsed contents of the repository's .gitea/ISSUE_TEMPLATE/* files. The same applies to /issue_config. Because the caller lacks the Code unit, every other Code-tree endpoint (/contents, /languages, …) correctly returns 404/403 for the same token — only these three return data.

Impact

A repository collaborator whose granted permissions exclude the Code unit can read the issue-template and issue-config files from the Code default branch of a private repository. The exposure is limited to those specific configuration files (not arbitrary Code-tree content), which is why this is rated low impact. It is nonetheless a unit-level authorization bypass: the endpoints disclose Code-unit content to callers the permission model is meant to exclude.

Suggested fix

Add the same unit guard the sibling endpoints use, in routers/api/v1/api.go:

m.Get("/issue_templates", reqRepoReader(unit.TypeCode), context.ReferencesGitRepo(), repo.GetIssueTemplates)
m.Get("/issue_config", reqRepoReader(unit.TypeCode), context.ReferencesGitRepo(), repo.GetIssueConfig)
m.Get("/issue_config/validate", reqRepoReader(unit.TypeCode), context.ReferencesGitRepo(), repo.ValidateIssueConfig)

(If issue templates are intended to be visible to Issues-unit users for issue creation, reqRepoReader(unit.TypeIssues) is the appropriate guard — but the current absence of any unit guard is the bug.)

References

• CWE-862 Missing Authorization
• CWE-284 Improper Access Control
• OWASP A01:2021 Broken Access Control