Add a way for the grader to request problems (#34)

cmd/omegaup-gitserver/auth.go

@@ -142,8 +142,8 @@ func (a *omegaupAuthorization) parseUsernameAndPassword(
 		return
 	}
 
-	if username == "omegaup:system" {
-		// omegaup:system can only log in using the auth token or the secret token.
+	if strings.HasPrefix(username, "omegaup:") {
+		// omegaup:system and friends can only log in using the auth token or the secret token.
 		a.log.Error(
 			"user tried to login with restricted user",
 			map[string]interface{}{
@@ -231,13 +231,15 @@ func (a *omegaupAuthorization) parseAuthorizationHeader(
 		}
 	}
 
-	if a.config.Gitserver.AllowSecretTokenAuthentication && a.config.Gitserver.SecretToken != "" {
-		if strings.EqualFold(tokens[0], omegaUpSharedSecretAuthenticationScheme) {
+	if a.config.Gitserver.AllowSecretTokenAuthentication &&
+		strings.EqualFold(tokens[0], omegaUpSharedSecretAuthenticationScheme) {
+		if a.config.Gitserver.SecretToken != "" || a.config.Gitserver.GraderSecretToken != "" {
 			if len(tokens) != 3 {
 				return
 			}
 
-			if tokens[1] != a.config.Gitserver.SecretToken {
+			if (tokens[1] != a.config.Gitserver.SecretToken) &&
+				(tokens[1] != a.config.Gitserver.GraderSecretToken || tokens[2] != "omegaup:grader") {
 				return
 			}
 
@@ -388,18 +390,25 @@ func (a *omegaupAuthorization) authorize(
 		// This is a legit health check, so we grant privileges to the test problem.
 		requestContext.Request.CanView = true
 		requestContext.Request.CanEdit = true
+		requestContext.Request.CanViewAllRefs = true
+	} else if username == "omegaup:grader" || *insecureSkipAuthorization {
+		// This is the grader, it has read-only privileges for all problems.
+		requestContext.Request.CanView = true
+		requestContext.Request.CanViewAllRefs = true
 	} else if username == "omegaup:system" || *insecureSkipAuthorization {
 		// This is the frontend, and we trust it completely.
 		requestContext.Request.IsSystem = true
 		requestContext.Request.IsAdmin = true
 		requestContext.Request.CanView = true
 		requestContext.Request.CanEdit = true
+		requestContext.Request.CanViewAllRefs = true
 	} else if requestContext.Request.Create {
 		// This is a repository creation request. There is nothing in the database
 		// yet, so grant them all privileges.
 		requestContext.Request.IsAdmin = true
 		requestContext.Request.CanView = true
 		requestContext.Request.CanEdit = true
+		requestContext.Request.CanViewAllRefs = true
 	} else {
 		auth, err := a.getAuthorizationFromFrontend(
 			username,
@@ -421,6 +430,7 @@ func (a *omegaupAuthorization) authorize(
 		requestContext.Request.IsAdmin = auth.IsAdmin
 		requestContext.Request.CanView = auth.CanView
 		requestContext.Request.CanEdit = auth.CanEdit
+		requestContext.Request.CanViewAllRefs = auth.CanEdit
 	}
 	a.log.Info(
 		"Auth",

cmd/omegaup-gitserver/config.go

@@ -37,6 +37,10 @@ type GitserverConfig struct {
 	// authenticate instead of using PKI, in both directions.
 	SecretToken string
 
+	// GraderSecretToken is a shared secret with the grader that can be used to
+	// authenticate instead of using PKI, in both directions.
+	GraderSecretToken string
+
 	// AllowSecretTokenAuthentication controls whether the SecretToken can be
 	// used to authenticate incoming requests, instead of just being used for
 	// outgoing requests towards the frontend.
@@ -84,6 +88,7 @@ var defaultConfig = Config{
 		RootPath:                               "/var/lib/omegaup/problems.git",
 		PublicKey:                              "gKEg5JlIOA1BsIxETZYhjd+ZGchY/rZeQM0GheAWvXw=",
 		SecretToken:                            "",
+		GraderSecretToken:                      "",
 		Port:                                   33861,
 		PprofPort:                              33862,
 		LibinteractivePath:                     "/usr/share/java/libinteractive.jar",

cmd/omegaup-gitserver/main.go

@@ -49,7 +49,7 @@ func referenceDiscovery(
 	referenceName string,
 ) bool {
 	requestContext := request.FromContext(ctx)
-	if requestContext.Request.CanEdit {
+	if requestContext.Request.CanViewAllRefs {
 		return true
 	}
 	if requestContext.Request.HasSolved {

request/request.go

@@ -14,15 +14,16 @@ const requestContextKey key = 0
 // Request stores the request-specific part of the Context, to make it easier
 // to serialize.
 type Request struct {
-	ProblemName string
-	Username    string
-	Create      bool
-	IsSystem    bool
-	IsAdmin     bool
-	CanView     bool
-	CanEdit     bool
-	HasSolved   bool
-	ReviewRef   string
+	ProblemName    string
+	Username       string
+	Create         bool
+	IsSystem       bool
+	IsAdmin        bool
+	CanView        bool
+	CanViewAllRefs bool
+	CanEdit        bool
+	HasSolved      bool
+	ReviewRef      string
 }
 
 // Context stores a few variables that are request-specific.