Feat: send additional build contexts for remote builds

Fixed the --build-context flag to properly send files for remote builds. Previously
only the main context was sent over as a tar while additional contexts were passed as
local paths and this would cause builds to fail since the files wouldn't exist.

New changes modifies the Build API to use multipart HTTP requests allowing multiple
build contexts to be used. Each additional context is packaged and
transferred based on its type:
- Local Directories: Sent as tar archives
- Git Repositories: link sent to the server where its then cloned
- Container Images: Image reference sent to the server, it then pulls the image there
- URLs/archives: URL sent to the server, which handles the download

Fixes: #23433

Signed-off-by: Joshua Arrevillaga <[email protected]>

Author: 2004joshua

pkg/api/handlers/compat/images_build.go

@@ -44,13 +44,20 @@ func genSpaceErr(err error) error {
 }
 
 func BuildImage(w http.ResponseWriter, r *http.Request) {
+	var multipart bool
 	if hdr, found := r.Header["Content-Type"]; found && len(hdr) > 0 {
 		contentType := hdr[0]
+		multipart = strings.HasPrefix(contentType, "multipart/form-data")
+		if multipart {
+			contentType = "multipart/form-data"
+		}
 		switch contentType {
 		case "application/tar":
 			logrus.Infof("tar file content type is  %s, should use \"application/x-tar\" content type", contentType)
 		case "application/x-tar":
 			break
+		case "multipart/form-data":
+			logrus.Debugf("Received multipart/form-data: %s", contentType)
 		default:
 			if utils.IsLibpodRequest(r) {
 				utils.BadRequest(w, "Content-Type", hdr[0],
@@ -81,10 +88,21 @@ func BuildImage(w http.ResponseWriter, r *http.Request) {
 		}
 	}()
 
-	contextDirectory, err := extractTarFile(anchorDir, r)
-	if err != nil {
-		utils.InternalServerError(w, genSpaceErr(err))
-		return
+	var contextDirectory string
+	var additionalBuildContextsFromMultipart map[string]*buildahDefine.AdditionalBuildContext
+
+	if multipart {
+		contextDirectory, additionalBuildContextsFromMultipart, err = handleMultipartBuild(anchorDir, r)
+		if err != nil {
+			utils.InternalServerError(w, fmt.Errorf("handling multipart request: %w", err))
+			return
+		}
+	} else {
+		contextDirectory, err = extractTarFile(anchorDir, r)
+		if err != nil {
+			utils.InternalServerError(w, genSpaceErr(err))
+			return
+		}
 	}
 
 	runtime := r.Context().Value(api.RuntimeKey).(*libpod.Runtime)
@@ -448,6 +466,14 @@ func BuildImage(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	if additionalBuildContextsFromMultipart != nil {
+		logrus.Debugf("Merging %d additional contexts from multipart", len(additionalBuildContextsFromMultipart))
+		for name, ctx := range additionalBuildContextsFromMultipart {
+			additionalBuildContexts[name] = ctx
+			logrus.Debugf("Added multipart context %q with path %q", name, ctx.Value)
+		}
+	}
+
 	var idMappingOptions buildahDefine.IDMappingOptions
 	if _, found := r.URL.Query()["idmappingoptions"]; found {
 		if err := json.Unmarshal([]byte(query.IDMappingOptions), &idMappingOptions); err != nil {
@@ -920,6 +946,122 @@ func BuildImage(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+func handleMultipartBuild(anchorDir string, r *http.Request) (contextDir string, additionalContexts map[string]*buildahDefine.AdditionalBuildContext, err error) {
+	reader, err := r.MultipartReader()
+	if err != nil {
+		return "", nil, fmt.Errorf("failed to create multipart reader: %w", err)
+	}
+
+	additionalContexts = make(map[string]*buildahDefine.AdditionalBuildContext)
+	for {
+		part, err := reader.NextPart()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return "", nil, fmt.Errorf("failed to read part: %w", err)
+		}
+
+		fieldName := part.FormName()
+		fileName := part.FileName()
+
+		logrus.Debugf("Processing part: field=%q, file=%q", fieldName, fileName)
+
+		switch {
+		case fieldName == "context" && fileName != "":
+			contextPath := filepath.Join(anchorDir, "context")
+			if err := os.MkdirAll(contextPath, 0755); err != nil {
+				part.Close()
+				return "", nil, fmt.Errorf("creating context directory: %w", err)
+			}
+
+			if err := archive.Untar(part, contextPath, nil); err != nil {
+				part.Close()
+				return "", nil, fmt.Errorf("extracting main context: %w", err)
+			}
+			contextDir = contextPath
+			logrus.Debugf("Extracted main context to %q", contextDir)
+			part.Close()
+
+		case strings.HasPrefix(fieldName, "buildcontext-url-"):
+			contextName := strings.TrimPrefix(fieldName, "buildcontext-url-")
+			urlBytes, err := io.ReadAll(part)
+			part.Close()
+			if err != nil {
+				return "", nil, fmt.Errorf("reading URL value: %w", err)
+			}
+			urlValue := string(urlBytes)
+
+			logrus.Debugf("Found URL context %q: %s", contextName, urlValue)
+
+			tempDir, subDir, err := buildahDefine.TempDirForURL(anchorDir, "buildah", urlValue)
+			if err != nil {
+				return "", nil, fmt.Errorf("downloading URL context %q: %w", contextName, err)
+			}
+
+			contextPath := filepath.Join(tempDir, subDir)
+			additionalContexts[contextName] = &buildahDefine.AdditionalBuildContext{
+				IsURL:           true,
+				IsImage:         false,
+				Value:           contextPath,
+				DownloadedCache: contextPath,
+			}
+			logrus.Debugf("Downloaded URL context %q to %q", contextName, contextPath)
+
+		case strings.HasPrefix(fieldName, "buildcontext-image-"):
+			contextName := strings.TrimPrefix(fieldName, "buildcontext-image-")
+			imageBytes, err := io.ReadAll(part)
+			part.Close()
+			if err != nil {
+				return "", nil, fmt.Errorf("reading image reference: %w", err)
+			}
+			imageRef := string(imageBytes)
+
+			logrus.Debugf("Found image context %q: %s", contextName, imageRef)
+
+			additionalContexts[contextName] = &buildahDefine.AdditionalBuildContext{
+				IsImage: true,
+				IsURL:   false,
+				Value:   imageRef,
+			}
+			logrus.Debugf("Added image context %q with reference %q", contextName, imageRef)
+
+		case strings.HasPrefix(fieldName, "buildcontext-local-") && fileName != "":
+			contextName := strings.TrimPrefix(fieldName, "buildcontext-local-")
+			additionalAnchor := filepath.Join(anchorDir, "additional", contextName)
+
+			if err := os.MkdirAll(additionalAnchor, 0700); err != nil {
+				part.Close()
+				return "", nil, fmt.Errorf("creating additional context directory %q: %w", contextName, err)
+			}
+
+			if err := archive.Untar(part, additionalAnchor, nil); err != nil {
+				part.Close()
+				return "", nil, fmt.Errorf("extracting additional context %q: %w", contextName, err)
+			}
+
+			additionalContexts[contextName] = &buildahDefine.AdditionalBuildContext{
+				IsURL:   false,
+				IsImage: false,
+				Value:   additionalAnchor,
+			}
+			logrus.Debugf("Extracted additional context %q to %q", contextName, additionalAnchor)
+			part.Close()
+
+		default:
+			part.Close()
+		}
+	}
+
+	if contextDir == "" {
+		return "", nil, fmt.Errorf("no main context provided in multipart form")
+	}
+
+	logrus.Debugf("Successfully parsed multipart form, main context: %q and additional contexts: %v", contextDir, additionalContexts)
+
+	return contextDir, additionalContexts, nil
+}
+
 func parseNetworkConfigurationPolicy(network string) buildah.NetworkConfigurationPolicy {
 	if val, err := strconv.Atoi(network); err == nil {
 		return buildah.NetworkConfigurationPolicy(val)