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feat(gateway): JSON and CBOR response formats (IPIP-328) (#9335)
#9335 ipfs/specs#328 Co-authored-by: Marcin Rataj <lidel@lidel.org>
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# dag-index-html | ||
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> HTML representation for non-UnixFS DAGs such as DAG-CBOR. |
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package corehttp | ||
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import ( | ||
"bytes" | ||
"context" | ||
"fmt" | ||
"html" | ||
"io" | ||
"net/http" | ||
"strings" | ||
"time" | ||
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cid "github.com/ipfs/go-cid" | ||
ipldlegacy "github.com/ipfs/go-ipld-legacy" | ||
ipath "github.com/ipfs/interface-go-ipfs-core/path" | ||
"github.com/ipfs/kubo/assets" | ||
dih "github.com/ipfs/kubo/assets/dag-index-html" | ||
"github.com/ipfs/kubo/tracing" | ||
"github.com/ipld/go-ipld-prime" | ||
"github.com/ipld/go-ipld-prime/multicodec" | ||
mc "github.com/multiformats/go-multicodec" | ||
"go.opentelemetry.io/otel/attribute" | ||
"go.opentelemetry.io/otel/trace" | ||
) | ||
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// codecToContentType maps the supported IPLD codecs to the HTTP Content | ||
// Type they should have. | ||
var codecToContentType = map[uint64]string{ | ||
uint64(mc.Json): "application/json", | ||
uint64(mc.Cbor): "application/cbor", | ||
uint64(mc.DagJson): "application/vnd.ipld.dag-json", | ||
uint64(mc.DagCbor): "application/vnd.ipld.dag-cbor", | ||
} | ||
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// contentTypeToCodecs maps the HTTP Content Type to the respective | ||
// possible codecs. If the original data is in one of those codecs, | ||
// we stream the raw bytes. Otherwise, we encode in the last codec | ||
// of the list. | ||
var contentTypeToCodecs = map[string][]uint64{ | ||
"application/json": {uint64(mc.Json), uint64(mc.DagJson)}, | ||
"application/vnd.ipld.dag-json": {uint64(mc.DagJson)}, | ||
"application/cbor": {uint64(mc.Cbor), uint64(mc.DagCbor)}, | ||
"application/vnd.ipld.dag-cbor": {uint64(mc.DagCbor)}, | ||
} | ||
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// contentTypeToExtension maps the HTTP Content Type to the respective file | ||
// extension, used in Content-Disposition header when downloading the file. | ||
var contentTypeToExtension = map[string]string{ | ||
"application/json": ".json", | ||
"application/vnd.ipld.dag-json": ".json", | ||
"application/cbor": ".cbor", | ||
"application/vnd.ipld.dag-cbor": ".cbor", | ||
} | ||
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func (i *gatewayHandler) serveCodec(ctx context.Context, w http.ResponseWriter, r *http.Request, resolvedPath ipath.Resolved, contentPath ipath.Path, begin time.Time, requestedContentType string) { | ||
ctx, span := tracing.Span(ctx, "Gateway", "ServeCodec", trace.WithAttributes(attribute.String("path", resolvedPath.String()), attribute.String("requestedContentType", requestedContentType))) | ||
defer span.End() | ||
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cidCodec := resolvedPath.Cid().Prefix().Codec | ||
responseContentType := requestedContentType | ||
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// If the resolved path still has some remainder, return error for now. | ||
// TODO: handle this when we have IPLD Patch (https://ipld.io/specs/patch/) via HTTP PUT | ||
// TODO: (depends on https://github.com/ipfs/kubo/issues/4801 and https://github.com/ipfs/kubo/issues/4782) | ||
if resolvedPath.Remainder() != "" { | ||
path := strings.TrimSuffix(resolvedPath.String(), resolvedPath.Remainder()) | ||
err := fmt.Errorf("%q of %q could not be returned: reading IPLD Kinds other than Links (CBOR Tag 42) is not implemented: try reading %q instead", resolvedPath.Remainder(), resolvedPath.String(), path) | ||
webError(w, "unsupported pathing", err, http.StatusNotImplemented) | ||
return | ||
} | ||
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// If no explicit content type was requested, the response will have one based on the codec from the CID | ||
if requestedContentType == "" { | ||
cidContentType, ok := codecToContentType[cidCodec] | ||
if !ok { | ||
// Should not happen unless function is called with wrong parameters. | ||
err := fmt.Errorf("content type not found for codec: %v", cidCodec) | ||
webError(w, "internal error", err, http.StatusInternalServerError) | ||
return | ||
} | ||
responseContentType = cidContentType | ||
} | ||
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// Set HTTP headers (for caching etc) | ||
modtime := addCacheControlHeaders(w, r, contentPath, resolvedPath.Cid()) | ||
name := setCodecContentDisposition(w, r, resolvedPath, responseContentType) | ||
w.Header().Set("Content-Type", responseContentType) | ||
w.Header().Set("X-Content-Type-Options", "nosniff") | ||
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// No content type is specified by the user (via Accept, or format=). However, | ||
// we support this format. Let's handle it. | ||
if requestedContentType == "" { | ||
isDAG := cidCodec == uint64(mc.DagJson) || cidCodec == uint64(mc.DagCbor) | ||
acceptsHTML := strings.Contains(r.Header.Get("Accept"), "text/html") | ||
download := r.URL.Query().Get("download") == "true" | ||
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if isDAG && acceptsHTML && !download { | ||
i.serveCodecHTML(ctx, w, r, resolvedPath, contentPath) | ||
} else { | ||
i.serveCodecRaw(ctx, w, r, resolvedPath, contentPath, name, modtime) | ||
} | ||
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return | ||
} | ||
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// Otherwise, the user has requested a specific content type. Let's first get | ||
// the codecs that can be used with this content type. | ||
codecs, ok := contentTypeToCodecs[requestedContentType] | ||
if !ok { | ||
// This is never supposed to happen unless function is called with wrong parameters. | ||
err := fmt.Errorf("unsupported content type: %s", requestedContentType) | ||
webError(w, err.Error(), err, http.StatusInternalServerError) | ||
return | ||
} | ||
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// If we need to convert, use the last codec (strict dag- variant) | ||
toCodec := codecs[len(codecs)-1] | ||
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// If the requested content type has "dag-", ALWAYS go through the encoding | ||
// process in order to validate the content. | ||
if strings.Contains(requestedContentType, "dag-") { | ||
i.serveCodecConverted(ctx, w, r, resolvedPath, contentPath, toCodec, modtime) | ||
return | ||
} | ||
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// Otherwise, check if the data is encoded with the requested content type. | ||
// If so, we can directly stream the raw data. serveRawBlock cannot be directly | ||
// used here as it sets different headers. | ||
for _, codec := range codecs { | ||
if resolvedPath.Cid().Prefix().Codec == codec { | ||
i.serveCodecRaw(ctx, w, r, resolvedPath, contentPath, name, modtime) | ||
return | ||
} | ||
} | ||
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// Finally, if nothing of the above is true, we have to actually convert the codec. | ||
i.serveCodecConverted(ctx, w, r, resolvedPath, contentPath, toCodec, modtime) | ||
} | ||
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func (i *gatewayHandler) serveCodecHTML(ctx context.Context, w http.ResponseWriter, r *http.Request, resolvedPath ipath.Resolved, contentPath ipath.Path) { | ||
// A HTML directory index will be presented, be sure to set the correct | ||
// type instead of relying on autodetection (which may fail). | ||
w.Header().Set("Content-Type", "text/html") | ||
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// Clear Content-Disposition -- we want HTML to be rendered inline | ||
w.Header().Del("Content-Disposition") | ||
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// Generated index requires custom Etag (output may change between Kubo versions) | ||
dagEtag := getDagIndexEtag(resolvedPath.Cid()) | ||
w.Header().Set("Etag", dagEtag) | ||
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// Remove Cache-Control for now to match UnixFS dir-index-html responses | ||
// (we don't want browser to cache HTML forever) | ||
// TODO: if we ever change behavior for UnixFS dir listings, same changes should be applied here | ||
w.Header().Del("Cache-Control") | ||
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cidCodec := mc.Code(resolvedPath.Cid().Prefix().Codec) | ||
if err := dih.DagIndexTemplate.Execute(w, dih.DagIndexTemplateData{ | ||
Path: contentPath.String(), | ||
CID: resolvedPath.Cid().String(), | ||
CodecName: cidCodec.String(), | ||
CodecHex: fmt.Sprintf("0x%x", uint64(cidCodec)), | ||
}); err != nil { | ||
webError(w, "failed to generate HTML listing for this DAG: try fetching raw block with ?format=raw", err, http.StatusInternalServerError) | ||
} | ||
} | ||
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func (i *gatewayHandler) serveCodecRaw(ctx context.Context, w http.ResponseWriter, r *http.Request, resolvedPath ipath.Resolved, contentPath ipath.Path, name string, modtime time.Time) { | ||
blockCid := resolvedPath.Cid() | ||
blockReader, err := i.api.Block().Get(ctx, resolvedPath) | ||
if err != nil { | ||
webError(w, "ipfs block get "+blockCid.String(), err, http.StatusInternalServerError) | ||
return | ||
} | ||
block, err := io.ReadAll(blockReader) | ||
if err != nil { | ||
webError(w, "ipfs block get "+blockCid.String(), err, http.StatusInternalServerError) | ||
return | ||
} | ||
content := bytes.NewReader(block) | ||
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// ServeContent will take care of | ||
// If-None-Match+Etag, Content-Length and range requests | ||
_, _, _ = ServeContent(w, r, name, modtime, content) | ||
} | ||
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func (i *gatewayHandler) serveCodecConverted(ctx context.Context, w http.ResponseWriter, r *http.Request, resolvedPath ipath.Resolved, contentPath ipath.Path, toCodec uint64, modtime time.Time) { | ||
obj, err := i.api.Dag().Get(ctx, resolvedPath.Cid()) | ||
if err != nil { | ||
webError(w, "ipfs dag get "+html.EscapeString(resolvedPath.String()), err, http.StatusInternalServerError) | ||
return | ||
} | ||
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universal, ok := obj.(ipldlegacy.UniversalNode) | ||
if !ok { | ||
err = fmt.Errorf("%T is not a valid IPLD node", obj) | ||
webError(w, err.Error(), err, http.StatusInternalServerError) | ||
return | ||
} | ||
finalNode := universal.(ipld.Node) | ||
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encoder, err := multicodec.LookupEncoder(toCodec) | ||
if err != nil { | ||
webError(w, err.Error(), err, http.StatusInternalServerError) | ||
return | ||
} | ||
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// Ensure IPLD node conforms to the codec specification. | ||
var buf bytes.Buffer | ||
err = encoder(finalNode, &buf) | ||
if err != nil { | ||
webError(w, err.Error(), err, http.StatusInternalServerError) | ||
return | ||
} | ||
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// Sets correct Last-Modified header. This code is borrowed from the standard | ||
// library (net/http/server.go) as we cannot use serveFile. | ||
if !(modtime.IsZero() || modtime.Equal(unixEpochTime)) { | ||
w.Header().Set("Last-Modified", modtime.UTC().Format(http.TimeFormat)) | ||
} | ||
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_, _ = w.Write(buf.Bytes()) | ||
} | ||
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func setCodecContentDisposition(w http.ResponseWriter, r *http.Request, resolvedPath ipath.Resolved, contentType string) string { | ||
var dispType, name string | ||
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ext, ok := contentTypeToExtension[contentType] | ||
if !ok { | ||
// Should never happen. | ||
ext = ".bin" | ||
} | ||
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if urlFilename := r.URL.Query().Get("filename"); urlFilename != "" { | ||
name = urlFilename | ||
} else { | ||
name = resolvedPath.Cid().String() + ext | ||
} | ||
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// JSON should be inlined, but ?download=true should still override | ||
if r.URL.Query().Get("download") == "true" { | ||
dispType = "attachment" | ||
} else { | ||
switch ext { | ||
case ".json": // codecs that serialize to JSON can be rendered by browsers | ||
dispType = "inline" | ||
default: // everything else is assumed binary / opaque bytes | ||
dispType = "attachment" | ||
} | ||
} | ||
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setContentDispositionHeader(w, name, dispType) | ||
return name | ||
} | ||
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func getDagIndexEtag(dagCid cid.Cid) string { | ||
return `"DagIndex-` + assets.AssetHash + `_CID-` + dagCid.String() + `"` | ||
} |
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