tor 2022-02-10 klockan 02:13 +0100 skrev Mark Gaiser:
> This patch adds support for:
> - ffplay ipfs://<cid>
> - ffplay ipns://<cid>
>
> IPFS data can be played from so called "ipfs gateways".
> A gateway is essentially a webserver that gives access to the
> distributed IPFS network.
>
> This protocol support (ipfs and ipns) therefore translates
> ipfs:// and ipns:// to a http:// url. This resulting url is
> then handled by the http protocol. It could also be https
> depending on the gateway provided.
>
> To use this protocol, a gateway must be provided.
> If you do nothing it will try to find it in your
> $HOME/.ipfs/gateway file. The ways to set it manually are:
> 1. Define a -gateway <url> to the gateway.
> 2. Define $IPFS_GATEWAY with the full http link to the gateway.
> 3. Define $IPFS_PATH and point it to the IPFS data path.
> 4. Have IPFS running in your local user folder (under $HOME/.ipfs).
>
> Signed-off-by: Mark Gaiser <mark...@gmail.com>
> ---
> configure | 2 +
> doc/protocols.texi | 30 ++++
> libavformat/Makefile | 2 +
> libavformat/ipfsgateway.c | 326
> ++++++++++++++++++++++++++++++++++++++
> libavformat/protocols.c | 2 +
> 5 files changed, 362 insertions(+)
> create mode 100644 libavformat/ipfsgateway.c
>
> diff --git a/configure b/configure
> index 5b19a35f59..6ff09e7974 100755
> --- a/configure
> +++ b/configure
> @@ -3585,6 +3585,8 @@ udp_protocol_select="network"
> udplite_protocol_select="network"
> unix_protocol_deps="sys_un_h"
> unix_protocol_select="network"
> +ipfs_protocol_select="https_protocol"
> +ipns_protocol_select="https_protocol"
>
> # external library protocols
> libamqp_protocol_deps="librabbitmq"
> diff --git a/doc/protocols.texi b/doc/protocols.texi
> index d207df0b52..7c9c0a4808 100644
> --- a/doc/protocols.texi
> +++ b/doc/protocols.texi
> @@ -2025,5 +2025,35 @@ decoding errors.
>
> @end table
>
> +@section ipfs
> +
> +InterPlanetary File System (IPFS) protocol support. One can access
> files stored
> +on the IPFS network through so called gateways. Those are http(s)
> endpoints.
> +This protocol wraps the IPFS native protocols (ipfs:// and ipns://)
> to be send
> +to such a gateway. Users can (and should) host their own node which
> means this
> +protocol will use your local machine gateway to access files on the
> IPFS network.
> +
> +If a user doesn't have a node of their own then the public gateway
> dweb.link is
> +used by default.
> +
> +You can use this protocol in 2 ways. Using IPFS:
> +@example
> +ffplay ipfs://QmbGtJg23skhvFmu9mJiePVByhfzu5rwo74MEkVDYAmF5T
> +@end example
> +
> +Or the IPNS protocol (IPNS is mutable IPFS):
> +@example
> +ffplay ipns://QmbGtJg23skhvFmu9mJiePVByhfzu5rwo74MEkVDYAmF5T
> +@end example
> +
> +You can also change the gateway to be used:
> +
> +@table @option
> +
> +@item gateway
> +Defines the gateway to use. When nothing is provided the protocol
> will first try
> +your local gateway. If that fails dweb.link will be used.
> +
> +@end table
>
> @c man end PROTOCOLS
> diff --git a/libavformat/Makefile b/libavformat/Makefile
> index 3dc6a479cc..4edce8420f 100644
> --- a/libavformat/Makefile
> +++ b/libavformat/Makefile
> @@ -656,6 +656,8 @@ OBJS-$(CONFIG_SRTP_PROTOCOL) +=
> srtpproto.o srtp.o
> OBJS-$(CONFIG_SUBFILE_PROTOCOL) += subfile.o
> OBJS-$(CONFIG_TEE_PROTOCOL) += teeproto.o tee_common.o
> OBJS-$(CONFIG_TCP_PROTOCOL) += tcp.o
> +OBJS-$(CONFIG_IPFS_PROTOCOL) += ipfsgateway.o
> +OBJS-$(CONFIG_IPNS_PROTOCOL) += ipfsgateway.o
> TLS-OBJS-$(CONFIG_GNUTLS) += tls_gnutls.o
> TLS-OBJS-$(CONFIG_LIBTLS) += tls_libtls.o
> TLS-OBJS-$(CONFIG_MBEDTLS) += tls_mbedtls.o
> diff --git a/libavformat/ipfsgateway.c b/libavformat/ipfsgateway.c
> new file mode 100644
> index 0000000000..9ebced10c7
> --- /dev/null
> +++ b/libavformat/ipfsgateway.c
> @@ -0,0 +1,326 @@
> +/*
> + * IPFS and IPNS protocol support through IPFS Gateway.
> + * Copyright (c) 2022 Mark Gaiser
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later
> version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> 02110-1301 USA
> + */
> +
> +#include "avformat.h"
> +#include "libavutil/avassert.h"
> +#include "libavutil/avstring.h"
> +#include "libavutil/internal.h"
> +#include "libavutil/opt.h"
> +#include "libavutil/tree.h"
> +#include <fcntl.h>
> +#if HAVE_IO_H
> +#include <io.h>
> +#endif
> +#if HAVE_UNISTD_H
> +#include <unistd.h>
> +#endif
> +#include "os_support.h"
> +#include "url.h"
> +#include <stdlib.h>
> +#include <sys/stat.h>
> +
> +typedef struct IPFSGatewayContext {
> + AVClass *class;
> + URLContext *inner;
> + char *gateway;
> +} IPFSGatewayContext;
> +
> +// A best-effort way to find the IPFS gateway.
> +// Only the most appropiate gateway is set. It's not actually
> requested
> +// (http call) to prevent a potential slowdown in startup. A
> potential timeout
> +// is handled by the HTTP protocol.
> +static int populate_ipfs_gateway(URLContext *h, char *gateway)
> +{
> + char ipfs_full_data_folder[PATH_MAX];
> + char ipfs_gateway_file[PATH_MAX];
> + struct stat st;
> + int stat_ret = 0;
> + int ret = AVERROR(EINVAL);
> + FILE *gateway_file = NULL;
> + char gateway_file_data[PATH_MAX];
> +
> + // We could already have a gateway (it would have been passed as
> -gateway).
> + if (*gateway != '\0') {
> + ret = 1;
> + goto err;
> + }
Why even call this function if this is the case?
> +
> + // Test $IPFS_GATEWAY.
> + if (getenv("IPFS_GATEWAY") != NULL) {
> + snprintf(gateway, PATH_MAX, "%s", getenv("IPFS_GATEWAY"));
Passing buffer length rather than assuming PATH_MAX would be better.
That way it can be changed without this breaking.
Or stick the buffer in IPFSGatewayContext and use sizeof()
> + ret = 1;
> + goto err;
> + } else
> + av_log(h, AV_LOG_DEBUG, "$IPFS_GATEWAY is empty.\n");
> +
> + // We need to know the IPFS folder to - eventually - read the
> contents of
> + // the "gateway" file which would tell us the gateway to use.
> + if (getenv("IPFS_PATH") == NULL) {
> + av_log(h, AV_LOG_DEBUG, "$IPFS_PATH is empty.\n");
> +
> + // Try via the home folder.
> + if (getenv("HOME") == NULL) {
> + av_log(h, AV_LOG_ERROR, "$HOME appears to be empty.\n");
> + ret = AVERROR(EINVAL);
> + goto err;
> + }
> +
> + // Verify the composed path fits.
> + if (snprintf(ipfs_full_data_folder, PATH_MAX, "%s/.ipfs/",
sizeof(ipfs_full_data_folder)
This goes for most PATH_MAX in here
> + getenv("HOME")) > PATH_MAX) {
> + av_log(h, AV_LOG_ERROR, "The IPFS data path exceeds the
> max path length (%i)\n", PATH_MAX);
> + ret = AVERROR(EINVAL);
> + goto err;
> + }
> +
> + // Stat the folder.
> + // It should exist in a default IPFS setup when run as local
> user.
> +#ifndef _WIN32
> + stat_ret = stat(ipfs_full_data_folder, &st);
> +#else
> + stat_ret = win32_stat(ipfs_full_data_folder, &st);
> +#endif
> + if (stat_ret < 0) {
> + av_log(h, AV_LOG_INFO, "Unable to find IPFS folder. We
> tried:\n");
> + av_log(h, AV_LOG_INFO, "- $IPFS_PATH, which was
> empty.\n");
> + av_log(h, AV_LOG_INFO, "- $HOME/.ipfs (full uri: %s)
> which doesn't exist.\n", ipfs_full_data_folder);
> + ret = AVERROR(ENOENT);
> + goto err;
> + }
Right. This makes more sense
> + } else
> + snprintf(ipfs_full_data_folder, PATH_MAX, "%s",
> getenv("IPFS_PATH"));
> +
> + // Copy the fully composed gateway path into ipfs_gateway_file.
> + if (snprintf(ipfs_gateway_file, PATH_MAX, "%sgateway",
> + ipfs_full_data_folder) > PATH_MAX) {
> + av_log(h, AV_LOG_ERROR, "The IPFS gateway file path exceeds
> the max path length (%i)\n", PATH_MAX);
> + ret = AVERROR(ENOENT);
> + goto err;
> + }
> +
> + // Get the contents of the gateway file.
> + gateway_file = av_fopen_utf8(ipfs_gateway_file, "r");
> + if (!gateway_file) {
> + av_log(h, AV_LOG_ERROR, "The IPFS gateway file (full uri:
> %s) doesn't exist. Is the gateway enabled?\n", ipfs_gateway_file);
> + ret = AVERROR(ENOENT);
> + goto err;
> + }
> +
> + // Read a single line (fgets stops at new line mark).
> + fgets(gateway_file_data, PATH_MAX - 1, gateway_file);
> +
> + // Replace the last char with \0
> + gateway_file_data[PATH_MAX - 1] = 0;
> +
> + // Replace first occurence of end of line with \0
> + gateway_file_data[strcspn(gateway_file_data, "\r\n")] = 0;
Won't this be just \n on Unix-like systems? Could be two lines, one
with strcspn(.., "\n") and the other with "\r".
> +
> + // If strlen finds anything longer then 0 characters then we
> have a
> + // potential gateway url.
> + if (strlen(gateway_file_data) < 1) {
> + av_log(h, AV_LOG_ERROR, "The IPFS gateway file (full uri:
> %s) appears to be empty. Is the gateway started?\n",
> ipfs_gateway_file);
> + ret = AVERROR(EILSEQ);
> + goto err;
> + }
> +
> + // At this point gateway_file_data contains at least something.
> + // Copy it into gateway.
> + if (snprintf(gateway, PATH_MAX, "%s", gateway_file_data) > 0) {
> + ret = 1;
> + goto err;
> + } else
> + av_log(h, AV_LOG_DEBUG, "Unknown error in the IPFS gateway
> file.\n");
> +
> +err:
> + if (gateway_file)
> + fclose(gateway_file);
> +
> + return ret;
> +}
> +
> +// For now just makes sure that the gateway ends in url we expect.
> +// Like http://localhost:8080/.
> +// Explicitly with the traling slash.
> +static int sanitize_ipfs_gateway(URLContext *h, char *gateway)
> +{
> + const char *url_without_protocol;
> + int ret = 1;
> +
> + // Test if the gateway starts with either http:// or https://
> + // The remainder is stored in url_without_protocol
> + if (av_stristart(gateway, "http://";, &url_without_protocol) == 0
> + && av_stristart(gateway, "https://";, &url_without_protocol)
> == 0) {
> + av_log(h, AV_LOG_ERROR, "The gateway URL didn't start with
> http:// or https:// and is therefore invalid.\n");
> + ret = AVERROR(EILSEQ);
> + goto err;
> + }
> +
> + // We now know the remainder of the url without the protocol.
> Check it for
> + // some length. At least 1 character.
> + if (strlen(url_without_protocol) < 1) {
> + av_log(h, AV_LOG_ERROR, "The gateway url (without the
> protocol part) is too short to be a valid URL.\n");
> + ret = AVERROR(EILSEQ);
> + goto err;
> + }
I think we can just rely on the http protocol stuff to deal with this
> +
> +
> + if (gateway[strlen(gateway) - 1] != '/') {
> + // Check if we have enough room to add a '/'
> + // We already know that it's bigger then 0 because that's
> handled
> + // in populate_ipfs_gateway
> +
> + if (strlen(gateway) < (PATH_MAX - 2)) {
> + // We have room. Get the length and add a '/' and a '\0'
> + int gateway_length = strlen(gateway);
> + gateway[gateway_length] = '/';
> + gateway[gateway_length + 1] = '\0';
> + } else
> + av_log(h, AV_LOG_ERROR, "The gateway url is longer then
> the allowed max path length (%i).\n", PATH_MAX);
> +
> + ret = 1;
> + goto err;
> + }
Rolling this into the snprintf() would be prettier
> +
> +err:
> + return ret;
> +}
> +
> +static int translate_ipfs_to_http(URLContext *h, const char *uri,
> + int flags, AVDictionary **options)
> +{
> + const char *ipfs_cid;
> + char *fulluri = NULL;
> + char ipfs_gateway[PATH_MAX];
> + int ret;
> + IPFSGatewayContext *c = h->priv_data;
> +
> + // Test for ipfs://, ipfs:, ipns:// and ipns:. This prefix is
> stripped from
> + // the string leaving just the CID in ipfs_cid.
> + int is_ipfs = av_stristart(uri, "ipfs://", &ipfs_cid);
> + int is_ipns = av_stristart(uri, "ipns://", &ipfs_cid);
> +
> + // We must have either ipns or ipfs.
> + if (!is_ipfs && !is_ipns) {
> + ret = AVERROR(EINVAL);
> + av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
> + goto err;
> + }
Shouldn't this check that the URL is precisely what the protocol
expects? ipfs for ff_ipfs_protocol and ipns for ff_ipns_protocol. Maybe
that's validated further up however..
/Tomas
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