128 lines
5.7 KiB
Markdown
128 lines
5.7 KiB
Markdown
# IPFS
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For an overview about IPFS, visit the [IPFS project site](https://ipfs.tech/).
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In IPFS there are two protocols. IPFS and IPNS (their workings are explained in detail [here](https://docs.ipfs.tech/concepts/)). The ideal way to access data on the IPFS network is through those protocols. For example to access the Big Buck Bunny video the ideal way to access it is like: `ipfs://bafybeigagd5nmnn2iys2f3doro7ydrevyr2mzarwidgadawmamiteydbzi`
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## IPFS Gateways
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IPFS Gateway acts as a bridge between traditional HTTP clients and IPFS.
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IPFS Gateway specifications of HTTP semantics can be found [here](https://specs.ipfs.tech/http-gateways/).
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### Deserialized responses
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By default, a gateway acts as a bridge between traditional HTTP clients and IPFS and performs necessary hash verification and deserialization. Through such gateway, users can download files, directories, and other content-addressed data stored with IPFS or IPNS as if they were stored in a traditional web server.
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### Verifiable responses
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By explicitly requesting [application/vnd.ipld.raw](https://www.iana.org/assignments/media-types/application/vnd.ipld.raw) or [application/vnd.ipld.car](https://www.iana.org/assignments/media-types/application/vnd.ipld.car) responses, by means defined in [Trustless Gateway Specification](https://specs.ipfs.tech/http-gateways/trustless-gateway/), the user is able to fetch raw content-addressed data and [perform hash verification themselves](https://docs.ipfs.tech/reference/http/gateway/#trustless-verifiable-retrieval).
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This enables users to use untrusted, public gateways without worrying they might return invalid/malicious bytes.
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## IPFS and IPNS protocol handling
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There are various ways to access data from the IPFS network. One such way is
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through the concept of public
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"[gateways](https://docs.ipfs.tech/concepts/ipfs-gateway/#overview)". The
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short version is that entities can offer gateway services. An example here
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that is hosted by Protocol Labs (who also makes IPFS) is `dweb.link` and
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`ipfs.io`. Both sites expose gateway functionality. Getting a file through
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`ipfs.io` looks like this:
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`https://ipfs.io/ipfs/bafybeigagd5nmnn2iys2f3doro7ydrevyr2mzarwidgadawmamiteydbzi`
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If you were to be [running your own IPFS
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node](https://docs.ipfs.tech/how-to/command-line-quick-start/) then you, by
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default, also have a [local gateway](https://specs.ipfs.tech/http-gateways/)
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running. In its default configuration the earlier example would then also work
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in this link:
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`http://127.0.0.1:8080/ipfs/bafybeigagd5nmnn2iys2f3doro7ydrevyr2mzarwidgadawmamiteydbzi`
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## cURL handling of the IPFS protocols
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The IPFS integration in cURL hides this gateway logic for you. Instead of
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providing a full URL to a file on IPFS like this:
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```
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curl http://127.0.0.1:8080/ipfs/bafybeigagd5nmnn2iys2f3doro7ydrevyr2mzarwidgadawmamiteydbzi
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```
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You can provide it with the IPFS protocol instead:
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```
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curl ipfs://bafybeigagd5nmnn2iys2f3doro7ydrevyr2mzarwidgadawmamiteydbzi
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```
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With the IPFS protocol way of asking a file, cURL still needs to know the
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gateway. curl essentially just rewrites the IPFS based URL to a gateway URL.
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### IPFS_GATEWAY environment variable
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If the `IPFS_GATEWAY` environment variable is found, its value is used as
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gateway.
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### Automatic gateway detection
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When you provide no additional details to cURL then it:
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1. First looks for the `IPFS_GATEWAY` environment variable and use that if it
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is set.
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2. Looks for the file: `~/.ipfs/gateway`. If it can find that file then it
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means that you have a local gateway running and that file contains the URL
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to your local gateway.
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If cURL fails, you are presented with an error message and a link to this page
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to the option most applicable to solving the issue.
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### `--ipfs-gateway` argument
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You can also provide a `--ipfs-gateway` argument to cURL. This overrules any
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other gateway setting. curl does not fallback to the other options if the
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provided gateway did not work.
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## Gateway redirects
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A gateway could redirect to another place. For example, `dweb.link` redirects
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[path based](https://docs.ipfs.tech/how-to/address-ipfs-on-web/#path-gateway)
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requests to [subdomain
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based](https://docs.ipfs.tech/how-to/address-ipfs-on-web/#subdomain-gateway)
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ones. A request using:
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curl ipfs://bafybeigagd5nmnn2iys2f3doro7ydrevyr2mzarwidgadawmamiteydbzi --ipfs-gateway https://dweb.link
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Which would be translated to:
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https://dweb.link/ipfs/bafybeigagd5nmnn2iys2f3doro7ydrevyr2mzarwidgadawmamiteydbzi
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redirects to:
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https://bafybeigagd5nmnn2iys2f3doro7ydrevyr2mzarwidgadawmamiteydbzi.ipfs.dweb.link
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If you trust this behavior from your gateway of choice then passing the `-L`
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option follows the redirect.
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## Error messages and hints
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Depending on the arguments, cURL could present the user with an error.
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### Gateway file and environment variable
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cURL tried to look for the file: `~/.ipfs/gateway` but could not find it. It
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also tried to look for the `IPFS_GATEWAY` environment variable but could not
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find that either. This happens when no extra arguments are passed to cURL and
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letting it try to figure it out [automatically](#automatic-gateway-detection).
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Any IPFS implementation that has gateway support should expose its URL in
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`~/.ipfs/gateway`. If you are already running a gateway, make sure it exposes
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the file where cURL expects to find it.
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Alternatively you could set the `IPFS_GATEWAY` environment variable or pass
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the `--ipfs-gateway` flag to the cURL command.
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### Malformed gateway URL
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The command executed evaluates in an invalid URL. This could be anywhere in
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the URL, but a likely point is a wrong gateway URL.
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Inspect the URL set via the `IPFS_GATEWAY` environment variable or passed with
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the `--ipfs-gateway` flag. Alternatively opt to go for the
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[automatic](#automatic-gateway-detection) gateway detection.
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