=Paper=
{{Paper
|id=Vol-3947/short6
|storemode=property
|title=Solid-cURL
|pdfUrl=https://ceur-ws.org/Vol-3947/short6.pdf
|volume=Vol-3947
|authors=Daniel Schraudner
}}
==Solid-cURL==
https://ceur-ws.org/Vol-3947/short6.pdf
Solid-cURL
Daniel Schraudner1
1
Friedrich-Alexander-Universität Erlangen-Nürnberg, Nuremberg, Germany
Abstract
We implemented Solid-cURL, a tool that extends cURL be adding Solid-OIDC authentication. Solid-cURL
can be used by Solid developers and researchers that aim to use a tool of the simple elegance as cURL but
do not want to handle the Solid authentication manually for every request. We described the different
components of Solid-cURL and how they interact with each other.
Keywords
Solid, Tool, Open ID Connect
1. Introduction
In their daily work, Solid developers and researchers often have to manually send specific HTTP
request to Solid servers. Doing this with a web browser is often not very practical as one first
has to login with Solid-Open ID Connect (Solid-OIDC) [1] using a Solid app. The requests that
can be send afterwards are only those that are allowed by the app.
Web developer and researchers in this situation used the widespread tool cURL1 . cURL is
a command line program that allows to specify the parameters of an HTTP request (method,
headers, etc.) in every detail. cURL executes this request and displays the result to the user.
Example 1. Creating a new RDF resource in a container on a Solid Pod that is publicly writeable:
curl -X POST https://dschraudner.solidcommunity.net/public/
-d "<> a ." -H "Content-Type: text/turtle"
As cURL allows to specify arbitrary headers for a request it could theoretically be used to
send authenticated requests to Solid servers by copying the Solid-OIDC specific headers (access
token [2] and Demonstrating Proof of Possession (DPoP) token [3]) to the cURL command line
parameters. This approach, however is very impractical, as the DPoP header changes every
time the request method or URI changes; the access token automatically expires after some
time.
Example 2. Creating a new RDF resource in a container on a Solid Pod with authentication:
curl -X POST https://dschraudner.solidcommunity.net/public/
The 1st Solid Symposium Poster Session, co-located with the 2nd Solid Symposium, May 02 – 03, 2024, Leuven, Belgium
$ daniel.schraudner@fau.de (D. Schraudner)
0000-0002-2660-676X (D. Schraudner)
© 2024 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
1
https://curl.se/
CEUR
ceur-ws.org
Workshop ISSN 1613-0073
Proceedings
-d "<> a ." -H "Content-Type: text/turtle"
-H "Authorization: DPoP eyJhbGciOiJFUzI1NiIsInR5cCI6ImF0K2p3dCIsImtpZCI
6IlJTWXloeE4wb1lsb0JOUVQ1OExZTkhpSzNOTWhRa1QyQ3FZMVJzbzd6N28ifQ.eyJ3ZW
JpZCI6Imh0dHBzOi8vdG9tLnNvbGlkLmFpZmIua2l0LmVkdS9wcm9maWxlL2NhcmQjbWUi
LCJqdGkiOiJ2dUJQVHVIcmRTZlVOS0ZCc0tQelEiLCJzdWIiOiJodHRwczovL3RvbS5zb2
xpZC5haWZiLmtpdC5lZHUvcHJvZmlsZS9jYXJkI21lIiwiaWF0IjoxNzE3NjY1NTI0LCJl
eHAiOjE3MTc2NjkxMjQsInNjb3BlIjoiIiwiY2xpZW50X2lkIjoiNl9sc0J4V2p0UzM3TV
hOLUdCQm8xIiwiaXNzIjoiaHR0cHM6Ly9zb2xpZC5haWZiLmtpdC5lZHUvIiwiYXVkIjoi
c29saWQiLCJjbmYiOnsiamt0IjoiQm1kY0tDdVJOTktsYy1yUmxsZzRKRnJsN3VDdnlSd
GUxeWVoRkpjRnFSayJ9fQ.PUHYhDLT4l9nHkmsXZXe0I_7nYJCQuq5vyBb8d1eYVlV55gu
JDacrN-HKNnPH6DrOkcCHjvqQxesGLvz7qXvUw"
-H "DPoP: eyJhbGciOiJFUzI1NiIsImp3ayI6eyJjcnYiOiJQLTI1NiIsImt0eSI6IkVD
IiwieCI6ImtHSk81QUx5emZnQlNsYXZTOUJrX2FOV1ZLR1pqaTY2NkJ1YTNGWUoyX28iLC
J5IjoiWHVlRWJfdmNVX2c0cGdaQS1TMHg2R3BYWE02Z2RwMUVWV19jTVdGb3VPSSIsImFs
ZyI6IkVTMjU2In0sInR5cCI6ImRwb3Arand0In0.eyJodHUiOiJodHRwczovL2Jhbmsuc2
9saWQuYWlmYi5raXQuZWR1L29mZmVyLzEiLCJodG0iOiJHRVQiLCJqdGkiOiI3YzJkNGRh
Zi00ZWYyLTQ1MWQtODY1MS1hMWE1ZjUwOThjZDgiLCJpYXQiOjE3MTc2NjU1MjV9.aK_Si
ndnZNLhjeSQnfX551lwMm6oW7Hw9RGXWNqESGPO3JqWEE9sSImATEfJR_iOF-nrqXz1zdH
BxztdwoG1Ww"
In this paper we present Solid-cURL. Solid-cURL is a program that tries to mimic the command
line interface and behaviour of cURL. Additionally it allows users to log in via Solid-OIDC.
The credentials can be stored and used for future HTTP request by specifying a command line
parameter.
Example 3. Creating a new RDF resource in a container on a Solid Pod using authentication
with solid-curl
solid-curl -X POST https://dschraudner.solidcommunity.net/public/
-d "<> a ." -H "Content-Type: text/turtle" -u daniel
In the remainder of this paper, we will give first go through related work, then give an
overview of the different components of Solid-cURL, introduce our implementation of Solid-
cURL and give a short outlook.
2. Related Work
Penny2 , Solid Filemanager3 , Solid IDE4 , and SolidOS5 are examples of Solid apps that work like
file managers. They allow to create new resources and containers on the Pod and allow to alter
and delete existing ones. They, however, do not let the user exercise such a fine-grained control
that is possible by manually sending HTTP request using cURL (e.g. setting specific headers).
2
https://penny.vincenttunru.com/
3
https://otto-aa.github.io/solid-filemanager/
4
https://jeff-zucker.github.io/solid-content-manager/
5
https://github.com/SolidOS/solidos
Figure 1: UML interaction diagram showing the different components of Solid-cURL and their interac-
tion
Solid-shell6 is a command line tool for managing data on a Solid Pod. It allows the user to log
in and use different file system-specific operations like copy, move, recursiveDelete, etc. Also
the names of the different HTTP methods are available as commands, they, however, only allow
to specify the URI and the body; headers and other additional settings that cURL is capable of
controlling are hidden for the user.
Bashlib7 is another command line tool whose main focus is to be used together with the
Community Solid Server [4]. It has a lot of capabilities like the usual file system operations but
it can also query a resource with SPARQL [5] or manipulate ACL permissions. Here, too, the
user has no fine-grained control over the exact HTTP request that is sent to the Solid Pod.
3. Components
In Figure 1 a UML interaction diagram showing the principal components can be seen and their
interaction.
The Command Line Parser is responsible for parsing and interpreting the command line input
of the user and giving it to the Main component of Solid-cURL. Based on the parameters (more
specifically, the Solid user specified as parameter) the Main component uses the Credential
Storage component to retrieved previously saved credentials. The credentials are then given to
the Authenticator component which carries out the login process (i.e. it retrieves and access
token and creates a DPoP). Access token and DPoP are given to the Request component who
carries out the actual request according to the command line parameters and with the correct
6
https://github.com/jeff-zucker/solid-shell/
7
https://github.com/SolidLabResearch/Bashlib
Solid-OIDC headers set. The response is then printed to the user on the command line.
4. Implementation
We implemented Solid-cURL in Javascript. The source code is available via GitHub8 and an
executable script can be installed using the Node Package Manager9 .
For the Command Line Parser component we used the Commander.js library10 . For the
Credential Storage component we used the operating system’s keychain accessed using the
keytar library11 . For the authenticator component we used the solid-client-authn-node library12
from Inrupt. For the request component we also used the solid-client-authn-node library or the
fetch provided by it, respectively.
5. Outlook
For the future we want to extend the capabilities (regarding the possible options and parameters)
of Solid-cURL to match those of the original cURL. For this we started to rewrite Solid-cURL
in C++13 to be able to use the libcurl library. cURL is also directly based on this library which
makes it easier to mimic cURL capabilities using this libraries. Implementing Solid-cURL in
C++ could also positively impact its performance, as JavaScript is usually compiled just-in-time
which leads to a warm-up delay when starting the program [6].
For C++, however, there exists to our knowledge no library for Solid-OIDC which means we
will have to handle all the different tokens used in the process manually.
Acknowledgments
This work is partially funded by the German Federal Ministry of Education and Research via
the MANDAT project (FKZ 16DTM107A).
References
[1] A. Coburn, D. Zagidulin, A. Migus, R. White, et al., Solid-oidc, Specification. Solid (2022).
[2] D. Hardt, The OAuth 2.0 authorization framework, Technical Report, 2012.
[3] D. Fett, Authlete, Campbell, OAuth 2.0 Demonstrating Proof of Possession (DPoP), Technical
Report, 2012.
[4] J. Van Herwegen, R. Verborgh, The community solid server: Supporting research & devel-
opment in an evolving ecosystem, Semantic Web Journal. https://doi. org/10.5281/zenodo
7595116 (????).
8
https://github.com/wintechis/solid-curl
9
https://www.npmjs.com/package/solid-curl
10
https://github.com/tj/commander.js?
11
https://github.com/atom/node-keytar
12
https://github.com/inrupt/solid-client-authn-js
13
https://purl.org/solid-curl/cpp
[5] J. Pérez, M. Arenas, C. Gutierrez, Semantics and complexity of sparql, ACM Transactions
on Database Systems (TODS) 34 (2009) 1–45.
[6] M. Selakovic, M. Pradel, Performance issues and optimizations in javascript: an empirical
study, in: Proceedings of the 38th International Conference on Software Engineering, 2016,
pp. 61–72.