How not to make networks
In the spring of 2016, information security competitions in Novosibirsk NSK CTF were held. Competitions were held two days in a row, the first day was given to schoolchildren, the second - to students. In total, 162 people, 19 school and 12 student teams took part. By the way, since the last competitions ( article about Sibsutis-CTF and video about Sibsutis school CTF 2015 ), interest in the event has only increased, as well as the level of training of participants. Is it that simple?
I decided to describe the process of setting up the network for the event, and at the same time talk about my impressions and problems. Perhaps the post will be useful to those who hold or are planning to hold competitions, as well as to everyone who wants to have fun. Please enjoy.
Competitions were held in the old and new building of the University of Communications SibGUTI. After the first day, it was necessary to collapse all network equipment and reconfigure it in another building.
One of the sponsors, D-link, without which these competitions would not have taken place, kindly provided us with a wide range of equipment, namely: DIR-300S, DIR-806A, DIR-815C1, DIR-645, DIR-640L, DES-1005A , DES-1008D, DAP-2590, DAP-2360.
The equipment is not new, working on lease and, I suspect, it was mainlyreal boys who handled it
Floor plans of the building.
According to the rules, one audience is placed in each audience, as well as a router or AP. And the IP plan for the audiences used (ip were distributed from the general network in case of using DAP and started with 20 to avoid address conflicts):
By a good tradition, all the most responsible preparations must be done right before the start.
Competitions begin at 9 am on April 10, at 18-00 on April 9.
Before the start of 15 hours:
Audiences are not ready, there is no Internet, interactives are not ready and the organizing team is not allowed into the audience, for a second the thought flashed through the head that in the morning the participants would see the inscription: “good try ....” on the gates. As often happens in our country, people want to stand out, show their importance, which negatively affects the process. They need to be cared for, cherished and persuaded like little children. However, the human factor affects all aspects in any activity and cannot be ignored.
Interactive The network setup team wasn’t the only one and there were people who were simultaneously engaged in the reconstruction of the labyrinth for the intelligence robot (with a Gauss gun), the preparation of the platform for virtual reality glasses, and the preparation of audiences for participants. Yes, interactions also needed to be moved.
A few photos of the interactive:
The same robot with radio control and a gauss gun. And screenshots of the application for BP:
By the beginning of competitions for the title of the best system administrator, the team did not sleep for about 12 hours, it is known that if a person does not sleep for a day or more, his reaction and mental abilities lose strength. Another factor is the nature of the activity. Hard work drains the body. Remember what it means to work hard or to hold a large event - by the end of the day they are squeezed like carrots on the moon. We get the ideal employee: tired, with poor memory and concentration, with wandering attention. You can forget about any creativity.
Before the start of 13 hours:
2 routers are configured. The points refuse to "rebuild." Wakefulness time - 14 hours, “intoxication with lack of sleep” begins to affect. Slowly adjust the points, test. Be sure to take into account the separation of channels in frequencies, as practice later showed, these are not empty words.
Before the start of 9 hours:
Points are set and set for audiences 451, 408, 420, 422. During testing: dns 8.8.8.8 and 195.149.200.230 (local provider) are not available, the situation is incomprehensible and mysterious. Parameters of one of the APs: 172.112.19.53, it is distributed via DHCP from 54 to 74. An antenna-feeder device receives signals of a new problem. People are frankly exhausted and simple work turns into a complex and lengthy process.
We were lucky, in the rooms there were computers connected by cable to the network. A good idea to check their settings paid off: ip: 192.168.0.33.
In these audiences, an internal network is configured, which goes through a firewall blocking any connections, except on sibsutis.ru. We love the good news. Very very.
In fact, there is 1 room in stock, and you can not use it. But in three other Internet should be. You ask: “And why not call the administrator, he will make the settings for the screen?” We will answer: “2 a.m.”
Theoretically, the Internet can be carried out with a cable of 449, but the distance of 3-4 building lengths for a twisted pair cable can not be mastered, despite the presence of switches. Trite is not enough cable.
The nearest outlet with the stupefying smell of the Internet is in 216 rooms. Decision made, network plan developed!
I will explain. Participants connect to unmanaged switches. APs connected to each other via WDS are also connected to them. About 20 people should use thiscrutch solution, and this is not browsing the Internet, like Habrahabr. It is assumed that people will download torrents and generate a large number of requests. Given the fact that the original channel had a low bandwidth and WDS itself cuts speed (many factors influence here: antenna directivity, radiation power, distance, obstacles), the maximum bandwidth was 31 Mb / s for Old Believers and almost 4 MB / s for everyone else. The main thing that was achieved was the stability of the channel in terms of speed and continuity of communication.
Before the start of 5 hours:
Points are configured and installed, there are only tests. They still spent 2 hours, since 2 APs were incorrectly configured.
3 hours before the start:
Everything is ready.
Despite concerns, this design worked stably all day. The main problem is the equipment, more precisely the stability and speed of its work. For a one-time setup and long-term use, this does not present a problem, but if you need to change them frequently, a lot of time is spent.
Soon the team will begin to prepare now the next school and inter-university competitions. It is nice that, despite all the problems, the city of Novosibirsk received its competitions of a decent level. And even more encouraging is the fact that there are people who are able to organize all this, assemble, test and accompany, quickly solving the inevitable problems that arise.
In conclusion, I will leave links to videos and photos from the competition.
» Video about the competition
» Photos from the competition
Interview fragment:
Anton Anatolievich Kiselev, Senior Lecturer, Department of Security and Management in Telecommunications, SibGUTI, curator of the CTF project in SibGUTI.
- How much time did the organizers take to prepare for the competition?
- It is impossible to measure. The skill, of course, is being developed, and it was already easier for us to cope than last year. This time it took us a week to the most intense part of the preparation. I know that in Tomsk they begin to prepare intensively in two weeks. But, in a good way, you need to start even earlier: a month to do everything slowly, and even better three months before the competition. After all, it is necessary to prepare documents, coordinate with the administration and so on. Most likely, we will do so, especially if we decide to conduct a selection in advance. For example, in Samara, at the Volga CTF international competitions, an online selection is held in a few months. This year 800 teams participated in it, and only five passed. Maybe in school competitions we will also come to a similar selection scheme: for example, we will miss the 15 best teams.
In any case, we got a good experience. Everyone was tired, but happy. Among us was a guy who decided to spend his whole birthday in competitions (from 7:00 to 21:00).
The competition was held in a task base format, and for a variety of activities 2 additional interactions were made: a scout robot with a real Gaussian gun and virtual reality glasses.
I decided to describe the process of setting up the network for the event, and at the same time talk about my impressions and problems. Perhaps the post will be useful to those who hold or are planning to hold competitions, as well as to everyone who wants to have fun. Please enjoy.
Competitions were held in the old and new building of the University of Communications SibGUTI. After the first day, it was necessary to collapse all network equipment and reconfigure it in another building.
One of the sponsors, D-link, without which these competitions would not have taken place, kindly provided us with a wide range of equipment, namely: DIR-300S, DIR-806A, DIR-815C1, DIR-645, DIR-640L, DES-1005A , DES-1008D, DAP-2590, DAP-2360.
The equipment is not new, working on lease and, I suspect, it was mainly
About the task
Floor plans of the building.
According to the rules, one audience is placed in each audience, as well as a router or AP. And the IP plan for the audiences used (ip were distributed from the general network in case of using DAP and started with 20 to avoid address conflicts):
| 219.172.112.19.20 | 359.172.113.59.20 |
| 263.172.112.63.20 | 408.172.114.8.20 |
| 333.172.113.33.20 | 420.172.114.20.20 |
| 335.172.113.35.20 | 422.172.114.22.20 |
| 346.172.113.46.20 | 449.172.114.49.20 |
| 347.172.113.47.20 | 451.172.114.51.20 |
| 349.172.113.49.20 | 457.172.114.57.20 |
| 358.172.113.58.20 |
By a good tradition, all the most responsible preparations must be done right before the start.
Competitions begin at 9 am on April 10, at 18-00 on April 9.
Development
Before the start of 15 hours:
Audiences are not ready, there is no Internet, interactives are not ready and the organizing team is not allowed into the audience, for a second the thought flashed through the head that in the morning the participants would see the inscription: “good try ....” on the gates. As often happens in our country, people want to stand out, show their importance, which negatively affects the process. They need to be cared for, cherished and persuaded like little children. However, the human factor affects all aspects in any activity and cannot be ignored.
Interactive The network setup team wasn’t the only one and there were people who were simultaneously engaged in the reconstruction of the labyrinth for the intelligence robot (with a Gauss gun), the preparation of the platform for virtual reality glasses, and the preparation of audiences for participants. Yes, interactions also needed to be moved.
A few photos of the interactive:
The same robot with radio control and a gauss gun. And screenshots of the application for BP:
By the beginning of competitions for the title of the best system administrator, the team did not sleep for about 12 hours, it is known that if a person does not sleep for a day or more, his reaction and mental abilities lose strength. Another factor is the nature of the activity. Hard work drains the body. Remember what it means to work hard or to hold a large event - by the end of the day they are squeezed like carrots on the moon. We get the ideal employee: tired, with poor memory and concentration, with wandering attention. You can forget about any creativity.
Before the start of 13 hours:
2 routers are configured. The points refuse to "rebuild." Wakefulness time - 14 hours, “intoxication with lack of sleep” begins to affect. Slowly adjust the points, test. Be sure to take into account the separation of channels in frequencies, as practice later showed, these are not empty words.
Before the start of 9 hours:
Points are set and set for audiences 451, 408, 420, 422. During testing: dns 8.8.8.8 and 195.149.200.230 (local provider) are not available, the situation is incomprehensible and mysterious. Parameters of one of the APs: 172.112.19.53, it is distributed via DHCP from 54 to 74. An antenna-feeder device receives signals of a new problem. People are frankly exhausted and simple work turns into a complex and lengthy process.
We were lucky, in the rooms there were computers connected by cable to the network. A good idea to check their settings paid off: ip: 192.168.0.33.
In these audiences, an internal network is configured, which goes through a firewall blocking any connections, except on sibsutis.ru. We love the good news. Very very.
In fact, there is 1 room in stock, and you can not use it. But in three other Internet should be. You ask: “And why not call the administrator, he will make the settings for the screen?” We will answer: “2 a.m.”
Theoretically, the Internet can be carried out with a cable of 449, but the distance of 3-4 building lengths for a twisted pair cable can not be mastered, despite the presence of switches. Trite is not enough cable.
The nearest outlet with the stupefying smell of the Internet is in 216 rooms. Decision made, network plan developed!
I will explain. Participants connect to unmanaged switches. APs connected to each other via WDS are also connected to them. About 20 people should use this
Before the start of 5 hours:
Points are configured and installed, there are only tests. They still spent 2 hours, since 2 APs were incorrectly configured.
3 hours before the start:
Everything is ready.
Summary
Despite concerns, this design worked stably all day. The main problem is the equipment, more precisely the stability and speed of its work. For a one-time setup and long-term use, this does not present a problem, but if you need to change them frequently, a lot of time is spent.
Soon the team will begin to prepare now the next school and inter-university competitions. It is nice that, despite all the problems, the city of Novosibirsk received its competitions of a decent level. And even more encouraging is the fact that there are people who are able to organize all this, assemble, test and accompany, quickly solving the inevitable problems that arise.
In conclusion, I will leave links to videos and photos from the competition.
» Video about the competition
» Photos from the competition