How not to do the network
In the spring of 2016, information security competitions were held in Novosibirsk NSK CTF. Competitions were held two days in a row, the first day was given to schoolchildren, the second - to students. Total participation was 162 people, 19 school and 12 student teams. By the way, since the last competitions ( an article about Sibsutis-CTF and a video about Sibsutis school CTF 2015 ), interest in the event only increases, as does the level of training of participants. Is it all so simple?
I decided to describe the process of setting up the network for the event, and at the same time talk about my experiences and problems. Perhaps the post will be useful to those who hold competitions or are going to hold, as well as to everyone who wants to have fun. Please enjoy.
Competitions were held in the old and new buildings of the University of Communications SibSUTI. After the first day, all the network equipment had to be turned off and reconfigured 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 in the lease and, I suspect, it was mostly treated byreal guys from the business, so the trivial reset of settings turned into an interesting and exciting quest called “find contact at the button”. As a result of experiments it has been established: Dlink points are equipped with a standard “counteraction to the admin” package. The dump took up to 10 minutes. Also, a strange feature of dir-300, dir-600, dir-1000 routers was revealed. The numbers in the title - the time that these routers need to run, presumably in minutes ... It's all the little things, but when you have to set up a large amount of equipment, time waste becomes very significant.
Floor plans of the building.
According to the rules, each team has one team, as well as a router or AP. And the IP plan for used audiences (ip was distributed from the general network in the case of using DAP and started from 20 to eliminate address conflicts):
According to good tradition, all the most important preparations should be made right before the start.
Competitions begin at 9 am on April 10, at 18-00 hours on April 9.
Before the start of 15 hours:
The audience is not ready, there is no Internet, interactives are not ready and the organizers are not allowed in the audience, for a second the thought flashed through my head that in the morning the participants at the gate would see the inscription: “good try ....”. As often happens in our country, people want to stand out, show their importance, which negatively affects the process. They need to be cherished, cherished and persuaded as little children. However, the human factor affects all aspects in any activity and it is impossible not to take it into account.
Interactives. The team for setting up the network is not the only one and there were people simultaneously involved in recreating a maze for a robot intelligence officer (with a gauss gun), preparing a site for virtual reality glasses and preparing audiences for participants. Yes, interactives also needed to be moved.
Some photos of interactivity:
The same robot with radio control and gauss gun. And screenshots of the application for BP:
By the beginning of the competition for the title of the best sysadmin, 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 will lose force. Another factor is the nature of the activity. Strenuous work depletes the body. Remember what it means to work hard or hold a big event - by the end of the day it is squeezed like a carrot on the moon. We get the perfect employee: tired, with poor memory and concentration, with wandering attention. About any work you can forget.
Before the start of 13 hours:
Configured 2 routers. Points refuse to "rebut". Time of wakefulness - 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 by frequency, as practice has later shown, these are not empty words.
Before start 9 hours:
Points are set and set for audiences 451, 408, 420, 422. When testing: dns 8.8.8.8 and 195.149.200.230 (local provider) are not available, the situation is incomprehensible and mysterious. The parameters of one of the TDs: 172.112.19.53, are distributed from 54 to 74 via DHCP. The antenna-feeder device receives signals of a new problem. People are frankly exhausted and simple work turns into a complex and protracted process.
We were lucky, there were computers in the rooms, connected by cable to the network. A good idea to check their settings has borne fruit: ip: 192.168.0.33.
In these classrooms, an internal network is configured that goes through a firewall that blocks all 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: "Why not call the admin, he will make the settings for the screen?" We will answer: "2 am".
Theoretically, the Internet can be made with cable from 449, but the distance of 3-4 construction lengths for twisted pair can not be mastered, despite the presence of switches. Tritely not enough cable.
The nearest outlet with the intoxicating smell of the Internet is in room 216. The decision is made, the network plan is developed!
I will explain. Participants connect to unmanaged switches. TDs connected to each other via WDS are connected to them. Approximately 20 people should use thiscrutch solution, and this is not browsing web pages, like some kind of Habrahabr. It is assumed that people will download torrents and generate a large number of requests. In terms of 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 on the way), the maximum bandwidth was 31 Mbps for Old Believers and almost 4 MB / s for all others. The main thing that was achieved was the stability of the channel in terms of speed and continuity of communication.
Before start 5 hours:
Points are configured and installed, only tests remained. They were still spent 2 hours, as 2 TDs were incorrectly configured.
To start 3 hours:
All is ready.
Despite the fears, this design has worked steadily throughout the day. The main problem is the equipment, more precisely the stability and speed of its work. For one-time setup and long-term use, this is not a problem, but if you need to change them often, a lot of time is spent.
Soon the team will start preparing the now regular school and intercollegiate competitions. It's nice that despite all the problems, the city of Novosibirsk received its worthy competitions. And even more pleased with the fact that there are people who are able to organize all this, assemble, test and accompany, promptly solving the inevitable problems.
At the end I will leave links to videos and photos from the competition.
» Video about the competition
» Photos from the competition
Fragment of the interview:
Anton Anatolyevich Kiselev, Senior Lecturer, Department of Security and Management in Telecommunications, SibSUTI, Curator of the CTF project in SibSUTI.
- How much time did the organizers take to prepare for the competition?
- It is impossible to measure. Of course, the skill is gained, and it was already easier for us to cope than last year. This time it took us a week to the most intensive part of the training. I know that in Tomsk they begin to prepare hard for two weeks. But, in an amicable way, you need to start even earlier: in a month, in order 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 it, especially if we decide to carry out the selection in advance. For example, in Samara, at international Volga CTF competitions, online selection takes place 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. All were tired, but satisfied. Among us was a guy who decided to spend the whole day of his birth at competitions (from 7:00 to 21:00).
')
The competitions were held in task base format, and for a variety of activity, 2 interactive actions were additionally made: a reconnaissance robot with a real gauss cannon 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 experiences and problems. Perhaps the post will be useful to those who hold competitions or are going to hold, as well as to everyone who wants to have fun. Please enjoy.
Competitions were held in the old and new buildings of the University of Communications SibSUTI. After the first day, all the network equipment had to be turned off and reconfigured 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 in the lease and, I suspect, it was mostly treated by
About the task
Floor plans of the building.
According to the rules, each team has one team, as well as a router or AP. And the IP plan for used audiences (ip was distributed from the general network in the case of using DAP and started from 20 to eliminate 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 |
According to good tradition, all the most important preparations should be made right before the start.
Competitions begin at 9 am on April 10, at 18-00 hours on April 9.
Development
Before the start of 15 hours:
The audience is not ready, there is no Internet, interactives are not ready and the organizers are not allowed in the audience, for a second the thought flashed through my head that in the morning the participants at the gate would see the inscription: “good try ....”. As often happens in our country, people want to stand out, show their importance, which negatively affects the process. They need to be cherished, cherished and persuaded as little children. However, the human factor affects all aspects in any activity and it is impossible not to take it into account.
Interactives. The team for setting up the network is not the only one and there were people simultaneously involved in recreating a maze for a robot intelligence officer (with a gauss gun), preparing a site for virtual reality glasses and preparing audiences for participants. Yes, interactives also needed to be moved.
Some photos of interactivity:
The same robot with radio control and gauss gun. And screenshots of the application for BP:
By the beginning of the competition for the title of the best sysadmin, 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 will lose force. Another factor is the nature of the activity. Strenuous work depletes the body. Remember what it means to work hard or hold a big event - by the end of the day it is squeezed like a carrot on the moon. We get the perfect employee: tired, with poor memory and concentration, with wandering attention. About any work you can forget.
Before the start of 13 hours:
Configured 2 routers. Points refuse to "rebut". Time of wakefulness - 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 by frequency, as practice has later shown, these are not empty words.
Before start 9 hours:
Points are set and set for audiences 451, 408, 420, 422. When testing: dns 8.8.8.8 and 195.149.200.230 (local provider) are not available, the situation is incomprehensible and mysterious. The parameters of one of the TDs: 172.112.19.53, are distributed from 54 to 74 via DHCP. The antenna-feeder device receives signals of a new problem. People are frankly exhausted and simple work turns into a complex and protracted process.
We were lucky, there were computers in the rooms, connected by cable to the network. A good idea to check their settings has borne fruit: ip: 192.168.0.33.
In these classrooms, an internal network is configured that goes through a firewall that blocks all 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: "Why not call the admin, he will make the settings for the screen?" We will answer: "2 am".
Theoretically, the Internet can be made with cable from 449, but the distance of 3-4 construction lengths for twisted pair can not be mastered, despite the presence of switches. Tritely not enough cable.
The nearest outlet with the intoxicating smell of the Internet is in room 216. The decision is made, the network plan is developed!
I will explain. Participants connect to unmanaged switches. TDs connected to each other via WDS are connected to them. Approximately 20 people should use this
Before start 5 hours:
Points are configured and installed, only tests remained. They were still spent 2 hours, as 2 TDs were incorrectly configured.
To start 3 hours:
All is ready.
Results
Despite the fears, this design has worked steadily throughout the day. The main problem is the equipment, more precisely the stability and speed of its work. For one-time setup and long-term use, this is not a problem, but if you need to change them often, a lot of time is spent.
Soon the team will start preparing the now regular school and intercollegiate competitions. It's nice that despite all the problems, the city of Novosibirsk received its worthy competitions. And even more pleased with the fact that there are people who are able to organize all this, assemble, test and accompany, promptly solving the inevitable problems.
At the end I will leave links to videos and photos from the competition.
» Video about the competition
» Photos from the competition
Source: https://habr.com/ru/post/311368/
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