20160927 – uphone

Step 1. 어휘 및 문장 Quiz
어려운 단어 없었음

Step 2. 1:1 말하기
1) Today’s Pattern
* I’m back to + Verb.

2) Key Expressions
* Can I pay for this with my credit card?
= Do you take credit cards?
= Do you accept credit cards?

Step 3. 실력 다지기
1) 발음 교정
– doctoral
– pharmacist
– to ride
– (Practice) delicious vs tasty
– I don’t
– I almost

2) Tongue Twister
– How much pot, could a pot roast roast, if a pot roast could roast pot.
– No nose knows like a gnome`s nose knows.

3) 문법 & 문장 교정
– Do you mean, do I supported by government? -> Do you mean , do I get supported by our government?
– I don’t have to have a license. -> I don’t need to have a license.
After entering the university I started drinking. -> When I entered the university, I started drinking.

Step 4. 1:1 글쓰기
1) 교정 이전
Usually, I do not take a pill even if I get a cold. I do not believe that a cold can be cured by taking pills. Taking pills just relieve the symptoms that are caused by a cold. Cold is not caused by bacteria, but caused by viruses. Viruses cannot be killed by pills. It can only be incapacitated by antibodies or destroyed by heat. I only take a pill when I believe that the pill can cure me. Even though I do not like to take a pill, I do depending on the situation. If I have an important meeting with other people, I would take a pill. Sometimes, relieving a symptom is critical. When I take a medicine, I prefer to take a tablet. It is convenient to bring and take. I only need the tablet and water to have it. I used to have vitamin tablets for my health. Currently, I do not have anything left. I have to buy one. Buying vitamin tablets is a cumbersome task. I have to search the web to find the best one. That is the reason why I have not bought tablets until now.

2) 교정 이후

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20160927

1. 시스템 보안 개론
* Code Reuse Attack
– DEP는 공격자가 삽입한 코드의 실행을 방지하므로, code reuse 방식으로 공격하면 된다.
– JIT CRA는 실행 시점에서 gadget의 위치를 파악한다.
– Stack pointer가 올바른 위치에 있는지 확인하는 방식도 있음.
– Return하는 시점에 올바른 주소로 돌아가는지 확인하는 방식도 있음.

* ROPGuard
– 2012년에 Microsoft BlueHat에서 수상함.
– 실제 Microsoft EMET에 구현됨.
– 중요 위치에 스택이 정상인지 확인하겠다는 것.
– Compile 시점에 명령어를 삽입하거나, 동적으로 바이너리를 수정한다.
– 보호하고자 하는 6가지: stack pointer가 올바른 주소 범위 안에 있는지, address of critical function이 수상하게 많이 쓰이는지, return address가 가능한 return address set 이내에 있는지(해당 함수를 호출하는 모든 주소), call stack, stack frame, function-specific.
– CET는 돌아와야 하는 주소를 정확히 지정해준다는 점에서 ROPGuard와 다르다(fine-grained vs coarse-grained).
– ret하는 시점에 코드 검증할 수 있을 것. ret 명령어의 의미를 바꾸는 것과 같음. dynamic binary instrumentation을 수행한다.

* fat pointer: 원래 pointer는 주소만 저장하는데, fat pointer는 할당된 메모리 영역에 대한 정보까지 담고 있다.

* kBouncer
– LBR은 최근에 실행된 branch에 대한 정보를 담고 있다(16개)
– 원래는 디버깅을 위해 사용하던 것.
– kBouncer에서는 LBR을 사용해 ROP를 막는 방법.
– 중요 함수 호출 이전에 LBR을 검토하여 정상적인 모습인지 아닌지 확인한다.
– illegal return이 존재하는지 아닌지 확인해야 한다.
– 하지만 여전히 소프트웨어가 LBR을 읽어야 하므로, 중요 함수가 호출되는 시점에서만 이를 확인한다.
– compiler-level 방어 기법은 소스 코드가 있어야 한다는 한계가 있고, 이 때문에 실제 적용이 어렵다는 문제점이 있다. Binary rewrite는 실행 바이너리를 수정하는 것. 5-byte 정도의 여유 공간이 있으면 이를 사용해 원하는 코드로 뛰도록 하는 것. Compiler-level보다 적용이 쉽다. Dynamic instrumentation은 명령어의 해석을 바꾸도록 하는 것. 하지만 오버헤드가 크다는 것이 문제. LBR 모니터링은 적은 오버헤드로 쉽게 적용할 수 있다.
– illegal return이 있는지, short return gadget이 연속되어 있는지 확인한다.


2. Scala 튜토리얼
https://www.tutorialspoint.com/scala/index.htm

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20160926 – uphone

Step 1. 어휘 및 문장 Quiz
어려운 단어 없었음

Step 2. 1:1 말하기
1) Today’s Pattern
When was the last time + Subject(주어) + Past(과거형)?

2) Key Expressions
* What kind of problem are you having?
= What is the matter?
= What kind of concerns do you have?

Step 3. 실력 다지기
1) 발음 교정
– to make an appointment
– had a physical
– to have a check-up
– the last time
– saw a doctor
– an emergency room

2) Tongue Twister
– How can a clam cram in a clean cream can?

3) 문법 & 문장 교정
– I think medical check up is important to find out … -> similar expression: I think medical check up is imperative to find out …
– It can be harmful to her health -> similar expression: It can be dangerous to her health
– She was worried about her. -> similar expression: She was so concerned about her
– I cannot remember exactly -> suggested expression: I barely remember exactly what happened
– It can be more easy to move out -> It can be much easier to move out
– Seeing a doctor can be helpful -> similar expression: Seeing a doctor is beneficial

Step 4. 1:1 글쓰기
1) 교정 이전
I see a doctor regularly for my medical checkup. In my university, submitting a medical checkup report is mandatory to live in a dormitory. It is mandatory for all residents for health. Previously, few students had tuberculosis in my university. Having a regular medical checkup is one of ways to prevent the spreading of tuberculosis. I think that having a regular medical checkup make me relieved because I can sure that I am healthy. Additionally, regular medical checkups can motivate me sometimes because the report shows my possible health problems. Thankfully, I do not have severe problem until now. I just needed an exercise for my health. I am quite sure that I would get a better report next year because I exercise regularly. In October, I have an another plan to see a doctor. I will see a dentist to make sure that my teeth healthy. Since some of my teeth are worn too much, I would like to make it filled. I think that it is so nice to live in today. If I was born in few decades ago, it would not be possible to make it filled.

2) 교정 이후

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20160923 – uphone

Step 1. 어휘 및 문장 Quiz
– damp: 눅눅한
– furnace: 보일러

Step 2. 1:1 말하기
1) Today’s Pattern
It’s the + Superlative(최상급) + Noun(명사) + in + something.

2) Key Expressions
* It also feels damp.
= It also feels wet.
= It also feels dank.

Step 3. 실력 다지기
1) 발음 교정
– nothing special
– is the rent
– first-floor units
– has been turned off
– ride my bicycle alone
– a little bit dark

2) Tongue Twister
– A loyal warrior will rarely worry why we rule.

3) 문법 & 문장 교정
I think it can help my health. -> It will help me become healthy.
– I think bicycle is a kind of working out. -> I think riding a bicycle is also a form of exercise.
I used to but not recently. -> (SUGGESTION) I no longer go to the gym.
– I don’t have that much time left. -> I don’t have enough time left.
– Person A is going to rent apartment. -> Person A is looking for an apartment for rent.
– It help me take a rest. -> It will help me feel comfortable when I am resting.

Step 4. 1:1 글쓰기
1) 교정 이전
Currently, I live in my dormitory and I am quite satisfied with my current dormitory room. It is the cheapest room that I have lived in. Additionally, the facilities are also good enough. My room has two beds, two desks, and two closets because the room is designed to be used by two residents. However, currently I am using the room alone. There is no roommate for me. I think that I am so lucky. One problem in my dormitory is that I can easily hear the noises from other rooms. The room where I lived before was terrible. I could clearly hear the snore of a person who lives in the next room. Although my current room is good, there was fungi everywhere in the previous room. I decided to move out from the room because of fungi. I think that home is very important for the quality of one’s life. A house is where a person stays and also takes a rest. If a house is not comfortable enough, people who live in there would not be happy. If I have a chance to live outside of my dormitory, I would investigate candidate rooms thoroughly.

2) 교정 이후
Currently, I live in my dormitory and I am quite satisfied with my current dormitory(X) room. It is the cheapest room that I have lived in. Additionally, the facilities are also good enough. My room has two beds, two desks, and two closets because the room is designed to be used by two residents. However, currently(,) I am using the room alone. There is no roommate for me (I have no roommate). I think that I am so lucky. One problem in my dormitory is that I can easily hear the noises (noise) from other rooms. The room where I lived before was terrible. I could clearly hear the snore of a person who lives in the next room. Although my current room is good, there was (is) fungi everywhere in the previous room. I decided to move out from the (that) room because of fungi. I think that (a) home is very important for the quality of one’s life. A house is where a person stays and also takes a rest. If a house is not comfortable enough, people who live in there would not be happy. If I have a chance to live outside of(X) my dormitory, I would investigate candidate (the) rooms thoroughly.

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