The PICO process (or framework) is a mnemonic used in evidence based practice (and specifically Evidence Based Medicine) to frame and answer a clinical or health care related question.[1] The PICO framework is also used to develop literature search strategies, for instance in systematic reviews.[2] The PICO acronym stands for[3][4]
- Pico 2019 Write Up Form
- Pico 2019 Write Up Letter
- Picoctf 2019 Writeup
- Pico 2019 Write Up Assignment
- Pico 2019 Write Up Template
- Pico 2019 Write Up Software
- P – Patient, Problem or Population
- I – Intervention
- C – Comparison, control or comparator[5]
- O – Outcome(s) (e.g. pain, fatigue, nausea, infections, death)
PicoCTF 2019 Writeup: Binary Exploitation Oct 12, 2019 00:00 5411 words 26 minute read ctf cyber-security write-up picoctf pwn handy-shellcode.
Jul 02, 2020 PICO Question Template Examples It can be helpful to classify your question based on the clinical domain(s) it falls under. See below for definitions, PICO templates, and example questions from the primary clinical domains: intervention, diagnosis, etiology, prevention, prognosis/prediction, quality of life/meaning, and therapy. Contribute to tcode2k16/picoctf-2019-writeup development by creating an account on GitHub.
Alternatives such as SPICE and PECO (among many others) can also be used. Some authors suggest adding T and S, as follows:
- T - Timing, duration or date of publication (e.g. measured at 1-month of follow-up, published between 1990 and 2000)
- S - Study type (e.g. randomized controlled trial, cohort study, etc.)
Examples[edit]
Clinical question: 'In children with headache, is paracetamol more effective than placebo against pain?'
- Population = Children with headaches; keywords = children + headache
- Intervention = Paracetamol; keyword = paracetamol
- Compared with = Placebo; keyword = placebo
- Outcome of interest = Pain; keyword = pain
Pubmed (health research database) search strategy: children headache paracetamol placebo pain
References[edit]
- ^Huang X, Lin J, Demner-Fushman D (2006). 'Evaluation of PICO as a knowledge representation for clinical questions'(PDF). AMIA Annu Symp Proc: 359–63. PMC1839740. PMID17238363.
- ^Schardt C, Adams MB, Owens T, Keitz S, Fontelo P (2007). 'Utilization of the PICO framework to improve searching PubMed for clinical questions'. BMC Med Inform Decis Mak. 7: 16. doi:10.1186/1472-6947-7-16. PMC1904193. PMID17573961.
- ^'Asking a Good Question (PICO)'. 17 November 2004. Retrieved 2010-05-18.
- ^Richardson, WS (1995). 'The well-built clinical question: a key to evidence based-decisions'. APC Journal Club. 123, 3: A12–A13.
- ^'Chapter 2. Systematic Review Methods -- AHRQ Technical Reviews and Summaries -- NCBI Bookshelf'. Retrieved 2010-05-18.
Retrieved from 'https://en.wikipedia.org/w/index.php?title=PICO_process&oldid=984297892'
sice_cream - 500 points
Challenge
Just pwn this program and get a flag. Connect with nc 2019shell1.picoctf.com 35993. libc.so.6 ld-2.23.so.
Pico 2019 Write Up Form
Hints
Make sure to both files are in the same directory as the executable, and set LD_PRELOAD to the path of libc.so.6
Solution
The problem specification contains the nc of a remote server, the binary it's running and the libraries it's loaded with. Apple com trailers.
Limitations:
- A fair amount of protections are on.
- As the binary starts, we don't have any sort of leak.
- Our only read option comes from the name field on the bss segment. We can't read chunk contents directly.
- We are restricted to a max malloc size of 85, which means only fastbins up to the 0x60 bin are allowed.
- Max 20 allocations.
Binary analysis indicates that freeing our chunks doesn't null their pointer and this obviously leads to a double free situation.
Our initial strategy then is:
1. Create fake chunk in name string, point to it with fastbin duplication.
We can use the double free to create a fastbin duplication attack that allows us to allocate a block anywhere in memory as long as its size field falls within the bin it's into.
The block we will inject will fall into the bss area containing our name buffer, 0x602040 - 0x602140.
We need to pass the fastbin security checks that will notice if a chunk is of an incorrect size for that bin:
The block we will inject will fall into the bss area containing our name buffer, 0x602040 - 0x602140.
We need to pass the fastbin security checks that will notice if a chunk is of an incorrect size for that bin:
2. Leak a libc offset from a free() operation.
Block #5 is now in a region where we have arbitrary read and write.
All heap overflow techniques are applicable.
This is the best point to leak libc. But how?
Some types of free() can leave a reference to arena_top or close libc areas into one of the pointers.
More specifically, blocks that are too large to fall into the fastbins (>= 0x90) will instead be stored into the unsorted bin until the next malloc.
We can change the chunk size with the rename option:
All heap overflow techniques are applicable.
This is the best point to leak libc. But how?
Some types of free() can leave a reference to arena_top or close libc areas into one of the pointers.
More specifically, blocks that are too large to fall into the fastbins (>= 0x90) will instead be stored into the unsorted bin until the next malloc.
We can change the chunk size with the rename option:
There's a lot of useless data here, the point is to change the chunk size into a smallbin-appropriate size.
Placing the block into the unsorted bin generates a double linked list into the current main_arena.
As long as we have a UAF, We can simply read the resulting pointers and we've found the libc location.
Placing the block into the unsorted bin generates a double linked list into the current main_arena.
As long as we have a UAF, We can simply read the resulting pointers and we've found the libc location.
3. Overwrite a location that grants us code execution.
We're still very limited here. We don't have a write-what-where of any kind.
Just as importantly, we don't have a stack leak. But there are more ways to control execution.
Just as importantly, we don't have a stack leak. But there are more ways to control execution.
A common technique here would be to overwrite the __malloc_hook symbol by using our previous fastbin duplication attack on the 0x70 bin.
(the trick here is that it can be misaligned, and as such we can take the most significant byte of a libc 0x7f.. address that's followed by enough null bytes)
But the binary explicitly bars us from allocating anything above the 0x60 chunk size.
(the trick here is that it can be misaligned, and as such we can take the most significant byte of a libc 0x7f.. address that's followed by enough null bytes)
But the binary explicitly bars us from allocating anything above the 0x60 chunk size.
Then how are we going to get execution?
Well there's this neat little thing called House of Orange..
It's complicated, and I certanly would explain it worse than what's already online. I would suggest reading these materials:
Well there's this neat little thing called House of Orange..
It's complicated, and I certanly would explain it worse than what's already online. I would suggest reading these materials:
- CTF-Wiki: the entire House of Orange and _IO_FILE related chapters, but especially the FSOP page
Code execution/flag retrieval candidates are:
We can control parameter 1 either way.
system('/bin/sh')
worked on the first try, so i kept it.Because of how the attack works, we require that:
Pico 2019 Write Up Letter
- The chunk in the unsorted bin is of size 0x60
- Its prev_size field is a valid string to pass as parameter 1 of whatever gadget you give it.
- Its back pointer is set to (target of the unsorted bin write - 0x10)
Picoctf 2019 Writeup
With these requisites, the block header becomes:
The attack will substitute the structure at _IO_list_all with our own 'table', which is actually just the arena.
We have to pass a few sanity checks, but the end result is the exit procedure will call offset 3 of our fake _IO_FILE jump table.
We have to pass a few sanity checks, but the end result is the exit procedure will call offset 3 of our fake _IO_FILE jump table.
Pico 2019 Write Up Assignment
To trigger the shell:
Pico 2019 Write Up Template
- request an allocation smaller than 0x58, so that the unsorted chunk will try to be processed.
- The unsorted bin write triggered in the process will set _IO_list_all to our arena top.
- The unsorted check itself will fail and trigger the abort sequence.
- The abort sequence will subsequently make the checks above. This convinces the program that our memory region is a valid _IO_FILE structure.
- As the procedure continues, it will call the jump table[3] function where our gadget is waiting.
- Win (hopefully). The script can occasionally cause a segmentation fault, possibly because of how the leaks are processed.
Pico 2019 Write Up Software
flag: flag{th3_r3al_questi0n_is_why_1s_libc_2.23_still_4_th1ng_b0a63afa}