Tags: misc
Rating: 5.0
# brie-man
**Category**: misc \
**Difficulty**: easy \
**Points**: 200 points (39 solves) \
**Author**: yyyyyyy
Do you ever dream of solving a famous open question?
(Now that we have your attention: Sorry, this challenge has nothing to do with Brie. ?)
Download: [brie_man.tar.xz](brie_man.tar.xz)
## Overview
Very short challenge:
```python
#!/usr/bin/env sage
import re
if sys.version_info.major < 3:
print('nope nope nope nope | https://hxp.io/blog/72')
exit(-2)
rx = re.compile(r'Dear Bernhard: Your conjecture is false, for ([^ ]{,40}) is a counterexample\.')
s = CC.to_prec(160)(rx.match(input()).groups()[0])
r = round(s.real())
assert not all((s==r, r<0, r%2==0)) # boring
assert not s.real() == 1/2 # boring
assert zeta(s) == 0 # uhm ok
print(open('flag.txt').read().strip())
```
The problem is referencing the
[Riemann hypothesis](https://en.wikipedia.org/wiki/Riemann_hypothesis).
## Solution
> Solved with @ndrewh
Satisfying the `assert` statements doesn't seem to be possible, but after
playing around with it for a while, I noticed some weird behavior:
```python
sage: CC.to_prec(160)('2i')
Traceback (most recent call last):
File "/home/plushie/.local/lib/python3.8/site-packages/IPython/core/interactiveshell.py", line 3437, in run_code
exec(code_obj, self.user_global_ns, self.user_ns)
File "<ipython-input-1-71bddf1253b5>", line 1, in <module>
CC.to_prec(Integer(160))('2i')
File "/usr/lib/python3/dist-packages/sage/rings/complex_field.py", line 387, in __call__
return Parent.__call__(self, x)
File "sage/structure/parent.pyx", line 900, in sage.structure.parent.Parent.__call__ (build/cythonized/sage/structure/parent.c:9218)
return mor._call_(x)
File "sage/structure/coerce_maps.pyx", line 161, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ (build/cythonized/sage/structure/coerce_maps.c:4556)
raise
File "sage/structure/coerce_maps.pyx", line 156, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ (build/cythonized/sage/structure/coerce_maps.c:4448)
return C._element_constructor(x)
File "/usr/lib/python3/dist-packages/sage/rings/complex_field.py", line 413, in _element_constructor_
sage_eval(x.replace(' ',''), locals={"I":self.gen(),"i":self.gen()}))
File "/usr/lib/python3/dist-packages/sage/misc/sage_eval.py", line 202, in sage_eval
return eval(source, sage.all.__dict__, locals)
File "<string>", line 1
2i
^
SyntaxError: unexpected EOF while parsing
```
Checking `_element_constructor_()` in `complex_field.py`, we see this mildy
suspicious comment.
```python
# TODO: this is probably not the best and most
# efficient way to do this. -- Martin Albrecht
return ComplexNumber(self,
sage_eval(x.replace(' ',''), locals={"I":self.gen(),"i":self.gen()}))
```
At the end of the backtrace, we also see
```python
return eval(source, sage.all.__dict__, locals)
```
```
$ nc 65.108.178.230 7904
Dear Bernhard: Your conjecture is false, for print(open('flag.txt').read()) is a counterexample.
hxp{0NE_M1LL10N_D0LLAR5}
```
## Note
This snippet was likely a hint, since the linked write-up shows a similar
solution for a challenge from DEF CON Quals 2020.
```python
if sys.version_info.major < 3:
print('nope nope nope nope | https://hxp.io/blog/72')
exit(-2)
```
