Erlang filelib how to#
Erlang filelib install#
Erlang filelib Patch#
Erlang filelib code#

These are hard problems to solve in a distributed system it will be some time before robust solutions are available. examples assume that the current directory is the top of an Erlang/OTP installation.

In summary: don’t expose a database directly to attackers, unless it’s been designed from the ground up to deal with multiple tenants, sandboxing, and resource allocation. filelib - File utilities, such as wildcard matching of filenames. You might also abuse the JS VM to escape the sandbox without any Erlang at all. It also doesn’t need to touch the disk you can abuse the scanner/parser to eval strings directly, though it’s a more convoluted road. This technique works reliably on single-node clusters, but could be trivially extended to work on any number of nodes. The payload /tmp/evil.erl removes itself as soon as it’s executed, for good measure. You can now ssh to using the corresponding private key. Return Īstute readers may recall path_eval ignores its first argument if the second is a file, making the value of the map phase redundant here. Now we can use the same trick with another 2-arity function to eval that payload in the Erlang VM.Ĭurl -X POST -H “content-type: application/json” Here, we take advantage of the fact that the riak user usually has a login shell enabled, and add an entry to. The Erlang/OTP version scheme is described in the Erlang/OTP Systems. Take a look at the Erlang/OTP 25 release description to see what changes Erlang/OTP 25 brings over the previous major version.

Erlang filelib install#

To install Erlang you can either build it from source or use a pre-built package. Erlang 25.1 Portugus stdlib/filelib Module Module filelib Module Summary Utilitrios de arquivo,tais como wildcard de correspondncia de nomes de arquivo. Este mdulo no suporta nomes de arquivos 'brutos' (aqueles arquivos que obedecem codificao esperada).

Erlang filelib how to#

See the TESTING and DEVELOPMENT HowTo guides for details about how to run test locally. The latest version of Erlang/OTP is 25.3. Erlang - Module Este mdulo contm utilitrios de nvel superior ao arquivo. It can do this across all machines in the cluster. To speed up review, make sure that you have read Contributing to Erlang/OTP and that all checks pass. Steal the cookie and give you a remote erlang shell.

Erlang filelib Patch#

It can patch the VM silently to steal or corrupt data. That binary string gets written to disk in /tmp. Arg is our payload, passed in the reduce phase’s argument.

Erlang filelib code#

test file readable return exit code error (non zero) if a file is not.

See it? Riak takes the lists returned by all the map phases (/tmp/evil.erl), and calls the Erlang function file:write_file(“/tmp/evil.erl”, Arg). main() -> case filelib:isfile(/etc/mtab) of true -> ok -> erlang:halt(1) end. Let’s create an object to mapreduce over.Ĭurl -X PUT -H “content-type: text/plain” Module:fun(, any_json_serializable_term).īut first things first. There are a lot of functions in Erlang which look like The reduce is called with a list, which is the output of the map phases it is aggregating. This is an attacker’s dream.įor instance, Riak reduce phases are given as a module, function name, and an argument. Mapreduce is code code which can have side effects code which is executed on your cluster. Riak, for instance, exposes mapreduce over its HTTP API. You’re begging for denial-of-service issues even if the operations are semantically valid, they’re running on a physical substrate with real limits. Then T is Erlang distributed with density f n, and its mean is E(T) E(T 1)+ + E(T n) n. Suppose that T is the sum of the independent, exponential random variables T 1.,T n, each with parameter. So a side issue is it'd be nice if either all OTP applications generated source to src instead of a dir like asn1 or to have a way to get the dirs where source is from for the modules in an Application consistently.Major thanks to John Muellerleile ( for his help in crafting this.Īctually, don’t expose pretty much any database directly to untrusted connections. When n 1 the Erlang and exponential distributions coincide. This problem partly arises because they include src in the release and relx copies only certain dirs where src files should be īecause of these warnings I looked into a way to get all source dirs for an application (aside from doing a filelib:wildcard('**/*.erl') - well something similar, it would need to be more complicated to ignore stuff like test/*.erl and examples/*.erl). See erlang/rebar3#2531 - there are issues open about as well this I believe. I ended up running into this due to warnings given by systools exref option when building releases with relx that include the public_key application. Filelib:find_source was introduced in OTP-20.