When to use Shell=True for Python subprocess module -


this question has answer here:

it seems whenever try use python's subprocess module, find still don't understand things. currently, trying join 3 mp4 files within python module.

when tried

z ='mp4box -cat test_0.mp4 -cat test_1.mp4 -cat test_2.mp4 -new test_012d.mp4' subprocess.popen(z,shell=true)

everything worked.

when tried

z = ['mp4box', '-cat test_0.mp4', '-cat test_1.mp4', '-cat test_2.mp4', '-new test_012d.mp4'] subprocess.popen(z,shell=false)

i got following error:

option -cat test_0.mp4 unknown. please check usage

i thought shell=false needed supply list first element executable wanted run , each succeeding element argument executable. mistaken in belief, or there correct way create command wanted use?

also, there rules using shell=true in subprocess.popen? far, know(?) "don't - can expose code shell injection attacks". why shell=false avoid problem? there ever actual advantage using 'shell=true`?

if shell true, specified command executed through shell. can useful if using python enhanced control flow offers on system shells , still want convenient access other shell features such shell pipes, filename wildcards, environment variable expansion, , expansion of ~ user’s home directory.

when shell=true dangerous?

if execute shell commands might include unsanitized input untrusted source, make program vulnerable shell injection, serious security flaw can result in arbitrary command execution. reason, use of shell=true discouraged in cases command string constructed external input

eg. (taken docs)

>>> subprocess import call >>> filename = input("what file display?\n") file display? non_existent; rm -rf / # >>> call("cat " + filename, shell=true) # uh-oh. end badly..

Comments

Post a Comment

Popular posts from this blog

c# - Validate object ID from GET to POST -

i have method allows user access comment have made on site. have post method lets them update comment. my normal solution send entire comment model through, let them update it, update on database when post back. involve sending commentid through in hiddenfor , can manipulated. how can verify commentid sent in get method same i'm getting in post , not able alter comment wish? how can verify commentid sent in method same i'm getting in post? basically have validate following things in post - user logged-in user. authenticated users post comments. commentid in post , should valid commentid , should present in database. userid associated logged-in user should same userid associated comment . comment should contain userid column, can check @ time of update. to make sure update happens comment has been sent in get - hold commentid in session , in post action compare commentid value in session .
Read more

node.js - Custom Model Validator SailsJS -

when using custom model validator checks record within model. return within spread doesn't seem end control flow. //post.js model /** * custom validator **/ types: { isuservalid: function(user_id) { var promise = require('bluebird'); promise.all([ user.findone({id: user_id}) ]) .spread(function(user) { console.log(user); if (user === null || user === undefined) { console.log('failed'); return false; }else{ console.log('passed'); return true; } }); } }, my response standard validation failed response. { "error": "e_validation", "status": 400, "summary": "1 attribute invalid", "model": "post", "invalidattributes": { "owner": [ { "rule": "isuservalid", ...
Read more

php - Find a regex to take part of Email -

i have following emails need extract part from: bestellnummer xxx: 1 von xxx, 1er pack ------------- anfang der nachricht ------------- foo bar baz foo bar baz // <<<<< need text here ------------- ende der nachricht ------------- ------------- anfang der nachricht ------------- foo bar baz foo bar baz ------------- ende der nachricht ------------- there 0 unlimited occurences of ------------- anfang der nachricht ------------- ------------- ende der nachricht ------------- and i'm able extract first part regex: $re = "/------------- .*? -------------.?(.*?).?------------- .*? -------------/s"; but, i'm quite new on learning regex, i'm pretty sure there must better regex extract part (foo bar baz foo bar baz) of text between ------------- anfang der nachricht ------------- ------------- ende der nachricht ------------- as can in different languages, i'm using .? to match between hyphens. i...
Read more