# A patch for HEAD - Thread: https://externals.io/message/44492 - Original archive: https://news-web.php.net/php.internals/44492 - Started by Gwynne Raskind on 2009-06-26T21:20:56+00:00 - Messages: 7 - Reply by email to internals@lists.php.net - More for agents: search with https://externals.io/search.md?q={query} · JSON API at https://externals.io/api · documentation at https://externals.io/llms.txt --- ## #44492 — Gwynne Raskind — 2009-06-26T21:20:56+00:00 URL: https://externals.io/message/44492#44492 I've just finished making this patch for my own use (diffed against 5.3 CVS): http://darkrainfall.org/php-5.3-shellbypass.patch In short, what it does is make `proc_open()`'s shell_bypass option available to UNIX systems. This is accomplished by allowing the "command" parameter to `proc_open()` to be an array of arguments to pass to execv[e](). I've included a few tests to check the functionality. (A few more tests could be devised to, for example, check that the correct warning is issued if you pass an array without bypass_shell set, or a string with it set, etc.) The exact behavior of the argument array is: 1) The array must contain at least one element, at index 0. 2) The element at index 0 is always the exact command path passed to execv[e]() (after being filtered through any safe_mode restrictions, as with the normal behavior of `proc_open()`). 3) Any other elements form the argv array passed to execv[e](). By convention the first of these arguments (argv[0] in the child process) is the same as the command path, however my patch does NOT enforce or assume this; it simply calls execv[e]($argument_array[0], array_slice($argument_array, 1)). This patch currently provides the only useful way to fork a process without running a shell (pcntl_fork() + `pcntl_exec()` are useless since there's no pcntl_dup2() to control the descriptors of the child). Why would you want to avoid the shell? - Efficiency. The shell is an extra, often unnecessary process, which must parse the commandline given to it into individual arguments according to all its various rules. Not to mention the overhead of setting up another entire process just to run a third process. - Resource control. The shell is an extra process. If you don't need it, and your system is tight on process space, best to avoid it. - Sanity. Correctly quoting arguments to a shell command ranges from mildly annoying (escapeshellarg() in simple cases) to nightmarish (manual parsing of a string in some edge cases). Passing arguments directly completely bypasses this, quite possibly saving you quite a bit of string parsing time if you were doing something like "$shell_args = implode(' ', array_map('escapeshellarg', $raw_args));". - Oddly enough, security. Since there's no shell, it's more difficult to subvert the child process to do other things than the coder intended (unless of course, said coder executes a shell this way). This patch does nothing on Windows, since the option was already implemented there. It also does nothing on Netware, since from what I could see in the code, Netware doesn't have a shell in the first place. I'm proposing the inclusion of this patch in HEAD (which I'll port it to if I get a thumbs-up here), and possibly 5.3.2. Criticism and angry flames welcome. Constructive critcism and good-natured comments will be ignored ;) (just kidding... or am I?). -- Gwynne --- ## #44494 — Andrei Zmievski — 2009-06-26T21:32:15+00:00 URL: https://externals.io/message/44492#44494 · In reply to: #44492 Gwynne Raskind wrote: > I'm proposing the inclusion of this patch in HEAD (which I'll port it to > if I get a thumbs-up here), and possibly 5.3.2. Criticism and angry > flames welcome. Constructive critcism and good-natured comments will be > ignored ;) (just kidding... or am I?). I'm fine with this in HEAD. -Andrei --- ## #44495 — Pierre Joye — 2009-06-26T21:35:00+00:00 URL: https://externals.io/message/44492#44495 · In reply to: #44494 same here :) > Gwynne Raskind wrote: > > […] > > I'm fine with this in HEAD. > > -Andrei > > -- > > > > -- Pierre http://blog.thepimp.net | http://www.libgd.org --- ## #44849 — Nuno Lopes — 2009-07-08T20:16:13+00:00 URL: https://externals.io/message/44492#44849 · In reply to: #44492 The idea is great. In fact this was in my todo list for php 5.3.. Please give me a few more days to review the patch. Nuno P.S.: you can add on more point to your list: you get to know the PID of the exec'ed process instead of the PID of the shell. ----- Original Message ----- > I've just finished making this patch for my own use (diffed against 5.3 > CVS): > > http://darkrainfall.org/php-5.3-shellbypass.patch > > In short, what it does is make `proc_open()`'s shell_bypass option > available to UNIX systems. This is accomplished by allowing the "command" > parameter to `proc_open()` to be an array of arguments to pass to > execv[e](). I've included a few tests to check the functionality. > > (A few more tests could be devised to, for example, check that the > correct warning is issued if you pass an array without bypass_shell set, > or a string with it set, etc.) > > The exact behavior of the argument array is: > 1) The array must contain at least one element, at index 0. > 2) The element at index 0 is always the exact command path passed to > execv[e]() (after being filtered through any safe_mode restrictions, as > with the normal behavior of `proc_open()`). > 3) Any other elements form the argv array passed to execv[e](). By > convention the first of these arguments (argv[0] in the child process) is > the same as the command path, however my patch does NOT enforce or assume > this; it simply calls execv[e]($argument_array[0], > array_slice($argument_array, 1)). > > This patch currently provides the only useful way to fork a process > without running a shell (pcntl_fork() + `pcntl_exec()` are useless since > there's no pcntl_dup2() to control the descriptors of the child). > > Why would you want to avoid the shell? > > - Efficiency. The shell is an extra, often unnecessary process, which > must parse the commandline given to it into individual arguments > according to all its various rules. Not to mention the overhead of > setting up another entire process just to run a third process. > > - Resource control. The shell is an extra process. If you don't need it, > and your system is tight on process space, best to avoid it. > > - Sanity. Correctly quoting arguments to a shell command ranges from > mildly annoying (escapeshellarg() in simple cases) to nightmarish (manual > parsing of a string in some edge cases). Passing arguments directly > completely bypasses this, quite possibly saving you quite a bit of string > parsing time if you were doing something like "$shell_args = implode(' ', > array_map('escapeshellarg', $raw_args));". > > - Oddly enough, security. Since there's no shell, it's more difficult to > subvert the child process to do other things than the coder intended > (unless of course, said coder executes a shell this way). > > This patch does nothing on Windows, since the option was already > implemented there. It also does nothing on Netware, since from what I > could see in the code, Netware doesn't have a shell in the first place. > > I'm proposing the inclusion of this patch in HEAD (which I'll port it to > if I get a thumbs-up here), and possibly 5.3.2. Criticism and angry > flames welcome. Constructive critcism and good-natured comments will be > ignored ;) (just kidding... or am I?). > > -- Gwynne --- ## #44983 — Nuno Lopes — 2009-07-15T20:20:33+00:00 URL: https://externals.io/message/44492#44983 · In reply to: #44492 Hi, So the patch looks generally good. Here are some minor comments about it: - I believe _php_array_to_argv() doesn't need TSRMLS_DC. If that's the case, please remove it. - in _php_array_to_argv() you modify the input array destructively (when calling convert_to_string_ex). You should not modify the input. - in _php_array_to_argv(), HASH_OF will never return `NULL` (because we already know that it's an array). - apparently the check 'if (cnt < 1) {' will never be true, as the array will always have one element. please verify that this special case does what you want (maybe change to 'cnt <= 1') - argvs with length==0 are perfectly valid, and so you shouldn't skip them. - the api is a little inconsistent, as you use the idx 0 to retrieve the command name, but then you use the array order to retrieve the rest of the elements (and thus if the idx 0 doesn't appear in the beginning your code will fail). I would just stick with the array order. e.g. array(1=>'/usr/bin/echo', 0=>'foo') or similar should print 'foo'. - in exit_fail you can remove the check for bypass_shell, as _php_free_argv() will check the argument against NULL. - the line 'proc->argv = (bypass_shell ? child_argv : NULL);' can be simplified to 'proc->argv = child_argv;' since child_argv is already initialized to `NULL` I think that's it :) It's only minor things, I guess. As soon as you fix these things, please go ahead and commit the patch, or mail it back to the ML in case you need me to do it. Nuno ----- Original Message ----- From: "Gwynne Raskind" To: "PHP internals" Sent: Friday, June 26, 2009 10:20 PM Subject: [PHP-DEV] A patch for HEAD > I've just finished making this patch for my own use (diffed against 5.3 > CVS): > > http://darkrainfall.org/php-5.3-shellbypass.patch > > In short, what it does is make `proc_open()`'s shell_bypass option > available to UNIX systems. This is accomplished by allowing the "command" > parameter to `proc_open()` to be an array of arguments to pass to > execv[e](). I've included a few tests to check the functionality. > > (A few more tests could be devised to, for example, check that the > correct warning is issued if you pass an array without bypass_shell set, > or a string with it set, etc.) > > The exact behavior of the argument array is: > 1) The array must contain at least one element, at index 0. > 2) The element at index 0 is always the exact command path passed to > execv[e]() (after being filtered through any safe_mode restrictions, as > with the normal behavior of `proc_open()`). > 3) Any other elements form the argv array passed to execv[e](). By > convention the first of these arguments (argv[0] in the child process) is > the same as the command path, however my patch does NOT enforce or assume > this; it simply calls execv[e]($argument_array[0], > array_slice($argument_array, 1)). > > This patch currently provides the only useful way to fork a process > without running a shell (pcntl_fork() + `pcntl_exec()` are useless since > there's no pcntl_dup2() to control the descriptors of the child). > > Why would you want to avoid the shell? > > - Efficiency. The shell is an extra, often unnecessary process, which > must parse the commandline given to it into individual arguments > according to all its various rules. Not to mention the overhead of > setting up another entire process just to run a third process. > > - Resource control. The shell is an extra process. If you don't need it, > and your system is tight on process space, best to avoid it. > > - Sanity. Correctly quoting arguments to a shell command ranges from > mildly annoying (escapeshellarg() in simple cases) to nightmarish (manual > parsing of a string in some edge cases). Passing arguments directly > completely bypasses this, quite possibly saving you quite a bit of string > parsing time if you were doing something like "$shell_args = implode(' ', > array_map('escapeshellarg', $raw_args));". > > - Oddly enough, security. Since there's no shell, it's more difficult to > subvert the child process to do other things than the coder intended > (unless of course, said coder executes a shell this way). > > This patch does nothing on Windows, since the option was already > implemented there. It also does nothing on Netware, since from what I > could see in the code, Netware doesn't have a shell in the first place. > > I'm proposing the inclusion of this patch in HEAD (which I'll port it to > if I get a thumbs-up here), and possibly 5.3.2. Criticism and angry > flames welcome. Constructive critcism and good-natured comments will be > ignored ;) (just kidding... or am I?). > > -- Gwynne --- ## #44996 — Gwynne Raskind — 2009-07-16T22:23:41+00:00 URL: https://externals.io/message/44492#44996 · In reply to: #44983 Alright, I've implemented pretty much every single suggestion you made :). Note that _php_array_to_envp() actually suffers the same "modify in place" problem, but because it iterates the array twice (is that REALLY so much better than allocating a few extra pointers or calling perealloc() a few times?), the fix for it isn't trivial, so I left it alone. The updated patch is (again) posted at: http://darkrainfall.org/php-5.3-shellbypass.patch > Hi, > > So the patch looks generally good. Here are some minor comments > about it: > > - I believe _php_array_to_argv() doesn't need TSRMLS_DC. If that's > the case, please remove it. > - in _php_array_to_argv() you modify the input array destructively > (when calling convert_to_string_ex). You should not modify the input. > - in _php_array_to_argv(), HASH_OF will never return `NULL` (because > we already know that it's an array). > - apparently the check 'if (cnt < 1) {' will never be true, as the > array will always have one element. please verify that this special > case does what you want (maybe change to 'cnt <= 1') > - argvs with length==0 are perfectly valid, and so you shouldn't > skip them. > - the api is a little inconsistent, as you use the idx 0 to retrieve > the command name, but then you use the array order to retrieve the > rest of the elements (and thus if the idx 0 doesn't appear in the > beginning your code will fail). I would just stick with the array > order. e.g. array(1=>'/usr/bin/echo', 0=>'foo') or similar should > print 'foo'. > - in exit_fail you can remove the check for bypass_shell, as > _php_free_argv() will check the argument against NULL. > - the line 'proc->argv = (bypass_shell ? child_argv : NULL);' can be > simplified to 'proc->argv = child_argv;' since child_argv is already > initialized to `NULL` > > I think that's it :) It's only minor things, I guess. > As soon as you fix these things, please go ahead and commit the > patch, or mail it back to the ML in case you need me to do it. > > Nuno > > > ----- Original Message ----- From: "Gwynne Raskind" > […] > To: "PHP internals" > Sent: Friday, June 26, 2009 10:20 PM > Subject: [PHP-DEV] A patch for HEAD > > > > […] > -- Gwynne --- ## #45033 — Nuno Lopes — 2009-07-19T18:13:28+00:00 URL: https://externals.io/message/44492#45033 · In reply to: #44996 Commited! Thanks, Nuno ----- Original Message ----- > Alright, I've implemented pretty much every single suggestion you made > :). Note that _php_array_to_envp() actually suffers the same "modify in > place" problem, but because it iterates the array twice (is that REALLY > so much better than allocating a few extra pointers or calling > perealloc() a few times?), the fix for it isn't trivial, so I left it > alone. The updated patch is (again) posted at: > > http://darkrainfall.org/php-5.3-shellbypass.patch > > > > […] > > -- Gwynne