One Article Review
| Source |  BAE |
|---|---|
| Identifiant | 352318 |
| Date de publication | 2017-03-06 12:15:21 (vue: 2017-03-06 12:15:21) |
| Titre | Security issues with Using PHP\'s Escapeshellarg |
| Texte |  Written by Eldar Marcussen, Cyber Security ConsultantUsing user supplied data on the command line is traditionally a security disaster waiting to happen. In an infinite universe there are however times when you might need to do just that. You will be glad to know that PHP provides two functions to aid you with security in those situations:escapeshellcmd and escapeshellarg.The PHP documentation defines these functions as:· escapeshellcmd() escapes any characters in a string that might be used to trick a shell command into executing arbitrary commands. This function should be used to make sure that any data coming from user input is escaped before this data is passed to the exec() or system() functions, or to the backtick operator. Following characters are preceded by a backslash: #&;`|*?~^()[]{}$\, \x0A and \xFF. ' and " are escaped only if they are not paired. In Windows, all these characters plus % are replaced by a space instead.· escapeshellarg() adds single quotes around a string and quotes/escapes any existing single quotes allowing you to pass a string directly to a shell function and having it be treated as a single safe argument. This function should be used to escape individual arguments to shell functions coming from user input. The shell functions include exec(), system() and the backtick operator. |
| Envoyé | Oui |
| Condensat | #&;`|* $fh marcussen# create a malicious file:$fh = fopen will you could use whatever binary you like$safe 4444 ;# i choose to use php here ;$safe ; # really a php script with a ;fclose ;fwrite >the adds aid all allowing alter any arbitrary are argument arguments around as:· backslash: backtick before behavior bind bug caveats cf export characters clearly closer code coming command commands compress concept consultantusing cover created cyber data defines directly disaster diverting documentation does doesn doing eldar escape escaped escapes escapeshellarg escapeshellcmd example: ls exec executing execution existing expected feel file file = escapeshellarg following from function functions glad happen have having help highlight however illustrate include individual infinite inject injection input inputs inside instead intended issues just know line look make marcussen may might myfile need net/manual/en/function not on escapeshellarg to only operation operator opts opts = escapeshellarg order paired parameters pass passed php php# written by eldar plus png png extensionsystem point port possible potential preceded print program=php programs proof protect provides quotes quotes/escapes referred relies replaced response reviews risk safe sanitise script security shell should simple single situations:escapeshellcmd and escapeshellarg some source space spawn string supplied sure switches switches:# poc exploit of php not escaping dash characters in escapeshellarg/cmd# reference: http://php system take tar tar $safe team text these those thus times traditionally treated trick two typically understand universe unsafe use used user using usingescapeshellarg view waiting ways when which will windows wireghoul would written x0a xff |
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