Commitd31a803

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Backport of SF patch 590294: os._execvpe security fix (Zack Weinberg).

1) Do not attempt to exec a file which does not existjust to find out what error the operating systemreturns. This is an exploitable race on all platformsthat support symbolic links.2) Immediately re-raise the exception if we get anerror other than errno.ENOENT or errno.ENOTDIR. Thismay need to be adapted for other platforms.

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Lib
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`‎Lib/os.py‎`

Lines changed: 6 additions & 21 deletions

Original file line number	Diff line number	Diff line change
`@@ -301,16 +301,17 @@ def execvpe(file, args, env):`
`301`	`301`
`302`	`302`	`__all__.extend(["execl","execle","execlp","execlpe","execvp","execvpe"])`
`303`	`303`
`304`		`-_notfound=None`
`305`	`304`	`def_execvpe(file,args,env=None):`
	`305`	`+fromerrnoimportENOENT,ENOTDIR`
	`306`	`+`
`306`	`307`	`ifenvisnotNone:`
`307`	`308`	`func=execve`
`308`	`309`	`argrest= (args,env)`
`309`	`310`	`else:`
`310`	`311`	`func=execv`
`311`	`312`	`argrest= (args,)`
`312`	`313`	`env=environ`
`313`		`-global_notfound`
	`314`	`+`
`314`	`315`	`head,tail=path.split(file)`
`315`	`316`	`ifhead:`
`316`	`317`	`apply(func, (file,)+argrest)`
`@@ -320,30 +321,14 @@ def _execvpe(file, args, env=None):`
`320`	`321`	`else:`
`321`	`322`	`envpath=defpath`
`322`	`323`	`PATH=envpath.split(pathsep)`
`323`		`-ifnot_notfound:`
`324`		`-ifsys.platform[:4]=='beos':`
`325`		`-# Process handling (fork, wait) under BeOS (up to 5.0)`
`326`		`-# doesn't interoperate reliably with the thread interlocking`
`327`		`-# that happens during an import. The actual error we need`
`328`		`-# is the same on BeOS for posix.open() et al., ENOENT.`
`329`		`-try:unlink('/_#.# ## #.#')`
`330`		`-excepterror,_notfound:pass`
`331`		`-else:`
`332`		`-importtempfile`
`333`		`-t=tempfile.mktemp()`
`334`		`-# Exec a file that is guaranteed not to exist`
`335`		`-try:execv(t, ('blah',))`
`336`		`-excepterror,_notfound:pass`
`337`		`-exc,arg=error,_notfound`
`338`	`324`	`fordirinPATH:`
`339`	`325`	`fullname=path.join(dir,file)`
`340`	`326`	`try:`
`341`	`327`	`apply(func, (fullname,)+argrest)`
`342`	`328`	`excepterror, (errno,msg):`
`343`		`-iferrno!=arg[0]:`
`344`		`-exc,arg=error, (errno,msg)`
`345`		`-raiseexc,arg`
`346`		`-`
	`329`	`+iferrno!=ENOENTanderrno!=ENOTDIR:`
	`330`	`+raise`
	`331`	`+raiseerror, (errno,msg)`
`347`	`332`
`348`	`333`	`# Change environ to automatically call putenv() if it exists`
`349`	`334`	`try:`

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`‎Lib/os.py‎`

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