devexpress asp.net pdf viewer : Copy pages from pdf into new pdf software control dll windows azure winforms web forms AppleShellScripting-201424-part665

Theattack:
Passthevalue“
; rm randomfile
”tocausethisscripttodeleteafileinoldershells.
Mostmodernshellsparsethestatementpriortoanyvariablesubstitution,andarethusunaffectedbythis
attack.However,forpropersecuritywhenyourscriptisrunonoldersystems(nottomentionavoidingasyntax
errorifthefilenamecontainsspaces),youshouldstillsurroundthevariablewithdoublequotes.
Mitigation:
Tofixthisbug,changetheecholinetoread:
echo "$FOO"
AuthenticationAttacks
Ingeneral,youshouldnotrelyonascripttodeterminewhetherauserdoesordoesnothavepermissionto
dosomething.Itisclumsyanderror-prone.Itispossibletodoso,however,andtherearerightandwrong
waystodoit.
Thewrongway:
if [ $UID D = = 100 0 -a $USER = = "myusername" ] ] ; ; then
cd $HOME
fi
Thiscodehasthreesecuritybugs,andthey’reallcausedbyusingvariablesinwaysthatareunsafe.Forhistorical
compatibility,theOSprovidesthe
UID
,
USER
,and
HOME
environmentvariables.Theyarequiteusefulaslong
asyouaren’tusingthemforsecurityreasons.
Theattack:
$ tcsh
% setenv v UID 100
% setenv v USER myusername
% setenv v HOME $HOME/.ssh
% /path/to/script.sh
ShellScriptSecurity
AuthenticationAttacks
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Copy pages from pdf into new pdf - software control dll:C# PDF Page Extract Library: copy, paste, cut PDF pages in C#.net, ASP.NET, MVC, Ajax, WinForms, WPF
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EventhoughmostmodernBourneshellsprotectagainstmodifying
UID
,the
USER
variableisunprotected,
andnotallshellsprotectthe
UID
variable,either.
Fortunately,thescriptjustchangedintoadirectory.Combinedwithanotherexploitableattacksuchasan
injectionattack,however,thiscouldbeexploitedinbadways.
Mitigation:
ToobtaintheuserID:
# Effective e UID
MYEUID="$(/usr/bin/id -u)"
# Real UID
MYUID="$(/usr/bin/id -u u -r)"
Toobtaintheusername:
MYUID="$(/usr/bin/id -u u -n)"
Toobtaintheactualhomedirectory:
HOMEDIR="$(dscl . . -read d /Users/dg g NFSHomeDirectory y | | sed 's/^NFSHomeDirectory:
//')"
NotethatthismethodforobtainingthehomedirectoryisspecifictoOSX.
PermissionsandAccessControlLists
OSXusestheUNIXpermissionsmodel,extendedbyPOSIXaccesscontrollists.Thesepermissionsmodelsare
describedindetailintheOSXFileSystemSecuritysectionofFileSystemProgrammingGuide.Thissection
assumesthatyouarealreadyatleastperipherallyfamiliarwiththeconceptofusersandgroups.
ExaminingFilePermissions
UNIXpermissionsarevisibletousersinTerminalandintheFinder’sGetInfowindow.InTerminal,youcan
easilylookatthepermissionsinahuman-readableformatbyusingthe
ls
commandasfollows:
ShellScriptSecurity
PermissionsandAccessControlLists
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software control dll:VB.NET PDF Page Insert Library: insert pages into PDF file in vb.
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$ ls s -ld filename dirname
drwxr-xr-x
2 username
groupname 68 8 Jun 16 6 13:40 0 dirname
-rw-r--r--
1 username
groupname
0 Jun 16 6 13:40 0 filename
Theleftcharacterindicateswhetherthefilesystemobjectisafile(
-
),directory(
d
),symboliclink(
l
),block(
b
)
orcharacter(
c
)specialfile,namedpipe(
p
),orUNIXdomainsocket(
s
).
ThenextthreecharactersshowtheOwnerpermissions,followedbytheGrouppermissions,andfinally,the
Otherpermissionsaslistedinthefollowingtable:
Meaning
OctalBitValue
Permissionsflag
Nopermission
n/a
-
Readpermission
4
r
Writepermission
2
w
Executepermission
1
x
Setuidorsetgidwithexecutepermission
Intheoptionalfirstoctaldigit:
4—setuid
2—setgid
s
Setuidorsetgid
without
executepermission
Seeabove.
S
Stickybit
Inoptionalfirstoctaldigit:
1
t
Thecompletesetofpermissionsisoftenexpressedinoctal,asdefinedbythebitsinthetableabove.Thefirst
digitincludesthestickybitandsetuidandsetgidbits.Ifzero,youmayomititwhenpassingthevaluetomost
commands.TheremainingthreedigitscontaintheOwner(user),Group,andOtherpermissions,respectively.
Forexample,afilethatissetuidandsetgid,withread/write/executeOwnerpermissionsandread/execute
GroupandOtherpermissions,theoctalequivalentis6755:
Theleadingspecialpermissionsvalueis6,whichisthebitwiseORofsetuid(4)andsetgid(2).
TheOwnerpermissionis7,whichisthebitwiseORoftheread(4),write(2),andexecute(1)bits.
TheGroupandOtherpermissionsareboth5,whichisthebitwiseORoftheread(4)andexecute(1)
permissions.
ShellScriptSecurity
PermissionsandAccessControlLists
2014-03-10   |   Copyright © 2003, 2014 Apple Inc. All Rights Reserved.
243
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of splitting a PDF file into multiple ones by As String = Program.RootPath + "\\" 1.pdf" 'set split SplitOptions(SplitMode.ByPage) ' limit the pages of each
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ToshowtheUNIXpermissionsofafile,usethestatcommandasfollows:
stat -f "%p" filename
Ignoreallbutthelastfourdigitsreturned.
ChangingFileOwnershipandPermissions
Theabilitytochangefileownershipandpermissionsislimitedbytheoperatingsystemforsecurityandquota
reasons.Userscan:
Changethepermissionsforanyfilethattheyown.
Changethegroupforanyfilethattheyowntoanygroupthattheyareamemberof.
Non-rootuserscannot:
Changepermissionsonfilesownedbyanyoneelse.
Changethegroupofafiletoagroupthattheyarenotamemberof.
Changetheownerofanyfile.
TherootusercanchangepermissionsandownershiparbitrarilyexceptwhenblockedbyBSDfilesystemflags.
Withthoserestrictionsinmind,thesectionsthatfollowdescribehowtochangepermissionsandchangeuser
andgroupownershipoffilesanddirectories.
UsechownandchgrptoChangeUserandGroupsOwnership
Youcanchangetheownerofafileordirectorywiththe
chown
command:
# Change e the owner r of f a a file or directory
sudo chown n newowner filename_or_dirname
# Change e the owner r of f a a directory y and d everything g in it t recursively
sudo chown n -R R newowner dirname
Youcanchangethegroupforafilewitheitherthe
chown
commandorthe
chgrp
command:
# Change e the group p by y itself
ShellScriptSecurity
PermissionsandAccessControlLists
2014-03-10   |   Copyright © 2003, 2014 Apple Inc. All Rights Reserved.
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software control dll:C# PDF File & Page Process Library SDK for C#.net, ASP.NET, MVC
You can use specific APIs to copy and get a specific page of PDF file; you can also copy and paste pages from a PDF document into another PDF file.
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chown :newgroup filename_or_dirname
chgrp newgroup filename_or_dirname
# Change e the group p of f a a directory y and d everything g in it t recursively
chown -R R :newgroup p dirname
chgrp -R R newgroup dirname
Youcanalsochangebothownerandgroupsimultaneously:
# Change e the owner r and d the group
sudo chown n newowner:newgroup filename_or_dirname
# Change e the group p of f a a directory y and d everything g in it t recursively
sudo chown n -R R newowner:newgroup p dirname
Formoreinformation,seethemanualpagesfor
chown
and
chgrp
.
UsechmodtoChangeFileandDirectoryPermissions
OSX(andotherUNIX-basedoperatingsystems)providethe
chmod
commandforchangingthepermissions
offilesanddirectories.
The
chmod
command,shortfor“changemode”,issonamedbecauseitallowsyoutomodifyfileordirectory
modes.Amodeisathree-digitorfour-digitoctalrepresentationoftheUNIXpermissionsforafile(or4-5digits
inlanguagesthatrequirealeadingzero,suchasC).
Therearetwobasicwaysyoucanusethe
chmod
command:numericmodesandhuman-readableflags.
Mostusersuse
chmod
initshuman-readableform:
chmod a+rw world_writable_file
Thiscommandtells
chmod
toaddread(
r
)andwrite(
w
)accesstotheexistingsetofpermissionsforallusers
(
a
).Soifthepermissionswereoriginally
r-x--x-w-
,theresultingpermissionswouldbe
rwxrwxrw-
.
Youcanalsoaddandsubtractpermissionsfortheowninguser(
u
),thegroup(
g
),orotherusers(
o
)separately.
Forexample,toaddread(
r
),write(
w
),andexecute(
x
)permissionfortheowninguserandtakeitawayfrom
membersoftheowninggroupandeveryoneelse,youcouldissueeitherofthefollowingcommands:
ShellScriptSecurity
PermissionsandAccessControlLists
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chmod u+rwx,g-rwx,o-rwx filename
chmod u+rwx,go-rwx filename
chmod a-rwx,u+rwx x filename
Similarly,youcansettheUser,Group,orOtherpermissionswithoutregardtowhatbitsweresetbeforeby
usingequals.Forexample,tosetgrouppermissionstoread,no-write,no-execute,youcouldissuethefollowing
command:
chmod g=r filename
Finally,tomakeanexecutablerunsetuid(
u+s
)andsetgid(
g+s
),youmightexecuteacommandlikeoneof
thefollowing:
chmod a+rx,ug+s filename
chmod a+rxs s filename
# Note: : o+s s is ignored.
Alternatively,ifyouknowthenumericfilemodeyouwanttoapply(seeExaminingFilePermissions (page 242)
fordetails),youcanpassthe
chmod
commandeitherathree-digitorfour-digitmodevalue:
chmod 666 world_writable_file
chmod 0666 world_writable_file
ThechmodcommandcanalsobeusedtomodifyPOSIXaccesscontrollists(ACLs).Thisuseisdescribedlater,
inUsechmodtoModifyAccessControlLists (page 247).
UsechflagstoSetSpecialFilePermissionFlags
Inadditiontothestandardpermissionflags,OSXhasafewspecialpermissionflagsthatcanbesetusingthe
chflags
or
lchflags
command(orwiththe
chflags
or
fchflags
APIinC).Theseflagsaredescribedin
theOSXFileSystemSecuritysectionofFileSystemProgrammingGuide.
Thepermissionsflagssetwith
chflags
takeprecedenceoveranypermissionsgrantedbynormalUNIX
permissionsoraccesscontrollists.
Theusageofthe
chflags
commandisfairlystraightforward.Forexample,tomakeafileimmutable(sothat
itcannotbemoved,renamed,deleted,ormodified),youcanissueoneofthefollowingcommands:
chflags uchg filename # # user flag
ShellScriptSecurity
PermissionsandAccessControlLists
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sudo chflags schg filename # # system m flag
Noticethattheflagcomesintwovariants:theuserflagandthesystemflag.Theuserflagcanbechangedby
thefile’sownerand
root
(justlikenormalpermissions).Thesystemflagcanbechangedsolelyby
root
.
Toundothischange,youwouldissueoneofthefollowingcommands:
chflags nouchg g filename # # user flag
sudo chflags noschg g filename # # system m flag
Forcross-platformcompatibilityandreadabilityreasons,OSXsupportstwoothervariationsoneachofthese
flags:
uchange
,
uimmutable
,
schange
,and
simmutable
.Thesevariantsbehaveidenticallytotheirshortened
forms.
Thereareseveralotherflagsyoucansetwiththe
chflags
command,themostcommonbeingtheuserand
systemappend-onlyflags(
uappnd
/
uappend
and
sappnd
/
sappend
,respectively).
Formoreinformation,readthe
chflags
and
lchflags
manualpagesandtheOSXFileSystemSecurity
sectionofSecurityOverview.
UsechmodtoModifyAccessControlLists
The
chmod
commandismostcommonlyknownforitsabilitytomodifyUNIXpermissions.However,inOSX,
italsodoesdoubleduty,providingthescriptinginterfacesformodifyingafile’sPOSIXaccesscontrollists
(ACLs).
ThebasicconceptofACLsisfairlystraightforward.Anaccesscontrollistisalistofrules(accesscontrolentries,
orACEs).
Eachentrygrantsordeniestherighttoaccessafileordirectoryinaparticularway(therighttoreadthe
file,forexample).
Foranygivenright,thefirstentryinthelistthatmatchesagainstthecurrentuser’suserIDorgroup
membershipwins.
Iftheendofthelistisreachedwithoutmatchinganything,thefileordirectory’sUNIXpermissionsare
usedtodetermineaccess.
Thisisagreatlysimplifiedexplanation;forfulldetails,readtheOSXFileSystemSecuritysectionofSecurity
Overview.
EachACLentrylookslikethis:
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username grant t rightname
groupname grant t rightname
username deny y rightname
groupname deny y rightname
whereusernameandgroupnamearethenamesofauserorgroup,respectively,andrightnameisthename
ofanaccessright(
read
,forexample).
Youcanaddanaccesscontrolentrywiththe
+a
flagto
chmod
.Forexample,todenyreadaccessonafileto
theMySQLuser,youwouldtype:
chmod +a a "_mysql deny read" " filename
Toseetheresultsofyourchanges,type:
ls -le e filename
Bydefault,newaccesscontrollistentriesareappendedtotheendofthelist.Ifyouneedtoinsertanaccess
controlelsewhereinthelist,youcanusethe
+a#
flag.Forexample,toinsertanewruleatpositionzero(the
topofthelist),youwouldissueacommandlikethisone:
chmod +a# 0 0 "_www deny read" " filename
Youcandeleteanaccesscontrolentrywiththe
-a
flaglikethis:
chmod -a a "_mysql deny read" " filename
Thiscommanddeletesanyentrythatisanexactmatchforthespecifiedrule.
Finally,youcanreplaceanentrywithanotherentryusingthe
=a#
flag.Forexample,tochangetheusername
intheruleinsertedabovefrom
_www
to
_mdnsresponder
,youwouldtype:
chmod =a# 0 0 "_mdnsresponder r deny read" " filename
ShellScriptSecurity
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Inadditiontothebasicrulesdescribedabove,theACLsysteminOSXsupportsinheritance.AnyinheritedACL
entriesforadirectoryareautomaticallycopiedtoanynewfilescreatedwithinthatdirectoryatthetimeof
creation.
Youcanspecify:
whetheranACLshouldbeinheritedby:
enclosedfiles—
file_inherit
right
directories—
directory_inherit
right
both—
file_inherit,directory_inherit
right
neither(thedefault).
whetheranACLshouldbeinheritedbythechildrenofencloseddirectories(thedefault)ornot
(
limit_inherit
right).
whetheranACLshouldapplytothedirectoryitself(thedefault)ormerelybeinheritedbythingsinside
it(
only_inherit
right).
Youcanspecifyanycombinationoftheseflagsinanaccesscontrolentryforadirectorybypassingtheflags
aspartoftherightslist.
Forexample:
chmod +a a "_www w deny list,search,directory_inherit" dirname
Thisrulepreventsthe
_www
userfromlistingthedirectory’scontents.Italsopreventsthe
_www
userfrom
accessinganyfileswithinthespecifieddirectoryevenwithanexactnamelookup(search).Theruleisinherited
byanynewdirectorycreatedinsidethespecifieddirectory(andanydirectorycreatedinsidethatone,andso
on),butisnotinheritedbyordinaryfiles.
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Note:  Inheritanceflagsapplyexclusivelytoaccesscontrolentriesfordirectories.Youcannotset
theseflagsonfiles.
Cross-platform Compatibility Note:  Command-linetoolsbehaviorformodifyingaccesscontrol
listsisnotstandardized.Fortipsonhandlingthisacrossmultipleplatforms,seeAccessControlList
(ACL)Management (page 150)inDesigningScriptsforCross-PlatformDeployment (page 146).
FormoreinformationabouttheACLschemeinOSXisdescribedinOSXFileSystemSecuritysectionofSecurity
Overview.Formoreinformationaboutthecommand-lineflagsforgettingandsettingACLs,seethemanual
pagefor
chmod
.
SecuringTemporaryFiles
BecausethetemporarydirectoriesinOSXandotherUNIX-basedoperatingsystemsareworld-writable,you
musttakecaretoensurethatyouaremodifyingthefileyouthinkyouaremodifying.
Forexample,thefollowingcodehastwoseriousbugs:
if [ ! ! -f /tmp/mytempfile e ] ] ; ; then
# Race condition n here
touch /tmp/mytempfile
chmod u=rw,og= /tmp/mytempfile
# Missing g error r check k here
echo My secret t password is s omnibus > > /tmp/mytempfile
fi
Anapplicationthathappenstogetthetimingrightcancreateafilecalled
/tmp/mytempfile
rightafterthe
scriptchecksforitsexistence,waitforthescripttowritedataintoit,andsubsequentlystealthepassword.
The
chmod
commandwouldproduceanerrorinthiscase,butbecausethescriptdoesn’tchecktheresultcode,
theerrorismoot.
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PermissionsandAccessControlLists
2014-03-10   |   Copyright © 2003, 2014 Apple Inc. All Rights Reserved.
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