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|000020f0| 66 69 6c 65 2c 20 6d 6f | 64 65 3d 27 72 27 2c 20 |file, mo|de='r', |
|00002100| 62 75 66 3d 2d 31 29 3a | 0a 20 20 20 20 20 20 20 |buf=-1):|.       |
|00002110| 20 69 66 20 6d 6f 64 65 | 20 69 6e 20 28 27 72 27 | if mode| in ('r'|
|00002120| 2c 20 27 72 62 27 29 3a | 0a 20 20 20 20 20 20 20 |, 'rb'):|.       |
|00002130| 20 20 20 20 20 70 61 73 | 73 0a 20 20 20 20 20 20 |     pas|s.      |
|00002140| 20 20 65 6c 69 66 20 6d | 6f 64 65 20 69 6e 20 28 |  elif m|ode in (|
|00002150| 27 77 27 2c 20 27 77 62 | 27 2c 20 27 61 27 2c 20 |'w', 'wb|', 'a', |
|00002160| 27 61 62 27 29 3a 0a 20 | 20 20 20 20 20 20 20 20 |'ab'):. |        |
|00002170| 20 20 20 23 20 63 68 65 | 63 6b 20 66 69 6c 65 6e |   # che|ck filen|
|00002180| 61 6d 65 20 3a 20 6d 75 | 73 74 20 62 65 67 69 6e |ame : mu|st begin|
|00002190| 20 77 69 74 68 20 2f 74 | 6d 70 2f 0a 20 20 20 20 | with /t|mp/.    |
|000021a0| 20 20 20 20 20 20 20 20 | 69 66 20 66 69 6c 65 5b |        |if file[|
|000021b0| 3a 35 5d 21 3d 27 2f 74 | 6d 70 2f 27 3a 20 0a 20 |:5]!='/t|mp/': . |
|000021c0| 20 20 20 20 20 20 20 20 | 20 20 20 20 20 20 20 72 |        |       r|
|000021d0| 61 69 73 65 20 49 4f 45 | 72 72 6f 72 2c 20 22 63 |aise IOE|rror, "c|
|000021e0| 61 6e 27 74 20 77 72 69 | 74 65 20 6f 75 74 73 69 |an't wri|te outsi|
|000021f0| 64 65 20 2f 74 6d 70 22 | 0a 20 20 20 20 20 20 20 |de /tmp"|.       |
|00002200| 20 20 20 20 20 65 6c 69 | 66 20 28 73 74 72 69 6e |     eli|f (strin|
|00002210| 67 2e 66 69 6e 64 28 66 | 69 6c 65 2c 20 27 2f 2e |g.find(f|ile, '/.|
|00002220| 2e 2f 27 29 20 3e 3d 20 | 30 20 6f 72 0a 20 20 20 |./') >= |0 or.   |
|00002230| 20 20 20 20 20 20 20 20 | 20 20 20 20 20 20 66 69 |        |      fi|
|00002240| 6c 65 5b 3a 33 5d 20 3d | 3d 20 27 2e 2e 2f 27 20 |le[:3] =|= '../' |
|00002250| 6f 72 20 66 69 6c 65 5b | 2d 33 3a 5d 20 3d 3d 20 |or file[|-3:] == |
|00002260| 27 2f 2e 2e 27 29 3a 0a | 20 20 20 20 20 20 20 20 |'/..'):.|        |
|00002270| 20 20 20 20 20 20 20 20 | 72 61 69 73 65 20 49 4f |        |raise IO|
|00002280| 45 72 72 6f 72 2c 20 22 | 27 2e 2e 27 20 69 6e 20 |Error, "|'..' in |
|00002290| 66 69 6c 65 6e 61 6d 65 | 20 66 6f 72 62 69 64 64 |filename| forbidd|
|000022a0| 65 6e 22 0a 20 20 20 20 | 20 20 20 20 65 6c 73 65 |en".    |    else|
|000022b0| 3a 20 72 61 69 73 65 20 | 49 4f 45 72 72 6f 72 2c |: raise |IOError,|
|000022c0| 20 22 49 6c 6c 65 67 61 | 6c 20 6f 70 65 6e 28 29 | "Illega|l open()|
|000022d0| 20 6d 6f 64 65 22 0a 20 | 20 20 20 20 20 20 20 72 | mode". |       r|
|000022e0| 65 74 75 72 6e 20 6f 70 | 65 6e 28 66 69 6c 65 2c |eturn op|en(file,|
|000022f0| 20 6d 6f 64 65 2c 20 62 | 75 66 29 0a 5c 65 6e 64 | mode, b|uf).\end|
|00002300| 7b 76 65 72 62 61 74 69 | 6d 7d 5c 65 63 6f 64 65 |{verbati|m}\ecode|
|00002310| 0a 0a 4e 6f 74 69 63 65 | 20 74 68 61 74 20 74 68 |..Notice| that th|
|00002320| 65 20 61 62 6f 76 65 20 | 63 6f 64 65 20 77 69 6c |e above |code wil|
|00002330| 6c 20 6f 63 63 61 73 69 | 6f 6e 61 6c 6c 79 20 66 |l occasi|onally f|
|00002340| 6f 72 62 69 64 20 61 20 | 70 65 72 66 65 63 74 6c |orbid a |perfectl|
|00002350| 79 20 76 61 6c 69 64 0a | 66 69 6c 65 6e 61 6d 65 |y valid.|filename|
|00002360| 3b 20 66 6f 72 20 65 78 | 61 6d 70 6c 65 2c 20 63 |; for ex|ample, c|
|00002370| 6f 64 65 20 69 6e 20 74 | 68 65 20 72 65 73 74 72 |ode in t|he restr|
|00002380| 69 63 74 65 64 20 65 6e | 76 69 72 6f 6e 6d 65 6e |icted en|vironmen|
|00002390| 74 20 77 6f 6e 27 74 20 | 62 65 0a 61 62 6c 65 20 |t won't |be.able |
|000023a0| 74 6f 20 6f 70 65 6e 20 | 61 20 66 69 6c 65 20 63 |to open |a file c|
|000023b0| 61 6c 6c 65 64 20 5c 66 | 69 6c 65 7b 2f 74 6d 70 |alled \f|ile{/tmp|
|000023c0| 2f 66 6f 6f 2f 2e 2e 2f | 62 61 72 7d 2e 20 20 54 |/foo/../|bar}.  T|
|000023d0| 6f 20 66 69 78 20 74 68 | 69 73 2c 20 74 68 65 0a |o fix th|is, the.|
|000023e0| 5c 63 6f 64 65 7b 72 5f | 6f 70 65 6e 7d 20 6d 65 |\code{r_|open} me|
|000023f0| 74 68 6f 64 20 77 6f 75 | 6c 64 20 68 61 76 65 20 |thod wou|ld have |
|00002400| 74 6f 20 73 69 6d 70 6c | 69 66 79 20 74 68 65 20 |to simpl|ify the |
|00002410| 66 69 6c 65 6e 61 6d 65 | 20 74 6f 0a 5c 66 69 6c |filename| to.\fil|
|00002420| 65 7b 2f 74 6d 70 2f 62 | 61 72 7d 2c 20 77 68 69 |e{/tmp/b|ar}, whi|
|00002430| 63 68 20 77 6f 75 6c 64 | 20 72 65 71 75 69 72 65 |ch would| require|
|00002440| 20 73 70 6c 69 74 74 69 | 6e 67 20 61 70 61 72 74 | splitti|ng apart|
|00002450| 20 74 68 65 20 66 69 6c | 65 6e 61 6d 65 20 61 6e | the fil|ename an|
|00002460| 64 0a 70 65 72 66 6f 72 | 6d 69 6e 67 20 76 61 72 |d.perfor|ming var|
|00002470| 69 6f 75 73 20 6f 70 65 | 72 61 74 69 6f 6e 73 20 |ious ope|rations |
|00002480| 6f 6e 20 69 74 2e 20 20 | 49 6e 20 63 61 73 65 73 |on it.  |In cases|
|00002490| 20 77 68 65 72 65 20 73 | 65 63 75 72 69 74 79 20 | where s|ecurity |
|000024a0| 69 73 20 61 74 0a 73 74 | 61 6b 65 2c 20 69 74 20 |is at.st|ake, it |
|000024b0| 6d 61 79 20 62 65 20 70 | 72 65 66 65 72 61 62 6c |may be p|referabl|
|000024c0| 65 20 74 6f 20 77 72 69 | 74 65 20 73 69 6d 70 6c |e to wri|te simpl|
|000024d0| 65 20 63 6f 64 65 20 77 | 68 69 63 68 20 69 73 20 |e code w|hich is |
|000024e0| 73 6f 6d 65 74 69 6d 65 | 73 0a 6f 76 65 72 6c 79 |sometime|s.overly|
|000024f0| 20 72 65 73 74 72 69 63 | 74 69 76 65 2c 20 69 6e | restric|tive, in|
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|00002520| 69 73 20 61 6c 73 6f 20 | 6d 6f 72 65 0a 63 6f 6d |is also |more.com|
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+--------+-------------------------+-------------------------+--------+--------+