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[3.7] bpo-43285 Make ftplib not trust the PASV response. (GH-24838) (GH-24881) #24883

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merged 3 commits into from Mar 16, 2021

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@miss-islington miss-islington commented Mar 15, 2021

bpo-43285: Make ftplib not trust the PASV response.

The IPv4 address value returned from the server in response to the PASV command
should not be trusted. This prevents a malicious FTP server from using the
response to probe IPv4 address and port combinations on the client network.

Instead of using the returned address, we use the IP address we're
already connected to. This is the strategy other ftp clients adopted,
and matches the only strategy available for the modern IPv6 EPSV command
where the server response must return a port number and nothing else.

For the rare user who wants this ugly behavior, set a trust_server_pasv_ipv4_address
attribute on your ftplib.FTP instance to True..
(cherry picked from commit 0ab152c)

Co-authored-by: Gregory P. Smith greg@krypto.org
(cherry picked from commit 664d1d1)

Co-authored-by: Gregory P. Smith greg@krypto.org

https://bugs.python.org/issue43285

) (pythonGH-24881)

bpo-43285: Make ftplib not trust the PASV response.

The IPv4 address value returned from the server in response to the PASV command
should not be trusted.  This prevents a malicious FTP server from using the
response to probe IPv4 address and port combinations on the client network.

Instead of using the returned address, we use the IP address we're
already connected to.  This is the strategy other ftp clients adopted,
and matches the only strategy available for the modern IPv6 EPSV command
where the server response must return a port number and nothing else.

For the rare user who _wants_ this ugly behavior, set a `trust_server_pasv_ipv4_address`
attribute on your `ftplib.FTP` instance to True..
(cherry picked from commit 0ab152c)

Co-authored-by: Gregory P. Smith <greg@krypto.org>
(cherry picked from commit 664d1d1)

Co-authored-by: Gregory P. Smith <greg@krypto.org>
@miss-islington
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@gpshead: Status check is done, and it's a success ✅ .

@gpshead gpshead changed the title [3.7] [3.8] bpo-43285 Make ftplib not trust the PASV response. (GH-24838) (GH-24881) [3.7] bpo-43285 Make ftplib not trust the PASV response. (GH-24838) (GH-24881) Mar 15, 2021
@miss-islington
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@gpshead: Status check is done, and it's a success ✅ .

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gpshead commented Mar 16, 2021

Added a What's New entry.

@ned-deily ned-deily merged commit 7937395 into python:3.7 Mar 16, 2021
@miss-islington miss-islington deleted the backport-664d1d1-3.7 branch March 16, 2021 21:20
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5 participants