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It's Dangerous, a Python cryptographic signing module

packages.python.org

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Re: It's Dangerous, a Python cryptographic signing module

#4

Post by JoachimSchipper »

obiterdictum wrote: post #2

Executive summary: - The signature: SHA1 HMAC of data and, optionally, a timestamp to expire signatures. - HMAC key derivation: SHA1 of a secret key and a salt.

> - HMAC key derivation: SHA1 of a secret key and a salt.

Note to non-cryptographers: do not use low-entropy (password-ish) secretswith this, they can be bruteforced. (Using bcrypt/scrypt/PBKDF2 instead would fix this.)

Re: It's Dangerous, a Python cryptographic signing module

#5

Post by jacques_chester »

ctz wrote: post #3

Use of SHA-1 for this signature/MAC purposes in new applications is deprecated and will be disallowed from next year (source: NIST). I repeat: do not use SHA-1 in new applications. Do not use this module.

To clarify very slightly, use SHA-256, SHA-384 or SHA-512 instead.

Sometime soon I believe SHA-3 will be chosen and we'll all be able to move onto that.

Re: It's Dangerous, a Python cryptographic signing module

#6

Post by Luit »

ctz wrote: post #3

Use of SHA-1 for this signature/MAC purposes in new applications is deprecated and will be disallowed from next year (source: NIST). I repeat: do not use SHA-1 in new applications. Do not use this module.

Well then fork it and make it use HMAC with SHA256/512... Additionally, "Do not use this module" is bad advice if it leads to someone making their own MAC implementation, because that's almost always a bad idea. HMAC-SHA1 still is good security for this purpose.

I bet that as soon as standards bodies (like NIST) actively encourage you to use better hash functions (which they will probably do soon) the developer of this module will decide on what is safe enough for this purpose.

Re: It's Dangerous, a Python cryptographic signing module

#7

Post by ch0wn »

Luit wrote: post #6
ctz wrote: post #3

Use of SHA-1 for this signature/MAC purposes in new applications is deprecated and will be disallowed from next year (source: NIST). I repeat: do not use SHA-1 in new applications. Do not use this module.

Well then fork it and make it use HMAC with SHA256/512... Additionally, "Do not use this module" is bad advice if it leads to someone making their own MAC implementation, because that's almost always a bad idea. HMAC-SHA1 still is good security for this purpose. I bet that as soon as standards bodies (like NIST) actively encourage you to use better hash functions (which they will probably do soon) the developer of th…

It shouldn't be more than changing those two lines:

https://github.com/mitsuhiko/itsdangerous/blob/59f3bf7877e21...

And the tests, of course.

Re: It's Dangerous, a Python cryptographic signing module

#8

Post by Luit »

ch0wn wrote: post #7
Luit wrote: post #6

Earlier quoted context omitted.

Well then fork it and make it use HMAC with SHA256/512... Additionally, "Do not use this module" is bad advice if it leads to someone making their own MAC implementation, because that's almost always a bad idea. HMAC-SHA1 still is good security for this purpose. I bet that as soon as standards bodies (like NIST) actively encourage you to use better hash functions (which they will probably do soon) the developer of th…

It shouldn't be more than changing those two lines: https://github.com/mitsuhiko/itsdangerous/blob/59f3bf7877e21... And the tests, of course.

My point exactly! Armin (the maker/maintainer of the module) will probably consider doing this somewhere in the future.

Re: It's Dangerous, a Python cryptographic signing module

#9

Post by gambler »

Luit wrote: post #6
ctz wrote: post #3

Use of SHA-1 for this signature/MAC purposes in new applications is deprecated and will be disallowed from next year (source: NIST). I repeat: do not use SHA-1 in new applications. Do not use this module.

Well then fork it and make it use HMAC with SHA256/512... Additionally, "Do not use this module" is bad advice if it leads to someone making their own MAC implementation, because that's almost always a bad idea. HMAC-SHA1 still is good security for this purpose. I bet that as soon as standards bodies (like NIST) actively encourage you to use better hash functions (which they will probably do soon) the developer of th…

You advise to "fork it", but immediately after that you add the notorious "do not write your own" meme. Can you see the inconsistency of the messages?

Part of security is being up-to-date in regards to things like hashes. If authors don't update their own libraries and you need to tweak them manually, how is it different from "writing your own"?

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