libssh2.h: Update Diffie Hellman group values #493
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File: libssh2.h Notes: Update the min, preferred and max DH group values based on RFC 8270. Credit: Will Cosgrove, noted from email list by Mitchell Holland
willco007
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File: libssh2.h Notes: Update the min, preferred and max DH group values based on RFC 8270. Credit: Will Cosgrove, noted from email list by Mitchell Holland
cy384
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File: libssh2.h Notes: Update the min, preferred and max DH group values based on RFC 8270. Credit: Will Cosgrove, noted from email list by Mitchell Holland
vszakats
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In 1c3a03e #493, `LIBSSH2_DH_GEX_MAXGROUP` was introduced to specify crypto-backend-specific modulus sizes. Unfortunately, the max size for the wincng DH modulus was defined to 8192, probably because this is the value most other backends support. According to Microsoft documentation [1], `BCryptGenerateKeyPair` currently only supports up to 4096-bit keys when the selected algorithm is `BCRYPT_DH_ALGORITHM`. Requesting larger keys when calling `BCryptGenerateKeyPair` in `_libssh2_dh_key_pair` always results in `STATUS_INVALID_PARAMETER` being returned and ultimately key exchange failing. When attempting to connect to any server that offers 8192 bit DH, this causes key exchange to always fail when using the wincng backend. Reducing `LIBSSH2_DH_GEX_MAXGROUP` to 4096 fixes the issue. [1] https://learn.microsoft.com/en-us/windows/win32/api/bcrypt/nf-bcrypt-bcryptgeneratekeypair Closes #1372
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Jul 14, 2024
In 1c3a03e libssh2#493, `LIBSSH2_DH_GEX_MAXGROUP` was introduced to specify crypto-backend-specific modulus sizes. Unfortunately, the max size for the wincng DH modulus was defined to 8192, probably because this is the value most other backends support. According to Microsoft documentation [1], `BCryptGenerateKeyPair` currently only supports up to 4096-bit keys when the selected algorithm is `BCRYPT_DH_ALGORITHM`. Requesting larger keys when calling `BCryptGenerateKeyPair` in `_libssh2_dh_key_pair` always results in `STATUS_INVALID_PARAMETER` being returned and ultimately key exchange failing. When attempting to connect to any server that offers 8192 bit DH, this causes key exchange to always fail when using the wincng backend. Reducing `LIBSSH2_DH_GEX_MAXGROUP` to 4096 fixes the issue. [1] https://learn.microsoft.com/en-us/windows/win32/api/bcrypt/nf-bcrypt-bcryptgeneratekeypair Closes libssh2#1372
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File: libssh2.h
Notes:
Update the min, preferred and max DH group values based on RFC 8270.
Credit:
Will Cosgrove, noted from email list by Mitchell Holland