segfault when compiled without libbsd #1233
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mbakke
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Oct 31, 2023
This time fixing a segfault reported & debugged entirely by graywolf. See: <OpenSMTPD/OpenSMTPD#1233> So, what went wrong here? Mostly me being entirely convinced, to the point of not even looking, that we have no opensmtpd system test. We do. Instead, I tested the update on my own mail server, which for entirely unhysterical raisins happens to link OpenSMTPd against OpenSSL and so just happens to sidestep this bug. Aiya. * gnu/packages/mail.scm (opensmtpd): Update to 7.4.0p0. [native-inputs]: Add pkg-config. [inputs]: Add libbsd. [arguments]: Add "--with-libbsd" to #:configure-flags. Co-authored-by: graywolf in #guix Change-Id: I5536b828eecd16f041ed9381b16bd7aa54158155
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@graywolf thanks for the detailed report and sorry for the delay. This happens to be a problem that was fixed in libressl 3.8 (libressl/portable@54b31ce) that no longer exports the compat symbols in libcrypto. Still, we can do something in configure to avoid this (i.e. checking arc4random() after libcrypto) |
omar-polo
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Nov 2, 2023
LibreSSL pre 3.8 leaks the symbols of their compats in libcrypto. This is particularly painful with arc4random() which, in our implementation, relies on libcrypto. LibreSSL' RAND_add() calls itself arc4random_buf() resulting in an infinite loop due to the symbol clash. Instead, check for arc4random() only after we've found libcrypto, and re-establish the prototype hack in openbsd-compat.h. Hopefully we'll be able to get rid of this workaround in a few releases. Issue reported by @graywolf, thank you! Fixes #1233
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#1234 should fix this by re-using Thanks! |
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@graywolf ah, please make sure to re-run |
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After applying the patch and running autoreconf -i (I overlook the bootstrap), it seems to work. Thank you for fixing it :) |
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Thank you for confirming the fix :) |
omar-polo
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Nov 6, 2023
LibreSSL pre 3.8 leaks the symbols of their compats in libcrypto. This is particularly painful with arc4random() which, in our implementation, relies on libcrypto. LibreSSL' RAND_add() calls itself arc4random_buf() resulting in an infinite loop due to the symbol clash. Instead, check for arc4random() only after we've found libcrypto, and re-establish the prototype hack in openbsd-compat.h. Hopefully we'll be able to get rid of this workaround in a few releases. Issue reported by @graywolf, thank you! Fixes #1233
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Hello,
when I compile opensmtpd without a libbsd, it fails to start with a segfault. Backtrace in the core dump:
That goes on for a while, I stopped the gdb when at #238808 stack depth. I believe the cause is _rs_stir calling RAND_bytes, which (only in libressl's implementation) calls arc4random_buf, leading to the loop.
libbsd does not use RAND_bytes, openssl does not use arc4random_buf, meaning both condition (no libbsd, use libressl) needs to be fulfilled for the crash to occur.
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