Your message dated Mon, 07 Feb 2022 21:43:10 +0000 with message-id <[email protected]> and subject line Bug#1004933: Removed package(s) from unstable has caused the Debian Bug report #1002621, regarding gif2apng: Stack based overflow in the handling of input and output file name to be marked as done.
This means that you claim that the problem has been dealt with. If this is not the case it is now your responsibility to reopen the Bug report if necessary, and/or fix the problem forthwith. (NB: If you are a system administrator and have no idea what this message is talking about, this may indicate a serious mail system misconfiguration somewhere. Please contact [email protected] immediately.) -- 1002621: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1002621 Debian Bug Tracking System Contact [email protected] with problems
--- Begin Message ---Package: gif2apng Version: 1.9+srconly-3 Severity: important Dear Maintainer, I found a stack based overflow in the handling of the command line arguments in the gif2apng package. The responsible code looks as follows: gif2apng.cpp (line 421-518): int main(int argc, char** argv) { [...] char szIn[256]; char szOut[256]; [...] szIn[0] = 0; szOut[0] = 0; for (i=1; i<argc; i++) { szOpt = argv[i]; if (szOpt[0] == '/' || szOpt[0] == '-') { [...] } else if (szIn[0] == 0) strcpy(szIn, szOpt, 255); else if (szOut[0] == 0) strcpy(szOut, szOpt); } As can be seen there are two buffers of size 256. The command line arguments for the input and output file names are copied into these buffers without any validation of their size. Providing a large enough filename will overwrite data on the stack, that is located after the buffer. To test this I provided a large filename to the program as a file name as follows: $gif2apng $(python3 -c "print('A'*10000)") This led to to the following output: *** buffer overflow detected ***: terminated This indicates, that the stack canary placed on the stack by gcc was overwritten by the input. So there seems to be a memory corruption issue here, which could allow the execution of arbitrary code in the context of the program depending on the other data on the stack or in combination with a memory leak. I tested this after installing the current version from the testing repositories on Debian 10. Patch suggestion: I think it should be enough to use strncpy instead of strcpy here and to ensure, that the string is zero terminated. There is a case later in the code where the input will be copied into an other buffer again using strcpy. This should also be changed, so that no out of bounds write is possible at this location. I changed the lines 512 to 532 of the gif2apng.cpp file as follows: [...] if (szIn[0] == 0) strncpy(szIn, szOpt, 255); // strcpy -> strncpy else if (szOut[0] == 0) strncpy(szOut, szOpt, 255); // strcpy -> strncpy } szIn[255] = 0; // Ensure, that the string is terminated with a zero byte szOut[255] = 0; if (deflate_method == 0) printf(" using ZLIB\n\n"); else if (deflate_method == 1) printf(" using 7ZIP with %d iterations\n\n", iter); else if (deflate_method == 2) printf(" using ZOPFLI with %d iterations\n\n", iter); if (szOut[0] == 0) { strncpy(szOut, szIn, 251); // Ensure, that with .png appended the string still fits into the buffer if ((szExt = strrchr(szOut, '.')) != NULL) *szExt = 0; strcat(szOut, ".png"); } [...] I was able to compile the code with these changes and the issue seemed to be fixed. Best regards Kolja -- System Information: Debian Release: 10.11 APT prefers oldstable-updates APT policy: (500, 'oldstable-updates'), (500, 'oldstable') Architecture: amd64 (x86_64) Kernel: Linux 4.19.0-18-amd64 (SMP w/8 CPU cores) Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE=de_DE.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /usr/bin/dash Init: systemd (via /run/systemd/system) LSM: AppArmor: enabled Versions of packages gif2apng depends on: ii libc6 2.28-10 ii libzopfli1 1.0.2-1 ii zlib1g 1:1.2.11.dfsg-1 gif2apng recommends no packages. Versions of packages gif2apng suggests: pn apng2gif <none> -- no debconf information
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--- Begin Message ---Version: 1.9+srconly-3+rm Dear submitter, as the package gif2apng has just been removed from the Debian archive unstable we hereby close the associated bug reports. We are sorry that we couldn't deal with your issue properly. For details on the removal, please see https://bugs.debian.org/1004933 The version of this package that was in Debian prior to this removal can still be found using http://snapshot.debian.org/. Please note that the changes have been done on the master archive and will not propagate to any mirrors until the next dinstall run at the earliest. This message was generated automatically; if you believe that there is a problem with it please contact the archive administrators by mailing [email protected]. Debian distribution maintenance software pp. Scott Kitterman (the ftpmaster behind the curtain)
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