Commit d3db2da1 authored by Matthias Andree's avatar Matthias Andree
Browse files

Fix --logfile and message truncation issue.

Regression in 6.4.20's security fix (Git commit c546c829).

We doubly incremented partial_message_size_used on modern systems
(stdard.h/vsnprintf), once in report_vbuild() and then again in
report_build(), so the 2nd and subsequent report_build() fragments
landed too late in the buffer.  This will not cause overruns due to the
reallocation prior to the vsnprintf/sprintf, but it write starts behind
the '\0' byte, instead of right over it, so the string also gets
truncated to the first fragment written with report_vbuild().

Fix by moving the increment back into the #else...#endif part that does
not use report_vbuild().

Reported by: Jürgen Edner, Erik Christiansen
parent f6ebe48b
......@@ -81,6 +81,24 @@ removed from a 6.5.0 or newer release.)
messages. This will not be fixed, because the maintainer has no Kerberos 5
server to test against. Use GSSAPI.
fetchmail-6.4.21 (released 2021-08-09, 30042 LoC):
* The new security fix in 6.4.20 for CVE-2021-36386 caused truncation of
messages logged to buffered outputs, predominantly --logfile.
This also caused lines in the logfile to run into one another because
the fragment containing the '\n' line-end character was usually lost.
Reason is that on all modern systems (with <stdarg.h> header and vsnprintf()
interface), the length of log message fragments was added up twice, so
that these ended too deep into a freshly allocated buffer, after the '\0'
byte. Unbuffered outputs flushed the fragments right away, which masked the
Reported by: Jürgen Edner, Erik Christiansen.
fetchmail-6.4.20 (released 2021-07-28, 30042 LoC):
......@@ -286,10 +286,11 @@ report_build (FILE *errfp, message, va_alist)
n = snprintf (partial_message + partial_message_size_used,
partial_message_size - partial_message_size_used,
message, a1, a2, a3, a4, a5, a6, a7, a8);
if (n > 0) partial_message_size_used += n;
if (unbuffered && partial_message_size_used != 0)
partial_message_size_used = 0;
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