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Avoid possibly-unsafe use of Windows' FormatMessage() function.

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Whenever this function is used with the FORMAT_MESSAGE_FROM_SYSTEM flag,
it's good practice to include FORMAT_MESSAGE_IGNORE_INSERTS as well.
Otherwise, if the message contains any %n insertion markers, the function
will try to fetch argument strings to substitute --- which we are not
passing, possibly leading to a crash.  This is exactly analogous to the
rule about not giving printf() a format string you're not in control of.

Noted and patched by Christian Ullrich.
Back-patch to all supported branches.
This commit is contained in:
Tom Lane
2016-03-29 11:54:57 -04:00
parent 61d66c44f1
commit 7abc157165
4 changed files with 15 additions and 5 deletions
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4
src/interfaces/libpq/fe-auth.c
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@ -234,7 +234,9 @@ pg_SSPI_error(PGconn *conn, const char *mprefix, SECURITY_STATUS r)
{
char sysmsg[256];
if (FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, r, 0,
if (FormatMessage(FORMAT_MESSAGE_IGNORE_INSERTS |
FORMAT_MESSAGE_FROM_SYSTEM,
NULL, r, 0,
sysmsg, sizeof(sysmsg), NULL) == 0)
printfPQExpBuffer(&conn->errorMessage, "%s: SSPI error %x\n",
mprefix, (unsigned int) r);