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From: Paul Mackerras <paulus@ozlabs.org>
Date: Mon, 3 Feb 2020 15:53:28 +1100
Subject: pppd: Fix bounds check in EAP code
Origin: https://github.com/paulusmack/ppp/commit/8d7970b8f3db727fe798b65f3377fe6787575426
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2020-8597
Bug-Debian: https://bugs.debian.org/950618
Given that we have just checked vallen < len, it can never be the case
that vallen >= len + sizeof(rhostname). This fixes the check so we
actually avoid overflowing the rhostname array.
Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
---
pppd/eap.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/pppd/eap.c b/pppd/eap.c
index 94407f56a336..1b93db01aebd 100644
--- a/pppd/eap.c
+++ b/pppd/eap.c
@@ -1420,7 +1420,7 @@ int len;
}
/* Not so likely to happen. */
- if (vallen >= len + sizeof (rhostname)) {
+ if (len - vallen >= sizeof (rhostname)) {
dbglog("EAP: trimming really long peer name down");
BCOPY(inp + vallen, rhostname, sizeof (rhostname) - 1);
rhostname[sizeof (rhostname) - 1] = '\0';
@@ -1846,7 +1846,7 @@ int len;
}
/* Not so likely to happen. */
- if (vallen >= len + sizeof (rhostname)) {
+ if (len - vallen >= sizeof (rhostname)) {
dbglog("EAP: trimming really long peer name down");
BCOPY(inp + vallen, rhostname, sizeof (rhostname) - 1);
rhostname[sizeof (rhostname) - 1] = '\0';
--
2.20.1
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