git: f9972532343b - stable/13 - libradius: Fix attribute length validation in rad_get_attr(3)

[Mark Johnston]

The branch stable/13 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=f9972532343bb1eb101bf7afef2966972eea3b5e

commit f9972532343bb1eb101bf7afef2966972eea3b5e
Author:     Mark Johnston <markj at FreeBSD.org>
AuthorDate: 2021-05-28 14:41:43 +0000
Commit:     Mark Johnston <markj at FreeBSD.org>
CommitDate: 2021-05-28 17:00:19 +0000

    libradius: Fix attribute length validation in rad_get_attr(3)
    
    The length of the attribute header needs to be excluded when comparing
    the attribute length against the length of the packet.  Otherwise,
    validation may incorrectly fail when fetching the final attribute in a
    message.
    
    Fixes:          8d5c78130 ("libradius: Fix input validation bugs")
    Reported by:    Peter Eriksson
    Tested by:      Peter Eriksson
    Sponsored by:   The FreeBSD Foundation
    
    (cherry picked from commit 6bb5699d2b59491097bc21ffa3c097cdd4853f89)
---
 lib/libradius/radlib.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/libradius/radlib.c b/lib/libradius/radlib.c
index 18aee8b53024..4d21887c4ee2 100644
--- a/lib/libradius/radlib.c
+++ b/lib/libradius/radlib.c
@@ -964,7 +964,12 @@ rad_get_attr(struct rad_handle *h, const void **value, size_t *lenp)
 	}
 	type = h->in[h->in_pos++];
 	len = h->in[h->in_pos++];
-	if (len < 2 || h->in_pos + len > h->in_len) {
+	if (len < 2) {
+		generr(h, "Malformed attribute in response");
+		return -1;
+	}
+	len -= 2;
+	if (h->in_pos + len > h->in_len) {
 		generr(h, "Malformed attribute in response");
 		return -1;
 	}