git: 4e2e151b2099 - releng/11.4 - libradius: Fix attribute length validation in rad_get_attr(3)

[Mark Johnston]

The branch releng/11.4 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=4e2e151b2099f3815ef1d170efc727c4b7cec98c

commit 4e2e151b2099f3815ef1d170efc727c4b7cec98c
Author:     Mark Johnston <markj at FreeBSD.org>
AuthorDate: 2021-05-28 14:41:43 +0000
Commit:     Mark Johnston <markj at FreeBSD.org>
CommitDate: 2021-06-01 20:32:50 +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.
    
    Approved by:    so
    Security:       FreeBSD-EN-21:17.libradius
    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)
    (cherry picked from commit f9972532343bb1eb101bf7afef2966972eea3b5e)
---
 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 acca95da6f66..e679b95089b0 100644
--- a/lib/libradius/radlib.c
+++ b/lib/libradius/radlib.c
@@ -949,7 +949,12 @@ 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;
 	}