From 709214f554355158b2c3e70c7f3424997e002cee Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <[email protected]>
Date: Thu, 23 Aug 2018 14:48:40 +0200
Subject: [PATCH] bus-message: avoid wrap-around when using length read from
 message

We would read (-1), and then add 1 to it, call message_peek_body(..., 0, ...),
and when trying to make use of the data.

The fuzzer test case is just for one site, but they all look similar.

v2: fix two UINT8_MAX/UINT32_MAX mismatches founds by LGTM
(cherry picked from commit 902000c19830f5e5a96e8948d691b42e91ecb1e7)

Resolves: #1696224
---
 src/libsystemd/sd-bus/bus-message.c           |  24 ++++++++++++++++++
 ...h-603dfd98252375ac7dbced53c2ec312671939a36 | Bin 0 -> 40 bytes
 2 files changed, 24 insertions(+)
 create mode 100644 test/fuzz/fuzz-bus-message/crash-603dfd98252375ac7dbced53c2ec312671939a36

diff --git a/src/libsystemd/sd-bus/bus-message.c b/src/libsystemd/sd-bus/bus-message.c
index 613722a1a0..53cbd675b7 100644
--- a/src/libsystemd/sd-bus/bus-message.c
+++ b/src/libsystemd/sd-bus/bus-message.c
@@ -3414,6 +3414,10 @@ _public_ int sd_bus_message_read_basic(sd_bus_message *m, char type, void *p) {
                                 return r;
 
                         l = BUS_MESSAGE_BSWAP32(m, *(uint32_t*) q);
+                        if (l == UINT32_MAX)
+                                /* avoid overflow right below */
+                                return -EBADMSG;
+
                         r = message_peek_body(m, &rindex, 1, l+1, &q);
                         if (r < 0)
                                 return r;
@@ -3436,6 +3440,10 @@ _public_ int sd_bus_message_read_basic(sd_bus_message *m, char type, void *p) {
                                 return r;
 
                         l = *(uint8_t*) q;
+                        if (l == UINT8_MAX)
+                                /* avoid overflow right below */
+                                return -EBADMSG;
+
                         r = message_peek_body(m, &rindex, 1, l+1, &q);
                         if (r < 0)
                                 return r;
@@ -3701,6 +3709,10 @@ static int bus_message_enter_variant(
                         return r;
 
                 l = *(uint8_t*) q;
+                if (l == UINT8_MAX)
+                        /* avoid overflow right below */
+                        return -EBADMSG;
+
                 r = message_peek_body(m, &rindex, 1, l+1, &q);
                 if (r < 0)
                         return r;
@@ -4269,6 +4281,10 @@ _public_ int sd_bus_message_peek_type(sd_bus_message *m, char *type, const char
                                         return r;
 
                                 l = *(uint8_t*) q;
+                                if (l == UINT8_MAX)
+                                        /* avoid overflow right below */
+                                        return -EBADMSG;
+
                                 r = message_peek_body(m, &rindex, 1, l+1, &q);
                                 if (r < 0)
                                         return r;
@@ -4849,6 +4865,10 @@ static int message_peek_field_string(
                 if (r < 0)
                         return r;
 
+                if (l == UINT32_MAX)
+                        /* avoid overflow right below */
+                        return -EBADMSG;
+
                 r = message_peek_fields(m, ri, 1, l+1, &q);
                 if (r < 0)
                         return r;
@@ -4900,6 +4920,10 @@ static int message_peek_field_signature(
                         return r;
 
                 l = *(uint8_t*) q;
+                if (l == UINT8_MAX)
+                        /* avoid overflow right below */
+                        return -EBADMSG;
+
                 r = message_peek_fields(m, ri, 1, l+1, &q);
                 if (r < 0)
                         return r;
diff --git a/test/fuzz/fuzz-bus-message/crash-603dfd98252375ac7dbced53c2ec312671939a36 b/test/fuzz/fuzz-bus-message/crash-603dfd98252375ac7dbced53c2ec312671939a36
new file mode 100644
index 0000000000000000000000000000000000000000..b3fee9e07af4f925697a549bbc8ffc03a277fac0
GIT binary patch
literal 40
mcmc~{Vqjzdg7laF|BC@>cE)0c{}2$`*K@IKT2AZ~5ElR}@e}O;

literal 0
HcmV?d00001