isisd: fix crash when reading asla

isisd is crashing when reading a ASLA sub-TLV with Application
Identifier Bit Mask length greater than 1 octet.

Set a limit of 8 bytes in accordance with RFC9479 and check that the
received value does not exceed the limit.

Reported-by: Iggy Frankovic <iggyfran@amazon.com>
Link: https://www.rfc-editor.org/rfc/rfc9479.html#name-application-identifier-bit-
Fixes: 5749ac83a8 ("isisd: add ASLA support")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>

diff --git a/isisd/isis_tlvs.c b/isisd/isis_tlvs.c
index c7f45b246948ea4727f2f2a04a50c2477a1274d9..d2dacdc113de4756ad616f221848ec62ff9c9a18 100644 (file)
--- a/isisd/isis_tlvs.c
+++ b/isisd/isis_tlvs.c
@@ -1914,8 +1914,8 @@ static int unpack_item_ext_subtlv_asla(uint16_t mtid, uint8_t subtlv_len,
        uint8_t sabm_flag_len;
        /* User-defined App Identifier Bit Flags/Length */
        uint8_t uabm_flag_len;
-       uint8_t sabm[ASLA_APP_IDENTIFIER_BIT_LENGTH] = {0};
-       uint8_t uabm[ASLA_APP_IDENTIFIER_BIT_LENGTH] = {0};
+       uint8_t sabm[ASLA_APP_IDENTIFIER_BIT_MAX_LENGTH] = { 0 };
+       uint8_t uabm[ASLA_APP_IDENTIFIER_BIT_MAX_LENGTH] = { 0 };
        uint8_t readable = subtlv_len;
        uint8_t subsubtlv_type;
        uint8_t subsubtlv_len;
@@ -1946,6 +1946,15 @@ static int unpack_item_ext_subtlv_asla(uint16_t mtid, uint8_t subtlv_len,
                return -1;
        }
 
+       if ((asla->standard_apps_length > ASLA_APP_IDENTIFIER_BIT_MAX_LENGTH) ||
+           (asla->user_def_apps_length > ASLA_APP_IDENTIFIER_BIT_MAX_LENGTH)) {
+               zlog_err("Standard or User-Defined Application Identifier Bit Mask Length greater than %u bytes. Received respectively a length of %u and %u bytes.",
+                        ASLA_APP_IDENTIFIER_BIT_MAX_LENGTH,
+                        asla->standard_apps_length, asla->user_def_apps_length);
+               stream_forward_getp(s, readable);
+               return -1;
+       }
+
        for (int i = 0; i < asla->standard_apps_length; i++)
                sabm[i] = stream_getc(s);
        for (int i = 0; i < asla->user_def_apps_length; i++)

diff --git a/isisd/isis_tlvs.h b/isisd/isis_tlvs.h
index 6ecd4c5f6ad88e645bc920aa25a2985a6be25c19..c64bbf7f697ca195f18288436fb5d54e0be1377c 100644 (file)
--- a/isisd/isis_tlvs.h
+++ b/isisd/isis_tlvs.h
@@ -717,6 +717,7 @@ struct isis_ext_subtlvs {
 #define ISIS_SABM_FLAG_X 0x10 /* Flex-Algorithm - RFC9350 */
 
 #define ASLA_APP_IDENTIFIER_BIT_LENGTH 1
+#define ASLA_APP_IDENTIFIER_BIT_MAX_LENGTH 8
 #define ASLA_LEGACY_FLAG 0x80
 #define ASLA_APPS_LENGTH_MASK 0x7f