net-snmp: add two new fuzzers and simplify build script. (#6091)

Signed-off-by: David Korczynski <david@adalogics.com>

3 files changed, 144 insertions, 4 deletions

diff --git a/projects/net-snmp/build.sh b/projects/net-snmp/build.sh
index 3c0265d5d..abc799a0c 100755
--- a/projects/net-snmp/build.sh
+++ b/projects/net-snmp/build.sh
@@ -21,11 +21,11 @@
 make
 
 # build fuzzers (remember to link statically)
-for fuzzname in snmp_pdu_parse_fuzzer snmp_parse_fuzzer snmp_scoped_pdu_parse_fuzzer agentx_parse_fuzzer; do
-  $CC $CFLAGS -c -Iinclude -Iagent/mibgroup/agentx $SRC/${fuzzname}.c -o $WORK/${fuzzname}.o
-  $CXX $CXXFLAGS $WORK/${fuzzname}.o \
+for fuzzname in snmp_pdu_parse snmp_parse snmp_scoped_pdu_parse agentx_parse snmp_octet snmp_mib; do
+  $CC $CFLAGS -c -Iinclude -Iagent/mibgroup/agentx $SRC/${fuzzname}_fuzzer.c -o $WORK/${fuzzname}_fuzzer.o
+  $CXX $CXXFLAGS $WORK/${fuzzname}_fuzzer.o \
         $LIB_FUZZING_ENGINE snmplib/.libs/libnetsnmp.a \
         agent/.libs/libnetsnmpagent.a \
         -Wl,-Bstatic -lcrypto -Wl,-Bdynamic -lm \
-        -o $OUT/${fuzzname}
+        -o $OUT/${fuzzname}_fuzzer
 done
diff --git a/projects/net-snmp/snmp_mib_fuzzer.c b/projects/net-snmp/snmp_mib_fuzzer.c
new file mode 100644
index 000000000..5d9dd9234
--- /dev/null
+++ b/projects/net-snmp/snmp_mib_fuzzer.c
@@ -0,0 +1,58 @@
+/*
+ * Copyright 2021 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <net-snmp/net-snmp-config.h>
+#include <net-snmp/net-snmp-includes.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+int LLVMFuzzerInitialize(int *argc, char ***argv) {
+    if (getenv("NETSNMP_DEBUGGING") != NULL) {
+        /*
+         * Turn on all debugging, to help understand what
+         * bits of the parser are running.
+         */
+        snmp_enable_stderrlog();
+        snmp_set_do_debugging(1);
+        debug_register_tokens("");
+    }
+    return 0;
+}
+
+int SecmodInMsg_CB(struct snmp_secmod_incoming_params *sp1) {
+    return SNMPERR_SUCCESS;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+    char *filename;
+    if (asprintf(&filename, "/tmp/fuzzed-mib.%d", getpid()) == -1) {
+        return 0;
+    }
+
+    FILE *fp = fopen(filename, "wb");
+    if (!fp) {
+        return 0;
+    }
+    fwrite(data, size, 1, fp);
+    fclose(fp);
+
+    // Read the file
+    read_mib(filename);
+
+    unlink(filename);
+    free(filename);
+    return 0;
+}
diff --git a/projects/net-snmp/snmp_octet_fuzzer.c b/projects/net-snmp/snmp_octet_fuzzer.c
new file mode 100644
index 000000000..ba15218ff
--- /dev/null
+++ b/projects/net-snmp/snmp_octet_fuzzer.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright 2021 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <net-snmp/net-snmp-config.h>
+#include <net-snmp/net-snmp-includes.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+int LLVMFuzzerInitialize(int *argc, char ***argv) {
+    if (getenv("NETSNMP_DEBUGGING") != NULL) {
+        /*
+         * Turn on all debugging, to help understand what
+         * bits of the parser are running.
+         */
+        snmp_enable_stderrlog();
+        snmp_set_do_debugging(1);
+        debug_register_tokens("");
+    }
+    return 0;
+}
+
+int SecmodInMsg_CB(struct snmp_secmod_incoming_params *sp1) {
+    return SNMPERR_SUCCESS;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+    // We need to have at least oen byte for our decider var.
+    if (size == 0) {
+        return 0;
+    }
+    const uint8_t decider = *data;
+    data += 1;
+    size -= 1;
+
+    char *new_str = malloc(size+1);
+    if (new_str == NULL){
+        return 0;
+    }
+    memcpy(new_str, data, size);
+    new_str[size] = '\0';
+
+    // This fuzzer hits multiple entrypoints, use the first byte of the fuzz
+    // data to decide which entrypoint. 
+    switch (decider % 3) {
+        case 0:  {
+            oid *root = malloc(MAX_OID_LEN * sizeof(oid));
+            size_t rootlen;
+            snmp_parse_oid(new_str, root, &rootlen);
+            free(root);
+            break;
+        }
+        case 1: {
+            oid *objid = malloc(MAX_OID_LEN * sizeof(oid));
+            size_t objidlen = MAX_OID_LEN;
+            read_objid(new_str, objid, &objidlen);
+            free(objid);
+            break;
+        }
+        case 2: {
+            unsigned char *new_val;
+            size_t new_val_len;
+            parse_octet_hint(new_str, new_str, &new_val, &new_val_len);
+            break;
+        }
+    }
+
+    free(new_str);
+    return 0; 
+}