cms: don't assert if eContent fails to be dissected

If eContent is not an octet string, content_tvb will be null, and
attempting to use it will trigger an assertion. Besides ill-formed
files, this can also occur in old-style PKCS #7 files, since in PKCS #7
the corresponding field has the ANY type, rather than OCTET STRING.

Change-Id: I9a5bce983aa82107a9602317737c183461cac7f3
Reviewed-on: https://code.wireshark.org/review/19448
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>

2 files changed, 21 insertions, 15 deletions

diff --git a/epan/dissectors/asn1/cms/cms.cnf b/epan/dissectors/asn1/cms/cms.cnf
index 045dca9e9e..af60947754 100644
--- a/epan/dissectors/asn1/cms/cms.cnf
+++ b/epan/dissectors/asn1/cms/cms.cnf
@@ -102,9 +102,12 @@ RevocationInfoChoice/other		otherRIC
 #.FN_BODY EncapsulatedContentInfo/eContent
 
   offset = dissect_ber_octet_string(FALSE, actx, tree, tvb, offset, hf_index, &content_tvb);
-  proto_item_set_text(actx->created_item, "eContent (%%u bytes)", tvb_reported_length (content_tvb));
 
-  call_ber_oid_callback(object_identifier_id, content_tvb, 0, actx->pinfo, top_tree ? top_tree : tree, NULL);
+  if(content_tvb) {
+    proto_item_set_text(actx->created_item, "eContent (%%u bytes)", tvb_reported_length (content_tvb));
+
+    call_ber_oid_callback(object_identifier_id, content_tvb, 0, actx->pinfo, top_tree ? top_tree : tree, NULL);
+  }
 
 #.FN_PARS OtherRecipientInfo/oriType
   FN_VARIANT = _str  VAL_PTR = &object_identifier_id
diff --git a/epan/dissectors/packet-cms.c b/epan/dissectors/packet-cms.c
index 482434de03..aafa52e46c 100644
--- a/epan/dissectors/packet-cms.c
+++ b/epan/dissectors/packet-cms.c
@@ -431,9 +431,12 @@ dissect_cms_T_eContent(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset
 #line 103 "./asn1/cms/cms.cnf"
 
   offset = dissect_ber_octet_string(FALSE, actx, tree, tvb, offset, hf_index, &content_tvb);
-  proto_item_set_text(actx->created_item, "eContent (%u bytes)", tvb_reported_length (content_tvb));
 
-  call_ber_oid_callback(object_identifier_id, content_tvb, 0, actx->pinfo, top_tree ? top_tree : tree, NULL);
+  if(content_tvb) {
+    proto_item_set_text(actx->created_item, "eContent (%u bytes)", tvb_reported_length (content_tvb));
+
+    call_ber_oid_callback(object_identifier_id, content_tvb, 0, actx->pinfo, top_tree ? top_tree : tree, NULL);
+  }
 
 
 
@@ -459,7 +462,7 @@ dissect_cms_EncapsulatedContentInfo(gboolean implicit_tag _U_, tvbuff_t *tvb _U_
 
 static int
 dissect_cms_T_attrType(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _U_, asn1_ctx_t *actx _U_, proto_tree *tree _U_, int hf_index _U_) {
-#line 130 "./asn1/cms/cms.cnf"
+#line 133 "./asn1/cms/cms.cnf"
   const char *name = NULL;
 
     offset = dissect_ber_object_identifier_str(implicit_tag, actx, tree, tvb, offset, hf_cms_attrType, &object_identifier_id);
@@ -479,7 +482,7 @@ dissect_cms_T_attrType(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset
 
 static int
 dissect_cms_AttributeValue(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _U_, asn1_ctx_t *actx _U_, proto_tree *tree _U_, int hf_index _U_) {
-#line 140 "./asn1/cms/cms.cnf"
+#line 143 "./asn1/cms/cms.cnf"
 
   offset=call_ber_oid_callback(object_identifier_id, tvb, offset, actx->pinfo, tree, NULL);
 
@@ -741,7 +744,7 @@ dissect_cms_T_otherRevInfoFormat(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, i
 
 static int
 dissect_cms_T_otherRevInfo(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _U_, asn1_ctx_t *actx _U_, proto_tree *tree _U_, int hf_index _U_) {
-#line 124 "./asn1/cms/cms.cnf"
+#line 127 "./asn1/cms/cms.cnf"
   offset=call_ber_oid_callback(object_identifier_id, tvb, offset, actx->pinfo, tree, NULL);
 
 
@@ -1078,7 +1081,7 @@ dissect_cms_T_keyAttrId(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset
 
 static int
 dissect_cms_T_keyAttr(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _U_, asn1_ctx_t *actx _U_, proto_tree *tree _U_, int hf_index _U_) {
-#line 119 "./asn1/cms/cms.cnf"
+#line 122 "./asn1/cms/cms.cnf"
   offset=call_ber_oid_callback(object_identifier_id, tvb, offset, actx->pinfo, tree, NULL);
 
 
@@ -1266,7 +1269,7 @@ dissect_cms_T_oriType(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _
 
 static int
 dissect_cms_T_oriValue(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _U_, asn1_ctx_t *actx _U_, proto_tree *tree _U_, int hf_index _U_) {
-#line 113 "./asn1/cms/cms.cnf"
+#line 116 "./asn1/cms/cms.cnf"
   offset=call_ber_oid_callback(object_identifier_id, tvb, offset, actx->pinfo, tree, NULL);
 
 
@@ -1343,14 +1346,14 @@ dissect_cms_ContentEncryptionAlgorithmIdentifier(gboolean implicit_tag _U_, tvbu
 
 static int
 dissect_cms_EncryptedContent(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _U_, asn1_ctx_t *actx _U_, proto_tree *tree _U_, int hf_index _U_) {
-#line 190 "./asn1/cms/cms.cnf"
+#line 193 "./asn1/cms/cms.cnf"
 	tvbuff_t *encrypted_tvb;
 	proto_item *item;
 
   offset = dissect_ber_octet_string(implicit_tag, actx, tree, tvb, offset, hf_index,
                                        &encrypted_tvb);
 
-#line 195 "./asn1/cms/cms.cnf"
+#line 198 "./asn1/cms/cms.cnf"
 
 	item = actx->created_item;
 
@@ -1508,7 +1511,7 @@ dissect_cms_AuthenticatedData(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int
 
 static int
 dissect_cms_MessageDigest(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _U_, asn1_ctx_t *actx _U_, proto_tree *tree _U_, int hf_index _U_) {
-#line 144 "./asn1/cms/cms.cnf"
+#line 147 "./asn1/cms/cms.cnf"
   proto_item *pi;
   int old_offset = offset;
 
@@ -1583,7 +1586,7 @@ dissect_cms_Countersignature(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int o
 
 static int
 dissect_cms_RC2ParameterVersion(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _U_, asn1_ctx_t *actx _U_, proto_tree *tree _U_, int hf_index _U_) {
-#line 180 "./asn1/cms/cms.cnf"
+#line 183 "./asn1/cms/cms.cnf"
   guint32 length = 0;
 
     offset = dissect_ber_integer(implicit_tag, actx, tree, tvb, offset, hf_index,
@@ -1651,7 +1654,7 @@ dissect_cms_DigestInfo(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset
 
 static int
 dissect_cms_T_capability(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _U_, asn1_ctx_t *actx _U_, proto_tree *tree _U_, int hf_index _U_) {
-#line 162 "./asn1/cms/cms.cnf"
+#line 165 "./asn1/cms/cms.cnf"
   const char *name = NULL;
 
     offset = dissect_ber_object_identifier_str(implicit_tag, actx, tree, tvb, offset, hf_cms_attrType, &object_identifier_id);
@@ -1672,7 +1675,7 @@ dissect_cms_T_capability(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offse
 
 static int
 dissect_cms_T_parameters(gboolean implicit_tag _U_, tvbuff_t *tvb _U_, int offset _U_, asn1_ctx_t *actx _U_, proto_tree *tree _U_, int hf_index _U_) {
-#line 173 "./asn1/cms/cms.cnf"
+#line 176 "./asn1/cms/cms.cnf"
 
   offset=call_ber_oid_callback(object_identifier_id, tvb, offset, actx->pinfo, tree, NULL);