profinet: Skip comments in GSD file

Bug: 13303
Change-Id: I9ab17ec25917723be06b36ab4c11fe67e6792715
Reviewed-on: https://code.wireshark.org/review/19593
Reviewed-by: Graham Bloice <graham.bloice@trihedral.com>
Petri-Dish: Graham Bloice <graham.bloice@trihedral.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>

4 files changed, 75 insertions, 8 deletions

diff --git a/plugins/profinet/packet-dcerpc-pn-io.c b/plugins/profinet/packet-dcerpc-pn-io.c
index f94c651865..5af67f3ce3 100644
--- a/plugins/profinet/packet-dcerpc-pn-io.c
+++ b/plugins/profinet/packet-dcerpc-pn-io.c
@@ -90,7 +90,6 @@ void proto_reg_handoff_pn_io(void);
 
 
 #define MAX_NAMELENGTH           200    /* max. length of the given paths */
-#define MAX_LINE_LENGTH          1024   /* used for fgets() */
 #define F_MESSAGE_TRAILER_4BYTE  4      /* PROFIsafe: Defines the Amount of Bytes for CRC and Status-/Controlbyte */
 #define PN_INPUT_CR              1      /* PROFINET Input Connect Request value */
 #define PN_INPUT_DATADESCRITPION 1      /* PROFINET Input Data Description value */
@@ -9313,7 +9312,7 @@ dissect_ExpectedSubmoduleBlockReq_block(tvbuff_t *tvb, int offset,
 
                     if(fp != NULL) {
                         /* ---- Get VendorID & DeviceID ---- */
-                        while(fgets(puffer, MAX_LINE_LENGTH, fp) != NULL) {
+                        while(pn_fgets(puffer, MAX_LINE_LENGTH, fp) != NULL) {
                             /* ----- VendorID ------ */
                             if((strstr(puffer, vendorIdStr)) != NULL) {
                                 memset (convertStr, 0, sizeof(*convertStr));
@@ -9460,7 +9459,7 @@ dissect_ExpectedSubmoduleBlockReq_block(tvbuff_t *tvb, int offset,
                 fseek(fp, 0, SEEK_SET);
 
                 /* Find Indexnumber for fParameter */
-                while(fgets(temp, MAX_LINE_LENGTH, fp) != NULL) {
+                while(pn_fgets(temp, MAX_LINE_LENGTH, fp) != NULL) {
                     if((strstr(temp, fParameterStr)) != NULL) {
                         memset (convertStr, 0, sizeof(*convertStr));
 
@@ -9475,7 +9474,7 @@ dissect_ExpectedSubmoduleBlockReq_block(tvbuff_t *tvb, int offset,
                 memset (temp, 0, sizeof(*temp));
                 fseek(fp, 0, SEEK_SET);                /* Set filepointer to the beginning */
 
-                while(fgets(temp, MAX_LINE_LENGTH, fp) != NULL) {
+                while(pn_fgets(temp, MAX_LINE_LENGTH, fp) != NULL) {
                     if((strstr(temp, moduleStr)) != NULL) {                         /* find the String "ModuleIdentNumber=" */
                         memset (convertStr, 0, sizeof(*convertStr));
                         pch = strstr(temp, moduleStr);                              /* search for "ModuleIdentNumber=\"" within GSD-file */
@@ -9486,7 +9485,7 @@ dissect_ExpectedSubmoduleBlockReq_block(tvbuff_t *tvb, int offset,
                             if (read_module_id == io_data_object->moduleIdentNr) {
                                 ++io_data_object->amountInGSDML;    /* Save the amount of same (!) Module- & SubmoduleIdentNr in one GSD-file */
 
-                                while(fgets(temp, MAX_LINE_LENGTH, fp) != NULL) {
+                                while(pn_fgets(temp, MAX_LINE_LENGTH, fp) != NULL) {
                                     if((strstr(temp, moduleNameInfo)) != NULL) {                    /* find the String "<Name" for the TextID */
                                         long filePosRecord;
 
@@ -9496,7 +9495,7 @@ dissect_ExpectedSubmoduleBlockReq_block(tvbuff_t *tvb, int offset,
                                         filePosRecord = ftell(fp);            /* save the current position of the filepointer (Offset) */
                                         /* ftell() may return -1 for error, don't move fp in this case */
                                         if (filePosRecord >= 0) {
-                                            while (fgets(temp, MAX_LINE_LENGTH, fp) != NULL && io_data_object->amountInGSDML == 1) {
+                                            while (pn_fgets(temp, MAX_LINE_LENGTH, fp) != NULL && io_data_object->amountInGSDML == 1) {
                                                 /* Find a String with the saved TextID and with a fitting value for it in the same line. This value is the name of the Module! */
                                                 if(((strstr(temp, tmp_moduletext)) != NULL) && ((strstr(temp, moduleValueInfo)) != NULL)) {
                                                     pch = strstr(temp, moduleValueInfo);
@@ -9523,7 +9522,7 @@ dissect_ExpectedSubmoduleBlockReq_block(tvbuff_t *tvb, int offset,
                                                     break;
                                                 }
                                                 else {    /* flag is not in the same line as Submoduleidentnumber -> search for it */
-                                                    while(fgets(temp, MAX_LINE_LENGTH, fp) != NULL) {
+                                                    while(pn_fgets(temp, MAX_LINE_LENGTH, fp) != NULL) {
                                                         if((strstr(temp, profisafeStr)) != NULL) {
                                                             io_data_object->profisafeSupported = TRUE;
                                                             break;    /* Found the PROFIsafeSupported flag of the module */
diff --git a/plugins/profinet/packet-pn-rtc-one.c b/plugins/profinet/packet-pn-rtc-one.c
index b89a73d092..0d52002beb 100644
--- a/plugins/profinet/packet-pn-rtc-one.c
+++ b/plugins/profinet/packet-pn-rtc-one.c
@@ -76,7 +76,6 @@
 #include "packet-pn.h"
 
 
-#define MAX_LINE_LENGTH          1024   /* used for fgets() */
 #define F_MESSAGE_TRAILER_4BYTE  4      /* PROFIsafe: Defines the Amount of Bytes for CRC and Status-/Controlbyte */
 #define PN_INPUT_CR              1      /* PROFINET Input Connect Request value */
 #define PN_INPUT_DATADESCRITPION 1      /* PROFINET Input Data Description value */
diff --git a/plugins/profinet/packet-pn.c b/plugins/profinet/packet-pn.c
index 5d6c38ad5c..7c2e013625 100644
--- a/plugins/profinet/packet-pn.c
+++ b/plugins/profinet/packet-pn.c
@@ -365,6 +365,69 @@ init_pn (int proto)
     expert_register_field_array(expert_pn, ei, array_length(ei));
 }
 
+/* Read a string from an "xml" file, dropping xml comment blocks */
+char *pn_fgets(char *str, int n, FILE *stream)
+{
+    const char XML_COMMENT_START[] = "<!--";
+    const char XML_COMMENT_END[] = "-->";
+
+    char *retVal = fgets(str, n, stream);
+    if (retVal == NULL) {
+        /* No input, we're done */
+        return retVal;
+    }
+
+    /* Search for the XML begin comment marker */
+    char *comment_start = strstr(str, XML_COMMENT_START);
+    char *common_start_end = comment_start + sizeof(XML_COMMENT_START) - 1;
+    if(comment_start == NULL) {
+        /* No comment start, we're done */
+        return retVal;
+    }
+
+    /* Terminate the input buffer at the comment start */
+    *comment_start = '\0';
+    size_t used_space = comment_start - str;
+    size_t remaining_space = n - used_space;
+
+    /* Read more data looking for the comment end */
+    char *comment_end = strstr(common_start_end, XML_COMMENT_END);
+    if (comment_end == NULL) {
+      // Not found in this line, read more lines until we do find it */
+      char *temp = (char*)wmem_alloc(wmem_packet_scope(), MAX_LINE_LENGTH);
+      char *next_line = temp;
+      while((comment_end == NULL) && (next_line != NULL)) {
+          next_line = fgets(temp, MAX_LINE_LENGTH, stream);
+          if (next_line == NULL) {
+              /* No more data, exit now */
+              break;
+          }
+          comment_start = next_line;
+          comment_end = strstr(next_line, XML_COMMENT_END);
+      }
+    }
+
+    if (comment_end == NULL) {
+        /* We didn't find the comment end, return what we have */
+        return retVal;
+    }
+
+    /* We did find a comment end, skip past the comment */
+    char *comment_end_end = comment_end + sizeof(XML_COMMENT_END) - 1;
+
+    /* Check we have space left in the buffer to move the trailing bytes after the comment end */
+    size_t remaining_bytes = strlen(comment_end_end) + 1;
+    if (remaining_bytes < remaining_space) {
+        g_strlcat(str, comment_end_end, n);
+    }
+    else {
+      /* Seek the file back to the comment end so the next read picks it up */
+      fseek(stream, -(long)(remaining_bytes), SEEK_CUR);
+    }
+
+    return retVal;
+}
+
 /*
  * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
  *
diff --git a/plugins/profinet/packet-pn.h b/plugins/profinet/packet-pn.h
index 9ac7c9eb6d..688c71bee6 100644
--- a/plugins/profinet/packet-pn.h
+++ b/plugins/profinet/packet-pn.h
@@ -164,3 +164,9 @@ extern int dissect_PNIO_C_SDU_RTC1(tvbuff_t *tvb, int offset, packet_info *pinfo
 extern void pn_append_info(packet_info *pinfo, proto_item *dcp_item, const char *text);
 
 extern gboolean dissect_CSF_SDU_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data);
+
+#define MAX_LINE_LENGTH          1024   /* used for fgets() */
+
+/* Read a string from an "xml" file, dropping xml comment blocks */
+#include <stdio.h>
+extern char *pn_fgets(char *str, int n, FILE *stream);