[PATCH 1/3] Improve mbox parsing to address ticket 415.

[Kevin J. McCarthy]

Check for newline separators between messages.  To allow parsing of
old mbox files, merely warn in the debug log, but continue allowing
parsing.

Track when a content-length delimited message is not follow by a From_
line.  In that case, abort since it means there is some kind of
corruption and a message will otherwise likely be silently ignored.
---
 mbox.c | 33 ++++++++++++++++++++++++++++++---
 mx.h   |  1 +
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/mbox.c b/mbox.c
index fc36ca22..a2a32d13 100644
--- a/mbox.c
+++ b/mbox.c
@@ -247,7 +247,8 @@ int mbox_parse_mailbox (CONTEXT *ctx)
   char buf[HUGE_STRING], return_path[STRING];
   HEADER *curhdr;
   time_t t;
-  int count = 0, lines = 0;
+  int count = 0, lines = 0, has_mbox_sep = 0;
+  int expect_from_line = 1;
   LOFF_T loc;
 #ifdef NFS_ATTRIBUTE_HACK
 #ifdef HAVE_UTIMENSAT
@@ -305,6 +306,12 @@ int mbox_parse_mailbox (CONTEXT *ctx)
       {
 #define PREV ctx->hdrs[ctx->msgcount-1]
 
+        if (!has_mbox_sep)
+        {
+          dprint (1, (debugfile, "mbox_parse_mailbox: missing separator at 
location: "
+                      OFF_T_FMT "\n", loc));
+        }
+
        if (PREV->content->length < 0)
        {
          PREV->content->length = loc - PREV->content->offset - 1;
@@ -316,6 +323,7 @@ int mbox_parse_mailbox (CONTEXT *ctx)
       }
 
       count++;
+      expect_from_line = 0;
 
       if (!ctx->quiet)
        mutt_progress_update (&progress, count,
@@ -392,9 +400,11 @@ int mbox_parse_mailbox (CONTEXT *ctx)
            }
          }
 
-         /* return to the offset of the next message separator */
-         if (fseeko (ctx->fp, tmploc, SEEK_SET) != 0)
+         /* return to the offset of the next *mbox* separator */
+         if (fseeko (ctx->fp, tmploc - 1, SEEK_SET) != 0)
            dprint (1, (debugfile, "mbox_parse_mailbox: fseek() failed\n"));
+
+          expect_from_line = 1;
        }
       }
 
@@ -407,9 +417,20 @@ int mbox_parse_mailbox (CONTEXT *ctx)
        curhdr->env->from = rfc822_cpy_adr (curhdr->env->return_path, 0);
 
       lines = 0;
+      has_mbox_sep = 0;
     }
     else
+    {
       lines++;
+      has_mbox_sep = !mutt_strcmp (MBOX_SEP, buf);
+      if (expect_from_line && !has_mbox_sep)
+      {
+        dprint (1, (debugfile, "mbox_parse_mailbox: missing From_ line at 
location: "
+                    OFF_T_FMT "\n", loc));
+        mutt_error _("Mailbox is corrupt!");
+        return (-1);
+      }
+    }
 
     loc = ftello (ctx->fp);
   }
@@ -422,6 +443,12 @@ int mbox_parse_mailbox (CONTEXT *ctx)
    */
   if (count > 0)
   {
+    if (!has_mbox_sep)
+    {
+      dprint (1, (debugfile, "mbox_parse_mailbox: missing separator at 
location: "
+                      OFF_T_FMT "\n", loc));
+    }
+
     if (PREV->content->length < 0)
     {
       PREV->content->length = ftello (ctx->fp) - PREV->content->offset - 1;
diff --git a/mx.h b/mx.h
index d9dc4da7..542d9dd8 100644
--- a/mx.h
+++ b/mx.h
@@ -45,6 +45,7 @@ enum
 WHERE short DefaultMagic INITVAL (MUTT_MBOX);
 
 #define MMDF_SEP "\001\001\001\001\n"
+#define MBOX_SEP "\n"
 #define MAXLOCKATTEMPT 5
 
 int mbox_lock_mailbox (CONTEXT *, int, int);
-- 
2.52.0