rlog: Handle unexpected byte in edit script

Reported by Ray Bellis:
https://mail.gnu.org/r/bug-rcs/2022-01/msg00000.html

* src/rlog.c (count_a_d): If the edit script stanza
does not start w/ the expected 'a' or 'd' dispatch,
display error message with diagnostic and abort.

2 files changed, 32 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index b6c904e..3d649a9 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,16 @@
 2022-01-27  Thien-Thi Nguyen  <ttn@gnu.org>
 
+	rlog: Handle unexpected byte in edit script
+
+	Reported by Ray Bellis:
+	https://mail.gnu.org/r/bug-rcs/2022-01/msg00000.html
+
+	* rlog.c (count_a_d): If the edit script stanza
+	does not start w/ the expected 'a' or 'd' dispatch,
+	display error message with diagnostic and abort.
+
+2022-01-27  Thien-Thi Nguyen  <ttn@gnu.org>
+
 	[int] Move USED_IF_HAVE_MADVISE to beginning of param decl
 
 	* b-fro.c (fro_trundling): ...here, for arg ‘sequential’.
diff --git a/src/rlog.c b/src/rlog.c
index 404ec86..2b4de4b 100644
--- a/src/rlog.c
+++ b/src/rlog.c
@@ -127,9 +127,29 @@ count_a_d (long *a, long *d, struct atat *edits)
 
   for (char const *p = s.string; p < end; p++)
     {
-      bool add = ('a' == *p++);
+      bool add = ('a' == *p);
       long count;
 
+      /* Sanity check.  */
+      if (! add && 'd' != *p)
+        {
+          long adjust = 0;
+          char const *before = s.string;
+          size_t remaining = p - before;
+
+          while (remaining && (before = memchr (before, '\n', remaining)))
+            {
+              before++;
+              adjust++;
+              remaining = p - before;
+            }
+          complain ("\n");
+          fatal_syntax (adjust + edits->lno,
+                        "unexpected byte in edit script: 0x%02x",
+                        *p);
+        }
+      p++;
+
       /* Skip the line number.  */
       p = strchr (p, ' ');
       count = read_positive_integer (&p);