unalf: Abort on ludicrously large sizes in the header. Add -F to bypass, warn the user this may cause an infinite loop.

1 files changed, 24 insertions, 5 deletions

diff --git a/src/unalf.rst b/src/unalf.rst
index 146e056..069fad1 100644
--- a/src/unalf.rst
+++ b/src/unalf.rst
@@ -89,6 +89,13 @@ OPTIONS
 
 .. fix (remove) junk at EOF.
 
+-F
+  Force **unalf** to continue after detecting an invalid compressed file
+  size in an *ALF* header. This isn't the default because it can cause
+  **unalf** to get stuck in an infinite loop.
+
+.. force uncompressing in case of invalid compressed size.
+
 -h, --help
    Show built-in help message.
 
@@ -242,6 +249,20 @@ Fatal errors
 **fatal: compressed data is truncated, EOF before end marker**
   Self-explanatory. The ALF file ends before the compressed data does.
 
+**header #<n> (compressed|original) size is impossibly large (>16MB)**
+  **unalf** can't handle files of more than 16MB in size. This isn't a
+  bug, it's just the way it was designed (in 1988, remember). Neither
+  **LZ.COM** nor **alf** will create files like this, so you *probably*
+  have a corrupt ALF archive.
+
+**compressed size for header #<n> is bigger than the rest of the file (truncated?)**
+  Normally this means a truncated *ALF* file, or one with a corrupted header.
+  You can use the **-F** option to turn this error into a non-fatal warning.
+
+**compressed size for header #<n> is over twice the uncompressed size (corrupt?)**
+  This generally means you have a corrupted *ALF* file.
+  You can use the **-F** option to turn this error into a non-fatal warning.
+
 Warnings
 --------
 
@@ -287,11 +308,9 @@ Warnings
   any unprintable characters as hex values (e.g. **$01**).
 
 **header #<n> (compressed|original) size is...**
-  Followed by "impossibly large", "suspiciously large", or "too large
-  to fit on a floppy disk". May indicate a corrupt archive, or someone
-  really might have created an ALF file with files this big... though
-  "impossibly large" means >=16MB. **unalf** can't extract a file
-  that big.
+  Followed by "suspiciously large" or "too large to fit on a floppy
+  disk". May indicate a corrupt archive, or someone really might have
+  created an ALF file with files this big.
 
 **ALF files don't normally contain other ALF files, are you trying to extract/list multiple ALF files at once?**
   You gave a *wildcard* argument that ends with *.alf*. This is OK if