From 04bada65513234d491d599bb58b1a27d7254d4fd Mon Sep 17 00:00:00 2001
From: Mikhail Novosyolov <m.novosyolov@rosalinux.ru>
Date: Wed, 10 Jul 2019 20:35:50 +0300
Subject: [PATCH] Fix regression introduced by CVE-2019-12900.patch (LP:
 #1834494)

---
 ...-selectors-as-the-file-format-allows.patch | 73 +++++++++++++++++++
 bzip2.spec                                    |  4 +-
 2 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 Accept-as-many-selectors-as-the-file-format-allows.patch

diff --git a/Accept-as-many-selectors-as-the-file-format-allows.patch b/Accept-as-many-selectors-as-the-file-format-allows.patch
new file mode 100644
index 0000000..e675ce7
--- /dev/null
+++ b/Accept-as-many-selectors-as-the-file-format-allows.patch
@@ -0,0 +1,73 @@
+From b357f4ec14a8b5b11b37621ee9f2a10f518b6c65 Mon Sep 17 00:00:00 2001
+From: Mark Wielaard <mark@klomp.org>
+Date: Wed, 3 Jul 2019 01:28:11 +0200
+Subject: [PATCH] Accept as many selectors as the file format allows.
+
+But ignore any larger than the theoretical maximum, BZ_MAX_SELECTORS.
+
+The theoretical maximum number of selectors depends on the maximum
+blocksize (900000 bytes) and the number of symbols (50) that can be
+encoded with a different Huffman tree. BZ_MAX_SELECTORS is 18002.
+
+But the bzip2 file format allows the number of selectors to be encoded
+with 15 bits (because 18002 isn't a factor of 2 and doesn't fit in
+14 bits). So the file format maximum is 32767 selectors.
+
+Some bzip2 encoders might actually have written out more selectors
+than the theoretical maximum because they rounded up the number of
+selectors to some convenient factor of 8.
+
+The extra 14766 selectors can never be validly used by the decompression
+algorithm. So we can read them, but then discard them.
+
+This is effectively what was done (by accident) before we added a
+check for nSelectors to be at most BZ_MAX_SELECTORS to mitigate
+CVE-2019-12900.
+
+The extra selectors were written out after the array inside the
+EState struct. But the struct has extra space allocated after the
+selector arrays of 18060 bytes (which is larger than 14766).
+All of which will be initialized later (so the overwrite of that
+space with extra selector values would have been harmless).
+diff --git a/compress.c b/compress.c
+index caf7696..19b662b 100644
+--- a/compress.c
++++ b/compress.c
+@@ -454,7 +454,7 @@ void sendMTFValues ( EState* s )
+ 
+    AssertH( nGroups < 8, 3002 );
+    AssertH( nSelectors < 32768 &&
+-            nSelectors <= (2 + (900000 / BZ_G_SIZE)),
++            nSelectors <= BZ_MAX_SELECTORS,
+             3003 );
+ 
+ 
+diff --git a/decompress.c b/decompress.c
+index b6e0a29..78060c9 100644
+--- a/decompress.c
++++ b/decompress.c
+@@ -287,7 +287,7 @@ Int32 BZ2_decompress ( DState* s )
+       GET_BITS(BZ_X_SELECTOR_1, nGroups, 3);
+       if (nGroups < 2 || nGroups > 6) RETURN(BZ_DATA_ERROR);
+       GET_BITS(BZ_X_SELECTOR_2, nSelectors, 15);
+-      if (nSelectors < 1 || nSelectors > BZ_MAX_SELECTORS) RETURN(BZ_DATA_ERROR);
++      if (nSelectors < 1) RETURN(BZ_DATA_ERROR);
+       for (i = 0; i < nSelectors; i++) {
+          j = 0;
+          while (True) {
+@@ -296,8 +296,14 @@ Int32 BZ2_decompress ( DState* s )
+             j++;
+             if (j >= nGroups) RETURN(BZ_DATA_ERROR);
+          }
+-         s->selectorMtf[i] = j;
++         /* Having more than BZ_MAX_SELECTORS doesn't make much sense
++            since they will never be used, but some implementations might
++            "round up" the number of selectors, so just ignore those. */
++         if (i < BZ_MAX_SELECTORS)
++           s->selectorMtf[i] = j;
+       }
++      if (nSelectors > BZ_MAX_SELECTORS)
++        nSelectors = BZ_MAX_SELECTORS;
+ 
+       /*--- Undo the MTF values for the selectors. ---*/
+       {
diff --git a/bzip2.spec b/bzip2.spec
index cf2e7f9..5f3e032 100644
--- a/bzip2.spec
+++ b/bzip2.spec
@@ -7,7 +7,7 @@
 Summary:	Extremely powerful file compression utility
 Name:		bzip2
 Version:	1.0.6
-Release:	18
+Release:	19
 License:	BSD
 Group:		Archiving/Compression
 Url:		http://www.bzip.org/index.html
@@ -18,6 +18,8 @@ Source3:	bzme.1
 Patch0:		bzip2-1.0.6-makefile.diff
 Patch1:		bzip2-1.0.6-CVE-2016-3189.patch
 Patch2:		CVE-2019-12900.patch
+# Fixes regression introduced by CVE-2019-12900.patch (LP: #1834494)
+Patch3:		Accept-as-many-selectors-as-the-file-format-allows.patch
 BuildRequires:	libtool
 BuildRequires:	texinfo
 %if %{with pdf}