dropbear: fix CVE-2023-36328

Integer Overflow vulnerability in mp_grow in libtom libtommath before
commit beba892bc0d4e4ded4d667ab1d2a94f4d75109a9, allows attackers to
execute arbitrary code and cause a denial of service (DoS).

References:
https://nvd.nist.gov/vuln/detail/CVE-2023-36328
https://github.com/libtom/libtommath/pull/546

Signed-off-by: Yogita Urade <yogita.urade@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 145 insertions, 0 deletions

diff --git a/meta/recipes-core/dropbear/dropbear/CVE-2023-36328.patch b/meta/recipes-core/dropbear/dropbear/CVE-2023-36328.patch
new file mode 100644
index 0000000000..ec50d69816
--- /dev/null
+++ b/meta/recipes-core/dropbear/dropbear/CVE-2023-36328.patch
@@ -0,0 +1,144 @@
+From beba892bc0d4e4ded4d667ab1d2a94f4d75109a9 Mon Sep 17 00:00:00 2001
+From: czurnieden <czurnieden@gmx.de>
+Date: Fri, 8 Sep 2023 10:07:32 +0000
+Subject: [PATCH] Fix possible integer overflow
+
+CVE: CVE-2023-36328
+
+Upstream-Status: Backport [https://github.com/libtom/libtommath/commit/beba892bc0d4e4ded4d667ab1d2a94f4d75109a9]
+
+Signed-off-by: Yogita Urade <yogita.urade@windriver.com>
+---
+ libtommath/bn_mp_2expt.c                | 4 ++++
+ libtommath/bn_mp_grow.c                 | 4 ++++
+ libtommath/bn_mp_init_size.c            | 5 +++++
+ libtommath/bn_mp_mul_2d.c               | 4 ++++
+ libtommath/bn_s_mp_mul_digs.c           | 4 ++++
+ libtommath/bn_s_mp_mul_digs_fast.c      | 4 ++++
+ libtommath/bn_s_mp_mul_high_digs.c      | 4 ++++
+ libtommath/bn_s_mp_mul_high_digs_fast.c | 4 ++++
+ 8 files changed, 33 insertions(+)
+
+diff --git a/libtommath/bn_mp_2expt.c b/libtommath/bn_mp_2expt.c
+index 0ae3df1..ca6fbc3 100644
+--- a/libtommath/bn_mp_2expt.c
++++ b/libtommath/bn_mp_2expt.c
+@@ -12,6 +12,10 @@ mp_err mp_2expt(mp_int *a, int b)
+ {
+    mp_err    err;
+
++   if (b < 0) {
++      return MP_VAL;
++   }
++
+    /* zero a as per default */
+    mp_zero(a);
+
+diff --git a/libtommath/bn_mp_grow.c b/libtommath/bn_mp_grow.c
+index 9e904c5..2b16826 100644
+--- a/libtommath/bn_mp_grow.c
++++ b/libtommath/bn_mp_grow.c
+@@ -9,6 +9,10 @@ mp_err mp_grow(mp_int *a, int size)
+    int     i;
+    mp_digit *tmp;
+
++   if (size < 0) {
++      return MP_VAL;
++   }
++
+    /* if the alloc size is smaller alloc more ram */
+    if (a->alloc < size) {
+       /* reallocate the array a->dp
+diff --git a/libtommath/bn_mp_init_size.c b/libtommath/bn_mp_init_size.c
+index d622687..5fefa96 100644
+--- a/libtommath/bn_mp_init_size.c
++++ b/libtommath/bn_mp_init_size.c
+@@ -6,6 +6,11 @@
+ /* init an mp_init for a given size */
+ mp_err mp_init_size(mp_int *a, int size)
+ {
++
++   if (size < 0) {
++      return MP_VAL;
++   }
++
+    size = MP_MAX(MP_MIN_PREC, size);
+
+    /* alloc mem */
+diff --git a/libtommath/bn_mp_mul_2d.c b/libtommath/bn_mp_mul_2d.c
+index 87354de..2744163 100644
+--- a/libtommath/bn_mp_mul_2d.c
++++ b/libtommath/bn_mp_mul_2d.c
+@@ -9,6 +9,10 @@ mp_err mp_mul_2d(const mp_int *a, int b, mp_int *c)
+    mp_digit d;
+    mp_err   err;
+
++   if (b < 0) {
++      return MP_VAL;
++   }
++
+    /* copy */
+    if (a != c) {
+       if ((err = mp_copy(a, c)) != MP_OKAY) {
+diff --git a/libtommath/bn_s_mp_mul_digs.c b/libtommath/bn_s_mp_mul_digs.c
+index 64509d4..2d2f5b0 100644
+--- a/libtommath/bn_s_mp_mul_digs.c
++++ b/libtommath/bn_s_mp_mul_digs.c
+@@ -16,6 +16,10 @@ mp_err s_mp_mul_digs(const mp_int *a, const mp_int *b, mp_int *c, int digs)
+    mp_word r;
+    mp_digit tmpx, *tmpt, *tmpy;
+
++   if (digs < 0) {
++      return MP_VAL;
++   }
++
+    /* can we use the fast multiplier? */
+    if ((digs < MP_WARRAY) &&
+        (MP_MIN(a->used, b->used) < MP_MAXFAST)) {
+diff --git a/libtommath/bn_s_mp_mul_digs_fast.c b/libtommath/bn_s_mp_mul_digs_fast.c
+index b2a287b..d6dd3cc 100644
+--- a/libtommath/bn_s_mp_mul_digs_fast.c
++++ b/libtommath/bn_s_mp_mul_digs_fast.c
+@@ -26,6 +26,10 @@ mp_err s_mp_mul_digs_fast(const mp_int *a, const mp_int *b, mp_int *c, int digs)
+    mp_digit W[MP_WARRAY];
+    mp_word  _W;
+
++   if (digs < 0) {
++      return MP_VAL;
++   }
++
+    /* grow the destination as required */
+    if (c->alloc < digs) {
+       if ((err = mp_grow(c, digs)) != MP_OKAY) {
+diff --git a/libtommath/bn_s_mp_mul_high_digs.c b/libtommath/bn_s_mp_mul_high_digs.c
+index 2bb2a50..c9dd355 100644
+--- a/libtommath/bn_s_mp_mul_high_digs.c
++++ b/libtommath/bn_s_mp_mul_high_digs.c
+@@ -15,6 +15,10 @@ mp_err s_mp_mul_high_digs(const mp_int *a, const mp_int *b, mp_int *c, int digs)
+    mp_word  r;
+    mp_digit tmpx, *tmpt, *tmpy;
+
++   if (digs < 0) {
++      return MP_VAL;
++   }
++
+    /* can we use the fast multiplier? */
+    if (MP_HAS(S_MP_MUL_HIGH_DIGS_FAST)
+        && ((a->used + b->used + 1) < MP_WARRAY)
+diff --git a/libtommath/bn_s_mp_mul_high_digs_fast.c b/libtommath/bn_s_mp_mul_high_digs_fast.c
+index a2c4fb6..afe3e4b 100644
+--- a/libtommath/bn_s_mp_mul_high_digs_fast.c
++++ b/libtommath/bn_s_mp_mul_high_digs_fast.c
+@@ -19,6 +19,10 @@ mp_err s_mp_mul_high_digs_fast(const mp_int *a, const mp_int *b, mp_int *c, int
+    mp_digit W[MP_WARRAY];
+    mp_word  _W;
+
++   if (digs < 0) {
++      return MP_VAL;
++   }
++
+    /* grow the destination as required */
+    pa = a->used + b->used;
+    if (c->alloc < pa) {
+--
+2.35.5
diff --git a/meta/recipes-core/dropbear/dropbear_2022.83.bb b/meta/recipes-core/dropbear/dropbear_2022.83.bb
index 0c7a8f4caa..12ac732f58 100644
--- a/meta/recipes-core/dropbear/dropbear_2022.83.bb
+++ b/meta/recipes-core/dropbear/dropbear_2022.83.bb
@@ -21,6 +21,7 @@ SRC_URI = "http://matt.ucc.asn.au/dropbear/releases/dropbear-${PV}.tar.bz2 \
            file://dropbear.default \
            ${@bb.utils.contains('DISTRO_FEATURES', 'pam', '${PAM_SRC_URI}', '', d)} \
            ${@bb.utils.contains('PACKAGECONFIG', 'disable-weak-ciphers', 'file://dropbear-disable-weak-ciphers.patch', '', d)} \
+           file://CVE-2023-36328.patch \
            "
 
 SRC_URI[sha256sum] = "bc5a121ffbc94b5171ad5ebe01be42746d50aa797c9549a4639894a16749443b"