Fix multiplication producing a negative zero
Fix mbedtls_mpi_mul_mpi() when one of the operands is zero and the
other is negative. The sign of the result must be 1, since some
library functions do not treat {-1, 0, NULL} or {-1, n, {0}} as
representing the value 0.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog b/ChangeLog
index 565ce1c..fcd8427 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -81,8 +81,12 @@
in line with version 1.0.0 of the specification. Fix #4162.
* Fix a bug in ECDSA that would cause it to fail when the hash is all-bits
zero. Fixes #1792
- * mbedtls_mpi_read_string on "-0" produced an MPI object that was not treated
- as equal to 0 in all cases. Fix it to produce the same object as "0".
+ * Fix some cases in the bignum module where the library constructed an
+ unintended representation of the value 0 which was not processed
+ correctly by some bignum operations. This could happen when
+ mbedtls_mpi_read_string() was called on "-0", or when
+ mbedtls_mpi_mul_mpi() and mbedtls_mpi_mul_int() was called with one of
+ the arguments being negative and the other being 0. Fixes #4643.
Changes
* Fix the setting of the read timeout in the DTLS sample programs.
