Fix buffer overflow in mbedtls_mpi_write_string()
Fix a buffer overflow when writting a string representation of an MPI
number to a buffer in hexadecimal. The problem occurs because hex
digits are written in pairs and this is not accounted for in the
calculation of the required buffer size when the number of digits is
odd.
diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index fa65b5f..da830fe 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -46,6 +46,9 @@
Test mpi_read_write_string #9 (Empty MPI -> dec)
mpi_read_write_string:16:"":10:"0":4:0:0
+Test mpi_write_string #10 (Negative hex with odd number of digits)
+mpi_read_write_string:16:"-1":16:"":3:0:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL
+
Base test mbedtls_mpi_read_binary #1
mbedtls_mpi_read_binary:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":10:"56125680981752282334141896320372489490613963693556392520816017892111350604111697682705498319512049040516698827829292076808006940873974979584527073481012636016353913462376755556720019831187364993587901952757307830896531678727717924"