diff --git a/ChangeLog.d/psa_util-bits-0.txt b/ChangeLog.d/psa_util-bits-0.txt
new file mode 100644
index 000000000..9aa70ad97
--- /dev/null
+++ b/ChangeLog.d/psa_util-bits-0.txt
@@ -0,0 +1,3 @@
+Bugfix
+   * Fix undefined behavior in some cases when mbedtls_psa_raw_to_der() or
+     mbedtls_psa_der_to_raw() is called with bits=0.
diff --git a/programs/ssl/ssl_fork_server.c b/programs/ssl/ssl_fork_server.c
index 9b3650778..1bd18c1f1 100644
--- a/programs/ssl/ssl_fork_server.c
+++ b/programs/ssl/ssl_fork_server.c
@@ -357,8 +357,6 @@ int main(void)
         goto exit;
     }
 
-    exit_code = MBEDTLS_EXIT_SUCCESS;
-
 exit:
     mbedtls_net_free(&client_fd);
     mbedtls_net_free(&listen_fd);
diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index 7213f8aea..43d2e8cf7 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -938,8 +938,6 @@ accept:
 
     }
 
-    exit_code = MBEDTLS_EXIT_SUCCESS;
-
 exit:
 
 #ifdef MBEDTLS_ERROR_C
diff --git a/tf-psa-crypto/drivers/builtin/include/mbedtls/psa_util.h b/tf-psa-crypto/drivers/builtin/include/mbedtls/psa_util.h
index 08fa5b374..bf2748a6d 100644
--- a/tf-psa-crypto/drivers/builtin/include/mbedtls/psa_util.h
+++ b/tf-psa-crypto/drivers/builtin/include/mbedtls/psa_util.h
@@ -161,6 +161,16 @@ static inline mbedtls_md_type_t mbedtls_md_type_from_psa_alg(psa_algorithm_t psa
  * \param[out]  der_len     On success it contains the amount of valid data
  *                          (in bytes) written to \p der. It's undefined
  *                          in case of failure.
+ *
+ * \note                    The behavior is undefined if \p der is null,
+ *                          even if \p der_size is 0.
+ *
+ * \return                  0 if successful.
+ * \return                  #MBEDTLS_ERR_ASN1_BUF_TOO_SMALL if \p der_size
+ *                          is too small or if \p bits is larger than the
+ *                          largest supported curve.
+ * \return                  #MBEDTLS_ERR_ASN1_INVALID_DATA if one of the
+ *                          numbers in the signature is 0.
  */
 int mbedtls_ecdsa_raw_to_der(size_t bits, const unsigned char *raw, size_t raw_len,
                              unsigned char *der, size_t der_size, size_t *der_len);
@@ -177,6 +187,15 @@ int mbedtls_ecdsa_raw_to_der(size_t bits, const unsigned char *raw, size_t raw_l
  * \param[out]  raw_len     On success it is updated with the amount of valid
  *                          data (in bytes) written to \p raw. It's undefined
  *                          in case of failure.
+ *
+ * \return                  0 if successful.
+ * \return                  #MBEDTLS_ERR_ASN1_BUF_TOO_SMALL if \p raw_size
+ *                          is too small or if \p bits is larger than the
+ *                          largest supported curve.
+ * \return                  #MBEDTLS_ERR_ASN1_INVALID_DATA if the data in
+ *                          \p der is inconsistent with \p bits.
+ * \return                  An \c MBEDTLS_ERR_ASN1_xxx error code if
+ *                          \p der is malformed.
  */
 int mbedtls_ecdsa_der_to_raw(size_t bits, const unsigned char *der, size_t der_len,
                              unsigned char *raw, size_t raw_size, size_t *raw_len);
diff --git a/tf-psa-crypto/drivers/builtin/src/psa_util.c b/tf-psa-crypto/drivers/builtin/src/psa_util.c
index 55803ea5e..b2d2cd9a7 100644
--- a/tf-psa-crypto/drivers/builtin/src/psa_util.c
+++ b/tf-psa-crypto/drivers/builtin/src/psa_util.c
@@ -440,6 +440,9 @@ int mbedtls_ecdsa_raw_to_der(size_t bits, const unsigned char *raw, size_t raw_l
     unsigned char *p = der + der_size;
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
+    if (bits == 0) {
+        return MBEDTLS_ERR_ASN1_INVALID_DATA;
+    }
     if (raw_len != (2 * coordinate_len)) {
         return MBEDTLS_ERR_ASN1_INVALID_DATA;
     }
@@ -559,6 +562,9 @@ int mbedtls_ecdsa_der_to_raw(size_t bits, const unsigned char *der, size_t der_l
     size_t coordinate_size = PSA_BITS_TO_BYTES(bits);
     int ret;
 
+    if (bits == 0) {
+        return MBEDTLS_ERR_ASN1_INVALID_DATA;
+    }
     /* The output raw buffer should be at least twice the size of a raw
      * coordinate in order to store r and s. */
     if (raw_size < coordinate_size * 2) {
diff --git a/tf-psa-crypto/tests/suites/test_suite_bignum.function b/tf-psa-crypto/tests/suites/test_suite_bignum.function
index 3d2b8a124..36f1476d7 100644
--- a/tf-psa-crypto/tests/suites/test_suite_bignum.function
+++ b/tf-psa-crypto/tests/suites/test_suite_bignum.function
@@ -212,28 +212,22 @@ void mpi_write_binary(char *input_X, data_t *input_A,
                       int output_size, int result)
 {
     mbedtls_mpi X;
-    unsigned char buf[1000];
-    size_t buflen;
-
-    memset(buf, 0x00, 1000);
-
     mbedtls_mpi_init(&X);
+    unsigned char *buf = NULL;
 
-    TEST_ASSERT(mbedtls_test_read_mpi(&X, input_X) == 0);
+    TEST_EQUAL(mbedtls_test_read_mpi(&X, input_X), 0);
 
-    buflen = mbedtls_mpi_size(&X);
-    if (buflen > (size_t) output_size) {
-        buflen = (size_t) output_size;
-    }
+    TEST_CALLOC(buf, output_size);
+
+    TEST_EQUAL(mbedtls_mpi_write_binary(&X, buf, output_size), result);
 
-    TEST_ASSERT(mbedtls_mpi_write_binary(&X, buf, buflen) == result);
     if (result == 0) {
-
-        TEST_ASSERT(mbedtls_test_hexcmp(buf, input_A->x,
-                                        buflen, input_A->len) == 0);
+        TEST_EQUAL(mbedtls_test_hexcmp(buf, input_A->x,
+                                       output_size, input_A->len), 0);
     }
 
 exit:
+    mbedtls_free(buf);
     mbedtls_mpi_free(&X);
 }
 /* END_CASE */
@@ -243,28 +237,22 @@ void mpi_write_binary_le(char *input_X, data_t *input_A,
                          int output_size, int result)
 {
     mbedtls_mpi X;
-    unsigned char buf[1000];
-    size_t buflen;
-
-    memset(buf, 0x00, 1000);
-
     mbedtls_mpi_init(&X);
+    unsigned char *buf = NULL;
 
-    TEST_ASSERT(mbedtls_test_read_mpi(&X, input_X) == 0);
+    TEST_EQUAL(mbedtls_test_read_mpi(&X, input_X), 0);
 
-    buflen = mbedtls_mpi_size(&X);
-    if (buflen > (size_t) output_size) {
-        buflen = (size_t) output_size;
-    }
+    TEST_CALLOC(buf, output_size);
+
+    TEST_EQUAL(mbedtls_mpi_write_binary_le(&X, buf, output_size), result);
 
-    TEST_ASSERT(mbedtls_mpi_write_binary_le(&X, buf, buflen) == result);
     if (result == 0) {
-
-        TEST_ASSERT(mbedtls_test_hexcmp(buf, input_A->x,
-                                        buflen, input_A->len) == 0);
+        TEST_EQUAL(mbedtls_test_hexcmp(buf, input_A->x,
+                                       output_size, input_A->len), 0);
     }
 
 exit:
+    mbedtls_free(buf);
     mbedtls_mpi_free(&X);
 }
 /* END_CASE */
diff --git a/tf-psa-crypto/tests/suites/test_suite_bignum.misc.data b/tf-psa-crypto/tests/suites/test_suite_bignum.misc.data
index de2ea8771..1228a4de5 100644
--- a/tf-psa-crypto/tests/suites/test_suite_bignum.misc.data
+++ b/tf-psa-crypto/tests/suites/test_suite_bignum.misc.data
@@ -92,7 +92,10 @@ Base test mbedtls_mpi_read_binary_le #1
 mpi_read_binary_le:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"24448B952FBBEF93F89286BA330E62528B151EAC265CC8CE3038519D09E148AF89288E91F48B41ACAD55D9DC5E2B18097C106BE4CE132721BF6359EAF403E7FF90623E8866EE5C192320418DAA682F144ADEDF84F25DE11F49D1FE009D374109"
 
 Base test mbedtls_mpi_write_binary #1
-mpi_write_binary:"941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":200:0
+mpi_write_binary:"941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"000000000941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":100:0
+
+Test mbedtls_mpi_write_binary #1 (Buffer is larger)
+mpi_write_binary:"123123123123123123123123123":"000123123123123123123123123123":15:0
 
 Test mbedtls_mpi_write_binary #1 (Buffer just fits)
 mpi_write_binary:"123123123123123123123123123":"0123123123123123123123123123":14:0
@@ -100,8 +103,17 @@ mpi_write_binary:"123123123123123123123123123":"0123123123123123123123123123":14
 Test mbedtls_mpi_write_binary #2 (Buffer too small)
 mpi_write_binary:"123123123123123123123123123":"23123123123123123123123123":13:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL
 
+Test mbedtls_mpi_write_binary: nonzero to NULL
+mpi_write_binary:"01":"":0:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL
+
+Test mbedtls_mpi_write_binary: 0 to NULL
+mpi_write_binary:"00":"":0:0
+
 Base test mbedtls_mpi_write_binary_le #1
-mpi_write_binary_le:"941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"24448b952fbbef93f89286ba330e62528b151eac265cc8ce3038519d09e148af89288e91f48b41acad55d9dc5e2b18097c106be4ce132721bf6359eaf403e7ff90623e8866ee5c192320418daa682f144adedf84f25de11f49d1fe009d374109":200:0
+mpi_write_binary_le:"941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"24448b952fbbef93f89286ba330e62528b151eac265cc8ce3038519d09e148af89288e91f48b41acad55d9dc5e2b18097c106be4ce132721bf6359eaf403e7ff90623e8866ee5c192320418daa682f144adedf84f25de11f49d1fe009d37410900000000":100:0
+
+Test mbedtls_mpi_write_binary_le #1 (Buffer is larger)
+mpi_write_binary_le:"123123123123123123123123123":"233112233112233112233112230100":15:0
 
 Test mbedtls_mpi_write_binary_le #1 (Buffer just fits)
 mpi_write_binary_le:"123123123123123123123123123":"2331122331122331122331122301":14:0
@@ -109,6 +121,12 @@ mpi_write_binary_le:"123123123123123123123123123":"2331122331122331122331122301"
 Test mbedtls_mpi_write_binary_le #2 (Buffer too small)
 mpi_write_binary_le:"123123123123123123123123123":"23311223311223311223311223":13:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL
 
+Test mbedtls_mpi_write_binary_le: nonzero to NULL
+mpi_write_binary_le:"01":"":0:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL
+
+Test mbedtls_mpi_write_binary_le: 0 to NULL
+mpi_write_binary_le:"00":"":0:0
+
 Base test mbedtls_mpi_read_file #1
 mpi_read_file:"../../framework/data_files/mpi_16":"01f55332c3a48b910f9942f6c914e58bef37a47ee45cb164a5b6b8d1006bf59a059c21449939ebebfdf517d2e1dbac88010d7b1f141e997bd6801ddaec9d05910f4f2de2b2c4d714e2c14a72fc7f17aa428d59c531627f09":0
 
diff --git a/tf-psa-crypto/tests/suites/test_suite_ccm.function b/tf-psa-crypto/tests/suites/test_suite_ccm.function
index dbb313b93..798be7701 100644
--- a/tf-psa-crypto/tests/suites/test_suite_ccm.function
+++ b/tf-psa-crypto/tests/suites/test_suite_ccm.function
@@ -79,11 +79,11 @@ void mbedtls_ccm_self_test()
 void mbedtls_ccm_setkey(int cipher_id, int key_size, int result)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     unsigned char key[32];
     int ret;
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
 
     memset(key, 0x2A, sizeof(key));
     TEST_ASSERT((unsigned) key_size <= 8 * sizeof(key));
@@ -101,6 +101,7 @@ exit:
 void ccm_lengths(int msg_len, int iv_len, int add_len, int tag_len, int res)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     unsigned char key[16];
     unsigned char msg[10];
     unsigned char iv[14];
@@ -110,7 +111,6 @@ void ccm_lengths(int msg_len, int iv_len, int add_len, int tag_len, int res)
     int decrypt_ret;
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
 
     TEST_CALLOC_OR_SKIP(add, add_len);
     memset(key, 0, sizeof(key));
@@ -146,6 +146,7 @@ void ccm_star_lengths(int msg_len, int iv_len, int add_len, int tag_len,
                       int res)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     unsigned char key[16];
     unsigned char msg[10];
     unsigned char iv[14];
@@ -155,7 +156,6 @@ void ccm_star_lengths(int msg_len, int iv_len, int add_len, int tag_len,
     int decrypt_ret;
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
 
     memset(key, 0, sizeof(key));
     memset(msg, 0, sizeof(msg));
@@ -191,6 +191,7 @@ void mbedtls_ccm_encrypt_and_tag(int cipher_id, data_t *key,
                                  data_t *add, data_t *result)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     size_t n1, n1_add;
     uint8_t *io_msg_buf = NULL;
     uint8_t *tag_buf = NULL;
@@ -207,7 +208,6 @@ void mbedtls_ccm_encrypt_and_tag(int cipher_id, data_t *key,
     TEST_CALLOC(tag_buf, expected_tag_len);
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     /* Test with input == output */
     TEST_EQUAL(mbedtls_ccm_encrypt_and_tag(&ctx, msg->len, iv->x, iv->len, add->x, add->len,
@@ -248,11 +248,11 @@ void mbedtls_ccm_star_no_tag(int cipher_id, int mode, data_t *key,
                              data_t *msg, data_t *iv, data_t *result)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t *output = NULL;
     size_t olen;
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     TEST_EQUAL(0, mbedtls_ccm_set_lengths(&ctx, 0, msg->len, 0));
@@ -277,6 +277,7 @@ void mbedtls_ccm_auth_decrypt(int cipher_id, data_t *key,
                               data_t *expected_msg)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     size_t n1, n1_add;
 
     const size_t expected_msg_len = msg->len - expected_tag_len;
@@ -290,7 +291,6 @@ void mbedtls_ccm_auth_decrypt(int cipher_id, data_t *key,
     }
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     /* Test with input == output */
     TEST_EQUAL(mbedtls_ccm_auth_decrypt(&ctx, expected_msg_len, iv->x, iv->len, add->x, add->len,
@@ -343,6 +343,7 @@ void mbedtls_ccm_star_encrypt_and_tag(int cipher_id,
 {
     unsigned char iv[13];
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     size_t iv_len, expected_tag_len;
     size_t n1, n1_add;
     uint8_t *io_msg_buf = NULL;
@@ -379,7 +380,6 @@ void mbedtls_ccm_star_encrypt_and_tag(int cipher_id,
     iv_len = sizeof(iv);
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id,
                                   key->x, key->len * 8), 0);
     /* Test with input == output */
@@ -430,6 +430,7 @@ void mbedtls_ccm_star_auth_decrypt(int cipher_id,
 {
     unsigned char iv[13];
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     size_t iv_len, expected_tag_len;
     size_t n1, n1_add;
 
@@ -460,7 +461,6 @@ void mbedtls_ccm_star_auth_decrypt(int cipher_id,
     iv_len = sizeof(iv);
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_ASSERT(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8) == 0);
     /* Test with input == output */
     TEST_EQUAL(mbedtls_ccm_star_auth_decrypt(&ctx, expected_msg_len, iv, iv_len,
@@ -507,6 +507,7 @@ void mbedtls_ccm_skip_ad(int cipher_id, int mode,
                          data_t *result, data_t *tag)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t *output = NULL;
     size_t olen;
 
@@ -514,7 +515,6 @@ void mbedtls_ccm_skip_ad(int cipher_id, int mode,
     TEST_EQUAL(msg->len, result->len);
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     TEST_EQUAL(0, mbedtls_ccm_set_lengths(&ctx, 0, msg->len, tag->len));
@@ -547,10 +547,10 @@ void mbedtls_ccm_skip_update(int cipher_id, int mode,
                              data_t *tag)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t *output = NULL;
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     TEST_EQUAL(0, mbedtls_ccm_set_lengths(&ctx, add->len, 0, tag->len));
@@ -577,9 +577,12 @@ void mbedtls_ccm_overflow_ad(int cipher_id, int mode,
                              data_t *add)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
+
+    /* This test can't be run with empty additional data */
+    TEST_LE_U(1, add->len);
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded values for msg length and tag length. They are not a part of this test
@@ -600,9 +603,9 @@ void mbedtls_ccm_unexpected_ad(int cipher_id, int mode,
                                data_t *add)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded values for msg length and tag length. They are not a part of this test
@@ -622,11 +625,11 @@ void mbedtls_ccm_unexpected_text(int cipher_id, int mode,
                                  data_t *add)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t *output = NULL;
     size_t olen;
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded value for tag length. It is not a part of this test
@@ -651,10 +654,13 @@ void mbedtls_ccm_incomplete_ad(int cipher_id, int mode,
                                data_t *key, data_t *iv, data_t *add)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t *output = NULL;
 
+    /* This test can't be run with empty additional data */
+    TEST_LE_U(1, add->len);
+
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded values for msg length and tag length. They are not a part of this test
@@ -680,9 +686,9 @@ void mbedtls_ccm_full_ad_and_overflow(int cipher_id, int mode,
                                       data_t *add)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded values for msg length and tag length. They are not a part of this test
@@ -706,13 +712,16 @@ void mbedtls_ccm_incomplete_ad_and_overflow(int cipher_id, int mode,
                                             data_t *add)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t add_second_buffer[2];
 
+    /* This test can't be run with empty additional data */
+    TEST_LE_U(1, add->len);
+
     add_second_buffer[0] = add->x[add->len - 1];
     add_second_buffer[1] = 0xAB; // some magic value
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded values for msg length and tag length. They are not a part of this test
@@ -735,11 +744,14 @@ void mbedtls_ccm_overflow_update(int cipher_id, int mode,
                                  data_t *add)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t *output = NULL;
     size_t olen;
 
+    /* This test can't be run with an empty message */
+    TEST_LE_U(1, msg->len);
+
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded value for tag length. It is a not a part of this test
@@ -765,11 +777,14 @@ void mbedtls_ccm_incomplete_update(int cipher_id, int mode,
                                    data_t *add)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t *output = NULL;
     size_t olen;
 
+    /* This test can't be run with an empty message */
+    TEST_LE_U(1, msg->len);
+
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded value for tag length. It is not a part of this test
@@ -801,11 +816,11 @@ void mbedtls_ccm_full_update_and_overflow(int cipher_id, int mode,
                                           data_t *add)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t *output = NULL;
     size_t olen;
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded value for tag length. It is a not a part of this test
@@ -834,15 +849,18 @@ void mbedtls_ccm_incomplete_update_overflow(int cipher_id, int mode,
                                             data_t *add)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t *output = NULL;
     size_t olen;
     uint8_t msg_second_buffer[2];
 
+    /* This test can't be run with an empty message */
+    TEST_LE_U(1, msg->len);
+
     msg_second_buffer[0] = msg->x[msg->len - 1];
     msg_second_buffer[1] = 0xAB; // some magic value
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded value for tag length. It is a not a part of this test
@@ -869,10 +887,10 @@ void mbedtls_ccm_instant_finish(int cipher_id, int mode,
                                 data_t *key, data_t *iv)
 {
     mbedtls_ccm_context ctx;
+    mbedtls_ccm_init(&ctx);
     uint8_t *output = NULL;
 
     BLOCK_CIPHER_PSA_INIT();
-    mbedtls_ccm_init(&ctx);
     TEST_EQUAL(mbedtls_ccm_setkey(&ctx, cipher_id, key->x, key->len * 8), 0);
     TEST_EQUAL(0, mbedtls_ccm_starts(&ctx, mode, iv->x, iv->len));
     // use hardcoded values for add length, msg length and tag length.
diff --git a/tf-psa-crypto/tests/suites/test_suite_psa_crypto_util.data b/tf-psa-crypto/tests/suites/test_suite_psa_crypto_util.data
index c84a8368c..a0ec9fd55 100644
--- a/tf-psa-crypto/tests/suites/test_suite_psa_crypto_util.data
+++ b/tf-psa-crypto/tests/suites/test_suite_psa_crypto_util.data
@@ -1,3 +1,12 @@
+# mbedtls_ecdsa_der_to_raw() doesn't accept a null output buffer,
+# even with otherwise invalid paramters,
+# so we pass it a (non-null) buffer of length 1.
+ECDSA Raw -> DER, 0bit
+ecdsa_raw_to_der:0:"":"00":MBEDTLS_ERR_ASN1_INVALID_DATA
+
+ECDSA DER -> Raw, 0bit
+ecdsa_der_to_raw:0:"":"":MBEDTLS_ERR_ASN1_INVALID_DATA
+
 ECDSA Raw -> DER, 256bit, Success
 depends_on:PSA_VENDOR_ECC_MAX_CURVE_BITS >= 256
 ecdsa_raw_to_der:256:"11111111111111111111111111111111111111111111111111111111111111112222222222222222222222222222222222222222222222222222222222222222":"30440220111111111111111111111111111111111111111111111111111111111111111102202222222222222222222222222222222222222222222222222222222222222222":0