Add tests for mbedtls_ctr_increment_counter

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>

tests/suites/test_suite_ctr_drbg.data

@@ -1105,3 +1105,48 @@ ctr_drbg_threads:"B10A961F2EA39927B4C48AEDDD299026":1:5
 
 CTR_DRBG self test
 ctr_drbg_selftest:
+
+Increment counter rollover
+ctr_increment_rollover
+
+Increment counter 00
+ctr_increment:"00"
+
+Increment counter ff00
+ctr_increment:"ff00"
+
+Increment counter ff0000
+ctr_increment:"ff0000"
+
+Increment counter ff000000
+ctr_increment:"ff000000"
+
+Increment counter ff00000000
+ctr_increment:"ff00000000"
+
+Increment counter ff0000000000
+ctr_increment:"ff0000000000"
+
+Increment counter ff000000000000
+ctr_increment:"ff000000000000"
+
+Increment counter 01
+ctr_increment:"01"
+
+Increment counter ff01
+ctr_increment:"ff01"
+
+Increment counter ff0001
+ctr_increment:"ff0001"
+
+Increment counter ff000001
+ctr_increment:"ff000001"
+
+Increment counter ff00000001
+ctr_increment:"ff00000001"
+
+Increment counter ff0000000001
+ctr_increment:"ff0000000001"
+
+Increment counter ff000000000001
+ctr_increment:"ff000000000001"

tests/suites/test_suite_ctr_drbg.function

@@ -2,6 +2,7 @@
 #include "mbedtls/entropy.h"
 #include "mbedtls/ctr_drbg.h"
 #include "string.h"
+#include "ctr.h"
 
 #if defined(MBEDTLS_THREADING_PTHREAD)
 #include "mbedtls/threading.h"
@@ -443,3 +444,75 @@ void ctr_drbg_selftest()
     AES_PSA_DONE();
 }
 /* END_CASE */
+
+/* BEGIN_CASE */
+void ctr_increment_rollover()
+{
+    uint8_t c[16];
+    uint8_t r[16];
+
+    // test all increments from 2^n - 1 to 2^n (i.e. where we roll over into the next bit)
+    for (int n = 0; n <= 128; n++) {
+        memset(c, 0, 16);
+        memset(r, 0, 16);
+
+        // set least significant (highest address) n bits to 1, i.e. generate (2^n - 1)
+        for (int i = 0; i < n; i++) {
+            int bit = i % 8;
+            int byte = (i / 8);
+            c[15 - byte] |= 1 << bit;
+        }
+        // increment to get 2^n
+        mbedtls_ctr_increment_counter(c);
+
+        // now generate a reference result equal to 2^n - i.e. set only bit (n + 1)
+        // if n == 127, this will not set any bits (i.e. wraps to 0).
+        int bit = n % 8;
+        int byte = n / 8;
+        if (byte < 16) {
+            r[15 - byte] = 1 << bit;
+        }
+
+        TEST_MEMORY_COMPARE(c, 16, r, 16);
+    }
+
+    uint64_t lsb = 10, msb = 20;
+    MBEDTLS_PUT_UINT64_BE(msb, c, 0);
+    MBEDTLS_PUT_UINT64_BE(lsb, c, 8);
+    memcpy(r, c, 16);
+    mbedtls_ctr_increment_counter(c);
+    for (int i = 15; i >= 0; i--) {
+        r[i] += 1;
+        if (r[i] != 0) {
+            break;
+        }
+    }
+    TEST_MEMORY_COMPARE(c, 16, r, 16);
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
+void ctr_increment(data_t *x)
+{
+    uint8_t c[16];
+    uint8_t r[16];
+
+    // initialise c and r from test argument
+    memset(c, 0, 16);
+    memcpy(c, x->x, x->len);
+    memcpy(r, c, 16);
+
+    // increment c
+    mbedtls_ctr_increment_counter(c);
+    // increment reference
+    for (int i = 15; i >= 0; i--) {
+        r[i] += 1;
+        if (r[i] != 0) {
+            break;
+        }
+    }
+
+    // test that mbedtls_ctr_increment_counter behaviour matches reference
+    TEST_MEMORY_COMPARE(c, 16, r, 16);
+}
+/* END_CASE */