From 4cad4fc8a94e1a42bae3f705a0d59f1022c1ea41 Mon Sep 17 00:00:00 2001
From: Przemyslaw Stekiel <przemyslaw.stekiel@mobica.com>
Date: Wed, 13 Oct 2021 11:12:08 +0200
Subject: [PATCH] psa_crypto.c: use switch instead if-else in
 psa_aead_check_nonce_length and psa_aead_set_lengths (fixes #5065)

Signed-off-by: Przemyslaw Stekiel <przemyslaw.stekiel@mobica.com>
---
 library/psa_crypto.c | 97 ++++++++++++++++++++++----------------------
 1 file changed, 49 insertions(+), 48 deletions(-)

diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index ece64b100..2299da3a5 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -3621,34 +3621,35 @@ static psa_status_t psa_aead_check_nonce_length( psa_algorithm_t alg,
 {
     psa_algorithm_t base_alg = psa_aead_get_base_algorithm( alg );
 
-#if defined(PSA_WANT_ALG_GCM)
-    if( base_alg == PSA_ALG_GCM )
+    switch(base_alg)
     {
-        /* Not checking max nonce size here as GCM spec allows almost
-         * arbitrarily large nonces. Please note that we do not generally
-         * recommend the usage of nonces of greater length than
-         * PSA_AEAD_NONCE_MAX_SIZE, as large nonces are hashed to a shorter
-         * size, which can then lead to collisions if you encrypt a very
-         * large number of messages.*/
-        if( nonce_length != 0 )
-            return( PSA_SUCCESS );
-    }
+#if defined(PSA_WANT_ALG_GCM)
+        case PSA_ALG_GCM:
+            /* Not checking max nonce size here as GCM spec allows almost
+            * arbitrarily large nonces. Please note that we do not generally
+            * recommend the usage of nonces of greater length than
+            * PSA_AEAD_NONCE_MAX_SIZE, as large nonces are hashed to a shorter
+            * size, which can then lead to collisions if you encrypt a very
+            * large number of messages.*/
+            if( nonce_length != 0 )
+                return( PSA_SUCCESS );
+            break;
 #endif /* PSA_WANT_ALG_GCM */
 #if defined(PSA_WANT_ALG_CCM)
-    if( base_alg == PSA_ALG_CCM )
-    {
-        if( nonce_length >= 7 && nonce_length <= 13 )
-            return( PSA_SUCCESS );
-    }
-    else
+        case PSA_ALG_CCM:
+            if( nonce_length >= 7 && nonce_length <= 13 )
+                return( PSA_SUCCESS );
+            break;
 #endif /* PSA_WANT_ALG_CCM */
 #if defined(PSA_WANT_ALG_CHACHA20_POLY1305)
-    if( base_alg == PSA_ALG_CHACHA20_POLY1305 )
-    {
-        if( nonce_length == 12 )
-            return( PSA_SUCCESS );
-    }
+        case PSA_ALG_CHACHA20_POLY1305:
+            if( nonce_length == 12 )
+                return( PSA_SUCCESS );
+            break;
 #endif /* PSA_WANT_ALG_CHACHA20_POLY1305 */
+        default:
+            break;
+    }
 
     return( PSA_ERROR_NOT_SUPPORTED );
 }
@@ -3950,40 +3951,40 @@ psa_status_t psa_aead_set_lengths( psa_aead_operation_t *operation,
         goto exit;
     }
 
-#if defined(PSA_WANT_ALG_GCM)
-    if( operation->alg == PSA_ALG_GCM )
+    switch(operation->alg)
     {
-        /* Lengths can only be too large for GCM if size_t is bigger than 32
-         * bits. Without the guard this code will generate warnings on 32bit
-         * builds. */
+#if defined(PSA_WANT_ALG_GCM)
+        case PSA_ALG_GCM:
+            /* Lengths can only be too large for GCM if size_t is bigger than 32
+            * bits. Without the guard this code will generate warnings on 32bit
+            * builds. */
 #if SIZE_MAX > UINT32_MAX
-        if( (( uint64_t ) ad_length ) >> 61 != 0 ||
-            (( uint64_t ) plaintext_length ) > 0xFFFFFFFE0ull )
-        {
-            status = PSA_ERROR_INVALID_ARGUMENT;
-            goto exit;
-        }
+            if( (( uint64_t ) ad_length ) >> 61 != 0 ||
+                (( uint64_t ) plaintext_length ) > 0xFFFFFFFE0ull )
+            {
+                status = PSA_ERROR_INVALID_ARGUMENT;
+                goto exit;
+            }
 #endif
-    }
-    else
+            break;
 #endif /* PSA_WANT_ALG_GCM */
 #if defined(PSA_WANT_ALG_CCM)
-    if( operation->alg == PSA_ALG_CCM )
-    {
-        if( ad_length > 0xFF00 )
-        {
-            status = PSA_ERROR_INVALID_ARGUMENT;
-            goto exit;
-        }
-    }
-    else
+        case PSA_ALG_CCM:
+            if( ad_length > 0xFF00 )
+            {
+                status = PSA_ERROR_INVALID_ARGUMENT;
+                goto exit;
+            }
+            break;
 #endif /* PSA_WANT_ALG_CCM */
 #if defined(PSA_WANT_ALG_CHACHA20_POLY1305)
-    if( operation->alg == PSA_ALG_CHACHA20_POLY1305 )
-    {
-        /* No length restrictions for ChaChaPoly. */
-    }
+        case PSA_ALG_CHACHA20_POLY1305:
+            /* No length restrictions for ChaChaPoly. */
+            break;
 #endif /* PSA_WANT_ALG_CHACHA20_POLY1305 */
+        default:
+            break;
+    }
 
     status = psa_driver_wrapper_aead_set_lengths( operation, ad_length,
                                                   plaintext_length );