Remove block_mask from EVP_CIPHER_CTX

The block mask is only used in EVP_{De,En}cryptUpdate(). There's no need to
hang it off the EVP_CIPHER_CTX since it is easy to compute and validate.

ok joshua jsing

2 files changed, 15 insertions, 7 deletions

diff --git a/src/lib/libcrypto/evp/evp_enc.c b/src/lib/libcrypto/evp/evp_enc.c
index 0c18a8833b..3322e4a05d 100644
--- a/src/lib/libcrypto/evp/evp_enc.c
+++ b/src/lib/libcrypto/evp/evp_enc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: evp_enc.c,v 1.68 2023/12/20 11:33:52 tb Exp $ */
+/* $OpenBSD: evp_enc.c,v 1.69 2023/12/20 14:10:03 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -122,7 +122,8 @@ EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher, ENGINE *impl,
                 EVPerror(EVP_R_NO_CIPHER_SET);
                 return 0;
         }
-        /* we assume block size is a power of 2 in *cryptUpdate */
+
+        /* Block sizes must be a power of 2 due to the use of block_mask. */
         if (ctx->cipher->block_size != 1 &&
             ctx->cipher->block_size != 8 &&
             ctx->cipher->block_size != 16) {
@@ -184,9 +185,10 @@ EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher, ENGINE *impl,
                 if (!ctx->cipher->init(ctx, key, iv, enc))
                         return 0;
         }
+
         ctx->partial_len = 0;
         ctx->final_used = 0;
-        ctx->block_mask = ctx->cipher->block_size - 1;
+
         return 1;
 }
 
@@ -297,12 +299,15 @@ EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
     const unsigned char *in, int inl)
 {
         const int block_size = ctx->cipher->block_size;
-        const int block_mask = ctx->block_mask;
+        const int block_mask = block_size - 1;
         int partial_len = ctx->partial_len;
         int len = 0, total_len = 0;
 
         *outl = 0;
 
+        if ((block_size & block_mask) != 0)
+                return 0;
+
         if (inl < 0)
                 return 0;
 
@@ -418,10 +423,14 @@ EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
     const unsigned char *in, int inl)
 {
         const int block_size = ctx->cipher->block_size;
+        const int block_mask = block_size - 1;
         int len = 0, total_len = 0;
 
         *outl = 0;
 
+        if ((block_size & block_mask) != 0)
+                return 0;
+
         if (inl < 0)
                 return 0;
 
@@ -445,7 +454,7 @@ EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
                  * length output from EVP_EncryptUpdate() is inl & ~block_mask.
                  * Ensure (inl & ~block_mask) + block_size doesn't overflow.
                  */
-                if ((inl & ~ctx->block_mask) > INT_MAX - block_size) {
+                if ((inl & ~block_mask) > INT_MAX - block_size) {
                         EVPerror(EVP_R_TOO_LARGE);
                         return 0;
                 }
diff --git a/src/lib/libcrypto/evp/evp_local.h b/src/lib/libcrypto/evp/evp_local.h
index 7bc266250c..36c373523f 100644
--- a/src/lib/libcrypto/evp/evp_local.h
+++ b/src/lib/libcrypto/evp/evp_local.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: evp_local.h,v 1.7 2023/12/20 11:31:17 tb Exp $ */
+/* $OpenBSD: evp_local.h,v 1.8 2023/12/20 14:10:03 tb Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2000.
  */
@@ -180,7 +180,6 @@ struct evp_cipher_ctx_st {
         unsigned long flags;    /* Various flags */
         void *cipher_data; /* per EVP data */
         int final_used;
-        int block_mask;
         unsigned char final[EVP_MAX_BLOCK_LENGTH];/* possible final block */
 } /* EVP_CIPHER_CTX */;