First cleanup pass over EVP_EncryptUpdate()

Use more sensible variable names in order to make the logic a bit easier
to follow. The variables may be renamed in a later pass. Unindent a block
that was squeezed too much to the right and make a few minor stylistic
tweaks.

ok jsing

1 files changed, 37 insertions, 36 deletions

diff --git a/src/lib/libcrypto/evp/evp_enc.c b/src/lib/libcrypto/evp/evp_enc.c
index edc15fdab4..47d062a6ba 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 1.61 2023/12/16 09:46:06 tb Exp $ */
+/* $OpenBSD: evp_enc.c,v 1.62 2023/12/16 15:22:40 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -296,7 +296,9 @@ int
 EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
     const unsigned char *in, int inl)
 {
-        int i, j, bl;
+        int block_size = ctx->cipher->block_size;
+        int block_mask = ctx->block_mask;
+        int buf_offset = ctx->buf_len;
         int len = 0, total_len = 0;
 
         *outl = 0;
@@ -310,49 +312,48 @@ EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
         if ((ctx->cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER) != 0)
                 return evp_cipher(ctx, out, outl, in, inl);
 
-        if (ctx->buf_len == 0 && (inl & ctx->block_mask) == 0)
+        if (buf_offset == 0 && (inl & block_mask) == 0)
                 return evp_cipher(ctx, out, outl, in, inl);
 
-        i = ctx->buf_len;
-        bl = ctx->cipher->block_size;
-        if ((size_t)bl > sizeof(ctx->buf)) {
+        /* XXX - check that block_size > buf_offset. */
+        if (block_size > sizeof(ctx->buf)) {
                 EVPerror(EVP_R_BAD_BLOCK_LENGTH);
                 return 0;
         }
-        if (i != 0) {
-                if (bl - i > inl) {
-                        memcpy(&(ctx->buf[i]), in, inl);
+
+        if (buf_offset != 0) {
+                int buf_avail;
+
+                if ((buf_avail = block_size - buf_offset) > inl) {
+                        memcpy(&ctx->buf[buf_offset], in, inl);
                         ctx->buf_len += inl;
                         return 1;
-                } else {
-                        j = bl - i;
+                }
 
-                        /*
-                         * Once we've processed the first j bytes from in, the
-                         * amount of data left that is a multiple of the block
-                         * length is (inl - j) & ~(bl - 1).  Ensure this plus
-                         * the block processed from ctx-buf doesn't overflow.
-                         */
-                        if (((inl - j) & ~(bl - 1)) > INT_MAX - bl) {
-                                EVPerror(EVP_R_TOO_LARGE);
-                                return 0;
-                        }
-                        memcpy(&(ctx->buf[i]), in, j);
+                /*
+                 * Once the first buf_avail bytes from in are processed, the
+                 * amount of data left that is a multiple of the block length is
+                 * (inl - buf_avail) & ~block_mask.  Ensure that this plus the
+                 * block processed from ctx->buf doesn't overflow.
+                 */
+                if (((inl - buf_avail) & ~block_mask) > INT_MAX - block_size) {
+                        EVPerror(EVP_R_TOO_LARGE);
+                        return 0;
+                }
+                memcpy(&ctx->buf[buf_offset], in, buf_avail);
 
-                        len = 0;
-                        if (!evp_cipher(ctx, out, &len, ctx->buf, bl))
-                                return 0;
-                        total_len = len;
+                len = 0;
+                if (!evp_cipher(ctx, out, &len, ctx->buf, block_size))
+                        return 0;
+                total_len = len;
 
-                        inl -= j;
-                        in += j;
-                        out += len;
-                }
+                inl -= buf_avail;
+                in += buf_avail;
+                out += len;
         }
 
-        i = inl&(bl - 1);
-        inl -= i;
-        if (inl > 0) {
+        buf_offset = inl & block_mask;
+        if ((inl -= buf_offset) > 0) {
                 if (INT_MAX - inl < total_len)
                         return 0;
                 len = 0;
@@ -363,9 +364,9 @@ EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
                 total_len += len;
         }
 
-        if (i != 0)
-                memcpy(ctx->buf, &(in[inl]), i);
-        ctx->buf_len = i;
+        if (buf_offset != 0)
+                memcpy(ctx->buf, &in[inl], buf_offset);
+        ctx->buf_len = buf_offset;
 
         *outl = total_len;