libbb/yescrypt: code shrink

function                                             old     new   delta
static.yescrypt_kdf32_body                           847     823     -24
yescrypt_r                                           805     767     -38
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-62)             Total: -62 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 28 insertions, 15 deletions

diff --git a/libbb/yescrypt/alg-yescrypt-common.c b/libbb/yescrypt/alg-yescrypt-common.c
index e48be6581..1c063b895 100644
--- a/libbb/yescrypt/alg-yescrypt-common.c
+++ b/libbb/yescrypt/alg-yescrypt-common.c
@@ -23,8 +23,8 @@
 #define decode64_uint32(dst, src, min) \
 ({ \
         uint32_t d32 = a2i64(*(src)); \
-        if (d32 > 47) \
-                goto fail; \
+        if (d32 > 47) \
+                goto fail; \
         *(dst) = d32 + (min); \
         ++src; \
 })
@@ -292,8 +292,12 @@ char *yescrypt_r(
                 const uint8_t *setting,
                 char *buf, size_t buflen)
 {
-        yescrypt_ctx_t yctx[1];
-        unsigned char hashbin32[32];
+        struct {
+                yescrypt_ctx_t yctx[1];
+                unsigned char hashbin32[32];
+        } u;
+#define yctx      u.yctx
+#define hashbin32 u.hashbin32
         char *dst;
         const uint8_t *src, *saltend;
         size_t need, prefixlen;
@@ -375,7 +379,7 @@ char *yescrypt_r(
 
         prefixlen = saltend - setting;
         need = prefixlen + 1 + YESCRYPT_HASH_LEN + 1;
-        if (need > buflen || need < prefixlen)
+        if (need > buflen /*overflow is quite unlikely: || need < prefixlen*/)
                 goto fail;
 
         if (yescrypt_kdf32(yctx, passwd, passwdlen, hashbin32)) {
@@ -390,10 +394,11 @@ char *yescrypt_r(
                 goto fail;
  ret:
         free_region(yctx->local);
-        explicit_bzero(yctx, sizeof(yctx));
-        explicit_bzero(hashbin32, sizeof(hashbin32));
+        explicit_bzero(&u, sizeof(u));
         return buf;
  fail:
         buf = NULL;
         goto ret;
+#undef yctx
+#undef hashbin32
 }
diff --git a/libbb/yescrypt/alg-yescrypt-kdf.c b/libbb/yescrypt/alg-yescrypt-kdf.c
index 112862ec9..29d9efc07 100644
--- a/libbb/yescrypt/alg-yescrypt-kdf.c
+++ b/libbb/yescrypt/alg-yescrypt-kdf.c
@@ -915,8 +915,13 @@ static int yescrypt_kdf32_body(
         size_t B_size, V_size, XY_size, need;
         uint8_t *B, *S;
         salsa20_blk_t *V, *XY;
-        uint8_t sha256[32];
-        uint8_t dk[sizeof(sha256)], *dkp = buf32;
+        struct {
+                uint8_t sha256[32];
+                uint8_t dk[32];
+        } u;
+#define sha256 u.sha256
+#define dk     u.dk
+        uint8_t *dkp = buf32;
         uint32_t r, p;
 
         /* Sanity-check parameters */
@@ -1083,15 +1088,16 @@ static int yescrypt_kdf32_body(
                         size_t clen = /*buflen:*/32;
                         if (clen > sizeof(dk))
                                 clen = sizeof(dk);
-                        sha256_block(sha256, sizeof(sha256), dk);
-                        memcpy(buf32, dk, clen);
+                        if (sizeof(dk) != 32) { /* not true, optimize it out */
+                                sha256_block(sha256, sizeof(sha256), dk);
+                                memcpy(buf32, dk, clen);
+                        } else {
+                                sha256_block(sha256, sizeof(sha256), buf32);
+                        }
                 }
         }
 
-        if (flags) {
-                explicit_bzero(sha256, sizeof(sha256));
-                explicit_bzero(dk, sizeof(dk));
-        }
+        explicit_bzero(&u, sizeof(u));
 
         /* Success! */
         return 0;
@@ -1099,6 +1105,8 @@ static int yescrypt_kdf32_body(
  out_EINVAL:
         //bbox does not need this: errno = EINVAL;
         return -1;
+#undef sha256
+#undef dk
 }
 
 /**