Add option LTC_SMALL_STACK.

sjaeckel · sjaeckel · commit 77afa82d1437 · 2026-04-09T15:40:07.000+02:00
Signed-off-by: Steffen Jaeckel &lt;s@jaeckel.eu&gt;
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
@@ -47,10 +47,12 @@ jobs:
           - { BUILDNAME: 'STOCK',                   BUILDOPTIONS: '',                                                                     BUILDSCRIPT: '.ci/run.sh' }
           - { BUILDNAME: 'STOCK-MPI',               BUILDOPTIONS: '-ULTM_DESC -UTFM_DESC -UUSE_LTM -UUSE_TFM',                            BUILDSCRIPT: '.ci/run.sh' }
           - { BUILDNAME: 'EASY',                    BUILDOPTIONS: '-DLTC_EASY',                                                           BUILDSCRIPT: '.ci/run.sh' }
-          - { BUILDNAME: 'SMALL',                   BUILDOPTIONS: '-DLTC_SMALL_CODE',                                                     BUILDSCRIPT: '.ci/run.sh' }
+          - { BUILDNAME: 'SMALL_CODE',              BUILDOPTIONS: '-DLTC_SMALL_CODE',                                                     BUILDSCRIPT: '.ci/run.sh' }
+          - { BUILDNAME: 'SMALL_STACK',             BUILDOPTIONS: '-DLTC_SMALL_STACK',                                                    BUILDSCRIPT: '.ci/run.sh' }
+          - { BUILDNAME: 'SMALL',                   BUILDOPTIONS: '-DLTC_SMALL_CODE -DLTC_SMALL_STACK',                                   BUILDSCRIPT: '.ci/run.sh' }
           - { BUILDNAME: 'NO_TABLES',               BUILDOPTIONS: '-DLTC_NO_TABLES',                                                      BUILDSCRIPT: '.ci/run.sh' }
           - { BUILDNAME: 'NO_FAST',                 BUILDOPTIONS: '-DLTC_NO_FAST',                                                        BUILDSCRIPT: '.ci/run.sh' }
-          - { BUILDNAME: 'NO_FAST+SMALL+NO_TABLES', BUILDOPTIONS: '-DLTC_NO_FAST -DLTC_SMALL_CODE -DLTC_NO_TABLES',                       BUILDSCRIPT: '.ci/run.sh' }
+          - { BUILDNAME: 'NO_FAST+SMALL+NO_TABLES', BUILDOPTIONS: '-DLTC_NO_FAST -DLTC_SMALL_CODE -DLTC_SMALL_STACK -DLTC_NO_TABLES',     BUILDSCRIPT: '.ci/run.sh' }
           - { BUILDNAME: 'NO_ASM',                  BUILDOPTIONS: '-DLTC_NO_ASM',                                                         BUILDSCRIPT: '.ci/run.sh' }
           - { BUILDNAME: 'NO_DEPRECATED_APIS',      BUILDOPTIONS: '-DLTC_NO_DEPRECATED_APIS',                                             BUILDSCRIPT: '.ci/run.sh' }
           - { BUILDNAME: 'NO_TIMING_RESISTANCE',    BUILDOPTIONS: '-DLTC_NO_ECC_TIMING_RESISTANT -DLTC_NO_RSA_BLINDING',                  BUILDSCRIPT: '.ci/run.sh' }
diff --git a/src/hashes/sha1.c b/src/hashes/sha1.c
@@ -4,12 +4,20 @@
 
 /**
   @file sha1.c
-  LTC_SHA1 code by Tom St Denis
+  SHA1 code by Tom St Denis
 */
 
 
 #ifdef LTC_SHA1
 
+/* While implementing the SMALL STACK option in https://github.com/libtom/libtomcrypt/pull/709
+ * we came to the conclusion that SHA1 profits from the SMALL STACK option when the SMALL CODE
+ * option is enabled, so let's do that.
+ */
+#if defined(LTC_SMALL_STACK) || defined(LTC_SMALL_CODE)
+#define LTC_SMALL_STACK_SHA1
+#endif
+
 const struct ltc_hash_descriptor sha1_desc =
 {
     "sha1",
@@ -39,7 +47,12 @@ static int ss_sha1_compress(hash_state *md, const unsigned char *buf)
 static int  s_sha1_compress(hash_state *md, const unsigned char *buf)
 #endif
 {
-    ulong32 a,b,c,d,e,W[16],i;
+    ulong32 a,b,c,d,e,i;
+#ifdef LTC_SMALL_STACK_SHA1
+    ulong32 W[16];
+#else
+    ulong32 W[80];
+#endif
 #ifdef LTC_SMALL_CODE
     ulong32 t;
 #endif
@@ -48,7 +61,6 @@ static int  s_sha1_compress(hash_state *md, const unsigned char *buf)
     for (i = 0; i < 16; i++) {
         LOAD32H(W[i], buf + (4*i));
     }
-    #define Wi(i) W[(i) % 16] = ROL(W[((i) - 3) % 16] ^ W[((i) - 8) % 16] ^ W[((i) - 14) % 16] ^ W[((i) - 16) % 16], 1);
 
     /* copy state */
     a = md->sha1.state[0];
@@ -57,12 +69,24 @@ static int  s_sha1_compress(hash_state *md, const unsigned char *buf)
     d = md->sha1.state[3];
     e = md->sha1.state[4];
 
+#ifdef LTC_SMALL_STACK_SHA1
+    #define Wi(i) do { W[(i) % 16] = ROL(W[((i) - 3) % 16] ^ W[((i) - 8) % 16] ^ W[((i) - 14) % 16] ^ W[((i) - 16) % 16], 1); } while(0)
+    #define Windex(i) ((i) % 16)
+#else
+    #define Wi(i) do { } while(0)
+    #define Windex(i) (i)
+    /* expand it */
+    for (i = 16; i < 80; i++) {
+        W[i] = ROL(W[i-3] ^ W[i-8] ^ W[i-14] ^ W[i-16], 1);
+    }
+#endif
+
     /* compress */
     /* round one */
-    #define FF0(a,b,c,d,e,i) e = (ROLc(a, 5) + F0(b,c,d) + e + W[(i) % 16] + 0x5a827999UL); b = ROLc(b, 30);
-    #define FF1(a,b,c,d,e,i) e = (ROLc(a, 5) + F1(b,c,d) + e + W[(i) % 16] + 0x6ed9eba1UL); b = ROLc(b, 30);
-    #define FF2(a,b,c,d,e,i) e = (ROLc(a, 5) + F2(b,c,d) + e + W[(i) % 16] + 0x8f1bbcdcUL); b = ROLc(b, 30);
-    #define FF3(a,b,c,d,e,i) e = (ROLc(a, 5) + F3(b,c,d) + e + W[(i) % 16] + 0xca62c1d6UL); b = ROLc(b, 30);
+    #define FF0(a,b,c,d,e,i) e = (ROLc(a, 5) + F0(b,c,d) + e + W[Windex(i)] + 0x5a827999UL); b = ROLc(b, 30);
+    #define FF1(a,b,c,d,e,i) e = (ROLc(a, 5) + F1(b,c,d) + e + W[Windex(i)] + 0x6ed9eba1UL); b = ROLc(b, 30);
+    #define FF2(a,b,c,d,e,i) e = (ROLc(a, 5) + F2(b,c,d) + e + W[Windex(i)] + 0x8f1bbcdcUL); b = ROLc(b, 30);
+    #define FF3(a,b,c,d,e,i) e = (ROLc(a, 5) + F3(b,c,d) + e + W[Windex(i)] + 0xca62c1d6UL); b = ROLc(b, 30);
 
 #ifdef LTC_SMALL_CODE
 
@@ -133,6 +157,7 @@ static int  s_sha1_compress(hash_state *md, const unsigned char *buf)
     #undef FF2
     #undef FF3
     #undef Wi
+    #undef Windex
 
     /* store */
     md->sha1.state[0] = md->sha1.state[0] + a;
diff --git a/src/hashes/sha2/sha256.c b/src/hashes/sha2/sha256.c
@@ -4,7 +4,7 @@
 
 /**
   @file sha256.c
-  LTC_SHA256 by Tom St Denis
+  SHA256 by Tom St Denis
 */
 
 #ifdef LTC_SHA256
@@ -27,6 +27,15 @@ const struct ltc_hash_descriptor sha256_desc =
     NULL
 };
 
+/* While implementing the SMALL STACK option in https://github.com/libtom/libtomcrypt/pull/709
+ * we came to the conclusion that SHA256 profits from the SMALL STACK option when the SMALL CODE
+ * option is disabled.
+ * So enable it either when it's enabled explicitly, or when SMALL CODE is disabled.
+ */
+#if !defined(LTC_SMALL_CODE) || defined(LTC_SMALL_STACK)
+#define LTC_SMALL_STACK_SHA256
+#endif
+
 #ifdef LTC_SMALL_CODE
 /* the K array */
 static const ulong32 K[64] = {
@@ -63,7 +72,12 @@ static int ss_sha256_compress(hash_state * md, const unsigned char *buf)
 static int s_sha256_compress(hash_state * md, const unsigned char *buf)
 #endif
 {
-    ulong32 S[8], W[16], t0, t1;
+    ulong32 S[8], t0, t1;
+#ifdef LTC_SMALL_STACK_SHA256
+    ulong32 W[16];
+#else
+    ulong32 W[64];
+#endif
 #ifdef LTC_SMALL_CODE
     ulong32 t;
 #endif
@@ -78,16 +92,29 @@ static int s_sha256_compress(hash_state * md, const unsigned char *buf)
     for (i = 0; i < 16; i++) {
         LOAD32H(W[i], buf + (4*i));
     }
+
+#ifdef LTC_SMALL_STACK_SHA256
     #define Wi(i) W[(i) % 16] = Gamma1(W[((i) - 2) % 16]) + W[((i) - 7) % 16] + Gamma0(W[((i) - 15) % 16]) + W[((i) - 16) % 16]
+    #define Windex(i) ((i) % 16)
+#else
+    #define Wi(i) do { } while(0)
+    #define Windex(i) (i)
+
+    /* fill W[16..63] */
+    for (i = 16; i < 64; i++) {
+        W[i] = Gamma1(W[i - 2]) + W[i - 7] + Gamma0(W[i - 15]) + W[i - 16];
+    }
+#endif
 
     /* Compress */
 #ifdef LTC_SMALL_CODE
-#define RND(a,b,c,d,e,f,g,h,i)                              \
-     t0 = h + Sigma1(e) + Ch(e, f, g) + K[i] + W[(i) % 16]; \
-     t1 = Sigma0(a) + Maj(a, b, c);                         \
-     d += t0;                                               \
+#define RND(a,b,c,d,e,f,g,h,i)                               \
+     t0 = h + Sigma1(e) + Ch(e, f, g) + K[i] + W[Windex(i)]; \
+     t1 = Sigma0(a) + Maj(a, b, c);                          \
+     d += t0;                                                \
      h  = t0 + t1;
 
+#ifdef LTC_SMALL_STACK_SHA256
      for (i = 0; i < 16; ++i) {
          RND(S[0],S[1],S[2],S[3],S[4],S[5],S[6],S[7],i);
          t = S[7]; S[7] = S[6]; S[6] = S[5]; S[5] = S[4];
@@ -100,10 +127,17 @@ static int s_sha256_compress(hash_state * md, const unsigned char *buf)
          S[4] = S[3]; S[3] = S[2]; S[2] = S[1]; S[1] = S[0]; S[0] = t;
      }
 #else
-#define RND(a,b,c,d,e,f,g,h,i,ki)                         \
-     t0 = h + Sigma1(e) + Ch(e, f, g) + ki + W[(i) % 16]; \
-     t1 = Sigma0(a) + Maj(a, b, c);                       \
-     d += t0;                                             \
+     for (i = 0; i < 64; ++i) {
+         RND(S[0],S[1],S[2],S[3],S[4],S[5],S[6],S[7],i);
+         t = S[7]; S[7] = S[6]; S[6] = S[5]; S[5] = S[4];
+         S[4] = S[3]; S[3] = S[2]; S[2] = S[1]; S[1] = S[0]; S[0] = t;
+     }
+#endif /* LTC_SMALL_STACK_SHA256 */
+#else
+#define RND(a,b,c,d,e,f,g,h,i,ki)                          \
+     t0 = h + Sigma1(e) + Ch(e, f, g) + ki + W[Windex(i)]; \
+     t1 = Sigma0(a) + Maj(a, b, c);                        \
+     d += t0;                                              \
      h  = t0 + t1;
 
     RND(S[0],S[1],S[2],S[3],S[4],S[5],S[6],S[7],0,0x428a2f98);
@@ -173,6 +207,7 @@ static int s_sha256_compress(hash_state * md, const unsigned char *buf)
 #endif
 #undef RND
 #undef Wi
+#undef Windex
 
     /* feedback */
     for (i = 0; i < 8; i++) {
diff --git a/src/hashes/sha2/sha512.c b/src/hashes/sha2/sha512.c
@@ -4,7 +4,7 @@
 
 /**
    @param sha512.c
-   LTC_SHA512 by Tom St Denis
+   SHA512 by Tom St Denis
 */
 
 #ifdef LTC_SHA512
@@ -88,7 +88,12 @@ static int ss_sha512_compress(hash_state * md, const unsigned char *buf)
 static int  s_sha512_compress(hash_state * md, const unsigned char *buf)
 #endif
 {
-    ulong64 S[8], W[16], t0, t1;
+    ulong64 S[8], t0, t1;
+#ifdef LTC_SMALL_STACK
+    ulong64 W[16];
+#else
+    ulong64 W[80];
+#endif
     int i;
 
     /* copy state into S */
@@ -100,12 +105,24 @@ static int  s_sha512_compress(hash_state * md, const unsigned char *buf)
     for (i = 0; i < 16; i++) {
         LOAD64H(W[i], buf + (8*i));
     }
+
+#ifdef LTC_SMALL_STACK
     #define Wi(i) W[(i) % 16] = Gamma1(W[((i) - 2) % 16]) + W[((i) - 7) % 16] + Gamma0(W[((i) - 15) % 16]) + W[((i) - 16) % 16];
+    #define Windex(i) ((i) % 16)
+#else
+    #define Wi(i) do { } while(0)
+    #define Windex(i) (i)
+
+    /* fill W[16..79] */
+    for (i = 16; i < 80; i++) {
+        W[i] = Gamma1(W[i - 2]) + W[i - 7] + Gamma0(W[i - 15]) + W[i - 16];
+    }
+#endif
 
     /* Compress */
 #ifdef LTC_SMALL_CODE
     for (i = 0; i < 16; i++) {
-        t0 = S[7] + Sigma1(S[4]) + Ch(S[4], S[5], S[6]) + K[i] + W[i % 16];
+        t0 = S[7] + Sigma1(S[4]) + Ch(S[4], S[5], S[6]) + K[i] + W[Windex(i)];
         t1 = Sigma0(S[0]) + Maj(S[0], S[1], S[2]);
         S[7] = S[6];
         S[6] = S[5];
@@ -118,7 +135,7 @@ static int  s_sha512_compress(hash_state * md, const unsigned char *buf)
     }
     for (; i < 80; i++) {
         Wi(i);
-        t0 = S[7] + Sigma1(S[4]) + Ch(S[4], S[5], S[6]) + K[i] + W[i % 16];
+        t0 = S[7] + Sigma1(S[4]) + Ch(S[4], S[5], S[6]) + K[i] + W[Windex(i)];
         t1 = Sigma0(S[0]) + Maj(S[0], S[1], S[2]);
         S[7] = S[6];
         S[6] = S[5];
@@ -130,10 +147,10 @@ static int  s_sha512_compress(hash_state * md, const unsigned char *buf)
         S[0] = t0 + t1;
     }
 #else
-#define RND(a,b,c,d,e,f,g,h,i)                              \
-     t0 = h + Sigma1(e) + Ch(e, f, g) + K[i] + W[(i) % 16]; \
-     t1 = Sigma0(a) + Maj(a, b, c);                         \
-     d += t0;                                               \
+#define RND(a,b,c,d,e,f,g,h,i)                               \
+     t0 = h + Sigma1(e) + Ch(e, f, g) + K[i] + W[Windex(i)]; \
+     t1 = Sigma0(a) + Maj(a, b, c);                          \
+     d += t0;                                                \
      h  = t0 + t1;
 
     for (i = 0; i < 16; i += 8) {
@@ -156,8 +173,10 @@ static int  s_sha512_compress(hash_state * md, const unsigned char *buf)
         Wi(i+6); RND(S[2],S[3],S[4],S[5],S[6],S[7],S[0],S[1],i+6);
         Wi(i+7); RND(S[1],S[2],S[3],S[4],S[5],S[6],S[7],S[0],i+7);
     }
+#undef RND
 #endif
 #undef Wi
+#undef Windex
 
 
     /* feedback */
diff --git a/src/misc/crypt/crypt.c b/src/misc/crypt/crypt.c
@@ -528,6 +528,9 @@ const char *crypt_build_settings =
 #if defined(LTC_SMALL_CODE)
     " LTC_SMALL_CODE "
 #endif
+#if defined(LTC_SMALL_STACK)
+    " LTC_SMALL_STACK "
+#endif
 #if defined(LTC_NO_FILE)
     " LTC_NO_FILE "
 #endif
