sha: reduce sha256/512 context size. Make sha1/sha256 code more similar

function                                             old     new   delta
sha512_end                                           182     204     +22
sha256_end                                           137     147     +10
sha1_hash                                            113     108      -5
sha1_end                                             143     129     -14
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/2 up/down: 32/-19)             Total: 13 bytes

2 files changed, 79 insertions, 72 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 3f566f8af..b04488a54 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1322,7 +1322,7 @@ void bb_uuencode(char *store, const void *s, int length, const char *tbl) FAST_F
 
 typedef struct sha1_ctx_t {
         uint64_t total64;
-        uint32_t wbuffer[16]; /* NB: always correctly aligned for uint64_t */
+        uint8_t wbuffer[64]; /* NB: always correctly aligned for uint64_t */
         uint32_t hash[5];
 } sha1_ctx_t;
 void sha1_begin(sha1_ctx_t *ctx) FAST_FUNC;
@@ -1331,7 +1331,7 @@ void sha1_end(void *resbuf, sha1_ctx_t *ctx) FAST_FUNC;
 typedef struct sha256_ctx_t {
         uint64_t total64;
         uint32_t hash[8];
-        char wbuffer[64*2]; /* NB: always correctly aligned for uint64_t */
+        uint8_t wbuffer[64]; /* NB: always correctly aligned for uint64_t */
 } sha256_ctx_t;
 void sha256_begin(sha256_ctx_t *ctx) FAST_FUNC;
 void sha256_hash(const void *buffer, size_t len, sha256_ctx_t *ctx) FAST_FUNC;
@@ -1339,7 +1339,7 @@ void sha256_end(void *resbuf, sha256_ctx_t *ctx) FAST_FUNC;
 typedef struct sha512_ctx_t {
         uint64_t total64[2];
         uint64_t hash[8];
-        char wbuffer[128*2]; /* NB: always correctly aligned for uint64_t */
+        uint8_t wbuffer[128]; /* NB: always correctly aligned for uint64_t */
 } sha512_ctx_t;
 void sha512_begin(sha512_ctx_t *ctx) FAST_FUNC;
 void sha512_hash(const void *buffer, size_t len, sha512_ctx_t *ctx) FAST_FUNC;
diff --git a/libbb/sha1.c b/libbb/sha1.c
index 765fedd9b..efdb0f58e 100644
--- a/libbb/sha1.c
+++ b/libbb/sha1.c
@@ -60,12 +60,13 @@ static void sha1_process_block64(sha1_ctx_t *ctx)
 {
         unsigned i;
         uint32_t w[80], a, b, c, d, e, t;
+        uint32_t *words;
 
-        /* note that words are compiled from the buffer into 32-bit */
-        /* words in big-endian order so an order reversal is needed */
-        /* here on little endian machines                           */
-        for (i = 0; i < SHA1_BLOCK_SIZE / 4; ++i)
-                w[i] = ntohl(ctx->wbuffer[i]);
+        words = (uint32_t*) ctx->wbuffer;
+        for (i = 0; i < SHA1_BLOCK_SIZE / 4; ++i) {
+                w[i] = ntohl(*words);
+                words++;
+        }
 
         for (/*i = SHA1_BLOCK_SIZE / 4*/; i < 80; ++i) {
                 t = w[i - 3] ^ w[i - 8] ^ w[i - 14] ^ w[i - 16];
@@ -232,7 +233,7 @@ static void sha256_process_block64(const void *buffer, size_t len, sha256_ctx_t
                 /* Compute the message schedule according to FIPS 180-2:6.2.2 step 2.  */
                 for (t = 0; t < 16; ++t) {
                         W[t] = ntohl(*words);
-                        ++words;
+                        words++;
                 }
 
                 for (/*t = 16*/; t < 64; ++t)
@@ -302,7 +303,7 @@ static void sha512_process_block128(const void *buffer, size_t len, sha512_ctx_t
                 /* Compute the message schedule according to FIPS 180-2:6.3.2 step 2.  */
                 for (t = 0; t < 16; ++t) {
                         W[t] = ntoh64(*words);
-                        ++words;
+                        words++;
                 }
                 for (/*t = 16*/; t < 80; ++t)
                         W[t] = R1(W[t - 2]) + W[t - 7] + R0(W[t - 15]) + W[t - 16];
@@ -399,7 +400,7 @@ void FAST_FUNC sha1_hash(const void *buffer, size_t len, sha1_ctx_t *ctx)
         ctx->total64 += len;
 
         while (len >= add) {    /* transfer whole blocks while possible  */
-                memcpy(((unsigned char *) ctx->wbuffer) + in_buf, buffer, add);
+                memcpy(ctx->wbuffer + in_buf, buffer, add);
                 buffer = (const char *)buffer + add;
                 len -= add;
                 add = SHA1_BLOCK_SIZE;
@@ -407,7 +408,7 @@ void FAST_FUNC sha1_hash(const void *buffer, size_t len, sha1_ctx_t *ctx)
                 sha1_process_block64(ctx);
         }
 
-        memcpy(((unsigned char *) ctx->wbuffer) + in_buf, buffer, len);
+        memcpy(ctx->wbuffer + in_buf, buffer, len);
 }
 
 void FAST_FUNC sha256_hash(const void *buffer, size_t len, sha256_ctx_t *ctx)
@@ -424,19 +425,14 @@ void FAST_FUNC sha256_hash(const void *buffer, size_t len, sha256_ctx_t *ctx)
         if (in_buf != 0) {
                 unsigned add;
 
-                /* NB: 1/2 of wbuffer is used only in sha256_end
-                 * when length field is added and hashed.
-                 * With buffer twice as small, it may happen that
-                 * we have it almost full and can't add length field.  */
-
-                add = sizeof(ctx->wbuffer)/2 - in_buf;
+                add = sizeof(ctx->wbuffer) - in_buf;
                 if (add > len)
                         add = len;
-                memcpy(&ctx->wbuffer[in_buf], buffer, add);
+                memcpy(ctx->wbuffer + in_buf, buffer, add);
                 in_buf += add;
 
                 /* If we still didn't collect full wbuffer, bail out */
-                if (in_buf < sizeof(ctx->wbuffer)/2)
+                if (in_buf < sizeof(ctx->wbuffer))
                         return;
 
                 sha256_process_block64(ctx->wbuffer, 64, ctx);
@@ -460,9 +456,8 @@ void FAST_FUNC sha256_hash(const void *buffer, size_t len, sha256_ctx_t *ctx)
         }
 
         /* Move remaining bytes into internal buffer.  */
-        if (len > 0) {
+        if (len > 0)
                 memcpy(ctx->wbuffer, buffer, len);
-        }
 }
 
 void FAST_FUNC sha512_hash(const void *buffer, size_t len, sha512_ctx_t *ctx)
@@ -479,13 +474,13 @@ void FAST_FUNC sha512_hash(const void *buffer, size_t len, sha512_ctx_t *ctx)
         if (in_buf != 0) {
                 unsigned add;
 
-                add = sizeof(ctx->wbuffer)/2 - in_buf;
+                add = sizeof(ctx->wbuffer) - in_buf;
                 if (add > len)
                         add = len;
-                memcpy(&ctx->wbuffer[in_buf], buffer, add);
+                memcpy(ctx->wbuffer + in_buf, buffer, add);
                 in_buf += add;
 
-                if (in_buf < sizeof(ctx->wbuffer)/2)
+                if (in_buf < sizeof(ctx->wbuffer))
                         return;
 
                 sha512_process_block128(ctx->wbuffer, 128, ctx);
@@ -507,9 +502,8 @@ void FAST_FUNC sha512_hash(const void *buffer, size_t len, sha512_ctx_t *ctx)
                 }
         }
 
-        if (len > 0) {
+        if (len > 0)
                 memcpy(ctx->wbuffer, buffer, len);
-        }
 }
 
 
@@ -517,31 +511,29 @@ void FAST_FUNC sha1_end(void *resbuf, sha1_ctx_t *ctx)
 {
         unsigned i, pad, in_buf;
 
-        /* Pad the buffer to the next 64-byte boundary with 0x80,0,0,0... */
         in_buf = ctx->total64 & SHA1_MASK;
-        ((uint8_t *)ctx->wbuffer)[in_buf++] = 0x80;
-        pad = SHA1_BLOCK_SIZE - in_buf;
-        memset(((uint8_t *)ctx->wbuffer) + in_buf, 0, pad);
-
-        /* We need 1+8 or more empty positions, one for the padding byte
-         * (above) and eight for the length count.
-         * If there is not enough space, empty the buffer. */
-        if (pad < 8) {
-                sha1_process_block64(ctx);
-                memset(ctx->wbuffer, 0, SHA1_BLOCK_SIZE - 8);
-                ((uint8_t *)ctx->wbuffer)[0] = 0x80;
-        }
+        /* Pad the buffer to the next 64-byte boundary with 0x80,0,0,0... */
+        ctx->wbuffer[in_buf++] = 0x80;
 
-        /* Store the 64-bit counter of bits in the buffer in BE format */
-        {
-                uint64_t t = ctx->total64 << 3;
-                t = hton64(t);
-                /* wbuffer is suitably aligned for this */
-                *(uint64_t *) &ctx->wbuffer[14] = t;
+        /* This loop iterates either once or twice, no more, no less */
+        while (1) {
+                pad = SHA1_BLOCK_SIZE - in_buf;
+                memset(ctx->wbuffer + in_buf, 0, pad);
+                in_buf = 0;
+                /* Do we have enough space for the length count? */
+                if (pad >= 8) {
+                        /* Store the 64-bit counter of bits in the buffer in BE format */
+                        uint64_t t = ctx->total64 << 3;
+                        t = hton64(t);
+                        /* wbuffer is suitably aligned for this */
+                        *(uint64_t *) (&ctx->wbuffer[SHA1_BLOCK_SIZE - 8]) = t;
+                }
+                sha1_process_block64(ctx);
+                if (pad >= 8)
+                        break;
         }
 
-        sha1_process_block64(ctx);
-
+        /* This way we do not impose alignment constraints on resbuf: */
 #if BB_LITTLE_ENDIAN
         for (i = 0; i < ARRAY_SIZE(ctx->hash); ++i)
                 ctx->hash[i] = htonl(ctx->hash[i]);
@@ -553,23 +545,25 @@ void FAST_FUNC sha256_end(void *resbuf, sha256_ctx_t *ctx)
 {
         unsigned i, pad, in_buf;
 
-        /* Pad the buffer to the next 64-byte boundary with 0x80,0,0,0...
-           (FIPS 180-2:5.1.1)  */
         in_buf = ctx->total64 & 63;
-        pad = (in_buf >= 56 ? 64 + 56 - in_buf : 56 - in_buf);
-        memset(&ctx->wbuffer[in_buf], 0, pad);
-        ctx->wbuffer[in_buf] = 0x80;
-
-        /* Put the 64-bit file length in *bits* at the end of the buffer.  */
-        {
-                uint64_t t = ctx->total64 << 3;
-                t = hton64(t);
-                /* wbuffer is suitably aligned for this */
-                *(uint64_t *) &ctx->wbuffer[in_buf + pad] = t;
-        }
+        /* Pad the buffer to the next 64-byte boundary with 0x80,0,0,0...
+         * (FIPS 180-2:5.1.1)
+         */
+        ctx->wbuffer[in_buf++] = 0x80;
 
-        /* Process last bytes.  */
-        sha256_process_block64(ctx->wbuffer, in_buf + pad + 8, ctx);
+        while (1) {
+                pad = 64 - in_buf;
+                memset(ctx->wbuffer + in_buf, 0, pad);
+                in_buf = 0;
+                if (pad >= 8) {
+                        uint64_t t = ctx->total64 << 3;
+                        t = hton64(t);
+                        *(uint64_t *) (&ctx->wbuffer[64 - 8]) = t;
+                }
+                sha256_process_block64(ctx->wbuffer, 64, ctx);
+                if (pad >= 8)
+                        break;
+        }
 
 #if BB_LITTLE_ENDIAN
         for (i = 0; i < ARRAY_SIZE(ctx->hash); ++i)
@@ -582,17 +576,30 @@ void FAST_FUNC sha512_end(void *resbuf, sha512_ctx_t *ctx)
 {
         unsigned i, pad, in_buf;
 
-        /* Pad the buffer to the next 128-byte boundary with 0x80,0,0,0...
-           (FIPS 180-2:5.1.2)  */
         in_buf = ctx->total64[0] & 127;
-        pad = in_buf >= 112 ? 128 + 112 - in_buf : 112 - in_buf;
-        memset(&ctx->wbuffer[in_buf], 0, pad);
-        ctx->wbuffer[in_buf] = 0x80;
-
-        *(uint64_t *) &ctx->wbuffer[in_buf + pad + 8] = hton64(ctx->total64[0] << 3);
-        *(uint64_t *) &ctx->wbuffer[in_buf + pad] = hton64((ctx->total64[1] << 3) | (ctx->total64[0] >> 61));
+        /* Pad the buffer to the next 128-byte boundary with 0x80,0,0,0...
+         * (FIPS 180-2:5.1.2)
+         */
+        ctx->wbuffer[in_buf++] = 0x80;
 
-        sha512_process_block128(ctx->wbuffer, in_buf + pad + 16, ctx);
+        while (1) {
+                pad = 128 - in_buf;
+                memset(ctx->wbuffer + in_buf, 0, pad);
+                in_buf = 0;
+                if (pad >= 16) {
+                        /* Store the 128-bit counter of bits in the buffer in BE format */
+                        uint64_t t;
+                        t = ctx->total64[0] << 3;
+                        t = hton64(t);
+                        *(uint64_t *) (&ctx->wbuffer[128 - 8]) = t;
+                        t = (ctx->total64[1] << 3) | (ctx->total64[0] >> 61);
+                        t = hton64(t);
+                        *(uint64_t *) (&ctx->wbuffer[128 - 16]) = t;
+                }
+                sha512_process_block128(ctx->wbuffer, 128, ctx);
+                if (pad >= 16)
+                        break;
+        }
 
 #if BB_LITTLE_ENDIAN
         for (i = 0; i < ARRAY_SIZE(ctx->hash); ++i)