[Numbers][PATCH] Make cryptoapi non-optional?

[Matt Mackall]

On Sun, Aug 10, 2003 at 09:54:22PM -0700, David S. Miller wrote:
> There is no reason why random.c's usage of the crypto-API cannot be
> done cleanly and efficiently such that it is both faster and resulting
> in smaller code size than what random.c uses now.  All of this _WITHOUT_
> bypassing and compromising the well designed crypto API interfaces to these
> transformations.

Alright, here's the current state of this, with some numbers to back
it up. Below is my current random -> cryptoapi patch, which sets up
per-cpu crypto tfms at init time and is fairly straightforward. Would
be nice if it didn't block preemption while hashing but that's a
general downside of anything per_cpu. It applies on top of a bunch of
other small stuff that I'll get around to posting eventually. But this
should be enough for discussion.

I built three 2.6.0-test3-mm1 kernels with gcc 3.3.1 for my Athlon:

native   - current /dev/random SHA1 plus some WIP, no cryptoapi
unrolled - /dev/random modified to use cryptoapi's unrolled SHA1
           with its own SHA code dropped
rolled   - like unrolled but with a cryptoapi SHA1 implementation as
           close to the original as reasonable

   text    data     bss     dec     hex filename bandwidth  code data
2413597  477694  157224 3048515  2e8443 native    17.6MB/s  1906  594
2421648  478951  157224 3057823  2ea89f rolled    14.0MB/s  1913  599
2427280  478944  157224 3063448  2ebe98 unrolled  17.5MB/s  1918  598

(bandwidth here is 'cat /dev/random | pipeview > /dev/null')

So the size penalty for cryptoapi in itself looks to be about 8k+5k
currently. Going to the unrolled SHA1 costs another 5k(!).

I also built a couple custom kernels to let me calculate the overhead
of various parts of the process and the raw algorithm speed.

1/o     = Null /dev/urandom hash function =  60.3MB/s
1/(o+c) = Null cryptoapi hash function    =  32.9MB/s

This lets us calculate:

1/c = cryptoapi null through (aka overhead)= 72.4MB/s (mostly memcpy?)
1/n = native SHA1 implementation           = 24.9MB/s
1/r = "rolled" cryptoapi SHA1 - overhead   = 24.4MB/s (extra memset)
1/u = unrolled SHA1 in cryptoapi - overhead= 37.4MB/s

So unrolled is about 50% faster and looking at the size of the .o
files (2.2 vs 7.8k), almost 4 times bigger. And about a third of the
time spent hashing with the cryptoapi is bookkeeping and buffering
overhead.

So we've got a few ways to proceed:

a) keep two copies of SHA around
b) cryptoapi+sha become non-optional (+optional rolled version)
c) somebody exports raw SHA transform and cryptoapi stays optional

(The big downside of c) is we won't be able to easily plugin different
transforms)

diff -urN -X dontdiff orig/drivers/char/mem.c work/drivers/char/mem.c
--- orig/drivers/char/mem.c	2003-07-13 22:34:32.000000000 -0500
+++ work/drivers/char/mem.c	2003-08-12 21:18:51.000000000 -0500
@@ -680,7 +680,6 @@
 				S_IFCHR | devlist[i].mode, devlist[i].name);
 	}
 	
-	rand_initialize();
 #if defined (CONFIG_FB)
 	fbmem_init();
 #endif
diff -urN -X dontdiff orig/drivers/char/random.c work/drivers/char/random.c
--- orig/drivers/char/random.c	2003-08-12 21:18:53.000000000 -0500
+++ work/drivers/char/random.c	2003-08-12 21:22:01.000000000 -0500
@@ -249,11 +249,16 @@
 #include <linux/genhd.h>
 #include <linux/interrupt.h>
 #include <linux/spinlock.h>
+#include <linux/crypto.h>
+#include <linux/cpu.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
 
 #include <asm/processor.h>
 #include <asm/uaccess.h>
 #include <asm/irq.h>
 #include <asm/io.h>
+#include <asm/scatterlist.h>
 
 /*
  * Configuration information
@@ -360,7 +365,7 @@
  * modulo the generator polymnomial.  Now, for random primitive polynomials,
  * this is a universal class of hash functions, meaning that the chance
  * of a collision is limited by the attacker's knowledge of the generator
- * polynomail, so if it is chosen at random, an attacker can never force
+ * polynomial, so if it is chosen at random, an attacker can never force
  * a collision.  Here, we use a fixed polynomial, but we *can* assume that
  * ###--> it is unknown to the processes generating the input entropy. <-###
  * Because of this important property, this is a good, collision-resistant
@@ -374,6 +379,8 @@
 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
 
+static DEFINE_PER_CPU(struct crypto_tfm *, sha_tfm);
+
 /*
  * Forward procedure declarations
  */
@@ -775,122 +782,6 @@
 	add_timer_randomness(disk->random, 0x100+MKDEV(disk->major, disk->first_minor));
 }
 
-/******************************************************************
- *
- * Hash function definition
- *
- *******************************************************************/
-
-/*
- * This chunk of code defines a function
- * void SHATransform(__u32 digest[HASH_BUFFER_SIZE + HASH_EXTRA_SIZE],
- * 		__u32 const data[16])
- * 
- * The function hashes the input data to produce a digest in the first
- * HASH_BUFFER_SIZE words of the digest[] array, and uses HASH_EXTRA_SIZE
- * more words for internal purposes.  (This buffer is exported so the
- * caller can wipe it once rather than this code doing it each call,
- * and tacking it onto the end of the digest[] array is the quick and
- * dirty way of doing it.)
- *
- * For /dev/random purposes, the length of the data being hashed is
- * fixed in length, so appending a bit count in the usual way is not
- * cryptographically necessary.
- */
-
-#define HASH_BUFFER_SIZE 5
-#define HASH_EXTRA_SIZE 80
-
-/*
- * SHA transform algorithm, taken from code written by Peter Gutmann,
- * and placed in the public domain.
- */
-
-/* The SHA f()-functions.  */
-
-#define f1(x,y,z)   ( z ^ (x & (y^z)) )		/* Rounds  0-19: x ? y : z */
-#define f2(x,y,z)   (x ^ y ^ z)			/* Rounds 20-39: XOR */
-#define f3(x,y,z)   ( (x & y) + (z & (x ^ y)) )	/* Rounds 40-59: majority */
-#define f4(x,y,z)   (x ^ y ^ z)			/* Rounds 60-79: XOR */
-
-/* The SHA Mysterious Constants */
-
-#define K1  0x5A827999L			/* Rounds  0-19: sqrt(2) * 2^30 */
-#define K2  0x6ED9EBA1L			/* Rounds 20-39: sqrt(3) * 2^30 */
-#define K3  0x8F1BBCDCL			/* Rounds 40-59: sqrt(5) * 2^30 */
-#define K4  0xCA62C1D6L			/* Rounds 60-79: sqrt(10) * 2^30 */
-
-#define ROTL(n,X)  ( ( ( X ) << n ) | ( ( X ) >> ( 32 - n ) ) )
-
-#define subRound(a, b, c, d, e, f, k, data) \
-    ( e += ROTL( 5, a ) + f( b, c, d ) + k + data, b = ROTL( 30, b ) )
-
-
-static void SHATransform(__u32 digest[85], __u32 const data[16])
-{
-    __u32 A, B, C, D, E;     /* Local vars */
-    __u32 TEMP;
-    int	i;
-#define W (digest + HASH_BUFFER_SIZE)	/* Expanded data array */
-
-    /*
-     * Do the preliminary expansion of 16 to 80 words.  Doing it
-     * out-of-line line like this is faster than doing it in-line on
-     * register-starved machines like the x86, and not really any
-     * slower on real processors.
-     */
-    memcpy(W, data, 16*sizeof(__u32));
-    for (i = 0; i < 64; i++) {
-	    TEMP = W[i] ^ W[i+2] ^ W[i+8] ^ W[i+13];
-	    W[i+16] = ROTL(1, TEMP);
-    }
-
-    /* Set up first buffer and local data buffer */
-    A = digest[ 0 ];
-    B = digest[ 1 ];
-    C = digest[ 2 ];
-    D = digest[ 3 ];
-    E = digest[ 4 ];
-
-    /* Heavy mangling, in 4 sub-rounds of 20 iterations each. */
-    for (i = 0; i < 80; i++) {
-	if (i < 40) {
-	    if (i < 20)
-		TEMP = f1(B, C, D) + K1;
-	    else
-		TEMP = f2(B, C, D) + K2;
-	} else {
-	    if (i < 60)
-		TEMP = f3(B, C, D) + K3;
-	    else
-		TEMP = f4(B, C, D) + K4;
-	}
-	TEMP += ROTL(5, A) + E + W[i];
-	E = D; D = C; C = ROTL(30, B); B = A; A = TEMP;
-    }
-
-    /* Build message digest */
-    digest[ 0 ] += A;
-    digest[ 1 ] += B;
-    digest[ 2 ] += C;
-    digest[ 3 ] += D;
-    digest[ 4 ] += E;
-
-	/* W is wiped by the caller */
-#undef W
-}
-
-#undef ROTL
-#undef f1
-#undef f2
-#undef f3
-#undef f4
-#undef K1	
-#undef K2
-#undef K3	
-#undef K4	
-#undef subRound
-
 /*********************************************************************
  *
  * Entropy extraction routines
@@ -899,8 +790,6 @@
 
 #define EXTRACT_ENTROPY_USER		1
 #define EXTRACT_ENTROPY_LIMIT		2
-#define TMP_BUF_SIZE			(HASH_BUFFER_SIZE + HASH_EXTRA_SIZE)
-#define SEC_XFER_SIZE			(TMP_BUF_SIZE*4)
 
 static ssize_t extract_entropy(struct entropy_store *r, void * buf,
 			       size_t nbytes, int flags);
@@ -912,7 +801,7 @@
  */
 static void reseed_pool(struct entropy_store *r, int margin, int wanted)
 {
-	__u32 tmp[TMP_BUF_SIZE];
+	__u32 tmp[32]; /* 256 bits */
 	int bytes;
 
 	DEBUG_ENT("reseed %s wants %d bits (margin %d)\n",
@@ -948,9 +837,10 @@
 			       size_t nbytes, int flags)
 {
 	ssize_t ret, i, pos;
-	__u32 tmp[TMP_BUF_SIZE];
-	__u32 x;
 	unsigned long cpuflags;
+	struct crypto_tfm *tfm;
+	struct scatterlist sg[1];
+	__u32 hash[5]; /* 160 bits */
 
 	/* Hold lock while accounting */
 	spin_lock_irqsave(&r->lock, cpuflags);
@@ -986,18 +876,15 @@
 			}
 
 			DEBUG_ENT("extract sleep (%d bytes left)\n", nbytes);
-
 			schedule();
-
 			DEBUG_ENT("extract wake\n");
 		}
 
-		/* Hash the pool to get the output */
-		tmp[0] = 0x67452301;
-		tmp[1] = 0xefcdab89;
-		tmp[2] = 0x98badcfe;
-		tmp[3] = 0x10325476;
-		tmp[4] = 0xc3d2e1f0;
+		/* Pick a position in the pool to hash from */
+		pos = r->pos;
+		if(pos > r->poolinfo->poolwords - 15)
+			pos=0;
+		r->pos = pos + 1;
 
 		/* Pick a position in the pool to hash from */
 		pos = r->pos;
@@ -1015,26 +902,32 @@
 		 * backtrack prevention over catastrophic reseeding.
 		 */
 
-		SHATransform(tmp, r->pool + pos);
-		add_entropy_words(r, tmp, HASH_BUFFER_SIZE);
+		sg[0].page = virt_to_page(r->pool + pos);
+		sg[0].offset = ((long)(r->pool + pos) & ~PAGE_MASK);
+		/* avoid padding overhead in cryptoapi */
+		sg[0].length = 56;
+		tfm=get_cpu_var(sha_tfm);
+		crypto_digest_digest(tfm, sg, 1, (char *)hash);
+		put_cpu_var(sha_tfm);
+		add_entropy_words(r, hash, 5);
 		
 		/* Copy data to destination buffer */
-		i = min(nbytes, HASH_BUFFER_SIZE*sizeof(__u32));
+		i = min(nbytes, sizeof(hash));
 		if (flags & EXTRACT_ENTROPY_USER) {
-			i -= copy_to_user(buf, (__u8 const *)tmp, i);
+			i -= copy_to_user(buf, (__u8 const *)hash, i);
 			if (!i) {
 				ret = -EFAULT;
 				break;
 			}
 		} else
-			memcpy(buf, (__u8 const *)tmp, i);
+			memcpy(buf, (__u8 const *)hash, i);
 		nbytes -= i;
 		buf += i;
 		ret += i;
 	}
 
 	/* Wipe data just returned from memory */
-	memset(tmp, 0, sizeof(tmp));
+	memset(hash, 0, sizeof(hash));
 	
 	return ret;
 }
@@ -1093,7 +986,25 @@
 	}
 }
 
-void __init rand_initialize(void)
+static int random_cpu_notify(struct notifier_block *self,
+				unsigned long action, void *hcpu)
+{
+	if (action == CPU_UP_PREPARE)
+	{
+		per_cpu(sha_tfm, (long)hcpu) = crypto_alloc_tfm("sha1", 0);
+
+		printk(KERN_NOTICE "random cpu %ld sha_tfm = %p\n",
+		       (long)hcpu, per_cpu(sha_tfm, (long)hcpu));
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block random_nb = {
+	.notifier_call = random_cpu_notify,
+};
+
+static int __init init_random(void)
 {
 	int i;
 
@@ -1103,10 +1014,14 @@
 						"nonblocking");
 
 	if(!(input_pool && blocking_pool && nonblocking_pool))
-		return;
+		return -ENOMEM;
 
-	if(batch_entropy_init(BATCH_ENTROPY_SIZE))
-		return;
+	if((i=batch_entropy_init(BATCH_ENTROPY_SIZE)) != 0)
+		return i;
+
+	random_cpu_notify(&random_nb, (unsigned long)CPU_UP_PREPARE,
+				(void *)(long)smp_processor_id());
+	register_cpu_notifier(&random_nb);
 
 	init_std_data(input_pool);
 	sysctl_init_random(input_pool);
@@ -1115,8 +1030,12 @@
 		irq_timer_state[i] = NULL;
 	memset(&keyboard_timer_state, 0, sizeof(struct timer_rand_state));
 	memset(&mouse_timer_state, 0, sizeof(struct timer_rand_state));
+
+	return 0;
 }
 
+__initcall(init_random);
+
 void rand_initialize_irq(int irq)
 {
 	struct timer_rand_state *state;
@@ -1153,15 +1072,10 @@
 static ssize_t
 random_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos)
 {
-	ssize_t			n, retval = 0, count = 0;
+	ssize_t	n, retval = 0, count = 0;
 	
-	if (nbytes == 0)
-		return 0;
-
 	while (nbytes > 0) {
-		n = nbytes;
-		if (n > SEC_XFER_SIZE)
-			n = SEC_XFER_SIZE;
+		n = min_t(size_t, nbytes, BLOCKING_POOL_SIZE/8);
 
 		/* We can take all the entropy in the input pool */
 		reseed_pool(blocking_pool, 0, n);
@@ -1839,13 +1753,16 @@
 #define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
 
 static int	syncookie_init;
-static __u32	syncookie_secret[2][16-3+HASH_BUFFER_SIZE];
+static __u32	syncookie_secret[2][16-3];
 
 __u32 secure_tcp_syn_cookie(__u32 saddr, __u32 daddr, __u16 sport,
 		__u16 dport, __u32 sseq, __u32 count, __u32 data)
 {
-	__u32 	tmp[16 + HASH_BUFFER_SIZE + HASH_EXTRA_SIZE];
-	__u32	seq;
+	__u32 tmp[16]; /* 512 bits */
+	__u32 hash[5]; /* 160 bits */
+	__u32 seq;
+	struct crypto_tfm *tfm;
+	struct scatterlist sg[1];
 
 	/*
 	 * Pick two random secrets the first time we need a cookie.
@@ -1866,22 +1783,27 @@
 	 * MSS into the second hash value.
 	 */
 
-	memcpy(tmp+3, syncookie_secret[0], sizeof(syncookie_secret[0]));
+	sg[0].page = virt_to_page(tmp);
+	sg[0].offset = ((long) tmp & ~PAGE_MASK);
+	sg[0].length = sizeof(tmp);
+
 	tmp[0]=saddr;
 	tmp[1]=daddr;
 	tmp[2]=(sport << 16) + dport;
-	SHATransform(tmp+16, tmp);
-	seq = tmp[17] + sseq + (count << COOKIEBITS);
+
+	memcpy(tmp+3, syncookie_secret[0], sizeof(syncookie_secret[0]));
+	tfm = get_cpu_var(sha_tfm);
+	crypto_digest_digest(tfm, sg, 1, (char *)hash);
+
+	seq = hash[1] + sseq + (count << COOKIEBITS);
 
 	memcpy(tmp+3, syncookie_secret[1], sizeof(syncookie_secret[1]));
-	tmp[0]=saddr;
-	tmp[1]=daddr;
-	tmp[2]=(sport << 16) + dport;
 	tmp[3] = count;	/* minute counter */
-	SHATransform(tmp+16, tmp);
+	crypto_digest_digest(tfm, sg, 1, (char *)hash);
+	put_cpu_var(sha_tfm);
 
 	/* Add in the second hash and the data */
-	return seq + ((tmp[17] + data) & COOKIEMASK);
+	return seq + ((hash[1] + data) & COOKIEMASK);
 }
 
 /*
@@ -1896,19 +1818,30 @@
 __u32 check_tcp_syn_cookie(__u32 cookie, __u32 saddr, __u32 daddr, __u16 sport,
 		__u16 dport, __u32 sseq, __u32 count, __u32 maxdiff)
 {
-	__u32 	tmp[16 + HASH_BUFFER_SIZE + HASH_EXTRA_SIZE];
-	__u32	diff;
+	__u32 tmp[16]; /* 512 bits */
+	__u32 hash[5]; /* 160 bits */
+	__u32 diff;
+	struct crypto_tfm *tfm;
+	struct scatterlist sg[1];
 
 	if (syncookie_init == 0)
 		return (__u32)-1;	/* Well, duh! */
 
-	/* Strip away the layers from the cookie */
-	memcpy(tmp+3, syncookie_secret[0], sizeof(syncookie_secret[0]));
+	sg[0].page = virt_to_page(tmp);
+	sg[0].offset = ((long) tmp & ~PAGE_MASK);
+	sg[0].length = sizeof(tmp);
+
 	tmp[0]=saddr;
 	tmp[1]=daddr;
 	tmp[2]=(sport << 16) + dport;
-	SHATransform(tmp+16, tmp);
-	cookie -= tmp[17] + sseq;
+
+	/* Strip away the layers from the cookie */
+	memcpy(tmp+3, syncookie_secret[0], sizeof(syncookie_secret[0]));
+	tfm = get_cpu_var(sha_tfm);
+	crypto_digest_digest(tfm, sg, 1, (char *)hash);
+	put_cpu_var(sha_tfm);
+
+	cookie -= hash[1] + sseq;
 	/* Cookie is now reduced to (count * 2^24) ^ (hash % 2^24) */
 
 	diff = (count - (cookie >> COOKIEBITS)) & ((__u32)-1 >> COOKIEBITS);
@@ -1916,13 +1849,12 @@
 		return (__u32)-1;
 
 	memcpy(tmp+3, syncookie_secret[1], sizeof(syncookie_secret[1]));
-	tmp[0] = saddr;
-	tmp[1] = daddr;
-	tmp[2] = (sport << 16) + dport;
 	tmp[3] = count - diff;	/* minute counter */
-	SHATransform(tmp+16, tmp);
+	tfm = get_cpu_var(sha_tfm);
+	crypto_digest_digest(tfm, sg, 1, (char *)hash);
+	put_cpu_var(sha_tfm);
 
-	return (cookie - tmp[17]) & COOKIEMASK;	/* Leaving the data behind */
+	return (cookie - hash[1]) & COOKIEMASK;	/* Leaving the data behind */
 }
 #endif
 


-- 
Matt Mackall : http://www.selenic.com : of or relating to the moon
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