Add aesni_gcm_mult()
diff --git a/library/aesni.c b/library/aesni.c
index 9b41c36..0431f78 100644
--- a/library/aesni.c
+++ b/library/aesni.c
@@ -25,6 +25,7 @@
/*
* [AES-WP] http://software.intel.com/en-us/articles/intel-advanced-encryption-standard-aes-instructions-set
+ * [CLMUL-WP] http://software.intel.com/en-us/articles/intel-carry-less-multiplication-instruction-and-its-usage-for-computing-the-gcm-mode/
*/
#include "polarssl/config.h"
@@ -101,6 +102,119 @@
return( 0 );
}
+
+/*
+ * GCM multiplication: c = a times b in GF(2^128)
+ * Based on [CLMUL-WP] algorithms 1 (with equation 27) and 5.
+ */
+int aesni_gcm_mult( unsigned char c[16],
+ const unsigned char a[16],
+ const unsigned char b[16] )
+{
+ unsigned char aa[16], bb[16], cc[16];
+ size_t i;
+
+ /* The inputs are in big-endian order, so byte-reverse them */
+ for( i = 0; i < 16; i++ )
+ {
+ aa[i] = a[15 - i];
+ bb[i] = b[15 - i];
+ }
+
+ asm( "movdqu (%0), %%xmm0 \n" // a1:a0
+ "movdqu (%1), %%xmm1 \n" // b1:b0
+
+ /*
+ * Caryless multiplication xmm2:xmm1 = xmm0 * xmm1
+ * using [CLMUL-WP] algorithm 1 (p. 13).
+ */
+ "movdqa %%xmm1, %%xmm2 \n" // copy of b1:b0
+ "movdqa %%xmm1, %%xmm3 \n" // same
+ "movdqa %%xmm1, %%xmm4 \n" // same
+ "pclmulqdq $0x00, %%xmm0, %%xmm1 \n" // a0*b0 = c1:c0
+ "pclmulqdq $0x11, %%xmm0, %%xmm2 \n" // a1*b1 = d1:d0
+ "pclmulqdq $0x10, %%xmm0, %%xmm3 \n" // a0*b1 = e1:e0
+ "pclmulqdq $0x01, %%xmm0, %%xmm4 \n" // a1*b0 = f1:f0
+ "pxor %%xmm3, %%xmm4 \n" // e1+f1:e0+f0
+ "movdqa %%xmm4, %%xmm3 \n" // same
+ "psrldq $8, %%xmm4 \n" // 0:e1+f1
+ "pslldq $8, %%xmm3 \n" // e0+f0:0
+ "pxor %%xmm4, %%xmm2 \n" // d1:d0+e1+f1
+ "pxor %%xmm3, %%xmm1 \n" // c1+e0+f1:c0
+
+ /*
+ * Now shift the result one bit to the left,
+ * taking advantage of [CLMUL-WP] eq 27 (p. 20)
+ */
+ "movdqa %%xmm1, %%xmm3 \n" // r1:r0
+ "movdqa %%xmm2, %%xmm4 \n" // r3:r2
+ "psllq $1, %%xmm1 \n" // r1<<1:r0<<1
+ "psllq $1, %%xmm2 \n" // r3<<1:r2<<1
+ "psrlq $63, %%xmm3 \n" // r1>>63:r0>>63
+ "psrlq $63, %%xmm4 \n" // r3>>63:r2>>63
+ "movdqa %%xmm3, %%xmm5 \n" // r1>>63:r0>>63
+ "pslldq $8, %%xmm3 \n" // r0>>63:0
+ "pslldq $8, %%xmm4 \n" // r2>>63:0
+ "psrldq $8, %%xmm5 \n" // 0:r1>>63
+ "por %%xmm3, %%xmm1 \n" // r1<<1|r0>>63:r0<<1
+ "por %%xmm4, %%xmm2 \n" // r3<<1|r2>>62:r2<<1
+ "por %%xmm5, %%xmm2 \n" // r3<<1|r2>>62:r2<<1|r1>>63
+
+ /*
+ * Now reduce modulo the GCM polynomial x^128 + x^7 + x^2 + x + 1
+ * using [CLMUL-WP] algorithm 5 (p. 20).
+ * Currently xmm2:xmm1 holds x3:x2:x1:x0 (already shifted).
+ */
+ /* Step 2 (1) */
+ "movdqa %%xmm1, %%xmm3 \n" // x1:x0
+ "movdqa %%xmm1, %%xmm4 \n" // same
+ "movdqa %%xmm1, %%xmm5 \n" // same
+ "psllq $63, %%xmm3 \n" // x1<<63:x0<<63 = stuff:a
+ "psllq $62, %%xmm4 \n" // x1<<62:x0<<62 = stuff:b
+ "psllq $57, %%xmm5 \n" // x1<<57:x0<<57 = stuff:c
+
+ /* Step 2 (2) */
+ "pxor %%xmm4, %%xmm3 \n" // stuff:a+b
+ "pxor %%xmm5, %%xmm3 \n" // stuff:a+b+c
+ "pslldq $8, %%xmm3 \n" // a+b+c:0
+ "pxor %%xmm3, %%xmm1 \n" // x1+a+b+c:x0 = d:x0
+
+ /* Steps 3 and 4 */
+ "movdqa %%xmm1,%%xmm0 \n" // d:x0
+ "movdqa %%xmm1,%%xmm4 \n" // same
+ "movdqa %%xmm1,%%xmm5 \n" // same
+ "psrlq $1, %%xmm0 \n" // e1:x0>>1 = e1:e0'
+ "psrlq $2, %%xmm4 \n" // f1:x0>>2 = f1:f0'
+ "psrlq $7, %%xmm5 \n" // g1:x0>>7 = g1:g0'
+ "pxor %%xmm4, %%xmm0 \n" // e1+f1:e0'+f0'
+ "pxor %%xmm5, %%xmm0 \n" // e1+f1+g1:e0'+f0'+g0'
+ // e0'+f0'+g0' is almost e0+f0+g0, except for some missing
+ // bits carried from d. Now get those bits back in.
+ "movdqa %%xmm1,%%xmm3 \n" // d:x0
+ "movdqa %%xmm1,%%xmm4 \n" // same
+ "movdqa %%xmm1,%%xmm5 \n" // same
+ "psllq $63, %%xmm3 \n" // d<<63:stuff
+ "psllq $62, %%xmm4 \n" // d<<62:stuff
+ "psllq $57, %%xmm5 \n" // d<<57:stuff
+ "pxor %%xmm4, %%xmm3 \n" // d<<63+d<<62:stuff
+ "pxor %%xmm5, %%xmm3 \n" // missing bits of d:stuff
+ "psrldq $8, %%xmm3 \n" // 0:missing bits of d
+ "pxor %%xmm3, %%xmm0 \n" // e1+f1+g1:e0+f0+g0
+ "pxor %%xmm1, %%xmm0 \n" // h1:h0
+ "pxor %%xmm2, %%xmm0 \n" // x3+h1:x2+h0
+
+ "movdqu %%xmm0, (%2) \n" // done
+ :
+ : "r" (aa), "r" (bb), "r" (cc)
+ : "memory", "cc", "xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5" );
+
+ /* Now byte-reverse the outputs */
+ for( i = 0; i < 16; i++ )
+ c[i] = cc[15 - i];
+
+ return( 0 );
+}
+
#endif /* POLARSSL_HAVE_X86_64 */
#endif /* POLARSSL_AESNI_C */