bug fixed in md5-asm.S ( wrong values for length_b%512=505..511 )

[avr-crypto-lib.git] / md5-asm.S

diff --git a/md5-asm.S b/md5-asm.S
index 469f9ab7535e56efdf255c739fb09e6b4df44547..de3b170092330281674357475131a58019413d22 100644 (file)
--- a/md5-asm.S
+++ b/md5-asm.S
@@ -785,6 +785,7 @@ md5_lastBlock:
        movw r16, r20 /* length_b  */ 
        movw r14, r22 /* block_ptr */
        movw r12, r24 /* state_ptr */
+       ldi r18, 64
 2:
        cpi r17, 2 /* hi8(512) */       
        brlo 2f
@@ -792,7 +793,6 @@ md5_lastBlock:
        movw r24, r12
        movw r22, r14
        rcall md5_nextBlock
-       ldi r18, 64
        add r14, r18
        adc r15, r1
        subi r17, 2
@@ -801,58 +801,59 @@ md5_lastBlock:
        pop r31
        pop r30
 
-       adiw r30, 1
+       adiw r30, 1 /* adjust Z to point to buffer */
        movw r26, r14
        movw r24, r16
        adiw r24, 7
 
        lsr r25
        ror r24
-       lsr r24
+       lsr r25
+       ror r24
        lsr r24 /* r24 now holds how many bytes are to copy */
-       ldi r18, 64
-       sub r18, r24
+    ldi r18, 64
+       sub r18, r24 /* r18 will hold the amount of used bytes in buffer */
        tst r24
 4:
        breq 5f
        ld r0, X+
-       st Z+, r0
+       st Z+, r0 
        dec r24
-       rjmp 4b
+       rjmp 4b /* Z points to the byte after msg in buffer */
 5:     /* append 1-bit */
        mov r20, r16
+       ldi r19, 0x80
        andi r20, 0x07
        brne bit_fucking
-       ldi r19, 0x80
        st Z+, r19
-       dec r18
+       dec r18 /* 'allocate' another byte in buffer */
        rjmp after_bit_fucking
 bit_fucking:
-       ldi r19, 0x80
 1:
        lsr r19
        dec r20
        brne 1b
        or r0, r19
        st -Z, r0
-       adiw r30, 1
+    adiw r30, 1
 after_bit_fucking:
        clt     
        cpi r18, 8
        brmi 2f
-       set         /* store in t if the counter will also fit in this block */
+       set         /* store in t if the counter will also fit in this block (1 if fit)*/
 2:
        tst r18
        breq 2f
-1:
+1: /* fill remaning buffer with zeros */
        st Z+, r1
        dec r18
        brne 1b
 2:
        sbiw r30, 63
        sbiw r30,  1
-       movw r14, r30   
+       movw r14, r30 /* r14:r15 now points to buffer */        
        brts load_counter
+       /* counter does not fit, finalize this block */
        movw r24, r12
        movw r22, r14
        rcall md5_nextBlock
@@ -864,13 +865,14 @@ after_bit_fucking:
        brne 3b
        
 load_counter:          
-       movw r26, r12
+       movw r26, r12 /* X points to state */
        adiw r26, 16
        ld r19, X+
        ld r20, X+
        ld r21, X+
        ld r22, X+
-       brts post_counter_decrement     
+       brts post_counter_decrement     /* do not decremen because counter fits */
+counter_decrement:
        subi r19, 1
        sbci r20, 0
        sbci r21, 0
@@ -883,8 +885,8 @@ post_counter_decrement:
        rol r21
        rol r22
        rol r23
-       add r18, r16
-       adc r19, r17
+       mov r18, r16 /* r16:r17 length_b */
+       add r19, r17
        adc r20, r1
        adc r21, r1
        adc r22, r1