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      1 /* SHA module */
      2 
      3 /* This module provides an interface to NIST's Secure Hash Algorithm */
      4 
      5 /* See below for information about the original code this module was
      6    based upon. Additional work performed by:
      7 
      8    Andrew Kuchling (amk (at) amk.ca)
      9    Greg Stein (gstein (at) lyra.org)
     10 
     11    Copyright (C) 2005   Gregory P. Smith (greg (at) krypto.org)
     12    Licensed to PSF under a Contributor Agreement.
     13 
     14 */
     15 
     16 /* SHA objects */
     17 
     18 #include "Python.h"
     19 #include "structmember.h"
     20 
     21 
     22 /* Endianness testing and definitions */
     23 #define TestEndianness(variable) {int i=1; variable=PCT_BIG_ENDIAN;\
     24         if (*((char*)&i)==1) variable=PCT_LITTLE_ENDIAN;}
     25 
     26 #define PCT_LITTLE_ENDIAN 1
     27 #define PCT_BIG_ENDIAN 0
     28 
     29 /* Some useful types */
     30 
     31 typedef unsigned char SHA_BYTE;
     32 
     33 #if SIZEOF_INT == 4
     34 typedef unsigned int SHA_INT32; /* 32-bit integer */
     35 #else
     36 /* not defined. compilation will die. */
     37 #endif
     38 
     39 /* The SHA block size and message digest sizes, in bytes */
     40 
     41 #define SHA_BLOCKSIZE    64
     42 #define SHA_DIGESTSIZE  20
     43 
     44 /* The structure for storing SHS info */
     45 
     46 typedef struct {
     47     PyObject_HEAD
     48     SHA_INT32 digest[5];                /* Message digest */
     49     SHA_INT32 count_lo, count_hi;       /* 64-bit bit count */
     50     SHA_BYTE data[SHA_BLOCKSIZE];       /* SHA data buffer */
     51     int Endianness;
     52     int local;                          /* unprocessed amount in data */
     53 } SHAobject;
     54 
     55 /* When run on a little-endian CPU we need to perform byte reversal on an
     56    array of longwords. */
     57 
     58 static void longReverse(SHA_INT32 *buffer, int byteCount, int Endianness)
     59 {
     60     SHA_INT32 value;
     61 
     62     if ( Endianness == PCT_BIG_ENDIAN )
     63         return;
     64 
     65     byteCount /= sizeof(*buffer);
     66     while (byteCount--) {
     67         value = *buffer;
     68         value = ( ( value & 0xFF00FF00L ) >> 8  ) | \
     69                 ( ( value & 0x00FF00FFL ) << 8 );
     70         *buffer++ = ( value << 16 ) | ( value >> 16 );
     71     }
     72 }
     73 
     74 static void SHAcopy(SHAobject *src, SHAobject *dest)
     75 {
     76     dest->Endianness = src->Endianness;
     77     dest->local = src->local;
     78     dest->count_lo = src->count_lo;
     79     dest->count_hi = src->count_hi;
     80     memcpy(dest->digest, src->digest, sizeof(src->digest));
     81     memcpy(dest->data, src->data, sizeof(src->data));
     82 }
     83 
     84 
     85 /* ------------------------------------------------------------------------
     86  *
     87  * This code for the SHA algorithm was noted as public domain. The original
     88  * headers are pasted below.
     89  *
     90  * Several changes have been made to make it more compatible with the
     91  * Python environment and desired interface.
     92  *
     93  */
     94 
     95 /* NIST Secure Hash Algorithm */
     96 /* heavily modified by Uwe Hollerbach <uh (at) alumni.caltech edu> */
     97 /* from Peter C. Gutmann's implementation as found in */
     98 /* Applied Cryptography by Bruce Schneier */
     99 /* Further modifications to include the "UNRAVEL" stuff, below */
    100 
    101 /* This code is in the public domain */
    102 
    103 /* UNRAVEL should be fastest & biggest */
    104 /* UNROLL_LOOPS should be just as big, but slightly slower */
    105 /* both undefined should be smallest and slowest */
    106 
    107 #define UNRAVEL
    108 /* #define UNROLL_LOOPS */
    109 
    110 /* The SHA f()-functions.  The f1 and f3 functions can be optimized to
    111    save one boolean operation each - thanks to Rich Schroeppel,
    112    rcs (at) cs.arizona.edu for discovering this */
    113 
    114 /*#define f1(x,y,z)     ((x & y) | (~x & z))            // Rounds  0-19 */
    115 #define f1(x,y,z)       (z ^ (x & (y ^ z)))             /* Rounds  0-19 */
    116 #define f2(x,y,z)       (x ^ y ^ z)                     /* Rounds 20-39 */
    117 /*#define f3(x,y,z)     ((x & y) | (x & z) | (y & z))   // Rounds 40-59 */
    118 #define f3(x,y,z)       ((x & y) | (z & (x | y)))       /* Rounds 40-59 */
    119 #define f4(x,y,z)       (x ^ y ^ z)                     /* Rounds 60-79 */
    120 
    121 /* SHA constants */
    122 
    123 #define CONST1          0x5a827999L                     /* Rounds  0-19 */
    124 #define CONST2          0x6ed9eba1L                     /* Rounds 20-39 */
    125 #define CONST3          0x8f1bbcdcL                     /* Rounds 40-59 */
    126 #define CONST4          0xca62c1d6L                     /* Rounds 60-79 */
    127 
    128 /* 32-bit rotate */
    129 
    130 #define R32(x,n)        ((x << n) | (x >> (32 - n)))
    131 
    132 /* the generic case, for when the overall rotation is not unraveled */
    133 
    134 #define FG(n)   \
    135     T = R32(A,5) + f##n(B,C,D) + E + *WP++ + CONST##n;  \
    136     E = D; D = C; C = R32(B,30); B = A; A = T
    137 
    138 /* specific cases, for when the overall rotation is unraveled */
    139 
    140 #define FA(n)   \
    141     T = R32(A,5) + f##n(B,C,D) + E + *WP++ + CONST##n; B = R32(B,30)
    142 
    143 #define FB(n)   \
    144     E = R32(T,5) + f##n(A,B,C) + D + *WP++ + CONST##n; A = R32(A,30)
    145 
    146 #define FC(n)   \
    147     D = R32(E,5) + f##n(T,A,B) + C + *WP++ + CONST##n; T = R32(T,30)
    148 
    149 #define FD(n)   \
    150     C = R32(D,5) + f##n(E,T,A) + B + *WP++ + CONST##n; E = R32(E,30)
    151 
    152 #define FE(n)   \
    153     B = R32(C,5) + f##n(D,E,T) + A + *WP++ + CONST##n; D = R32(D,30)
    154 
    155 #define FT(n)   \
    156     A = R32(B,5) + f##n(C,D,E) + T + *WP++ + CONST##n; C = R32(C,30)
    157 
    158 /* do SHA transformation */
    159 
    160 static void
    161 sha_transform(SHAobject *sha_info)
    162 {
    163     int i;
    164     SHA_INT32 T, A, B, C, D, E, W[80], *WP;
    165 
    166     memcpy(W, sha_info->data, sizeof(sha_info->data));
    167     longReverse(W, (int)sizeof(sha_info->data), sha_info->Endianness);
    168 
    169     for (i = 16; i < 80; ++i) {
    170         W[i] = W[i-3] ^ W[i-8] ^ W[i-14] ^ W[i-16];
    171 
    172         /* extra rotation fix */
    173         W[i] = R32(W[i], 1);
    174     }
    175     A = sha_info->digest[0];
    176     B = sha_info->digest[1];
    177     C = sha_info->digest[2];
    178     D = sha_info->digest[3];
    179     E = sha_info->digest[4];
    180     WP = W;
    181 #ifdef UNRAVEL
    182     FA(1); FB(1); FC(1); FD(1); FE(1); FT(1); FA(1); FB(1); FC(1); FD(1);
    183     FE(1); FT(1); FA(1); FB(1); FC(1); FD(1); FE(1); FT(1); FA(1); FB(1);
    184     FC(2); FD(2); FE(2); FT(2); FA(2); FB(2); FC(2); FD(2); FE(2); FT(2);
    185     FA(2); FB(2); FC(2); FD(2); FE(2); FT(2); FA(2); FB(2); FC(2); FD(2);
    186     FE(3); FT(3); FA(3); FB(3); FC(3); FD(3); FE(3); FT(3); FA(3); FB(3);
    187     FC(3); FD(3); FE(3); FT(3); FA(3); FB(3); FC(3); FD(3); FE(3); FT(3);
    188     FA(4); FB(4); FC(4); FD(4); FE(4); FT(4); FA(4); FB(4); FC(4); FD(4);
    189     FE(4); FT(4); FA(4); FB(4); FC(4); FD(4); FE(4); FT(4); FA(4); FB(4);
    190     sha_info->digest[0] += E;
    191     sha_info->digest[1] += T;
    192     sha_info->digest[2] += A;
    193     sha_info->digest[3] += B;
    194     sha_info->digest[4] += C;
    195 #else /* !UNRAVEL */
    196 #ifdef UNROLL_LOOPS
    197     FG(1); FG(1); FG(1); FG(1); FG(1); FG(1); FG(1); FG(1); FG(1); FG(1);
    198     FG(1); FG(1); FG(1); FG(1); FG(1); FG(1); FG(1); FG(1); FG(1); FG(1);
    199     FG(2); FG(2); FG(2); FG(2); FG(2); FG(2); FG(2); FG(2); FG(2); FG(2);
    200     FG(2); FG(2); FG(2); FG(2); FG(2); FG(2); FG(2); FG(2); FG(2); FG(2);
    201     FG(3); FG(3); FG(3); FG(3); FG(3); FG(3); FG(3); FG(3); FG(3); FG(3);
    202     FG(3); FG(3); FG(3); FG(3); FG(3); FG(3); FG(3); FG(3); FG(3); FG(3);
    203     FG(4); FG(4); FG(4); FG(4); FG(4); FG(4); FG(4); FG(4); FG(4); FG(4);
    204     FG(4); FG(4); FG(4); FG(4); FG(4); FG(4); FG(4); FG(4); FG(4); FG(4);
    205 #else /* !UNROLL_LOOPS */
    206     for (i =  0; i < 20; ++i) { FG(1); }
    207     for (i = 20; i < 40; ++i) { FG(2); }
    208     for (i = 40; i < 60; ++i) { FG(3); }
    209     for (i = 60; i < 80; ++i) { FG(4); }
    210 #endif /* !UNROLL_LOOPS */
    211     sha_info->digest[0] += A;
    212     sha_info->digest[1] += B;
    213     sha_info->digest[2] += C;
    214     sha_info->digest[3] += D;
    215     sha_info->digest[4] += E;
    216 #endif /* !UNRAVEL */
    217 }
    218 
    219 /* initialize the SHA digest */
    220 
    221 static void
    222 sha_init(SHAobject *sha_info)
    223 {
    224     TestEndianness(sha_info->Endianness)
    225 
    226     sha_info->digest[0] = 0x67452301L;
    227     sha_info->digest[1] = 0xefcdab89L;
    228     sha_info->digest[2] = 0x98badcfeL;
    229     sha_info->digest[3] = 0x10325476L;
    230     sha_info->digest[4] = 0xc3d2e1f0L;
    231     sha_info->count_lo = 0L;
    232     sha_info->count_hi = 0L;
    233     sha_info->local = 0;
    234 }
    235 
    236 /* update the SHA digest */
    237 
    238 static void
    239 sha_update(SHAobject *sha_info, SHA_BYTE *buffer, unsigned int count)
    240 {
    241     unsigned int i;
    242     SHA_INT32 clo;
    243 
    244     clo = sha_info->count_lo + ((SHA_INT32) count << 3);
    245     if (clo < sha_info->count_lo) {
    246         ++sha_info->count_hi;
    247     }
    248     sha_info->count_lo = clo;
    249     sha_info->count_hi += (SHA_INT32) count >> 29;
    250     if (sha_info->local) {
    251         i = SHA_BLOCKSIZE - sha_info->local;
    252         if (i > count) {
    253             i = count;
    254         }
    255         memcpy(((SHA_BYTE *) sha_info->data) + sha_info->local, buffer, i);
    256         count -= i;
    257         buffer += i;
    258         sha_info->local += i;
    259         if (sha_info->local == SHA_BLOCKSIZE) {
    260             sha_transform(sha_info);
    261         }
    262         else {
    263             return;
    264         }
    265     }
    266     while (count >= SHA_BLOCKSIZE) {
    267         memcpy(sha_info->data, buffer, SHA_BLOCKSIZE);
    268         buffer += SHA_BLOCKSIZE;
    269         count -= SHA_BLOCKSIZE;
    270         sha_transform(sha_info);
    271     }
    272     memcpy(sha_info->data, buffer, count);
    273     sha_info->local = count;
    274 }
    275 
    276 /* finish computing the SHA digest */
    277 
    278 static void
    279 sha_final(unsigned char digest[20], SHAobject *sha_info)
    280 {
    281     int count;
    282     SHA_INT32 lo_bit_count, hi_bit_count;
    283 
    284     lo_bit_count = sha_info->count_lo;
    285     hi_bit_count = sha_info->count_hi;
    286     count = (int) ((lo_bit_count >> 3) & 0x3f);
    287     ((SHA_BYTE *) sha_info->data)[count++] = 0x80;
    288     if (count > SHA_BLOCKSIZE - 8) {
    289         memset(((SHA_BYTE *) sha_info->data) + count, 0,
    290                SHA_BLOCKSIZE - count);
    291         sha_transform(sha_info);
    292         memset((SHA_BYTE *) sha_info->data, 0, SHA_BLOCKSIZE - 8);
    293     }
    294     else {
    295         memset(((SHA_BYTE *) sha_info->data) + count, 0,
    296                SHA_BLOCKSIZE - 8 - count);
    297     }
    298 
    299     /* GJS: note that we add the hi/lo in big-endian. sha_transform will
    300        swap these values into host-order. */
    301     sha_info->data[56] = (hi_bit_count >> 24) & 0xff;
    302     sha_info->data[57] = (hi_bit_count >> 16) & 0xff;
    303     sha_info->data[58] = (hi_bit_count >>  8) & 0xff;
    304     sha_info->data[59] = (hi_bit_count >>  0) & 0xff;
    305     sha_info->data[60] = (lo_bit_count >> 24) & 0xff;
    306     sha_info->data[61] = (lo_bit_count >> 16) & 0xff;
    307     sha_info->data[62] = (lo_bit_count >>  8) & 0xff;
    308     sha_info->data[63] = (lo_bit_count >>  0) & 0xff;
    309     sha_transform(sha_info);
    310     digest[ 0] = (unsigned char) ((sha_info->digest[0] >> 24) & 0xff);
    311     digest[ 1] = (unsigned char) ((sha_info->digest[0] >> 16) & 0xff);
    312     digest[ 2] = (unsigned char) ((sha_info->digest[0] >>  8) & 0xff);
    313     digest[ 3] = (unsigned char) ((sha_info->digest[0]      ) & 0xff);
    314     digest[ 4] = (unsigned char) ((sha_info->digest[1] >> 24) & 0xff);
    315     digest[ 5] = (unsigned char) ((sha_info->digest[1] >> 16) & 0xff);
    316     digest[ 6] = (unsigned char) ((sha_info->digest[1] >>  8) & 0xff);
    317     digest[ 7] = (unsigned char) ((sha_info->digest[1]      ) & 0xff);
    318     digest[ 8] = (unsigned char) ((sha_info->digest[2] >> 24) & 0xff);
    319     digest[ 9] = (unsigned char) ((sha_info->digest[2] >> 16) & 0xff);
    320     digest[10] = (unsigned char) ((sha_info->digest[2] >>  8) & 0xff);
    321     digest[11] = (unsigned char) ((sha_info->digest[2]      ) & 0xff);
    322     digest[12] = (unsigned char) ((sha_info->digest[3] >> 24) & 0xff);
    323     digest[13] = (unsigned char) ((sha_info->digest[3] >> 16) & 0xff);
    324     digest[14] = (unsigned char) ((sha_info->digest[3] >>  8) & 0xff);
    325     digest[15] = (unsigned char) ((sha_info->digest[3]      ) & 0xff);
    326     digest[16] = (unsigned char) ((sha_info->digest[4] >> 24) & 0xff);
    327     digest[17] = (unsigned char) ((sha_info->digest[4] >> 16) & 0xff);
    328     digest[18] = (unsigned char) ((sha_info->digest[4] >>  8) & 0xff);
    329     digest[19] = (unsigned char) ((sha_info->digest[4]      ) & 0xff);
    330 }
    331 
    332 /*
    333  * End of copied SHA code.
    334  *
    335  * ------------------------------------------------------------------------
    336  */
    337 
    338 static PyTypeObject SHAtype;
    339 
    340 
    341 static SHAobject *
    342 newSHAobject(void)
    343 {
    344     return (SHAobject *)PyObject_New(SHAobject, &SHAtype);
    345 }
    346 
    347 /* Internal methods for a hashing object */
    348 
    349 static void
    350 SHA_dealloc(PyObject *ptr)
    351 {
    352     PyObject_Del(ptr);
    353 }
    354 
    355 
    356 /* External methods for a hashing object */
    357 
    358 PyDoc_STRVAR(SHA_copy__doc__, "Return a copy of the hashing object.");
    359 
    360 static PyObject *
    361 SHA_copy(SHAobject *self, PyObject *unused)
    362 {
    363     SHAobject *newobj;
    364 
    365     if ( (newobj = newSHAobject())==NULL)
    366         return NULL;
    367 
    368     SHAcopy(self, newobj);
    369     return (PyObject *)newobj;
    370 }
    371 
    372 PyDoc_STRVAR(SHA_digest__doc__,
    373 "Return the digest value as a string of binary data.");
    374 
    375 static PyObject *
    376 SHA_digest(SHAobject *self, PyObject *unused)
    377 {
    378     unsigned char digest[SHA_DIGESTSIZE];
    379     SHAobject temp;
    380 
    381     SHAcopy(self, &temp);
    382     sha_final(digest, &temp);
    383     return PyString_FromStringAndSize((const char *)digest, sizeof(digest));
    384 }
    385 
    386 PyDoc_STRVAR(SHA_hexdigest__doc__,
    387 "Return the digest value as a string of hexadecimal digits.");
    388 
    389 static PyObject *
    390 SHA_hexdigest(SHAobject *self, PyObject *unused)
    391 {
    392     unsigned char digest[SHA_DIGESTSIZE];
    393     SHAobject temp;
    394     PyObject *retval;
    395     char *hex_digest;
    396     int i, j;
    397 
    398     /* Get the raw (binary) digest value */
    399     SHAcopy(self, &temp);
    400     sha_final(digest, &temp);
    401 
    402     /* Create a new string */
    403     retval = PyString_FromStringAndSize(NULL, sizeof(digest) * 2);
    404     if (!retval)
    405             return NULL;
    406     hex_digest = PyString_AsString(retval);
    407     if (!hex_digest) {
    408             Py_DECREF(retval);
    409             return NULL;
    410     }
    411 
    412     /* Make hex version of the digest */
    413     for(i=j=0; i<sizeof(digest); i++) {
    414         char c;
    415         c = (digest[i] >> 4) & 0xf;
    416         c = (c>9) ? c+'a'-10 : c + '0';
    417         hex_digest[j++] = c;
    418         c = (digest[i] & 0xf);
    419         c = (c>9) ? c+'a'-10 : c + '0';
    420         hex_digest[j++] = c;
    421     }
    422     return retval;
    423 }
    424 
    425 PyDoc_STRVAR(SHA_update__doc__,
    426 "Update this hashing object's state with the provided string.");
    427 
    428 static PyObject *
    429 SHA_update(SHAobject *self, PyObject *args)
    430 {
    431     Py_buffer view;
    432     Py_ssize_t n;
    433     unsigned char *buf;
    434 
    435     if (!PyArg_ParseTuple(args, "s*:update", &view))
    436         return NULL;
    437 
    438     n = view.len;
    439     buf = (unsigned char *) view.buf;
    440     while (n > 0) {
    441         Py_ssize_t nbytes;
    442         if (n > INT_MAX)
    443             nbytes = INT_MAX;
    444         else
    445             nbytes = n;
    446         sha_update(self, buf,
    447                    Py_SAFE_DOWNCAST(nbytes, Py_ssize_t, unsigned int));
    448         buf += nbytes;
    449         n -= nbytes;
    450     }
    451 
    452     PyBuffer_Release(&view);
    453     Py_RETURN_NONE;
    454 }
    455 
    456 static PyMethodDef SHA_methods[] = {
    457     {"copy",      (PyCFunction)SHA_copy,      METH_NOARGS,  SHA_copy__doc__},
    458     {"digest",    (PyCFunction)SHA_digest,    METH_NOARGS,  SHA_digest__doc__},
    459     {"hexdigest", (PyCFunction)SHA_hexdigest, METH_NOARGS,  SHA_hexdigest__doc__},
    460     {"update",    (PyCFunction)SHA_update,    METH_VARARGS, SHA_update__doc__},
    461     {NULL,        NULL}         /* sentinel */
    462 };
    463 
    464 static PyObject *
    465 SHA_get_block_size(PyObject *self, void *closure)
    466 {
    467     return PyInt_FromLong(SHA_BLOCKSIZE);
    468 }
    469 
    470 static PyObject *
    471 SHA_get_digest_size(PyObject *self, void *closure)
    472 {
    473     return PyInt_FromLong(SHA_DIGESTSIZE);
    474 }
    475 
    476 static PyObject *
    477 SHA_get_name(PyObject *self, void *closure)
    478 {
    479     return PyString_FromStringAndSize("SHA1", 4);
    480 }
    481 
    482 static PyGetSetDef SHA_getseters[] = {
    483     {"digest_size",
    484      (getter)SHA_get_digest_size, NULL,
    485      NULL,
    486      NULL},
    487     {"block_size",
    488      (getter)SHA_get_block_size, NULL,
    489      NULL,
    490      NULL},
    491     {"name",
    492      (getter)SHA_get_name, NULL,
    493      NULL,
    494      NULL},
    495     /* the old md5 and sha modules support 'digest_size' as in PEP 247.
    496      * the old sha module also supported 'digestsize'.  ugh. */
    497     {"digestsize",
    498      (getter)SHA_get_digest_size, NULL,
    499      NULL,
    500      NULL},
    501     {NULL}  /* Sentinel */
    502 };
    503 
    504 static PyTypeObject SHAtype = {
    505     PyVarObject_HEAD_INIT(NULL, 0)
    506     "_sha.sha",         /*tp_name*/
    507     sizeof(SHAobject),  /*tp_size*/
    508     0,                  /*tp_itemsize*/
    509     /* methods */
    510     SHA_dealloc,        /*tp_dealloc*/
    511     0,                  /*tp_print*/
    512     0,                  /*tp_getattr*/
    513     0,                  /*tp_setattr*/
    514     0,                  /*tp_compare*/
    515     0,                  /*tp_repr*/
    516     0,                  /*tp_as_number*/
    517     0,                  /*tp_as_sequence*/
    518     0,                  /*tp_as_mapping*/
    519     0,                  /*tp_hash*/
    520     0,                  /*tp_call*/
    521     0,                  /*tp_str*/
    522     0,                  /*tp_getattro*/
    523     0,                  /*tp_setattro*/
    524     0,                  /*tp_as_buffer*/
    525     Py_TPFLAGS_DEFAULT, /*tp_flags*/
    526     0,                  /*tp_doc*/
    527     0,                  /*tp_traverse*/
    528     0,                  /*tp_clear*/
    529     0,                  /*tp_richcompare*/
    530     0,                  /*tp_weaklistoffset*/
    531     0,                  /*tp_iter*/
    532     0,                  /*tp_iternext*/
    533     SHA_methods,        /* tp_methods */
    534     0,                  /* tp_members */
    535     SHA_getseters,      /* tp_getset */
    536 };
    537 
    538 
    539 /* The single module-level function: new() */
    540 
    541 PyDoc_STRVAR(SHA_new__doc__,
    542 "Return a new SHA hashing object.  An optional string argument\n\
    543 may be provided; if present, this string will be automatically\n\
    544 hashed.");
    545 
    546 static PyObject *
    547 SHA_new(PyObject *self, PyObject *args, PyObject *kwdict)
    548 {
    549     static char *kwlist[] = {"string", NULL};
    550     SHAobject *new;
    551     Py_buffer view = { 0 };
    552     Py_ssize_t n;
    553     unsigned char *buf;
    554 
    555     if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|s*:new", kwlist,
    556                                      &view)) {
    557         return NULL;
    558     }
    559 
    560     if ((new = newSHAobject()) == NULL) {
    561         PyBuffer_Release(&view);
    562         return NULL;
    563     }
    564 
    565     sha_init(new);
    566 
    567     if (PyErr_Occurred()) {
    568         Py_DECREF(new);
    569         PyBuffer_Release(&view);
    570         return NULL;
    571     }
    572 
    573     n = view.len;
    574     buf = (unsigned char *) view.buf;
    575     while (n > 0) {
    576         Py_ssize_t nbytes;
    577         if (n > INT_MAX)
    578             nbytes = INT_MAX;
    579         else
    580             nbytes = n;
    581         sha_update(new, buf,
    582                    Py_SAFE_DOWNCAST(nbytes, Py_ssize_t, unsigned int));
    583         buf += nbytes;
    584         n -= nbytes;
    585     }
    586 
    587     PyBuffer_Release(&view);
    588 
    589     return (PyObject *)new;
    590 }
    591 
    592 
    593 /* List of functions exported by this module */
    594 
    595 static struct PyMethodDef SHA_functions[] = {
    596     {"new", (PyCFunction)SHA_new, METH_VARARGS|METH_KEYWORDS, SHA_new__doc__},
    597     {NULL,      NULL}            /* Sentinel */
    598 };
    599 
    600 
    601 /* Initialize this module. */
    602 
    603 #define insint(n,v) { PyModule_AddIntConstant(m,n,v); }
    604 
    605 PyMODINIT_FUNC
    606 init_sha(void)
    607 {
    608     PyObject *m;
    609 
    610     Py_TYPE(&SHAtype) = &PyType_Type;
    611     if (PyType_Ready(&SHAtype) < 0)
    612         return;
    613     m = Py_InitModule("_sha", SHA_functions);
    614     if (m == NULL)
    615         return;
    616 
    617     /* Add some symbolic constants to the module */
    618     insint("blocksize", 1);  /* For future use, in case some hash
    619                                 functions require an integral number of
    620                                 blocks */
    621     insint("digestsize", 20);
    622     insint("digest_size", 20);
    623 }
    624