Implemented public Base64 interface
Base64 is required for vCard avatars. It will also be useful for an authentication mechanism with future xmpp_connect_raw() interface.
This commit is contained in:
Dmitry Podgorny
279
src/crypto.c
279
src/crypto.c
@@ -16,6 +16,9 @@
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/** @defgroup Digests Message digests
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*/
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/** @defgroup Encodings Encodings
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*/
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#include <assert.h>
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#include <string.h> /* memset, memcpy */
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@@ -182,3 +185,279 @@ void xmpp_sha1_to_digest(xmpp_sha1_t *sha1, unsigned char *digest)
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assert(SHA1_DIGEST_SIZE == XMPP_SHA1_DIGEST_SIZE);
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memcpy(digest, sha1->digest, SHA1_DIGEST_SIZE);
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}
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/* Base64 encoding routines. Implemented according to RFC 3548. */
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/* map of all byte values to the base64 values, or to
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'65' which indicates an invalid character. '=' is '64' */
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static const unsigned char _base64_invcharmap[256] = {
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65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
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65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
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65,65,65,65, 65,65,65,65, 65,65,65,62, 65,65,65,63,
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52,53,54,55, 56,57,58,59, 60,61,65,65, 65,64,65,65,
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65, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11,12,13,14,
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15,16,17,18, 19,20,21,22, 23,24,25,65, 65,65,65,65,
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65,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
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41,42,43,44, 45,46,47,48, 49,50,51,65, 65,65,65,65,
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65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
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65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
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65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
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65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
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65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
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65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
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65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
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65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65
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};
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/* map of all 6-bit values to their corresponding byte
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in the base64 alphabet. Padding char is the value '64' */
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static const char _base64_charmap[65] = {
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'A','B','C','D', 'E','F','G','H',
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'I','J','K','L', 'M','N','O','P',
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'Q','R','S','T', 'U','V','W','X',
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'Y','Z','a','b', 'c','d','e','f',
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'g','h','i','j', 'k','l','m','n',
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'o','p','q','r', 's','t','u','v',
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'w','x','y','z', '0','1','2','3',
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'4','5','6','7', '8','9','+','/',
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'='
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};
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static size_t base64_encoded_len(const size_t len)
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{
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/* encoded steam is 4 bytes for every three, rounded up */
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return ((len + 2)/3) << 2;
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}
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static char *base64_encode(xmpp_ctx_t *ctx,
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const unsigned char * const buffer, const size_t len)
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{
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size_t clen;
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char *cbuf, *c;
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uint32_t word, hextet;
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size_t i;
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clen = base64_encoded_len(len);
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cbuf = xmpp_alloc(ctx, clen + 1);
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if (cbuf != NULL) {
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c = cbuf;
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/* loop over data, turning every 3 bytes into 4 characters */
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for (i = 0; i + 2 < len; i += 3) {
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word = buffer[i] << 16 | buffer[i+1] << 8 | buffer[i+2];
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hextet = (word & 0x00FC0000) >> 18;
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*c++ = _base64_charmap[hextet];
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hextet = (word & 0x0003F000) >> 12;
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*c++ = _base64_charmap[hextet];
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hextet = (word & 0x00000FC0) >> 6;
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*c++ = _base64_charmap[hextet];
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hextet = (word & 0x000003F);
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*c++ = _base64_charmap[hextet];
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}
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/* zero, one or two bytes left */
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switch (len - i) {
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case 0:
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break;
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case 1:
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hextet = (buffer[len-1] & 0xFC) >> 2;
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*c++ = _base64_charmap[hextet];
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hextet = (buffer[len-1] & 0x03) << 4;
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*c++ = _base64_charmap[hextet];
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*c++ = _base64_charmap[64]; /* pad */
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*c++ = _base64_charmap[64]; /* pad */
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break;
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case 2:
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hextet = (buffer[len-2] & 0xFC) >> 2;
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*c++ = _base64_charmap[hextet];
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hextet = ((buffer[len-2] & 0x03) << 4) |
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((buffer[len-1] & 0xF0) >> 4);
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*c++ = _base64_charmap[hextet];
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hextet = (buffer[len-1] & 0x0F) << 2;
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*c++ = _base64_charmap[hextet];
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*c++ = _base64_charmap[64]; /* pad */
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break;
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}
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/* add a terminal null */
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*c = '\0';
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}
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return cbuf;
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}
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static size_t base64_decoded_len(const char * const buffer, const size_t len)
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{
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size_t nudge = 0;
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unsigned char c;
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size_t i;
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if (len < 4) return 0;
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/* count the padding characters for the remainder */
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for (i = len; i > 0; --i) {
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c = _base64_invcharmap[(unsigned char)buffer[i-1]];
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if (c < 64) break;
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if (c == 64) ++nudge;
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if (c > 64) return 0;
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}
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if (nudge > 2) return 0;
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/* decoded steam is 3 bytes for every four */
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return 3 * (len >> 2) - nudge;
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}
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static void base64_decode(xmpp_ctx_t *ctx,
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const char * const buffer, const size_t len,
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unsigned char **out, size_t *outlen)
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{
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size_t dlen;
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unsigned char *dbuf, *d;
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uint32_t word, hextet = 0;
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size_t i;
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/* len must be a multiple of 4 */
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if (len & 0x03) goto _base64_error;
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dlen = base64_decoded_len(buffer, len);
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if (dlen == 0) goto _base64_error;
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dbuf = xmpp_alloc(ctx, dlen + 1);
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if (dbuf != NULL) {
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d = dbuf;
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/* loop over each set of 4 characters, decoding 3 bytes */
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for (i = 0; i + 3 < len; i += 4) {
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hextet = _base64_invcharmap[(unsigned char)buffer[i]];
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if (hextet & 0xC0) break;
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word = hextet << 18;
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hextet = _base64_invcharmap[(unsigned char)buffer[i+1]];
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if (hextet & 0xC0) break;
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word |= hextet << 12;
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hextet = _base64_invcharmap[(unsigned char)buffer[i+2]];
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if (hextet & 0xC0) break;
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word |= hextet << 6;
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hextet = _base64_invcharmap[(unsigned char)buffer[i+3]];
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if (hextet & 0xC0) break;
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word |= hextet;
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*d++ = (word & 0x00FF0000) >> 16;
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*d++ = (word & 0x0000FF00) >> 8;
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*d++ = (word & 0x000000FF);
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}
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if (hextet > 64) goto _base64_decode_error;
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/* handle the remainder */
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switch (dlen % 3) {
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case 0:
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/* nothing to do */
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break;
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case 1:
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/* redo the last quartet, checking for correctness */
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hextet = _base64_invcharmap[(unsigned char)buffer[len-4]];
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if (hextet & 0xC0) goto _base64_decode_error;
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word = hextet << 2;
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hextet = _base64_invcharmap[(unsigned char)buffer[len-3]];
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if (hextet & 0xC0) goto _base64_decode_error;
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word |= hextet >> 4;
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*d++ = word & 0xFF;
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hextet = _base64_invcharmap[(unsigned char)buffer[len-2]];
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if (hextet != 64) goto _base64_decode_error;
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hextet = _base64_invcharmap[(unsigned char)buffer[len-1]];
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if (hextet != 64) goto _base64_decode_error;
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break;
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case 2:
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/* redo the last quartet, checking for correctness */
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hextet = _base64_invcharmap[(unsigned char)buffer[len-4]];
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if (hextet & 0xC0) goto _base64_decode_error;
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word = hextet << 10;
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hextet = _base64_invcharmap[(unsigned char)buffer[len-3]];
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if (hextet & 0xC0) goto _base64_decode_error;
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word |= hextet << 4;
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hextet = _base64_invcharmap[(unsigned char)buffer[len-2]];
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if (hextet & 0xC0) goto _base64_decode_error;
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word |= hextet >> 2;
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*d++ = (word & 0xFF00) >> 8;
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*d++ = (word & 0x00FF);
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hextet = _base64_invcharmap[(unsigned char)buffer[len-1]];
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if (hextet != 64) goto _base64_decode_error;
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break;
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}
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*d = '\0';
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}
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*out = dbuf;
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*outlen = dbuf == NULL ? 0 : dlen;
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return;
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_base64_decode_error:
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/* invalid character; abort decoding! */
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xmpp_free(ctx, dbuf);
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_base64_error:
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*out = NULL;
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*outlen = 0;
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}
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/** Base64 encoding routine
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* Returns an allocated string which must be freed with xmpp_free().
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*
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* @param ctx a Strophe context
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* @param data buffer to encode
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* @param len size of the data buffer
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*
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* @return an allocated null-terminated string or NULL on error
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*
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* @ingroup Encodings
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*/
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char *xmpp_base64_encode(xmpp_ctx_t *ctx, const unsigned char *data, size_t len)
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{
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return base64_encode(ctx, data, len);
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}
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/** Base64 decoding routine
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* Returns an allocated string which must be freed with xmpp_free(). User
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* calls this function when the result must be a string. When decoded buffer
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* contains '\0' NULL is returned.
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*
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* @param ctx a Strophe context
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* @param base64 encoded buffer
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* @param len size of the buffer
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*
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* @return an allocated null-terminated string or NULL on error
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*
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* @ingroup Encodings
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*/
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char *xmpp_base64_decode_str(xmpp_ctx_t *ctx, const char *base64, size_t len)
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{
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unsigned char *buf = NULL;
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size_t buflen;
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if (len == 0) {
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/* handle empty string */
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buf = xmpp_alloc(ctx, 1);
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if (buf)
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buf[0] = '\0';
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buflen = 0;
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} else {
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base64_decode(ctx, base64, len, &buf, &buflen);
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}
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if (buf) {
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if (buflen != strlen((char *)buf)) {
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xmpp_free(ctx, buf);
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buf = NULL;
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}
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}
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return (char *)buf;
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}
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/** Base64 decoding routine
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* Returns an allocated buffer which must be freed with xmpp_free().
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*
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* @param ctx a Strophe context
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* @param base64 encoded buffer
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* @param len size of the encoded buffer
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* @param out allocated buffer is stored here
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* @param outlen size of the allocated buffer
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*
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* @note on an error the `*out` will be NULL
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*
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* @ingroup Encodings
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*/
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void xmpp_base64_decode_bin(xmpp_ctx_t *ctx, const char *base64, size_t len,
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unsigned char **out, size_t *outlen)
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{
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base64_decode(ctx, base64, len, out, outlen);
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}
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