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libstrophe-gh/src/crypto.c
Dmitry Podgorny 2ffb278aa4 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.
2016-04-30 18:09:01 +00:00

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/* crypto.c
* strophe XMPP client library -- public interface for digests, encodings
*
* Copyright (C) 2016 Dmitry Podgorny <pasis.ua@gmail.com>
*
* This software is provided AS-IS with no warranty, either express
* or implied.
*
* This program is dual licensed under the MIT and GPLv3 licenses.
*/
/** @file
* Public interface for digests and encodings used in XEPs.
*/
/** @defgroup Digests Message digests
*/
/** @defgroup Encodings Encodings
*/
#include <assert.h>
#include <string.h> /* memset, memcpy */
#include "common.h" /* xmpp_alloc */
#include "ostypes.h" /* uint8_t, size_t */
#include "sha1.h"
#include "snprintf.h" /* xmpp_snprintf */
#include "strophe.h" /* xmpp_ctx_t, xmpp_free */
struct _xmpp_sha1_t {
xmpp_ctx_t *xmpp_ctx;
SHA1_CTX ctx;
uint8_t digest[SHA1_DIGEST_SIZE];
};
static char *digest_to_string(const uint8_t *digest, char *s, size_t len)
{
int i;
if (len < SHA1_DIGEST_SIZE * 2 + 1)
return NULL;
for (i = 0; i < SHA1_DIGEST_SIZE; ++i)
xmpp_snprintf(s + i * 2, 3, "%02x", digest[i]);
return s;
}
static char *digest_to_string_alloc(xmpp_ctx_t *ctx, const uint8_t *digest)
{
char *s;
size_t slen;
slen = SHA1_DIGEST_SIZE * 2 + 1;
s = xmpp_alloc(ctx, slen);
if (s) {
s = digest_to_string(digest, s, slen);
assert(s != NULL);
}
return s;
}
/** Compute SHA1 message digest
* Returns an allocated string which represents SHA1 message digest in
* hexadecimal notation. The string must be freed with xmpp_free().
*
* @param ctx a Strophe context object
* @param data buffer for digest computation
* @param len size of the data buffer
*
* @return an allocated string or NULL on allocation error
*
* @ingroup Digests
*/
char *xmpp_sha1(xmpp_ctx_t *ctx, const unsigned char *data, size_t len)
{
uint8_t digest[SHA1_DIGEST_SIZE];
crypto_SHA1((const uint8_t *)data, len, digest);
return digest_to_string_alloc(ctx, digest);
}
/** Create new SHA1 object
*
* @param ctx a Strophe context onject
*
* @return new SHA1 object
*
* @ingroup Digests
*/
xmpp_sha1_t *xmpp_sha1_new(xmpp_ctx_t *ctx)
{
xmpp_sha1_t *sha1;
sha1 = xmpp_alloc(ctx, sizeof(*sha1));
if (sha1) {
memset(sha1, 0, sizeof(*sha1));
crypto_SHA1_Init(&sha1->ctx);
sha1->xmpp_ctx = ctx;
}
return sha1;
}
/** Destroy SHA1 object
*
* @param sha1 a SHA1 object
*
* @ingroup Digests
*/
void xmpp_sha1_free(xmpp_sha1_t *sha1)
{
xmpp_free(sha1->xmpp_ctx, sha1);
}
/** Update SHA1 context with the next portion of data
* Can be called repeatedly.
*
* @param sha1 a SHA1 object
* @param data pointer to a buffer to be hashed
* @param len size of the data buffer
*
* @ingroup Digests
*/
void xmpp_sha1_update(xmpp_sha1_t *sha1, const unsigned char *data, size_t len)
{
crypto_SHA1_Update(&sha1->ctx, data, len);
}
/** Finish SHA1 computation
* Don't call xmpp_sha1_update() after this function. Retrieve resulting
* message digest with xmpp_sha1_to_string() or xmpp_sha1_to_digest().
*
* @param sha1 a SHA1 object
*
* @ingroup Digests
*/
void xmpp_sha1_final(xmpp_sha1_t *sha1)
{
crypto_SHA1_Final(&sha1->ctx, sha1->digest);
}
/** Return message digest rendered as a string
* Stores the string to a user's buffer and returns the buffer. Call this
* function after xmpp_sha1_final().
*
* @param sha1 a SHA1 object
* @param s output string
* @param slen size reserved for the string including '\0'
*
* @return pointer s or NULL if resulting string is bigger than slen bytes
*
* @ingroup Digests
*/
char *xmpp_sha1_to_string(xmpp_sha1_t *sha1, char *s, size_t slen)
{
return digest_to_string(sha1->digest, s, slen);
}
/** Return message digest rendered as a string
* Returns an allocated string. Free the string using the Strophe context
* which is passed to xmpp_sha1_new(). Call this function after
* xmpp_sha1_final().
*
* @param sha1 a SHA1 object
*
* @return an allocated string
*
* @ingroup Digests
*/
char *xmpp_sha1_to_string_alloc(xmpp_sha1_t *sha1)
{
return digest_to_string_alloc(sha1->xmpp_ctx, sha1->digest);
}
/** Stores message digest to a user's buffer
*
* @param sha1 a SHA1 object
* @param digest output buffer of XMPP_SHA1_DIGEST_SIZE bytes
*
* @ingroup Digests
*/
void xmpp_sha1_to_digest(xmpp_sha1_t *sha1, unsigned char *digest)
{
assert(SHA1_DIGEST_SIZE == XMPP_SHA1_DIGEST_SIZE);
memcpy(digest, sha1->digest, SHA1_DIGEST_SIZE);
}
/* Base64 encoding routines. Implemented according to RFC 3548. */
/* map of all byte values to the base64 values, or to
'65' which indicates an invalid character. '=' is '64' */
static const unsigned char _base64_invcharmap[256] = {
65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
65,65,65,65, 65,65,65,65, 65,65,65,62, 65,65,65,63,
52,53,54,55, 56,57,58,59, 60,61,65,65, 65,64,65,65,
65, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11,12,13,14,
15,16,17,18, 19,20,21,22, 23,24,25,65, 65,65,65,65,
65,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
41,42,43,44, 45,46,47,48, 49,50,51,65, 65,65,65,65,
65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65,
65,65,65,65, 65,65,65,65, 65,65,65,65, 65,65,65,65
};
/* map of all 6-bit values to their corresponding byte
in the base64 alphabet. Padding char is the value '64' */
static const char _base64_charmap[65] = {
'A','B','C','D', 'E','F','G','H',
'I','J','K','L', 'M','N','O','P',
'Q','R','S','T', 'U','V','W','X',
'Y','Z','a','b', 'c','d','e','f',
'g','h','i','j', 'k','l','m','n',
'o','p','q','r', 's','t','u','v',
'w','x','y','z', '0','1','2','3',
'4','5','6','7', '8','9','+','/',
'='
};
static size_t base64_encoded_len(const size_t len)
{
/* encoded steam is 4 bytes for every three, rounded up */
return ((len + 2)/3) << 2;
}
static char *base64_encode(xmpp_ctx_t *ctx,
const unsigned char * const buffer, const size_t len)
{
size_t clen;
char *cbuf, *c;
uint32_t word, hextet;
size_t i;
clen = base64_encoded_len(len);
cbuf = xmpp_alloc(ctx, clen + 1);
if (cbuf != NULL) {
c = cbuf;
/* loop over data, turning every 3 bytes into 4 characters */
for (i = 0; i + 2 < len; i += 3) {
word = buffer[i] << 16 | buffer[i+1] << 8 | buffer[i+2];
hextet = (word & 0x00FC0000) >> 18;
*c++ = _base64_charmap[hextet];
hextet = (word & 0x0003F000) >> 12;
*c++ = _base64_charmap[hextet];
hextet = (word & 0x00000FC0) >> 6;
*c++ = _base64_charmap[hextet];
hextet = (word & 0x000003F);
*c++ = _base64_charmap[hextet];
}
/* zero, one or two bytes left */
switch (len - i) {
case 0:
break;
case 1:
hextet = (buffer[len-1] & 0xFC) >> 2;
*c++ = _base64_charmap[hextet];
hextet = (buffer[len-1] & 0x03) << 4;
*c++ = _base64_charmap[hextet];
*c++ = _base64_charmap[64]; /* pad */
*c++ = _base64_charmap[64]; /* pad */
break;
case 2:
hextet = (buffer[len-2] & 0xFC) >> 2;
*c++ = _base64_charmap[hextet];
hextet = ((buffer[len-2] & 0x03) << 4) |
((buffer[len-1] & 0xF0) >> 4);
*c++ = _base64_charmap[hextet];
hextet = (buffer[len-1] & 0x0F) << 2;
*c++ = _base64_charmap[hextet];
*c++ = _base64_charmap[64]; /* pad */
break;
}
/* add a terminal null */
*c = '\0';
}
return cbuf;
}
static size_t base64_decoded_len(const char * const buffer, const size_t len)
{
size_t nudge = 0;
unsigned char c;
size_t i;
if (len < 4) return 0;
/* count the padding characters for the remainder */
for (i = len; i > 0; --i) {
c = _base64_invcharmap[(unsigned char)buffer[i-1]];
if (c < 64) break;
if (c == 64) ++nudge;
if (c > 64) return 0;
}
if (nudge > 2) return 0;
/* decoded steam is 3 bytes for every four */
return 3 * (len >> 2) - nudge;
}
static void base64_decode(xmpp_ctx_t *ctx,
const char * const buffer, const size_t len,
unsigned char **out, size_t *outlen)
{
size_t dlen;
unsigned char *dbuf, *d;
uint32_t word, hextet = 0;
size_t i;
/* len must be a multiple of 4 */
if (len & 0x03) goto _base64_error;
dlen = base64_decoded_len(buffer, len);
if (dlen == 0) goto _base64_error;
dbuf = xmpp_alloc(ctx, dlen + 1);
if (dbuf != NULL) {
d = dbuf;
/* loop over each set of 4 characters, decoding 3 bytes */
for (i = 0; i + 3 < len; i += 4) {
hextet = _base64_invcharmap[(unsigned char)buffer[i]];
if (hextet & 0xC0) break;
word = hextet << 18;
hextet = _base64_invcharmap[(unsigned char)buffer[i+1]];
if (hextet & 0xC0) break;
word |= hextet << 12;
hextet = _base64_invcharmap[(unsigned char)buffer[i+2]];
if (hextet & 0xC0) break;
word |= hextet << 6;
hextet = _base64_invcharmap[(unsigned char)buffer[i+3]];
if (hextet & 0xC0) break;
word |= hextet;
*d++ = (word & 0x00FF0000) >> 16;
*d++ = (word & 0x0000FF00) >> 8;
*d++ = (word & 0x000000FF);
}
if (hextet > 64) goto _base64_decode_error;
/* handle the remainder */
switch (dlen % 3) {
case 0:
/* nothing to do */
break;
case 1:
/* redo the last quartet, checking for correctness */
hextet = _base64_invcharmap[(unsigned char)buffer[len-4]];
if (hextet & 0xC0) goto _base64_decode_error;
word = hextet << 2;
hextet = _base64_invcharmap[(unsigned char)buffer[len-3]];
if (hextet & 0xC0) goto _base64_decode_error;
word |= hextet >> 4;
*d++ = word & 0xFF;
hextet = _base64_invcharmap[(unsigned char)buffer[len-2]];
if (hextet != 64) goto _base64_decode_error;
hextet = _base64_invcharmap[(unsigned char)buffer[len-1]];
if (hextet != 64) goto _base64_decode_error;
break;
case 2:
/* redo the last quartet, checking for correctness */
hextet = _base64_invcharmap[(unsigned char)buffer[len-4]];
if (hextet & 0xC0) goto _base64_decode_error;
word = hextet << 10;
hextet = _base64_invcharmap[(unsigned char)buffer[len-3]];
if (hextet & 0xC0) goto _base64_decode_error;
word |= hextet << 4;
hextet = _base64_invcharmap[(unsigned char)buffer[len-2]];
if (hextet & 0xC0) goto _base64_decode_error;
word |= hextet >> 2;
*d++ = (word & 0xFF00) >> 8;
*d++ = (word & 0x00FF);
hextet = _base64_invcharmap[(unsigned char)buffer[len-1]];
if (hextet != 64) goto _base64_decode_error;
break;
}
*d = '\0';
}
*out = dbuf;
*outlen = dbuf == NULL ? 0 : dlen;
return;
_base64_decode_error:
/* invalid character; abort decoding! */
xmpp_free(ctx, dbuf);
_base64_error:
*out = NULL;
*outlen = 0;
}
/** Base64 encoding routine
* Returns an allocated string which must be freed with xmpp_free().
*
* @param ctx a Strophe context
* @param data buffer to encode
* @param len size of the data buffer
*
* @return an allocated null-terminated string or NULL on error
*
* @ingroup Encodings
*/
char *xmpp_base64_encode(xmpp_ctx_t *ctx, const unsigned char *data, size_t len)
{
return base64_encode(ctx, data, len);
}
/** Base64 decoding routine
* Returns an allocated string which must be freed with xmpp_free(). User
* calls this function when the result must be a string. When decoded buffer
* contains '\0' NULL is returned.
*
* @param ctx a Strophe context
* @param base64 encoded buffer
* @param len size of the buffer
*
* @return an allocated null-terminated string or NULL on error
*
* @ingroup Encodings
*/
char *xmpp_base64_decode_str(xmpp_ctx_t *ctx, const char *base64, size_t len)
{
unsigned char *buf = NULL;
size_t buflen;
if (len == 0) {
/* handle empty string */
buf = xmpp_alloc(ctx, 1);
if (buf)
buf[0] = '\0';
buflen = 0;
} else {
base64_decode(ctx, base64, len, &buf, &buflen);
}
if (buf) {
if (buflen != strlen((char *)buf)) {
xmpp_free(ctx, buf);
buf = NULL;
}
}
return (char *)buf;
}
/** Base64 decoding routine
* Returns an allocated buffer which must be freed with xmpp_free().
*
* @param ctx a Strophe context
* @param base64 encoded buffer
* @param len size of the encoded buffer
* @param out allocated buffer is stored here
* @param outlen size of the allocated buffer
*
* @note on an error the `*out` will be NULL
*
* @ingroup Encodings
*/
void xmpp_base64_decode_bin(xmpp_ctx_t *ctx, const char *base64, size_t len,
unsigned char **out, size_t *outlen)
{
base64_decode(ctx, base64, len, out, outlen);
}
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