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/*
* cram.c : Minimal standalone CRAM-MD5 implementation
*
* ====================================================================
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
* ====================================================================
*/
#define APR_WANT_STRFUNC
#define APR_WANT_STDIO
#include <apr_want.h>
#include <apr_general.h>
#include <apr_strings.h>
#include <apr_network_io.h>
#include <apr_time.h>
#include <apr_md5.h>
#include "svn_types.h"
#include "svn_string.h"
#include "svn_error.h"
#include "svn_ra_svn.h"
#include "svn_config.h"
#include "svn_private_config.h"
#include "ra_svn.h"
static int hex_to_int(char c)
{
return (c >= '0' && c <= '9') ? c - '0'
: (c >= 'a' && c <= 'f') ? c - 'a' + 10
: -1;
}
static char int_to_hex(int v)
{
return (char)((v < 10) ? '0' + v : 'a' + (v - 10));
}
static svn_boolean_t hex_decode(unsigned char *hashval, const char *hexval)
{
int i, h1, h2;
for (i = 0; i < APR_MD5_DIGESTSIZE; i++)
{
h1 = hex_to_int(hexval[2 * i]);
h2 = hex_to_int(hexval[2 * i + 1]);
if (h1 == -1 || h2 == -1)
return FALSE;
hashval[i] = (unsigned char)((h1 << 4) | h2);
}
return TRUE;
}
static void hex_encode(char *hexval, const unsigned char *hashval)
{
int i;
for (i = 0; i < APR_MD5_DIGESTSIZE; i++)
{
hexval[2 * i] = int_to_hex((hashval[i] >> 4) & 0xf);
hexval[2 * i + 1] = int_to_hex(hashval[i] & 0xf);
}
}
static void compute_digest(unsigned char *digest, const char *challenge,
const char *password)
{
unsigned char secret[64];
apr_size_t len = strlen(password), i;
apr_md5_ctx_t ctx;
/* Munge the password into a 64-byte secret. */
memset(secret, 0, sizeof(secret));
if (len <= sizeof(secret))
memcpy(secret, password, len);
else
apr_md5(secret, password, len);
/* Compute MD5(secret XOR opad, MD5(secret XOR ipad, challenge)),
* where ipad is a string of 0x36 and opad is a string of 0x5c. */
for (i = 0; i < sizeof(secret); i++)
secret[i] ^= 0x36;
apr_md5_init(&ctx);
apr_md5_update(&ctx, secret, sizeof(secret));
apr_md5_update(&ctx, challenge, strlen(challenge));
apr_md5_final(digest, &ctx);
for (i = 0; i < sizeof(secret); i++)
secret[i] ^= (0x36 ^ 0x5c);
apr_md5_init(&ctx);
apr_md5_update(&ctx, secret, sizeof(secret));
apr_md5_update(&ctx, digest, APR_MD5_DIGESTSIZE);
apr_md5_final(digest, &ctx);
}
/* Fail the authentication, from the server's perspective. */
static svn_error_t *fail(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
const char *msg)
{
SVN_ERR(svn_ra_svn_write_tuple(conn, pool, "w(c)", "failure", msg));
return svn_ra_svn_flush(conn, pool);
}
/* If we can, make the nonce with random bytes. If we can't... well,
* it just has to be different each time. The current time isn't
* absolutely guaranteed to be different for each connection, but it
* should prevent replay attacks in practice. */
static apr_status_t make_nonce(apr_uint64_t *nonce)
{
#if APR_HAS_RANDOM
return apr_generate_random_bytes((unsigned char *) nonce, sizeof(*nonce));
#else
*nonce = apr_time_now();
return APR_SUCCESS;
#endif
}
svn_error_t *svn_ra_svn_cram_server(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
svn_config_t *pwdb, const char **user,
svn_boolean_t *success)
{
apr_status_t status;
apr_uint64_t nonce;
char hostbuf[APRMAXHOSTLEN + 1];
unsigned char cdigest[APR_MD5_DIGESTSIZE], sdigest[APR_MD5_DIGESTSIZE];
const char *challenge, *sep, *password;
svn_ra_svn_item_t *item;
svn_string_t *resp;
*success = FALSE;
/* Send a challenge. */
status = make_nonce(&nonce);
if (!status)
status = apr_gethostname(hostbuf, sizeof(hostbuf), pool);
if (status)
return fail(conn, pool, "Internal server error in authentication");
challenge = apr_psprintf(pool,
"<%" APR_UINT64_T_FMT ".%" APR_TIME_T_FMT "@%s>",
nonce, apr_time_now(), hostbuf);
SVN_ERR(svn_ra_svn_write_tuple(conn, pool, "w(c)", "step", challenge));
/* Read the client's response and decode it into *user and cdigest. */
SVN_ERR(svn_ra_svn_read_item(conn, pool, &item));
if (item->kind != SVN_RA_SVN_STRING) /* Very wrong; don't report failure */
return SVN_NO_ERROR;
resp = item->u.string;
sep = strrchr(resp->data, ' ');
if (!sep || resp->len - (sep + 1 - resp->data) != APR_MD5_DIGESTSIZE * 2
|| !hex_decode(cdigest, sep + 1))
return fail(conn, pool, "Malformed client response in authentication");
*user = apr_pstrmemdup(pool, resp->data, sep - resp->data);
/* Verify the digest against the password in pwfile. */
svn_config_get(pwdb, &password, SVN_CONFIG_SECTION_USERS, *user, NULL);
if (!password)
return fail(conn, pool, "Username not found");
compute_digest(sdigest, challenge, password);
if (memcmp(cdigest, sdigest, sizeof(sdigest)) != 0)
return fail(conn, pool, "Password incorrect");
*success = TRUE;
return svn_ra_svn_write_tuple(conn, pool, "w()", "success");
}
svn_error_t *svn_ra_svn__cram_client(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
const char *user, const char *password,
const char **message)
{
const char *status, *str, *reply;
unsigned char digest[APR_MD5_DIGESTSIZE];
char hex[2 * APR_MD5_DIGESTSIZE + 1];
/* Read the server challenge. */
SVN_ERR(svn_ra_svn_read_tuple(conn, pool, "w(?c)", &status, &str));
if (strcmp(status, "failure") == 0 && str)
{
*message = str;
return SVN_NO_ERROR;
}
else if (strcmp(status, "step") != 0 || !str)
return svn_error_create(SVN_ERR_RA_NOT_AUTHORIZED, NULL,
_("Unexpected server response to authentication"));
/* Write our response. */
compute_digest(digest, str, password);
hex_encode(hex, digest);
hex[sizeof(hex) - 1] = '\0';
reply = apr_psprintf(pool, "%s %s", user, hex);
SVN_ERR(svn_ra_svn_write_cstring(conn, pool, reply));
/* Read the success or failure response from the server. */
SVN_ERR(svn_ra_svn_read_tuple(conn, pool, "w(?c)", &status, &str));
if (strcmp(status, "failure") == 0 && str)
{
*message = str;
return SVN_NO_ERROR;
}
else if (strcmp(status, "success") != 0 || str)
return svn_error_create(SVN_ERR_RA_NOT_AUTHORIZED, NULL,
_("Unexpected server response to authentication"));
*message = NULL;
return SVN_NO_ERROR;
}
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