text_backend.cc

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/*
 * Copyright (C) 1996-2023 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */
 
/*
 * AUTHOR: Robert Collins.
 *  Based on ncsa_auth.c by Arjan de Vet <Arjan.deVet@adv.iae.nl>
 *
 * Example digest auth text backend for Squid, based on the original
 * proxy_auth code from client_side.c, written by
 * Jon Thackray <jrmt@uk.gdscorp.com>.
 *
 * - comment lines are possible and should start with a '#';
 * - empty or blank lines are possible;
 * - file format is username:plaintext or username:realm:HA1
 *
 * To build a directory integrated backend, you need to be able to
 * calculate the HA1 returned to squid. To avoid storing a plaintext
 * password you can calculate MD5(username:realm:password) when the
 * user changes their password, and store the tuple username:realm:HA1.
 * then find the matching username:realm when squid asks for the
 * HA1.
 *
 * This implementation could be improved by using such a triple for
 * the file format.  However storing such a triple does little to
 * improve security: If compromised the username:realm:HA1 combination
 * is "plaintext equivalent" - for the purposes of digest authentication
 * they allow the user access. Password synchronization is not tackled
 * by digest - just preventing on the wire compromise.
 *
 * Copyright (c) 2003  Robert Collins  <robertc@squid-cache.org>
 */
 
#include "squid.h"
#include "auth/digest/file/text_backend.h"
 
static hash_table *hash = nullptr;
static HASHFREE my_free;
static char *passwdfile = nullptr;
static int ha1mode = 0;
static time_t change_time = 0;
 
typedef struct _user_data {
    hash_link hash;
    char *passwd;
    char *ha1;
} user_data;
 
static void
my_free(void *p)
{
    user_data *u = static_cast<user_data*>(p);
    xfree(u->hash.key);
    xfree(u->passwd);
    xfree(u);
}
 
static void
read_passwd_file(const char *passwordFile, int isHa1Mode)
{
    char buf[8192];
    user_data *u;
    char *user;
    char *passwd;
    char *ha1 = nullptr;
    char *realm;
 
    if (hash != nullptr) {
        hashFreeItems(hash, my_free);
    }
    /* initial setup */
    hash = hash_create((HASHCMP *) strcmp, 7921, hash_string);
    if (nullptr == hash) {
        fprintf(stderr, "digest_file_auth: cannot create hash table\n");
        exit(EXIT_FAILURE);
    }
    FILE *f = fopen(passwordFile, "r");
    if (!f) {
        int xerrno = errno;
        fprintf(stderr, "digest_file_auth: cannot open password file: %s\n", xstrerr(xerrno));
        exit(EXIT_FAILURE);
    }
    unsigned int lineCount = 0;
    while (fgets(buf, sizeof(buf), f) != nullptr) {
        ++lineCount;
        if ((buf[0] == '#') || (buf[0] == ' ') || (buf[0] == '\t') ||
                (buf[0] == '\n'))
            continue;
        user = strtok(buf, ":\n");
        if (!user) {
            fprintf(stderr, "digest_file_auth: missing user name at line %u in '%s'\n", lineCount, passwordFile);
            continue;
        }
        realm = strtok(nullptr, ":\n");
        passwd = strtok(nullptr, ":\n");
        if (!passwd) {
            passwd = realm;
            realm = nullptr;
        }
        if ((strlen(user) > 0) && passwd) {
            if (strncmp(passwd, "{HHA1}", 6) == 0) {
                ha1 = passwd + 6;
                passwd = nullptr;
            } else if (isHa1Mode) {
                ha1 = passwd;
                passwd = nullptr;
            }
            if (ha1 && strlen(ha1) != 32) {
                /* We cannot accept plaintext passwords when using HA1 encoding,
                 * as the passwords may be output to cache.log if debugging is on.
                 */
                fprintf(stderr, "digest_file_auth: ignoring invalid password for %s\n", user);
                continue;
            }
            u = static_cast<user_data*>(xcalloc(1, sizeof(*u)));
            if (realm) {
                int len = strlen(user) + strlen(realm) + 2;
                u->hash.key = xmalloc(len);
                snprintf(static_cast<char*>(u->hash.key), len, "%s:%s", user, realm);
            } else {
                u->hash.key = xstrdup(user);
            }
            if (ha1)
                u->ha1 = xstrdup(ha1);
            else
                u->passwd = xstrdup(passwd);
            hash_join(hash, &u->hash);
        }
    }
    fclose(f);
}
 
/* replace when changing the backend */
void
TextArguments(int argc, char **argv)
{
    struct stat sb;
    if (argc == 2)
        passwdfile = argv[1];
    if ((argc == 3) && !strcmp("-c", argv[1])) {
        ha1mode = 1;
        passwdfile = argv[2];
    }
    if (!passwdfile) {
        fprintf(stderr, "Usage: digest_file_auth [OPTIONS] <passwordfile>\n");
        fprintf(stderr, "  -c   accept digest hashed passwords rather than plaintext in passwordfile\n");
        exit(EXIT_FAILURE);
    }
    if (stat(passwdfile, &sb) != 0) {
        fprintf(stderr, "cannot stat %s\n", passwdfile);
        exit(EXIT_FAILURE);
    }
}
 
static const user_data *
GetPassword(RequestData * requestData)
{
    user_data *u;
    struct stat sb;
    char buf[256];
    int len;
    if (stat(passwdfile, &sb) == 0) {
        if (sb.st_mtime != change_time) {
            read_passwd_file(passwdfile, ha1mode);
            change_time = sb.st_mtime;
        }
    }
    if (!hash)
        return nullptr;
    len = snprintf(buf, sizeof(buf), "%s:%s", requestData->user, requestData->realm);
    if (len >= static_cast<int>(sizeof(buf)))
        return nullptr;
    u = (user_data*)hash_lookup(hash, buf);
    if (u)
        return u;
    u = (user_data*)hash_lookup(hash, requestData->user);
    return u;
}
 
void
TextHHA1(RequestData * requestData)
{
    const user_data *u = GetPassword(requestData);
    if (!u) {
        requestData->error = -1;
        return;
    }
    if (u->ha1) {
        xstrncpy(requestData->HHA1, u->ha1, sizeof(requestData->HHA1));
    } else {
        HASH HA1;
        DigestCalcHA1("md5", requestData->user, requestData->realm, u->passwd, nullptr, nullptr, HA1, requestData->HHA1);
    }
}