if( nAllocQP<=nUsedQP ){
    nAllocQP = nAllocQP*2 + 10;
    aParamQP = realloc( aParamQP, nAllocQP*sizeof(aParamQP[0]) );
    if( aParamQP==0 ) exit(1);
  }
  aParamQP[nUsedQP].zName = zName;
  aParamQP[nUsedQP].zValue = zValue;
  if( g.fHttpTrace ){
    fprintf(stderr, "# cgi: %s = [%s]\n", zName, zValue);
  }
  aParamQP[nUsedQP].seq = seqQP++;
  nUsedQP++;
  sortQP = 1;
}

/*
** Add another query parameter or cookie to the parameter set.

          if( child>0 ) nchildren++;
          close(connection);
        }else{
          close(0);
          dup(connection);
          close(1);
          dup(connection);
          if( !g.fHttpTrace && !g.fSqlTrace ){
            close(2);
            dup(connection);
          }
          close(connection);
          return 0;
        }
      }

}

/*
** This function registers auxiliary functions when the SQLite
** database connection is first established.
*/
LOCAL void db_connection_init(void){


  sqlite3_exec(g.db, "PRAGMA foreign_keys=OFF;", 0, 0, 0);
  sqlite3_create_function(g.db, "user", 0, SQLITE_ANY, 0, db_sql_user, 0, 0);
  sqlite3_create_function(g.db, "cgi", 1, SQLITE_ANY, 0, db_sql_cgi, 0, 0);
  sqlite3_create_function(g.db, "cgi", 2, SQLITE_ANY, 0, db_sql_cgi, 0, 0);
  sqlite3_create_function(g.db, "print", -1, SQLITE_UTF8, 0,db_sql_print,0,0);
  sqlite3_create_function(
    g.db, "file_is_selected", 1, SQLITE_UTF8, 0, file_is_selected,0,0
  );
  if( g.fSqlTrace ){
    sqlite3_trace(g.db, db_sql_trace, 0);


  }
}

/*
** Return true if the string zVal represents "true" (or "false").
*/
int is_truth(const char *zVal){

** of all payload that follows the login card.  SIGNATURE is the sha1
** checksum of the nonce followed by the user password.
**
** Write the constructed login card into pLogin.  pLogin is initialized
** by this routine.
*/
static void http_build_login_card(Blob *pPayload, Blob *pLogin){
  Blob nonce;          /* The nonce */
  const char *zLogin;  /* The user login name */
  const char *zPw;     /* The user password */
  Blob pw;             /* The nonce with user password appended */
  Blob sig;            /* The signature field */

  blob_zero(&nonce);
  blob_zero(&pw);
  sha1sum_blob(pPayload, &nonce);
  blob_copy(&pw, &nonce);
  blob_zero(pLogin);
  if( g.urlUser==0 ){
    user_select();
    zPw = db_text("", "SELECT pw FROM user WHERE uid=%d", g.userUid);

    zLogin = g.zLogin;
  }else{
    if( g.urlPasswd==0 ){
      if( strcmp(g.urlUser,"anonymous")!=0 ){
        char *zPrompt = mprintf("password for %s: ", g.urlUser);
        Blob x;
        prompt_for_password(zPrompt, &x, 0);
        free(zPrompt);
        g.urlPasswd = blob_str(&x);
      }else{
        g.urlPasswd = "";
      }
    }
    zPw = g.urlPasswd;
    zLogin = g.urlUser;
  }

  /* The login card wants the SHA1 hash of the password, so convert the
  ** password to its SHA1 hash it it isn't already a SHA1 hash.
  **
  ** Except, if the password begins with "*" then use the characters
  ** after the "*" as a cleartext password.  Put an "*" at the beginning
  ** of the password to trick a newer client to use the cleartext password
  ** protocol required by legacy servers.
  */
  if( zPw && zPw[0] ){
    if( zPw[0]=='*' ){
      zPw++;
    }else{
      zPw = sha1_shared_secret(zPw, zLogin);
    }
  }

  blob_append(&pw, zPw, -1);
  sha1sum_blob(&pw, &sig);
  blob_appendf(pLogin, "login %F %b %b\n", zLogin, &nonce, &sig);

  blob_reset(&pw);
  blob_reset(&sig);
  blob_reset(&nonce);
}

/*
** Construct an appropriate HTTP request header.  Write the header
** into pHdr.  This routine initializes the pHdr blob.  pPayload is
** the complete payload (including the login card) already compressed.
*/

void login_page(void){
  const char *zUsername, *zPasswd;
  const char *zNew1, *zNew2;
  const char *zAnonPw = 0;
  int anonFlag;
  char *zErrMsg = "";
  int uid;                     /* User id loged in user */
  char *zSha1Pw;

  login_check_credentials();
  zUsername = P("u");
  zPasswd = P("p");
  anonFlag = P("anon")!=0;
  if( P("out")!=0 ){
    const char *zCookieName = login_cookie_name();
    cgi_set_cookie(zCookieName, "", 0, -86400);
    redirect_to_g();
  }
  if( g.okPassword && zPasswd && (zNew1 = P("n1"))!=0 && (zNew2 = P("n2"))!=0 ){
    zSha1Pw = sha1_shared_secret(zPasswd, g.zLogin);
    if( db_int(1, "SELECT 0 FROM user"
                  " WHERE uid=%d AND (pw=%Q OR pw=%Q)", 
                  g.userUid, zPasswd, zSha1Pw) ){
      sleep(1);
      zErrMsg = 
         @ <p><font color="red">
         @ You entered an incorrect old password while attempting to change
         @ your password.  Your password is unchanged.
         @ </font></p>
      ;
    }else if( strcmp(zNew1,zNew2)!=0 ){
      zErrMsg = 
         @ <p><font color="red">
         @ The two copies of your new passwords do not match.
         @ Your password is unchanged.
         @ </font></p>
      ;
    }else{
      char *zNewPw = sha1_shared_secret(zNew1, g.zLogin);
      db_multi_exec(
         "UPDATE user SET pw=%Q WHERE uid=%d", zNewPw, g.userUid
      );
      redirect_to_g();
      return;
    }
  }
  uid = isValidAnonymousLogin(zUsername, zPasswd);
  if( uid>0 ){

    zCookie = sqlite3_mprintf("anon/%s/%s", zNow, blob_buffer(&b));
    blob_reset(&b);
    free(zNow);
    cgi_set_cookie(zCookieName, zCookie, 0, 6*3600);
    redirect_to_g();
  }
  if( zUsername!=0 && zPasswd!=0 && zPasswd[0]!=0 ){
    zSha1Pw = sha1_shared_secret(zPasswd, zUsername);
    uid = db_int(0,
        "SELECT uid FROM user"
        " WHERE login=%Q"
        "   AND login NOT IN ('anonymous','nobody','developer','reader')"
        "   AND (pw=%Q OR pw=%Q)",
        zUsername, zPasswd, zSha1Pw
    );
    if( uid<=0 ){
      sleep(1);
      zErrMsg = 
         @ <p><font color="red">
         @ You entered an unknown user or an incorrect password.
         @ </font></p>

      zCap = db_column_malloc(&s, 1);
    }
    db_finalize(&s);
    if( zCap==0 ){
      zCap = "";
    }
  }
  if( g.fHttpTrace && g.zLogin ){
    fprintf(stderr, "# login: [%s] with capabilities [%s]\n", g.zLogin, zCap);
  }

  /* Set the global variables recording the userid and login.  The
  ** "nobody" user is a special case in that g.zLogin==0.
  */
  g.userUid = uid;
  if( g.zLogin && strcmp(g.zLogin,"nobody")==0 ){
    g.zLogin = 0;

  }
  db_close();
  if( cgi_http_server(iPort, mxPort, zBrowserCmd) ){
    fossil_fatal("unable to listen on TCP socket %d", iPort);
  }
  g.httpIn = stdin;
  g.httpOut = stdout;
  if( g.fHttpTrace || g.fSqlTrace ){
    fprintf(stderr, "====== SERVER pid %d =======\n", getpid());
  }
  g.cgiPanic = 1;
  if( g.argc==2 ){
    db_must_be_within_tree();
  }else{
    db_open_repository(g.argv[2]);

@   uid INTEGER REFERENCES user,    -- User login
@   mtime DATETIME,                 -- Time or receipt
@   nonce TEXT UNIQUE,              -- Nonce used for login
@   ipaddr TEXT                     -- Remote IP address.  NULL for direct.
@ );
@
@ -- Information about users
@ --
@ -- The user.pw field can be either cleartext of the password, or
@ -- a SHA1 hash of the password.  If the user.pw field is exactly 40
@ -- characters long we assume it is a SHA1 hash.  Otherwise, it is
@ -- cleartext.  The sha1_shared_secret() routine computes the password
@ -- hash based on the project-code, the user login, and the cleartext
@ -- password.
@ --
@ CREATE TABLE user(
@   uid INTEGER PRIMARY KEY,        -- User ID
@   login TEXT,                     -- login name of the user
@   pw TEXT,                        -- password
@   cap TEXT,                       -- Capabilities of this user
@   cookie TEXT,                    -- WWW login cookie

    if( au ){ zCap[i++] = 'u'; }
    if( av ){ zCap[i++] = 'v'; }
    if( aw ){ zCap[i++] = 'w'; }
    if( az ){ zCap[i++] = 'z'; }

    zCap[i] = 0;
    zPw = P("pw");
    zLogin = P("login");
    if( isValidPwString(zPw) ){
      zPw = sha1_shared_secret(zPw, zLogin);
    }else{
      zPw = db_text(0, "SELECT pw FROM user WHERE uid=%d", uid);
    }

    if( uid>0 &&
        db_exists("SELECT 1 FROM user WHERE login=%Q AND uid!=%d", zLogin, uid)
    ){
      style_header("User Creation Error");
      @ <font color="red">Login "%h(zLogin)" is already used by a different
      @ user.</font>
      @

  @    <input type="checkbox" name="aw"%s(oaw)/>%s(B('w'))Write Tkt<br>
  @    <input type="checkbox" name="at"%s(oat)/>%s(B('t'))Tkt Report<br>
  @    <input type="checkbox" name="az"%s(oaz)/>%s(B('z'))Download Zip
  @   </td>
  @ </tr>
  @ <tr>
  @   <td align="right">Password:</td>


  if( zPw[0] ){
    /* Obscure the password for all users */
    @   <td><input type="password" name="pw" value="**********"></td>
  }else{
    /* Show an empty password as an empty input field */
    @   <td><input type="password" name="pw" value=""></td>
  }
  @ </tr>
  if( !higherUser ){

  }
  blob_resize(pCksum, 40);
  SHA1Result(&ctx, zResult);
  DigestToBase16(zResult, blob_buffer(pCksum));
  return 0;
}

/*
** Compute the SHA1 checksum of a zero-terminated string.  The
** result is held in memory obtained from mprintf().
*/
char *sha1sum(const char *zIn){
  SHA1Context ctx;
  unsigned char zResult[20];
  char zDigest[41];

  SHA1Reset(&ctx);
  SHA1Input(&ctx, (unsigned const char*)zIn, strlen(zIn));
  SHA1Result(&ctx, zResult);
  DigestToBase16(zResult, zDigest);
  return mprintf("%s", zDigest);
}

/*
** Convert a cleartext password for a specific user into a SHA1 hash.
** 
** The algorithm here is:
**
**       SHA1( project-code + "/" + login + "/" + password )
**
** In words: The users login name and password are appended to the
** project ID code and the SHA1 hash of the result is computed.
**
** The result of this function is the shared secret used by a client
** to authenticate to a server for the sync protocol.  It is also the
** value stored in the USER.PW field of the database.  By mixing in the
** login name and the project id with the hash, different shared secrets
** are obtained even if two users select the same password, or if a 
** single user selects the same password for multiple projects.
*/
char *sha1_shared_secret(const char *zPw, const char *zLogin){
  static char *zProjectId = 0;
  SHA1Context ctx;
  unsigned char zResult[20];
  char zDigest[41];

  SHA1Reset(&ctx);
  if( zProjectId==0 ){
    zProjectId = db_get("project-code", 0);

    /* On the first xfer request of a clone, the project-code is not yet
    ** known.  Use the cleartext password, since that is all we have.
    */
    if( zProjectId==0 ){
      return mprintf("%s", zPw);
    }
  }
  SHA1Input(&ctx, (unsigned char*)zProjectId, strlen(zProjectId));
  SHA1Input(&ctx, (unsigned char*)"/", 1);
  SHA1Input(&ctx, (unsigned char*)zLogin, strlen(zLogin));
  SHA1Input(&ctx, (unsigned char*)"/", 1);
  SHA1Input(&ctx, (unsigned const char*)zPw, strlen(zPw));
  SHA1Result(&ctx, zResult);
  DigestToBase16(zResult, zDigest);
  return mprintf("%s", zDigest);
}

/*
** COMMAND: sha1sum
** %fossil sha1sum FILE...
**
** Compute an SHA1 checksum of all files named on the command-line.
** If an file is named "-" then take its content from standard input.

  db_find_and_open_repository(1);
  if( g.argc<3 ){
    usage("capabilities|default|list|new|password ...");
  }
  n = strlen(g.argv[2]);
  if( n>=2 && strncmp(g.argv[2],"new",n)==0 ){
    Blob passwd, login, contact;
    char *zPw;

    if( g.argc>=4 ){
      blob_init(&login, g.argv[3], -1);
    }else{
      prompt_user("login: ", &login);
    }
    if( db_exists("SELECT 1 FROM user WHERE login=%B", &login) ){
      fossil_fatal("user %b already exists", &login);
    }
    if( g.argc>=5 ){
      blob_init(&contact, g.argv[4], -1);
    }else{
      prompt_user("contact-info: ", &contact);
    }
    if( g.argc>=6 ){
      blob_init(&passwd, g.argv[5], -1);
    }else{
      prompt_for_password("password: ", &passwd, 1);
    }
    zPw = sha1_shared_secret(blob_str(&passwd), blob_str(&login));
    db_multi_exec(
      "INSERT INTO user(login,pw,cap,info)"
      "VALUES(%B,%Q,'v',%B)",
      &login, zPw, &contact
    );
    free(zPw);
  }else if( n>=2 && strncmp(g.argv[2],"default",n)==0 ){
    user_select();
    if( g.argc==3 ){
      printf("%s\n", g.zLogin);
    }else{
      if( !db_exists("SELECT 1 FROM user WHERE login=%Q", g.argv[3]) ){
        fossil_fatal("no such user: %s", g.argv[3]);

    }else{
      zPrompt = mprintf("new passwd for %s: ", g.argv[3]);
      prompt_for_password(zPrompt, &pw, 1);
    }
    if( blob_size(&pw)==0 ){
      printf("password unchanged\n");
    }else{
      char *zSecret = sha1_shared_secret(blob_str(&pw), g.argv[3]);
      db_multi_exec("UPDATE user SET pw=%Q WHERE uid=%d", zSecret, uid);
      free(zSecret);
    }
  }else if( n>=2 && strncmp(g.argv[2],"capabilities",2)==0 ){
    int uid;
    if( g.argc!=4 && g.argc!=5 ){
      usage("user capabilities USERNAME ?PERMISSIONS?");
    }
    uid = db_int(0, "SELECT uid FROM user WHERE login=%Q", g.argv[3]);

      "INSERT INTO user(login, pw, cap, info)"
      "VALUES('anonymous', '', 'cfghjkmnoqw', '')"
    );
    g.userUid = db_last_insert_rowid();
    g.zLogin = "anonymous";
  }
}

/*
** Compute the shared secret for a user.
*/
static void user_sha1_shared_secret_func(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  char *zPw;
  char *zLogin;
  assert( argc==2 );
  zPw = (char*)sqlite3_value_text(argv[0]);
  zLogin = (char*)sqlite3_value_text(argv[1]);
  if( zPw && zLogin ){ 
    sqlite3_result_text(context, sha1_shared_secret(zPw, zLogin), -1, free);
  }
}

/*
** COMMAND: test-hash-passwords
**
** Usage: %fossil test-hash-passwords REPOSITORY
**
** Convert all local password storage to use a SHA1 hash of the password
** rather than cleartext.  Passwords that are already stored as the SHA1
** has are unchanged.
*/
void user_hash_passwords_cmd(void){
  if( g.argc!=3 ) usage("REPOSITORY");
  db_open_repository(g.argv[2]);
  sqlite3_create_function(g.db, "sha1_shared_secret", 2, SQLITE_UTF8, 0,
                          user_sha1_shared_secret_func, 0, 0);
  db_multi_exec(
    "UPDATE user SET pw=sha1_shared_secret(pw,login)"
    " WHERE length(pw)>0 AND length(pw)!=40"
  );
}

  sha1sum_blob(&tail, &h2);
  rc = blob_compare(pHash, &h2);
  blob_reset(&h2);
  blob_reset(&tail);
  return rc==0;
}


/*
** Check the signature on an application/x-fossil payload received by
** the HTTP server.  The signature is a line of the following form:
**
**        login LOGIN NONCE SIGNATURE
**
** The NONCE is the SHA1 hash of the remainder of the input.  

     "SELECT pw, cap, uid FROM user"
     " WHERE login=%Q"
     "   AND login NOT IN ('anonymous','nobody','developer','reader')"
     "   AND length(pw)>0",
     zLogin
  );
  if( db_step(&q)==SQLITE_ROW ){
    int szPw;
    Blob pw, combined, hash;
    blob_zero(&pw);
    db_ephemeral_blob(&q, 0, &pw);
    szPw = blob_size(&pw);
    blob_zero(&combined);
    blob_copy(&combined, pNonce);
    blob_append(&combined, blob_buffer(&pw), szPw);

    sha1sum_blob(&combined, &hash);
    assert( blob_size(&hash)==40 );
    rc = blob_compare(&hash, pSig);
    blob_reset(&hash);
    blob_reset(&combined);
    if( rc!=0 && szPw!=40 ){
      /* If this server stores cleartext passwords and the password did not
      ** match, then perhaps the client is sending SHA1 passwords.  Try
      ** again with the SHA1 password.
      */
      const char *zPw = db_column_text(&q, 0);
      char *zSecret = sha1_shared_secret(zPw, blob_str(pLogin));
      blob_zero(&combined);
      blob_copy(&combined, pNonce);
      blob_append(&combined, zSecret, -1);
      free(zSecret);
      sha1sum_blob(&combined, &hash);
      rc = blob_compare(&hash, pSig);
      blob_reset(&hash);
      blob_reset(&combined);
    }
    if( rc==0 ){
      const char *zCap;
      zCap = db_column_text(&q, 1);
      login_set_capabilities(zCap);
      g.userUid = db_column_int(&q, 2);
      g.zLogin = mprintf("%b", pLogin);
      g.zNonce = mprintf("%b", pNonce);
      if( g.fHttpTrace ){
        fprintf(stderr, "# login [%s] with capabilities [%s]\n", g.zLogin,zCap);
      }
    }
  }
  db_finalize(&q);

  if( rc==0 ){
    /* If the login was successful. */
    login_set_anon_nobody_capabilities();

    }else
  
    
    /*    pull  SERVERCODE  PROJECTCODE
    **    push  SERVERCODE  PROJECTCODE
    **
    ** The client wants either send or receive.  The server should
    ** verify that the project code matches.

    */
    if( xfer.nToken==3
     && (blob_eq(&xfer.aToken[0], "pull") || blob_eq(&xfer.aToken[0], "push"))
     && blob_is_uuid(&xfer.aToken[1])
     && blob_is_uuid(&xfer.aToken[2])
    ){
      const char *zPCode;






















      zPCode = db_get("project-code", 0);
      if( zPCode==0 ){
        fossil_panic("missing project code");
      }
      if( !blob_eq_str(&xfer.aToken[2], zPCode, -1) ){
        cgi_reset_content();
        @ error wrong\sproject

    **
    ** The client knows nothing.  Tell all.
    */
    if( blob_eq(&xfer.aToken[0], "clone") ){
      login_check_credentials();
      if( !g.okClone ){
        cgi_reset_content();
        @ push %s(db_get("server-code", "x")) %s(db_get("project-code", "x"))
        @ error not\sauthorized\sto\sclone
        nErr++;
        break;
      }
      isClone = 1;
      isPull = 1;
      deltaFlag = 1;

    "CREATE TEMP TABLE onremote(rid INTEGER PRIMARY KEY);"
  );
  blobarray_zero(xfer.aToken, count(xfer.aToken));
  blob_zero(&send);
  blob_zero(&recv);
  blob_zero(&xfer.err);
  blob_zero(&xfer.line);
  origConfigRcvMask = 0;

  /*
  ** Always begin with a clone, pull, or push message
  */
  if( cloneFlag ){
    blob_appendf(&send, "clone\n");
    pushFlag = 0;

      request_phantoms(&xfer, mxPhantomReq);
    }
    if( pushFlag ){
      send_unsent(&xfer);
      nCardSent += send_unclustered(&xfer);
    }

    /* Send configuration parameter requests.  On a clone, delay sending
    ** this until the second cycle since the login card might fail on 
    ** the first cycle.
    */
    if( configRcvMask && (cloneFlag==0 || nCycle>0) ){
      const char *zName;
      zName = configure_first_name(configRcvMask);
      while( zName ){
        blob_appendf(&send, "reqconfig %s\n", zName);
        zName = configure_next_name(configRcvMask);
        nCardSent++;
      }
      if( configRcvMask & (CONFIGSET_USER|CONFIGSET_TKT) ){
        configure_prepare_to_receive(0);
      }
      origConfigRcvMask = configRcvMask;
      configRcvMask = 0;
    }

    /* Send configuration parameters being pushed */
    if( configSendMask ){
      const char *zName;
      zName = configure_first_name(configSendMask);
      while( zName ){
        send_config_card(&xfer, zName);
        zName = configure_next_name(configSendMask);
        nCardSent++;
      }
      configSendMask = 0;
    }

    /* Append randomness to the end of the message.  This makes all
    ** messages unique so that that the login-card nonce will always
    ** be unique.
    */
    zRandomness = db_text(0, "SELECT hex(randomblob(20))");
    blob_appendf(&send, "# %s\n", zRandomness);
    free(zRandomness);

    /* Exchange messages with the server */
    nFileSend = xfer.nFileSent + xfer.nDeltaSent;
    printf(zValueFormat, "Send:",

        char *zMsg = blob_terminate(&xfer.aToken[1]);
        defossilize(zMsg);
        printf("\rServer says: %s\n", zMsg);
      }else

      /*   error MESSAGE
      **
      ** Report an error and abandon the sync session.
      **
      ** Except, when cloning we will sometimes get an error on the
      ** first message exchange because the project-code is unknown
      ** and so the login card on the request was invalid.  The project-code
      ** is returned in the reply before the error card, so second and 
      ** subsequent messages should be OK.  Nevertheless, we need to ignore
      ** the error card on the first message of a clone.
      */        
      if( blob_eq(&xfer.aToken[0],"error") && xfer.nToken==2 ){
        if( !cloneFlag || nCycle>0 ){
          char *zMsg = blob_terminate(&xfer.aToken[1]);
          defossilize(zMsg);
          blob_appendf(&xfer.err, "server says: %s", zMsg);
          printf("Server Error: %s\n", zMsg);
        }
      }else

      /* Unknown message */
      {
        if( blob_str(&xfer.aToken[0])[0]=='<' ){
          fossil_fatal(
            "server replies with HTML instead of fossil sync protocol:\n%b",

    /* If we have one or more files queued to send, then go
    ** another round 
    */
    if( xfer.nFileSent+xfer.nDeltaSent>0 ){
      go = 1;
    }

    /* If this is a clone, the go at least two rounds */
    if( cloneFlag && nCycle==1 ) go = 1;
  };
  transport_stats(&nSent, &nRcvd, 1);
  printf("Total network traffic: %d bytes sent, %d bytes received\n",
         nSent, nRcvd);
  transport_close();
  socket_global_shutdown();
  db_multi_exec("DROP TABLE onremote");
  manifest_crosslink_end();
  db_end_transaction(0);
}

<title>Fossil Password Management</title>
<h1 align="center">Password Management</h1>

Fossil handles user authentication using passwords.
Passwords are unique to each repository.  Passwords are not part of the
persistent state of a project.  Passwords are not versioned and
are not transmitted from one repository to another during a sync.
Passwords are local configuration information that can (and usually does)
vary from one repository to the next within the same project.

Passwords are stored in the PW field of the USER table.
In older versions of Fossil (prior to 
[/timeline?c=2010-01-10+20:56:30 | 2010-01-11]) the password 
is stored as cleartext.  In newer versions of Fossil, the password
can be either cleartext or an SHA1 hash (written as a 40-character
lower-case hexadecimal number).  If the USER.PW field contains
a 40-character string, that string is assumed to be a SHA1 hash.
If the size of USER.PW is anything other than 40 characters, then
it is understood as a plain-text password.

The SHA1 hash in the USER.PW field is a hash of a string composed of
the project-code, the user login, and the user cleartext password.
Suppose user "alice" with password "asdfg" had an account on the
Fossil self-hosting repository.  Then the value of USER.PW
for alice would be the SHA1 hash of

<blockquote>
CE59BB9F186226D80E49D1FA2DB29F935CCA0333/alice/asdfg
</blockquote>

That hash value is "f1b699cc9af3eeb98e5de244ca7802ae38e77bae".  Note
that by including the project-code and the login as part of the hash,
a different USER.PW value results even if two or more users on the
repository select the same "asdfg" password or if user alice reuses the
same password on multiple projects.

Whenever a password is changed using the web interface or using the
"user" command-line method, the new password is stored using the SHA1
encoding.  Thus, cleartext passwords will gradually migrate to become
SHA1 passwords.  All remaining cleartext passwords can be converted to
SHA1 passwords using the following command:

<blockquote><pre>
fossil test-hash-passwords <i>REPOSITORY-NAME</i>
</pre></blockquote>

Remember that converting from cleartext to SHA1 passwords is an
irreversible operation.

The only way to insert a new cleartext password into the USER table
is to do so manually using SQL commands.  For example:

<blockquote><pre>
UPDATE user SET pw='asdfg' WHERE login='alice';
</pre></blockquote>

Note that an password that is an empty string or NULL will disable
all login for that user.   Thus, to lock a user out of the system,
one has only to set their password to an empty string, using either
the web interface or direct SQL manipulation of the USER table.
Note also that the password field is
essentially ignored for the special users named "anonymous", "developer",
"reader", and "nobody".  It is not possible to authenticate as users
"developer", "reader", or "nobody" and the authentication protocol
for "anonymous" use one-time captchas not persistent passwords.

<h2>Web Interface Authtentication</h2>

When a user logs into Fossil using the web interface, the login name
and password are sent in the clear to the server.  The server then
hashes the password and compares it against the value stored in USER.PW.
If they match, the server sets a cookie on the client to record the
login.  This cookie contains a large amount of high-quality randomness
and is thus impossible to guess.  The value of the cookie and the IP
address of the client is stored in the USER.COOKIE and USER.IPADDR fields
of the USER table on the server.  
The USER.CEXPIRE field holds an expiration date
for the cookie, encoded as a julian day number.  On all subsequent
HTTP requests, the cookie value is matched against the USER table to 
enable access to the repository.

A login cookie will only work if the IP address matches.  This feature
is designed to make it more difficult for an attacker to sniff the cookie
and take over the connection.  A cookie-sniffing attack will only work
if the attacker is able to send and receive from the same IP address as
the original login.  However, we found that doing an exact IP match
caused problems for some users who are behind proxy firewalls where the proxy
might use a different IP address for each query.  To work around this
problem, newer versions of fossil only check the first 16 bits of the
32-bit IP address.  This makes a cookie sniffing attack easier since now
the attacker only has to send and receive from any IP address in a range
of IPs that are similar to the initial login.  But that is seen as an
acceptable compromise in exchange for ease of use.  If higher security
is really needed, then HTTPS can be used instead of HTTP.

Note that in order to log into a Fossil server, it is necessary to
write information into the repository database.  Hence, login is not
possible on a Fossil repository with a read-only database file.

The user password is sent over the wire as cleartext on the initial
login attempt.  The plan moving forward is to compute the SHA1 hash of
the password on the client using javascript and then send only the hash
over the wire, but that plan has not yet been set in code.

<h2>Sync Protocol Authentication</h2>

A different authentication mechanism is used when one repository wants
to sync (or push or pull or clone) another respository.  When two
respositories are syncing, the one that initiates the transaction is
the client and the repository that responds is the server.  The client
works by sending HTTP requests to the server with a method of "xfer"
and a content-type of "application/x-fossil".  The content is Zlib-compressed
text consisting of "cards" of instructions.  The first card of this content
is a "login" card responsible for authentication.  The login card contains
the login name of the user and a "signature" where the signature is the
SHA1 hash of a nonce and the value of USER.PW.  The nonce is the
SHA1 hash of the remainder of the request content after the newline
(ASCII 14) character that terminates the login card.

Using this approach, the USER.PW value is treated as a shared secret
between the client and server.  The USER.PW value is never sent over
the wire, but the protocol establishes that both client and server know
the value of USER.PW.  Furthermore, the use of a SHA1 hash over the entire
message prevents an attacker from sniffing a valid login from a legitimate
users and then replaying the message modified content.

If the USER.PW on the server holds a cleartext password, then the
server will also accept a login-card signature that is constructed
using either the cleartext password or the SHA1 hash of the password.
This means that when USER.PW holds a cleartext password, the login card
will work for both older and newer clients.  If the USER.PW on the server
only holds the SHA1 hash of the password, then only newer clients will be
able to authenticate to the server.

The client normally gets the login and password from the "remote URL".

<blockquote><pre>
http://<font color="blue">login:password</font>@servername.org/path
</pre></blockquote>

For older clients, the password is used for the shared secret as stated
in the URL and with no encoding.  
For newer clients, the shared secret is derived from the password 
by transformed the password using the SHA1 hash encoding
described above.  However, if the first character of the password is
"*" (ASCII 0x2a) then the "*" is skipped and the rest of the password
is used directly as the share secret without the SHA1 encoding.

<blockquote><pre>
http://<font color="blue">login:*password</font>@servername.org/path
</pre></blockquote>

This *-before-the-password trick can be used by newer clients to
sync against a legacy server that does not understand the new SHA1
password encoding.