src/lookups/pgsql.c

/*************************************************
*     Exim - an Internet mail transport agent    *
*************************************************/

/* Copyright (c) University of Cambridge 1995 - 2018 */
/* Copyright (c) The Exim Maintainers 2020 */
/* See the file NOTICE for conditions of use and distribution. */

/* Thanks to Petr Cech for contributing the original code for these
functions. Thanks to Joachim Wieland for the initial patch for the Unix domain
socket extension. */

#include "../exim.h"
#include "lf_functions.h"

#include <libpq-fe.h>       /* The system header */

/* Structure and anchor for caching connections. */

typedef struct pgsql_connection {
  struct pgsql_connection *next;
  uschar *server;
  PGconn *handle;
} pgsql_connection;

static pgsql_connection *pgsql_connections = NULL;


/*************************************************
*              Open entry point                  *
*************************************************/

/* See local README for interface description. */

static void *
pgsql_open(const uschar * filename, uschar ** errmsg)
{
return (void *)(1);    /* Just return something non-null */
}


/*************************************************
*               Tidy entry point                 *
*************************************************/

/* See local README for interface description. */

static void
pgsql_tidy(void)
{
pgsql_connection *cn;
while ((cn = pgsql_connections) != NULL)
  {
  pgsql_connections = cn->next;
  DEBUG(D_lookup) debug_printf_indent("close PGSQL connection: %s\n", cn->server);
  PQfinish(cn->handle);
  }
}


/*************************************************
*       Notice processor function for pgsql      *
*************************************************/

/* This function is passed to pgsql below, and called for any PostgreSQL
"notices". By default they are written to stderr, which is undesirable.

Arguments:
  arg        an opaque user cookie (not used)
  message    the notice

Returns:     nothing
*/

static void
notice_processor(void *arg, const char *message)
{
arg = arg;   /* Keep compiler happy */
DEBUG(D_lookup) debug_printf_indent("PGSQL: %s\n", message);
}


/*************************************************
*        Internal search function                *
*************************************************/

/* This function is called from the find entry point to do the search for a
single server. The server string is of the form "server/dbname/user/password".

PostgreSQL supports connections through Unix domain sockets. This is usually
faster and costs less cpu time than a TCP/IP connection. However it can only be
used if the mail server runs on the same machine as the database server. A
configuration line for PostgreSQL via Unix domain sockets looks like this:

hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password[:<nextserver>]

We enclose the path name in parentheses so that its slashes aren't visually
confused with the delimiters for the other pgsql_server settings.

For TCP/IP connections, the server is a host name and optional port (with a
colon separator).

NOTE:
 1) All three '/' must be present.
 2) If host is omitted the local unix socket is used.

Arguments:
  query        the query string
  server       the server string; this is in dynamic memory and can be updated
  resultptr    where to store the result
  errmsg       where to point an error message
  defer_break  set TRUE if no more servers are to be tried after DEFER
  do_cache     set FALSE if data is changed
  opts	       options list

Returns:       OK, FAIL, or DEFER
*/

static int
perform_pgsql_search(const uschar *query, uschar *server, uschar **resultptr,
  uschar **errmsg, BOOL *defer_break, uint *do_cache, const uschar * opts)
{
PGconn *pg_conn = NULL;
PGresult *pg_result = NULL;

gstring * result = NULL;
int yield = DEFER;
unsigned int num_fields, num_tuples;
pgsql_connection *cn;
rmark reset_point = store_mark();
uschar *server_copy = NULL;
uschar *sdata[3];

/* Disaggregate the parameters from the server argument. The order is host or
path, database, user, password. We can write to the string, since it is in a
nextinlist temporary buffer. The copy of the string that is used for caching
has the password removed. This copy is also used for debugging output. */

for (int i = 2; i >= 0; i--)
  {
  uschar *pp = Ustrrchr(server, '/');
  if (!pp)
    {
    *errmsg = string_sprintf("incomplete pgSQL server data: %s",
      (i == 2)? server : server_copy);
    *defer_break = TRUE;
    return DEFER;
    }
  *pp++ = 0;
  sdata[i] = pp;
  if (i == 2) server_copy = string_copy(server);  /* sans password */
  }

/* The total server string has now been truncated so that what is left at the
start is the identification of the server (host or path). See if we have a
cached connection to the server. */

for (cn = pgsql_connections; cn; cn = cn->next)
  if (Ustrcmp(cn->server, server_copy) == 0)
    {
    pg_conn = cn->handle;
    break;
    }

/* If there is no cached connection, we must set one up. */

if (!cn)
  {
  uschar *port = US"";

  /* For a Unix domain socket connection, the path is in parentheses */

  if (*server == '(')
    {
    uschar *last_slash, *last_dot, *p;

    p = ++server;
    while (*p && *p != ')') p++;
    *p = 0;

    last_slash = Ustrrchr(server, '/');
    last_dot = Ustrrchr(server, '.');

    DEBUG(D_lookup) debug_printf_indent("PGSQL new connection: socket=%s "
      "database=%s user=%s\n", server, sdata[0], sdata[1]);

    /* A valid socket name looks like this: /var/run/postgresql/.s.PGSQL.5432
    We have to call PQsetdbLogin with '/var/run/postgresql' as the hostname
    argument and put '5432' into the port variable. */

    if (!last_slash || !last_dot)
      {
      *errmsg = string_sprintf("PGSQL invalid filename for socket: %s", server);
      *defer_break = TRUE;
      return DEFER;
      }

    /* Terminate the path name and set up the port: we'll have something like
    server = "/var/run/postgresql" and port = "5432". */

    *last_slash = 0;
    port = last_dot + 1;
    }

  /* Host connection; sort out the port */

  else
    {
    uschar *p;
    if ((p = Ustrchr(server, ':')))
      {
      *p++ = 0;
      port = p;
      }

    if (Ustrchr(server, '/'))
      {
      *errmsg = string_sprintf("unexpected slash in pgSQL server hostname: %s",
        server);
      *defer_break = TRUE;
      return DEFER;
      }

    DEBUG(D_lookup) debug_printf_indent("PGSQL new connection: host=%s port=%s "
      "database=%s user=%s\n", server, port, sdata[0], sdata[1]);
    }

  /* If the database is the empty string, set it NULL - the query must then
  define it. */

  if (sdata[0][0] == 0) sdata[0] = NULL;

  /* Get store for a new handle, initialize it, and connect to the server */

  pg_conn=PQsetdbLogin(
    /*  host      port  options tty   database       user       passwd */
    CS server, CS port,  NULL, NULL, CS sdata[0], CS sdata[1], CS sdata[2]);

  if(PQstatus(pg_conn) == CONNECTION_BAD)
    {
    reset_point = store_reset(reset_point);
    *errmsg = string_sprintf("PGSQL connection failed: %s",
      PQerrorMessage(pg_conn));
    PQfinish(pg_conn);
    goto PGSQL_EXIT;
    }

  /* Set the client encoding to SQL_ASCII, which means that the server will
  not try to interpret the query as being in any fancy encoding such as UTF-8
  or other multibyte code that might cause problems with escaping. */

  PQsetClientEncoding(pg_conn, "SQL_ASCII");

  /* Set the notice processor to prevent notices from being written to stderr
  (which is what the default does). Our function (above) just produces debug
  output. */

  PQsetNoticeProcessor(pg_conn, notice_processor, NULL);

  /* Add the connection to the cache */

  cn = store_get(sizeof(pgsql_connection), FALSE);
  cn->server = server_copy;
  cn->handle = pg_conn;
  cn->next = pgsql_connections;
  pgsql_connections = cn;
  }

/* Else use a previously cached connection */

else
  {
  DEBUG(D_lookup) debug_printf_indent("PGSQL using cached connection for %s\n",
    server_copy);
  }

/* Run the query */

pg_result = PQexec(pg_conn, CS query);
switch(PQresultStatus(pg_result))
  {
  case PGRES_EMPTY_QUERY:
  case PGRES_COMMAND_OK:
    /* The command was successful but did not return any data since it was
    not SELECT but either an INSERT, UPDATE or DELETE statement. Tell the
    high level code to not cache this query, and clean the current cache for
    this handle by setting *do_cache zero. */

    result = string_cat(result, US PQcmdTuples(pg_result));
    *do_cache = 0;
    DEBUG(D_lookup) debug_printf_indent("PGSQL: command does not return any data "
      "but was successful. Rows affected: %s\n", string_from_gstring(result));
    break;

  case PGRES_TUPLES_OK:
    break;

  default:
    /* This was the original code:
    *errmsg = string_sprintf("PGSQL: query failed: %s\n",
			     PQresultErrorMessage(pg_result));
    This was suggested by a user:
    */

    *errmsg = string_sprintf("PGSQL: query failed: %s (%s) (%s)\n",
			   PQresultErrorMessage(pg_result),
			   PQresStatus(PQresultStatus(pg_result)), query);
    goto PGSQL_EXIT;
  }

/* Result is in pg_result. Find the number of fields returned. If this is one,
we don't add field names to the data. Otherwise we do. If the query did not
return anything we skip the for loop; this also applies to the case
PGRES_COMMAND_OK. */

num_fields = PQnfields(pg_result);
num_tuples = PQntuples(pg_result);

/* Get the fields and construct the result string. If there is more than one
row, we insert '\n' between them. */

for (int i = 0; i < num_tuples; i++)
  {
  if (result)
    result = string_catn(result, US"\n", 1);

  if (num_fields == 1)
    result = string_catn(result,
	US PQgetvalue(pg_result, i, 0), PQgetlength(pg_result, i, 0));
  else
    for (int j = 0; j < num_fields; j++)
      {
      uschar *tmp = US PQgetvalue(pg_result, i, j);
      result = lf_quote(US PQfname(pg_result, j), tmp, Ustrlen(tmp), result);
      }
  }

/* If result is NULL then no data has been found and so we return FAIL. */

if (!result)
  {
  yield = FAIL;
  *errmsg = US"PGSQL: no data found";
  }

/* Get here by goto from various error checks. */

PGSQL_EXIT:

/* Free store for any result that was got; don't close the connection, as
it is cached. */

if (pg_result) PQclear(pg_result);

/* Non-NULL result indicates a successful result */

if (result)
  {
  gstring_release_unused(result);
  *resultptr = string_from_gstring(result);
  return OK;
  }
else
  {
  DEBUG(D_lookup) debug_printf_indent("%s\n", *errmsg);
  return yield;      /* FAIL or DEFER */
  }
}


/*************************************************
*               Find entry point                 *
*************************************************/

/* See local README for interface description. The handle and filename
arguments are not used. The code to loop through a list of servers while the
query is deferred with a retryable error is now in a separate function that is
shared with other SQL lookups. */

static int
pgsql_find(void * handle, const uschar * filename, const uschar * query,
  int length, uschar ** result, uschar ** errmsg, uint * do_cache,
  const uschar * opts)
{
return lf_sqlperform(US"PostgreSQL", US"pgsql_servers", pgsql_servers, query,
  result, errmsg, do_cache, opts, perform_pgsql_search);
}


/*************************************************
*               Quote entry point                *
*************************************************/

/* The characters that always need to be quoted (with backslash) are newline,
tab, carriage return, backspace, backslash itself, and the quote characters.

The original code quoted single quotes as \' which is documented as valid in
the O'Reilly book "Practical PostgreSQL" (first edition) as an alternative to
the SQL standard '' way of representing a single quote as data. However, in
June 2006 there was some security issue with using \' and so this has been
changed.

[Note: There is a function called PQescapeStringConn() that quotes strings.
This cannot be used because it needs a PGconn argument (the connection handle).
Why, I don't know. Seems odd for just string escaping...]

Arguments:
  s          the string to be quoted
  opt        additional option text or NULL if none

Returns:     the processed string or NULL for a bad option
*/

static uschar *
pgsql_quote(uschar *s, uschar *opt)
{
register int c;
int count = 0;
uschar *t = s;
uschar *quoted;

if (opt != NULL) return NULL;     /* No options recognized */

while ((c = *t++) != 0)
  if (Ustrchr("\n\t\r\b\'\"\\", c) != NULL) count++;

if (count == 0) return s;
t = quoted = store_get(Ustrlen(s) + count + 1, is_tainted(s));

while ((c = *s++) != 0)
  {
  if (c == '\'')
    {
    *t++ = '\'';
    *t++ = '\'';
    }
  else if (Ustrchr("\n\t\r\b\"\\", c) != NULL)
    {
    *t++ = '\\';
    switch(c)
      {
      case '\n': *t++ = 'n';
      break;
      case '\t': *t++ = 't';
      break;
      case '\r': *t++ = 'r';
      break;
      case '\b': *t++ = 'b';
      break;
      default:   *t++ = c;
      break;
      }
    }
  else *t++ = c;
  }

*t = 0;
return quoted;
}


/*************************************************
*         Version reporting entry point          *
*************************************************/

/* See local README for interface description. */

#include "../version.h"

void
pgsql_version_report(FILE *f)
{
#ifdef DYNLOOKUP
fprintf(f, "Library version: PostgreSQL: Exim version %s\n", EXIM_VERSION_STR);
#endif

/* Version reporting: there appears to be no available information about
the client library in libpq-fe.h; once you have a connection object, you
can access the server version and the chosen protocol version, but those
aren't really what we want.  It might make sense to debug_printf those
when the connection is established though? */
}


static lookup_info _lookup_info = {
  .name = US"pgsql",			/* lookup name */
  .type = lookup_querystyle,		/* query-style lookup */
  .open = pgsql_open,			/* open function */
  .check = NULL,			/* no check function */
  .find = pgsql_find,			/* find function */
  .close = NULL,			/* no close function */
  .tidy = pgsql_tidy,			/* tidy function */
  .quote = pgsql_quote,			/* quoting function */
  .version_report = pgsql_version_report           /* version reporting */
};

#ifdef DYNLOOKUP
#define pgsql_lookup_module_info _lookup_module_info
#endif

static lookup_info *_lookup_list[] = { &_lookup_info };
lookup_module_info pgsql_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };

/* End of lookups/pgsql.c */