/*-------------------------------------------------------------------------

 *

 * be-secure-common.c

 *

 * common implementation-independent SSL support code

 *

 * While be-secure.c contains the interfaces that the rest of the

 * communications code calls, this file contains support routines that are

 * used by the library-specific implementations such as be-secure-openssl.c.

 *

 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group

 * Portions Copyright (c) 1994, Regents of the University of California

 *

 * IDENTIFICATION

 *    src/backend/libpq/be-secure-common.c

 *

 *-------------------------------------------------------------------------

 */

#include "postgres.h"

#include <sys/stat.h>

#include <unistd.h>

#include "common/percentrepl.h"

#include "common/string.h"

#include "libpq/libpq.h"

#include "storage/fd.h"

/*

 * Run ssl_passphrase_command

 *

 * prompt will be substituted for %p.  is_server_start determines the loglevel

 * of error messages.

 *

 * The result will be put in buffer buf, which is of size size.  The return

 * value is the length of the actual result.

 */

int

run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)

{

  int     loglevel = is_server_start ? ERROR : LOG;

  char     *command;

  FILE     *fh;

  int     pclose_rc;

  size_t    len = 0;

  Assert(prompt);

  Assert(size > 0);

  buf[0] = '\0';

  command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);

  fh = OpenPipeStream(command, "r");

  if (fh == NULL)

  {

    ereport(loglevel,

        (errcode_for_file_access(),

         errmsg("could not execute command \"%s\": %m",

            command)));

    goto error;

  }

  if (!fgets(buf, size, fh))

  {

    if (ferror(fh))

    {

      explicit_bzero(buf, size);

      ereport(loglevel,

          (errcode_for_file_access(),

           errmsg("could not read from command \"%s\": %m",

              command)));

      goto error;

    }

  }

  pclose_rc = ClosePipeStream(fh);

  if (pclose_rc == -1)

  {

    explicit_bzero(buf, size);

    ereport(loglevel,

        (errcode_for_file_access(),

         errmsg("could not close pipe to external command: %m")));

    goto error;

  }

  else if (pclose_rc != 0)

  {

    char     *reason;

    explicit_bzero(buf, size);

    reason = wait_result_to_str(pclose_rc);

    ereport(loglevel,

        (errcode_for_file_access(),

         errmsg("command \"%s\" failed",

            command),

         errdetail_internal("%s", reason)));

    pfree(reason);

    goto error;

  }

  /* strip trailing newline and carriage return */

  len = pg_strip_crlf(buf);

error:

  pfree(command);

  return len;

}

/*

 * Check permissions for SSL key files.

 */

bool

check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)

{

  int     loglevel = isServerStart ? FATAL : LOG;

  struct stat buf;

  if (stat(ssl_key_file, &buf) != 0)

  {

    ereport(loglevel,

        (errcode_for_file_access(),

         errmsg("could not access private key file \"%s\": %m",

            ssl_key_file)));

    return false;

  }

  /* Key file must be a regular file */

  if (!S_ISREG(buf.st_mode))

  {

    ereport(loglevel,

        (errcode(ERRCODE_CONFIG_FILE_ERROR),

         errmsg("private key file \"%s\" is not a regular file",

            ssl_key_file)));

    return false;

  }

  /*

   * Refuse to load key files owned by users other than us or root, and

   * require no public access to the key file.  If the file is owned by us,

   * require mode 0600 or less.  If owned by root, require 0640 or less to

   * allow read access through either our gid or a supplementary gid that

   * allows us to read system-wide certificates.

   *

   * Note that roughly similar checks are performed in

   * src/interfaces/libpq/fe-secure-openssl.c so any changes here may need

   * to be made there as well.  The environment is different though; this

   * code can assume that we're not running as root.

   *

   * Ideally we would do similar permissions checks on Windows, but it is

   * not clear how that would work since Unix-style permissions may not be

   * available.

   */

#if !defined(WIN32) && !defined(__CYGWIN__)

  if (buf.st_uid != geteuid() && buf.st_uid != 0)

  {

    ereport(loglevel,

        (errcode(ERRCODE_CONFIG_FILE_ERROR),

         errmsg("private key file \"%s\" must be owned by the database user or root",

            ssl_key_file)));

    return false;

  }

  if ((buf.st_uid == geteuid() && buf.st_mode & (S_IRWXG | S_IRWXO)) ||

    (buf.st_uid == 0 && buf.st_mode & (S_IWGRP | S_IXGRP | S_IRWXO)))

  {

    ereport(loglevel,

        (errcode(ERRCODE_CONFIG_FILE_ERROR),

         errmsg("private key file \"%s\" has group or world access",

            ssl_key_file),

         errdetail("File must have permissions u=rw (0600) or less if owned by the database user, or permissions u=rw,g=r (0640) or less if owned by root.")));

    return false;

  }

#endif

  return true;

}