libpq: fix unlikely memory leak

The attached patch fixes a theoretical memory leak in libpq: if the
second malloc() fails due to OOM, the memory returned by the first
(successful) malloc() will be leaked.

Barring any objections I'll apply this tomorrow.

Per report from EnterpriseDB's Coverity analysis.

-Neil
Index: src/interfaces/libpq/fe-auth.c
===================================================================
RCS file: /var/lib/cvs/pgsql/src/interfaces/libpq/fe-auth.c,v
retrieving revision 1.102
diff -c -r1.102 fe-auth.c
*** src/interfaces/libpq/fe-auth.c    27 Jun 2005 02:04:26 -0000    1.102
--- src/interfaces/libpq/fe-auth.c    29 Jun 2005 03:09:01 -0000
***************
*** 407,434 ****
              {
                  char       *crypt_pwd2;

!                 if (!(crypt_pwd = malloc(MD5_PASSWD_LEN + 1)) ||
!                     !(crypt_pwd2 = malloc(MD5_PASSWD_LEN + 1)))
                  {
                      fprintf(stderr, libpq_gettext("out of memory\n"));
!                     return STATUS_ERROR;
                  }
                  if (!EncryptMD5(password, conn->pguser,
                                  strlen(conn->pguser), crypt_pwd2))
!                 {
!                     free(crypt_pwd);
!                     free(crypt_pwd2);
!                     return STATUS_ERROR;
!                 }
                  if (!EncryptMD5(crypt_pwd2 + strlen("md5"), conn->md5Salt,
                                  sizeof(conn->md5Salt), crypt_pwd))
!                 {
!                     free(crypt_pwd);
!                     free(crypt_pwd2);
!                     return STATUS_ERROR;
!                 }
                  free(crypt_pwd2);
                  break;
              }
          case AUTH_REQ_CRYPT:
              {
--- 407,438 ----
              {
                  char       *crypt_pwd2;

!                 crypt_pwd = malloc(MD5_PASSWD_LEN + 1);
!                 crypt_pwd2 = malloc(MD5_PASSWD_LEN + 1);
!
!                 if (crypt_pwd == NULL || crypt_pwd2 == NULL)
                  {
                      fprintf(stderr, libpq_gettext("out of memory\n"));
!                     goto md5_error;
                  }
+
                  if (!EncryptMD5(password, conn->pguser,
                                  strlen(conn->pguser), crypt_pwd2))
!                     goto md5_error;
!
                  if (!EncryptMD5(crypt_pwd2 + strlen("md5"), conn->md5Salt,
                                  sizeof(conn->md5Salt), crypt_pwd))
!                     goto md5_error;
!
                  free(crypt_pwd2);
                  break;
+
+         md5_error:
+                 if (crypt_pwd)
+                     free(crypt_pwd);
+                 if (crypt_pwd2)
+                     free(crypt_pwd2);
+                 return STATUS_ERROR;
              }
          case AUTH_REQ_CRYPT:
              {