Eliminate fixed token-length limit in hba.c.

Historically, hba.c limited tokens in the authentication configuration
files (pg_hba.conf and pg_ident.conf) to less than 256 bytes.  We have
seen a few reports of this limit causing problems; notably, for
moderately-complex LDAP configurations.  Let's get rid of the fixed
limit by using a StringInfo instead of a fixed-size buffer.
This actually takes less code than before, since we can get rid of
a nontrivial error recovery stanza.  It's doubtless a hair slower,
but parsing the content of the HBA files should in no way be
performance-critical.

Although this is a pretty straightforward patch, it doesn't seem
worth the risk to back-patch given the small number of complaints
to date.  In released branches, we'll just raise MAX_TOKEN to
ameliorate the problem.

Discussion: https://postgr.es/m/1588937.1690221208@sss.pgh.pa.us

diff --git a/src/backend/libpq/hba.c b/src/backend/libpq/hba.c
index 5d4ddbb04daf5be4304c39c15300a8af88836e32..ac602bfc3792466a634111390b099ff329f3bd57 100644 (file)
--- a/src/backend/libpq/hba.c
+++ b/src/backend/libpq/hba.c
@@ -56,8 +56,6 @@
 #endif
 
 
-#define MAX_TOKEN  256
-
 /* callback data for check_network_callback */
 typedef struct check_network_data
 {
@@ -161,8 +159,8 @@ pg_isblank(const char c)
  * commas, beginning of line, and end of line.  Blank means space or tab.
  *
  * Tokens can be delimited by double quotes (this allows the inclusion of
- * blanks or '#', but not newlines).  As in SQL, write two double-quotes
- * to represent a double quote.
+ * commas, blanks, and '#', but not newlines).  As in SQL, write two
+ * double-quotes to represent a double quote.
  *
  * Comments (started by an unquoted '#') are skipped, i.e. the remainder
  * of the line is ignored.
@@ -171,8 +169,8 @@ pg_isblank(const char c)
  * Thus, if a continuation occurs within quoted text or a comment, the
  * quoted text or comment is considered to continue to the next line.)
  *
- * The token, if any, is returned at *buf (a buffer of size bufsz), and
- * *lineptr is advanced past the token.
+ * The token, if any, is returned into buf (replacing any previous
+ * contents), and *lineptr is advanced past the token.
  *
  * Also, we set *initial_quote to indicate whether there was quoting before
  * the first character.  (We use that to prevent "@x" from being treated
@@ -180,30 +178,25 @@ pg_isblank(const char c)
  * we want to allow that to support embedded spaces in file paths.)
  *
  * We set *terminating_comma to indicate whether the token is terminated by a
- * comma (which is not returned).
+ * comma (which is not returned, nor advanced over).
  *
- * In event of an error, log a message at ereport level elevel, and also
- * set *err_msg to a string describing the error.  Currently the only
- * possible error is token too long for buf.
+ * The only possible error condition is lack of terminating quote, but we
+ * currently do not detect that, but just return the rest of the line.
  *
- * If successful: store null-terminated token at *buf and return true.
- * If no more tokens on line: set *buf = '\0' and return false.
- * If error: fill buf with truncated or misformatted token and return false.
+ * If successful: store dequoted token in buf and return true.
+ * If no more tokens on line: set buf to empty and return false.
  */
 static bool
-next_token(char **lineptr, char *buf, int bufsz,
-          bool *initial_quote, bool *terminating_comma,
-          int elevel, char **err_msg)
+next_token(char **lineptr, StringInfo buf,
+          bool *initial_quote, bool *terminating_comma)
 {
    int         c;
-   char       *start_buf = buf;
-   char       *end_buf = buf + (bufsz - 1);
    bool        in_quote = false;
    bool        was_quote = false;
    bool        saw_quote = false;
 
-   Assert(end_buf > start_buf);
-
+   /* Initialize output parameters */
+   resetStringInfo(buf);
    *initial_quote = false;
    *terminating_comma = false;
 
@@ -226,22 +219,6 @@ next_token(char **lineptr, char *buf, int bufsz,
            break;
        }
 
-       if (buf >= end_buf)
-       {
-           *buf = '\0';
-           ereport(elevel,
-                   (errcode(ERRCODE_CONFIG_FILE_ERROR),
-                    errmsg("authentication file token too long, skipping: \"%s\"",
-                           start_buf)));
-           *err_msg = "authentication file token too long";
-           /* Discard remainder of line */
-           while ((c = (*(*lineptr)++)) != '\0')
-               ;
-           /* Un-eat the '\0', in case we're called again */
-           (*lineptr)--;
-           return false;
-       }
-
        /* we do not pass back a terminating comma in the token */
        if (c == ',' && !in_quote)
        {
@@ -250,7 +227,7 @@ next_token(char **lineptr, char *buf, int bufsz,
        }
 
        if (c != '"' || was_quote)
-           *buf++ = c;
+           appendStringInfoChar(buf, c);
 
        /* Literal double-quote is two double-quotes */
        if (in_quote && c == '"')
@@ -262,7 +239,7 @@ next_token(char **lineptr, char *buf, int bufsz,
        {
            in_quote = !in_quote;
            saw_quote = true;
-           if (buf == start_buf)
+           if (buf->len == 0)
                *initial_quote = true;
        }
 
@@ -275,9 +252,7 @@ next_token(char **lineptr, char *buf, int bufsz,
     */
    (*lineptr)--;
 
-   *buf = '\0';
-
-   return (saw_quote || buf > start_buf);
+   return (saw_quote || buf->len > 0);
 }
 
 /*
@@ -409,21 +384,22 @@ static List *
 next_field_expand(const char *filename, char **lineptr,
                  int elevel, int depth, char **err_msg)
 {
-   char        buf[MAX_TOKEN];
+   StringInfoData buf;
    bool        trailing_comma;
    bool        initial_quote;
    List       *tokens = NIL;
 
+   initStringInfo(&buf);
+
    do
    {
-       if (!next_token(lineptr, buf, sizeof(buf),
-                       &initial_quote, &trailing_comma,
-                       elevel, err_msg))
+       if (!next_token(lineptr, &buf,
+                       &initial_quote, &trailing_comma))
            break;
 
        /* Is this referencing a file? */
-       if (!initial_quote && buf[0] == '@' && buf[1] != '\0')
-           tokens = tokenize_expand_file(tokens, filename, buf + 1,
+       if (!initial_quote && buf.len > 1 && buf.data[0] == '@')
+           tokens = tokenize_expand_file(tokens, filename, buf.data + 1,
                                          elevel, depth + 1, err_msg);
        else
        {
@@ -434,11 +410,13 @@ next_field_expand(const char *filename, char **lineptr,
             * for the list of tokens.
             */
            oldcxt = MemoryContextSwitchTo(tokenize_context);
-           tokens = lappend(tokens, make_auth_token(buf, initial_quote));
+           tokens = lappend(tokens, make_auth_token(buf.data, initial_quote));
            MemoryContextSwitchTo(oldcxt);
        }
    } while (trailing_comma && (*err_msg == NULL));
 
+   pfree(buf.data);
+
    return tokens;
 }