Remove undesirable libpq dependency on stringinfo.c.

Commit c0cb87fbb unwisely introduced a dependency on the StringInfo
machinery in fe-connect.c.  We must not use that in libpq, because
it will do a summary exit(1) if it hits OOM, and that is not
appropriate behavior for a general-purpose library.  The goal of
allowing arbitrary line lengths in service files doesn't seem like
it's worth a lot of effort, so revert back to the previous method
of using a stack-allocated buffer and failing on buffer overflow.

This isn't an exact revert though.  I kept that patch's refactoring
to have a single exit path, as that seems cleaner than having each
error path know what to do to clean up.  Also, I made the fixed-size
buffer 1024 bytes not 256, just to push off the need for an expandable
buffer some more.

There is more to do here; in particular the lack of any mechanical
check for this type of mistake now seems pretty hazardous.  But this
fix gets us back to the level of robustness we had in v13, anyway.

Discussion: https://postgr.es/m/daeb22ec6ca8ef61e94d766a9b35fb03cabed38e.camel@vmware.com

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 80703698b81e0086ba8ab04f7866567febebee14..3faf05a7e71877540938165c626e968712b30771 100644 (file)
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -28,7 +28,6 @@
 #include "fe-auth.h"
 #include "libpq-fe.h"
 #include "libpq-int.h"
-#include "lib/stringinfo.h"
 #include "mb/pg_wchar.h"
 #include "pg_config_paths.h"
 #include "port/pg_bswap.h"
@@ -5163,7 +5162,7 @@ parseServiceFile(const char *serviceFile,
                                i;
        FILE       *f;
        char       *line;
-       StringInfoData linebuf;
+       char            buf[1024];
 
        *group_found = false;
 
@@ -5175,18 +5174,26 @@ parseServiceFile(const char *serviceFile,
                return 1;
        }
 
-       initStringInfo(&linebuf);
-
-       while (pg_get_line_buf(f, &linebuf))
+       while ((line = fgets(buf, sizeof(buf), f)) != NULL)
        {
+               int                     len;
+
                linenr++;
 
-               /* ignore whitespace at end of line, especially the newline */
-               while (linebuf.len > 0 &&
-                          isspace((unsigned char) linebuf.data[linebuf.len - 1]))
-                       linebuf.data[--linebuf.len] = '\0';
+               if (strlen(line) >= sizeof(buf) - 1)
+               {
+                       appendPQExpBuffer(errorMessage,
+                                                         libpq_gettext("line %d too long in service file \"%s\"\n"),
+                                                         linenr,
+                                                         serviceFile);
+                       result = 2;
+                       goto exit;
+               }
 
-               line = linebuf.data;
+               /* ignore whitespace at end of line, especially the newline */
+               len = strlen(line);
+               while (len > 0 && isspace((unsigned char) line[len - 1]))
+                       line[--len] = '\0';
 
                /* ignore leading whitespace too */
                while (*line && isspace((unsigned char) line[0]))
@@ -5303,7 +5310,6 @@ parseServiceFile(const char *serviceFile,
 
 exit:
        fclose(f);
-       pfree(linebuf.data);
 
        return result;
 }