httpd: handle bare "Location: URL" redirects from CGIs

Many sites on the Web give those as valid CGI examples -
no "Status:", just "Location:".

function                                             old     new   delta
cgi_io_loop_and_exit                                 620     684     +64
log_cgi_status                                         -      49     +49
.rodata                                           106846  106861     +15
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 2/0 up/down: 128/0)             Total: 128 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 29 insertions, 14 deletions

diff --git a/networking/httpd.c b/networking/httpd.c
index cdcae01fb..3739fd55f 100644
--- a/networking/httpd.c
+++ b/networking/httpd.c
@@ -1409,6 +1409,13 @@ static unsigned get_line(void)
 }
 
 #if ENABLE_FEATURE_HTTPD_CGI || ENABLE_FEATURE_HTTPD_PROXY
+static void log_cgi_status(const char *pfx, const char *st, unsigned len)
+{
+        unsigned char *end = (void*)st;
+        while (*end >= ' ' && *end < 0x7f && len > 0)
+                end++, len--;
+        bb_error_msg("cgi %s:'%.*s'", pfx, (int)((char *)end - st), st);
+}
 
 /* gcc 4.2.1 fares better with NOINLINE */
 static NOINLINE void cgi_io_loop_and_exit(int fromCgi_rd, int toCgi_wr) NORETURN;
@@ -1416,7 +1423,7 @@ static NOINLINE void cgi_io_loop_and_exit(int fromCgi_rd, int toCgi_wr)
 {
         enum { FROM_CGI = 1, TO_CGI = 2 }; /* indexes in pfd[] */
         struct pollfd pfd[3];
-        int out_cnt; /* we buffer a bit of initial CGI output */
+        int out_cnt;
         int count;
 
         /* iobuf is used for CGI -> network data,
@@ -1435,8 +1442,15 @@ static NOINLINE void cgi_io_loop_and_exit(int fromCgi_rd, int toCgi_wr)
         G.POST_len -= hdr_cnt;
         //bb_error_msg("G.POST_len:%d", G.POST_len);
 
-        /* NB: breaking out of this loop jumps to log_and_exit() */
+        /* If it's really CGI, we buffer a bit of initial CGI output and handle "Status:" etc */
+        /* If it's proxying, then no buffering/conversion is needed (out_cnt set to -1)*/
+#if ENABLE_FEATURE_HTTPD_PROXY
+        out_cnt = - (fromCgi_rd == toCgi_wr);
+#else
         out_cnt = 0;
+#endif
+
+        /* NB: breaking out of this loop jumps to log_and_exit() */
         pfd[FROM_CGI].fd = fromCgi_rd;
         pfd[FROM_CGI].events = POLLIN;
         pfd[TO_CGI].fd = toCgi_wr;
@@ -1552,8 +1566,8 @@ static NOINLINE void cgi_io_loop_and_exit(int fromCgi_rd, int toCgi_wr)
                                  * CGI may output a few first bytes and then wait
                                  * for POSTDATA without closing stdout.
                                  * With full_read we may wait here forever. */
-                                count = safe_read(fromCgi_rd, iobuf + out_cnt, IOBUF_SIZE - 8);
-// "- 8" is important, out_cnt can be up to 7
+                                count = safe_read(fromCgi_rd, iobuf + out_cnt, IOBUF_SIZE - 16);
+// "- 16" is important, out_cnt can be up to 9
                                 if (count <= 0) {
                                         /* EOF (or error, and out_cnt=0..7
                                          * send "HTTP/1.1 200 OK\r\n", then send received 0..7 bytes */
@@ -1563,9 +1577,8 @@ static NOINLINE void cgi_io_loop_and_exit(int fromCgi_rd, int toCgi_wr)
                                 }
                                 out_cnt += count;
                                 count = 0;
-                                if (out_cnt >= 8) {
+                                if (out_cnt >= 10) {
 //FIXME: "Status: " is not required to be the first header! It can be anywhere!
-//FIXME: many servers also check "Location: ". If it exists but "Status: " does _not_, "302 Found" is assumed instead of "200 OK".
                                         uint64_t str8 = *(uint64_t*)iobuf;
                                         //bb_error_msg("from cgi:'%.*s'", out_cnt, iobuf);
 
@@ -1577,18 +1590,20 @@ static NOINLINE void cgi_io_loop_and_exit(int fromCgi_rd, int toCgi_wr)
                                                 memmove(iobuf + 1, iobuf, out_cnt);
                                                 out_cnt += 1;
                                                 memcpy(iobuf, HTTP_200, 9);
-                                                if (verbose) {
-                                                        char *end = iobuf + 9;
-                                                        int cnt = out_cnt - 9;
-                                                        while ((unsigned char)*end >= ' ' && (unsigned char)*end < 0x7f && cnt > 0)
-                                                                end++, cnt--;
-                                                        bb_error_msg("cgi response:'%.*s'", (int)(end - (iobuf + 9)), iobuf + 9);
-                                                }
+                                                if (verbose)
+                                                        log_cgi_status("response", iobuf + 9, out_cnt - 9);
+                                        }
+                                        else
+                                        if (str8 == PACK64_LITERAL_STR("Location") && iobuf[8] == ':' && iobuf[9] == ' ') {
+#define HTTP_302 "HTTP/1.1 302 Found\r\n"
+                                                if (full_write(STDOUT_FILENO, HTTP_302, sizeof(HTTP_302)-1) != sizeof(HTTP_302)-1)
+                                                        break;
+                                                if (verbose)
+                                                        log_cgi_status("redirect", iobuf + 10, out_cnt - 10);
                                         }
 //NB: Apache has no such autodetection. It always adds its own HTTP/1.x header,
 //unless the CGI name starts with "nph-", in which case it passes its output verbatim to network.
                                         else /* Did CGI send "HTTP/1.1"? */
-                                        //if (memcmp(iobuf, HTTP_200, 8) != 0)
                                         if (str8 != PACK64_LITERAL_STR(HTTP_200)) {
  write_HTTP_200_OK:
                                                 /* no, send "HTTP/1.1 200 OK\r\n" ourself */