sss: sss-encrypt must read pipe data until EOF is reached

anatol · anatol · commit 8d3a80dfb346 · 2022-11-02T11:48:24.000-07:00
With current implementation sss-encrypt opens a pipe to the child pin, then tries to read this pipe *only once*. This might return only partial data or not data at all in case if the child pin response is slow. Fix it by reading the pipe until it is closed, and only then process the data. Also increase the response buffer from 1024 bytes to 4096 bytes to accound for larger subpin responses that can be larger than 1024 bytes. Fixes latchset#389
diff --git a/src/pins/sss/clevis-encrypt-sss.c b/src/pins/sss/clevis-encrypt-sss.c
@@ -115,26 +115,34 @@ encrypt_frag(json_t *sss, const char *pin, const json_t *cfg, int assume_yes)
     if (!pipe)
         return NULL;
 
+    char buf[4096] = {};
+    size_t rd = 0;
+    json_t *tmp = NULL;
     while (!feof(pipe)) {
-        char buf[1024] = {};
-        json_t *tmp = NULL;
-        size_t rd = 0;
+        char tmp_buf[4096] = {};
+        size_t tmp_rd = 0;
 
-        rd = fread(buf, 1, sizeof(buf), pipe);
+        tmp_rd = fread(tmp_buf, 1, sizeof(tmp_buf), pipe);
         if (ferror(pipe)) {
             fclose(pipe);
             return NULL;
         }
-
-        tmp = json_pack("s+%", json_string_value(jwe), buf, rd);
-        if (!tmp) {
+        if (rd + tmp_rd > sizeof(buf)) {
             fclose(pipe);
+            fprintf(stderr, "sss: read buffer overflow\n");
             return NULL;
         }
-
-        json_decref(jwe);
-        jwe = tmp;
+        memcpy(buf + rd, tmp_buf, tmp_rd);
+        rd += tmp_rd;
     }
+    tmp = json_pack("s+%", json_string_value(jwe), buf, rd);
+    if (!tmp) {
+        fclose(pipe);
+        return NULL;
+    }
+
+    json_decref(jwe);
+    jwe = tmp;
 
     fclose(pipe);
     waitpid(pid, &status, 0);
