commit 055111e47d7e43a6c5b78c8e05045437cc48a7bd
author Laurence Lundblade <lgl@securitytheory.com> Wed Feb 17 13:30:57 2021 -0700
committer Laurence Lundblade <lgl@securitytheory.com> Wed Feb 17 13:30:57 2021 -0700
tree 63e7ed77a59a6ba2d37de326da76d9c6794c9557
parent 9bcadf24cb33e61fa16f6de80341150791dc7f89

rewinding wrapped byte strings works, but needs more tests

src/qcbor_decode.c

diff --git a/src/qcbor_decode.c b/src/qcbor_decode.c
index 2ad00b0..19c6a97 100644
--- a/src/qcbor_decode.c
+++ b/src/qcbor_decode.c
@@ -3522,8 +3522,14 @@
       uError = QCBOR_ERR_INPUT_TOO_LARGE;
       goto Done;
    }
-   const size_t uEndOfBstr   = UsefulInputBuf_Tell(&(pMe->InBuf));
-   const size_t uStartOfBstr = uEndOfBstr - pItem->val.string.len;
+   const size_t uStartOfBstr = UsefulInputBuf_PointerToOffset(&(pMe->InBuf), pItem->val.string.ptr);
+
+   if(uStartOfBstr == SIZE_MAX) {
+      uError = QCBOR_ERR_INPUT_TOO_LARGE;
+      goto Done;
+   }
+
+   const size_t uEndOfBstr = uStartOfBstr + pItem->val.string.len;
    UsefulInputBuf_Seek(&(pMe->InBuf), uStartOfBstr);
    UsefulInputBuf_SetBufferLength(&(pMe->InBuf), uEndOfBstr);