[Rpm-maint] [rpm-software-management/rpm] Harden against crafted inputs (#1471)

[Demi Marie Obenour]

@DemiMarie commented on this pull request.



> @@ -169,8 +169,8 @@ rpmRC rpmpkgRead(struct rpmvs_s *vs, FD_t fd,
 	goto exit;
     }
 
-    /* Read the signature header. Might not be in a contiguous region. */
-    if (hdrblobRead(fd, 1, 0, RPMTAG_HEADERSIGNATURES, sigblob, &msg))
+    /* Read the signature header. Must be in a contiguous region. */
+    if (hdrblobRead(fd, 1, 1, RPMTAG_HEADERSIGNATURES, sigblob, &msg))

Personally, I would prefer to revert https://github.com/rpm-software-management/rpm/commit/34c2ba3c6a80a778cdf2e42a9193b3264e08e1b3.  The reason is attack surface: we run quite a bit of code for non-contiguous headers that we don’t run for contiguous headers.  Since this code is run before signature verification, this is significant.  I would rather not increase our attack surface to work around broken third-party signers.

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