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authorVladimír Čunát <vcunat@gmail.com>2016-11-06T21·13+0100
committerVladimír Čunát <vcunat@gmail.com>2016-11-06T21·17+0100
commit818aad3ec44473b5b3d08191488c824688653ba1 (patch)
treeb1acb2f61ca0e256f424031687cc75c66052420b
parenteec5409a69054cf21214c3f5846ec0310fcb8228 (diff)
Detect and disallow base32 hash overflow
Example (before this commit):
$ nix-hash --type sha256 --to-base16 4n0igfxbd3kqvvj2k2xgysrp63l4v2gd110fwkk4apfpm0hvzwh0 \
    | xargs nix-hash --type sha256 --to-base32
0n0igfxbd3kqvvj2k2xgysrp63l4v2gd110fwkk4apfpm0hvzwh0

It's a real-life example:
https://github.com/NixOS/nixpkgs/pull/20208/files#r86695567
-rw-r--r--src/libutil/hash.cc8
1 files changed, 7 insertions, 1 deletions
diff --git a/src/libutil/hash.cc b/src/libutil/hash.cc
index 81aced0fde16..aa50fceb9e3e 100644
--- a/src/libutil/hash.cc
+++ b/src/libutil/hash.cc
@@ -165,7 +165,13 @@ Hash parseHash32(HashType ht, const string & s)
         unsigned int i = b / 8;
         unsigned int j = b % 8;
         hash.hash[i] |= digit << j;
-        if (i < hash.hashSize - 1) hash.hash[i + 1] |= digit >> (8 - j);
+
+        if (i < hash.hashSize - 1) {
+            hash.hash[i + 1] |= digit >> (8 - j);
+        } else {
+            if (digit >> (8 - j))
+                throw BadHash(format("invalid base-32 hash ‘%1%’") % s);
+        }
     }
 
     return hash;