try not to call memcpy with length 0 in hash calculations

memcpy is marked as nonnull for its input, but ignores the input anyhow
if the declared length is zero. Our SHA2 implementations do this as
well, it was "just" MD5 and SHA1 missing, so we add the length check
here as well as along the callstack as it is really pointless to do all
these method calls for "nothing".

Reported-By: gcc -fsanitize=undefined

1 files changed, 1 insertions, 1 deletions

diff --git a/apt-pkg/contrib/sha1.h b/apt-pkg/contrib/sha1.h
index 1c5cb5aa1..3387c1cfd 100644
--- a/apt-pkg/contrib/sha1.h
+++ b/apt-pkg/contrib/sha1.h
@@ -37,7 +37,7 @@ class SHA1Summation : public SummationImplementation
    bool Done;
    
    public:
-   bool Add(const unsigned char *inbuf, unsigned long long inlen) APT_OVERRIDE;
+   bool Add(const unsigned char *inbuf, unsigned long long inlen) APT_OVERRIDE APT_NONNULL(2);
    using SummationImplementation::Add;
 
    SHA1SumValue Result();