From 0aae6d14390193e25ab6d0fd49295bd7b131954f Mon Sep 17 00:00:00 2001 From: David Kalnischkies Date: Thu, 15 Aug 2013 16:49:51 +0200 Subject: ensure that pkgTagFile isn't writing past Buffer length In 91c4cc14d3654636edf997d23852f05ad3de4853 I removed the +256 from the pkgTagFile call parsing Release files as I couldn't find a mentioning of a reason for why and it was marked as XXX which suggested that at least someone else was suspicious. It turns out that it is indeed "documented", it just didn't found it at first but the changelog of apt 0.6.6 (29. Dec 2003) mentions: * Restore the ugly hack I removed from indexRecords::Load which set the pkgTagFile buffer size to (file size)+256. This is concealing a bug, but I can't fix it right now. This should fix the segfaults that folks are seeing with 0.6.[45]. The bug it is "hiding" is that if pkgTagFile works with a file which doesn't end in a double newline it will be adding it without checking if the Buffer is big enough to store them. Its also not a good idea to let the End pointer be past the end of our space, even if we don't access the data. Closes: 719629 --- apt-pkg/tagfile.cc | 33 ++++++++++++++++++++++++--------- apt-pkg/tagfile.h | 1 + 2 files changed, 25 insertions(+), 9 deletions(-) diff --git a/apt-pkg/tagfile.cc b/apt-pkg/tagfile.cc index 1c79ee74f..aa0f1eee8 100644 --- a/apt-pkg/tagfile.cc +++ b/apt-pkg/tagfile.cc @@ -50,6 +50,11 @@ public: /* */ pkgTagFile::pkgTagFile(FileFd *pFd,unsigned long long Size) { + /* The size is increased by 4 because if we start with the Size of the + filename we need to try to read 1 char more to see an EOF faster, 1 + char the end-pointer can be on and maybe 2 newlines need to be added + to the end of the file -> 4 extra chars */ + Size += 4; d = new pkgTagFilePrivate(pFd, Size); if (d->Fd.IsOpen() == false) @@ -89,17 +94,21 @@ unsigned long pkgTagFile::Offset() */ bool pkgTagFile::Resize() { - char *tmp; - unsigned long long EndSize = d->End - d->Start; - // fail is the buffer grows too big if(d->Size > 1024*1024+1) return false; + return Resize(d->Size * 2); +} +bool pkgTagFile::Resize(unsigned long long const newSize) +{ + unsigned long long const EndSize = d->End - d->Start; + char *tmp; + // get new buffer and use it - tmp = new char[2*d->Size]; + tmp = new char[newSize]; memcpy(tmp, d->Buffer, d->Size); - d->Size = d->Size*2; + d->Size = newSize; delete [] d->Buffer; d->Buffer = tmp; @@ -152,9 +161,10 @@ bool pkgTagFile::Fill() if (d->Done == false) { // See if only a bit of the file is left - if (d->Fd.Read(d->End, d->Size - (d->End - d->Buffer),&Actual) == false) + unsigned long long const dataSize = d->Size - ((d->End - d->Buffer) + 1); + if (d->Fd.Read(d->End, dataSize, &Actual) == false) return false; - if (Actual != d->Size - (d->End - d->Buffer)) + if (Actual != dataSize || d->Fd.Eof() == true) d->Done = true; d->End += Actual; } @@ -171,8 +181,13 @@ bool pkgTagFile::Fill() for (const char *E = d->End - 1; E - d->End < 6 && (*E == '\n' || *E == '\r'); E--) if (*E == '\n') LineCount++; - for (; LineCount < 2; LineCount++) - *d->End++ = '\n'; + if (LineCount < 2) + { + if ((unsigned)(d->End - d->Buffer) >= d->Size) + Resize(d->Size + 3); + for (; LineCount < 2; LineCount++) + *d->End++ = '\n'; + } return true; } diff --git a/apt-pkg/tagfile.h b/apt-pkg/tagfile.h index fedd72701..66c56799d 100644 --- a/apt-pkg/tagfile.h +++ b/apt-pkg/tagfile.h @@ -95,6 +95,7 @@ class pkgTagFile bool Fill(); bool Resize(); + bool Resize(unsigned long long const newSize); public: -- cgit v1.2.3