[release-branch.go1.19] net/textproto: avoid overpredicting the number of MIME header keys
A parsed MIME header is a map[string][]string. In the common case,
a header contains many one-element []string slices. To avoid
allocating a separate slice for each key, ReadMIMEHeader looks
ahead in the input to predict the number of keys that will be
parsed, and allocates a single []string of that length.
The individual slices are then allocated out of the larger one.
The prediction of the number of header keys was done by counting
newlines in the input buffer, which does not take into account
header continuation lines (where a header key/value spans multiple
lines) or the end of the header block and the start of the body.
This could lead to a substantial amount of overallocation, for
example when the body consists of nothing but a large block of
newlines.
Fix header key count prediction to take into account the end of
the headers (indicated by a blank line) and continuation lines
(starting with whitespace).
Thanks to Jakob Ackermann (@das7pad) for reporting this issue.
Fixes CVE-2023-24534
For #58975
Fixes #59267
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/
1802452
Run-TryBot: Damien Neil <dneil@google.com>
Reviewed-by: Roland Shoemaker <bracewell@google.com>
Reviewed-by: Julie Qiu <julieqiu@google.com>
(cherry picked from commit
f739f080a72fd5b06d35c8e244165159645e2ed6)
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/
1802393
Reviewed-by: Damien Neil <dneil@google.com>
Run-TryBot: Roland Shoemaker <bracewell@google.com>
Change-Id: I675451438d619a9130360c56daf529559004903f
Reviewed-on: https://go-review.googlesource.com/c/go/+/481982
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>