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@pks-t pks-t released this Oct 26, 2018 · 68 commits to maint/v0.27 since this release

This as a security release fixing the following list of issues:

  • The function family git__strtol is used to parse integers
    from a buffer. As the functions do not take a buffer length as
    argument, they will scan either until the end of the current
    number or until a NUL byte is encountered. Many callers have
    been misusing the function and called it on potentially
    non-NUL-terminated buffers, resulting in possible out-of-bounds
    reads. Callers have been fixed to use git__strntol functions
    instead and git__strtol functions were removed.

  • The function git__strntol64 relied on the undefined behavior
    of signed integer overflows. While the code tried to detect
    such overflows after they have happened, this is unspecified
    behavior and may lead to weird behavior on uncommon platforms.

  • In the case where git__strntol32 was unable to parse an
    integer because it doesn't fit into an int32_t, it printed an
    error message containing the string that is currently being
    parsed. The code didn't truncate the string though, which
    caused it to print the complete string until a NUL byte is
    encountered and not only the currently parsed number. In case
    where the string was not NUL terminated, this could have lead
    to an out-of-bounds read.

  • When parsing tags, all unknown fields that appear before the
    tag message are skipped. This skipping is done by using a plain
    strstr(buffer, "\n\n") to search for the two newlines that
    separate tag fields from tag message. As it is not possible to
    supply a buffer length to strstr, this call may skip over the
    buffer's end and thus result in an out of bounds read. As
    strstr may return a pointer that is out of bounds, the
    following computation of buffer_end - buffer will overflow
    and result in an allocation of an invalid length. Note that
    when reading objects from the object database, we make sure to
    always NUL terminate them, making the use of strstr safe.

  • When parsing the "encoding" field of a commit, we may perform
    an out of bounds read due to using git__prefixcmp instead of
    git__prefixncmp. This can result in the parsed commit object
    containing uninitialized data in both its message encoding and
    message fields. Note that when reading objects from the object
    database, we make sure to always NUL terminate them, making the
    use of strstr safe.

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