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Diffstat (limited to 'docs/afl-fuzz_approach.md')
| -rw-r--r-- | docs/afl-fuzz_approach.md | 27 |
1 files changed, 13 insertions, 14 deletions
diff --git a/docs/afl-fuzz_approach.md b/docs/afl-fuzz_approach.md index 3e4faaec..242104f7 100644 --- a/docs/afl-fuzz_approach.md +++ b/docs/afl-fuzz_approach.md @@ -103,8 +103,8 @@ will be allowed to run for months. There's one important thing to watch out for: if the tool is not finding new paths within several minutes of starting, you're probably not invoking the -target binary correctly and it never gets to parse the input files we're -throwing at it; other possible explanations are that the default memory limit +target binary correctly and it never gets to parse the input files that are +thrown at it; other possible explanations are that the default memory limit (`-m`) is too restrictive and the program exits after failing to allocate a buffer very early on; or that the input files are patently invalid and always fail a basic header check. @@ -172,10 +172,9 @@ processed path is not "favored" (a property discussed later on). The section provides some trivia about the coverage observed by the instrumentation embedded in the target binary. -The first line in the box tells you how many branch tuples we have already hit, -in proportion to how much the bitmap can hold. The number on the left describes -the current input; the one on the right is the value for the entire input -corpus. +The first line in the box tells you how many branch tuples already were hit, in +proportion to how much the bitmap can hold. The number on the left describes the +current input; the one on the right is the value for the entire input corpus. Be wary of extremes: @@ -194,7 +193,7 @@ Be wary of extremes: The other line deals with the variability in tuple hit counts seen in the binary. In essence, if every taken branch is always taken a fixed number of -times for all the inputs we have tried, this will read `1.00`. As we manage to +times for all the inputs that were tried, this will read `1.00`. As we manage to trigger other hit counts for every branch, the needle will start to move toward `8.00` (every bit in the 8-bit map hit), but will probably never reach that extreme. @@ -295,9 +294,9 @@ exceed it by a margin sufficient to be classified as hangs. +-----------------------------------------------------+ ``` -This is just another nerd-targeted section keeping track of how many paths we -have netted, in proportion to the number of execs attempted, for each of the -fuzzing strategies discussed earlier on. This serves to convincingly validate +This is just another nerd-targeted section keeping track of how many paths were +netted, in proportion to the number of execs attempted, for each of the fuzzing +strategies discussed earlier on. This serves to convincingly validate assumptions about the usefulness of the various approaches taken by afl-fuzz. The trim strategy stats in this section are a bit different than the rest. The @@ -339,10 +338,10 @@ fuzzing yet. The same stat is also given for "favored" entries that the fuzzer really wants to get to in this queue cycle (the non-favored entries may have to wait a couple of cycles to get their chance). -Next, we have the number of new paths found during this fuzzing section and -imported from other fuzzer instances when doing parallelized fuzzing; and the -extent to which identical inputs appear to sometimes produce variable behavior -in the tested binary. +Next is the number of new paths found during this fuzzing section and imported +from other fuzzer instances when doing parallelized fuzzing; and the extent to +which identical inputs appear to sometimes produce variable behavior in the +tested binary. That last bit is actually fairly interesting: it measures the consistency of observed traces. If a program always behaves the same for the same input data, |