Skip to content

Commit

Permalink
Protect against re-using digested context
Browse files Browse the repository at this point in the history 
Prevent users from calling `update!` on a context that has already been
finalized, and warn against doing this in the docstring of `digest!`
  • Loading branch information
@jakobnissen @staticfloat
jakobnissen authored and staticfloat committed Jun 20, 2023
1 parent 2d1f84e commit 5e3a676
Show file tree
Hide file tree
Showing 4 changed files with 82 additions and 39 deletions.
28 changes: 19 additions & 9 deletions src/common.jl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ julia> update!(ctx, b"data to to be hashed")
```
"""
function update!(context::T, data::U, datalen=length(data)) where {T<:SHA_CTX, U<:AbstractBytes}
context.used && error("Cannot update CTX after `digest!` has been called on it")
# We need to do all our arithmetic in the proper bitwidth
UIntXXX = typeof(context.bytecount)

Expand Down Expand Up @@ -82,6 +83,7 @@ end
digest!(context)
Finalize the SHA context and return the hash as array of bytes (Array{Uint8, 1}).
Updating the context after calling `digest!` on it will error.
# Examples
```julia-repl
Expand All @@ -97,18 +99,26 @@ julia> digest!(ctx)
⋮
0x89
0xf5
julia> update!(ctx, b"more data")
ERROR: Cannot update CTX after `digest!` has been called on it
[...]
```
"""
function digest!(context::T) where T<:SHA_CTX
pad_remainder!(context)
# Store the length of the input data (in bits) at the end of the padding
bitcount_idx = div(short_blocklen(T), sizeof(context.bytecount)) + 1
pbuf = Ptr{typeof(context.bytecount)}(pointer(context.buffer))
unsafe_store!(pbuf, bswap(context.bytecount * 8), bitcount_idx)

# Final transform:
transform!(context)
if !context.used
pad_remainder!(context)
# Store the length of the input data (in bits) at the end of the padding
bitcount_idx = div(short_blocklen(T), sizeof(context.bytecount)) + 1
pbuf = Ptr{typeof(context.bytecount)}(pointer(context.buffer))
unsafe_store!(pbuf, bswap(context.bytecount * 8), bitcount_idx)

# Final transform:
transform!(context)
bswap!(context.state)
context.used = true
end

# Return the digest
return reinterpret(UInt8, bswap!(context.state))[1:digestlen(T)]
return reinterpret(UInt8, context.state)[1:digestlen(T)]
end
39 changes: 21 additions & 18 deletions src/sha3.jl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -55,26 +55,29 @@ end

# Finalize data in the buffer, append total bitlength, and return our precious hash!
function digest!(context::T) where {T<:SHA3_CTX}
usedspace = context.bytecount % blocklen(T)
# If we have anything in the buffer still, pad and transform that data
if usedspace < blocklen(T) - 1
# Begin padding with a 0x06
context.buffer[usedspace+1] = 0x06
# Fill with zeros up until the last byte
context.buffer[usedspace+2:end-1] .= 0x00
# Finish it off with a 0x80
context.buffer[end] = 0x80
else
# Otherwise, we have to add on a whole new buffer just for the zeros and 0x80
context.buffer[end] = 0x06
transform!(context)
if !context.used
usedspace = context.bytecount % blocklen(T)
# If we have anything in the buffer still, pad and transform that data
if usedspace < blocklen(T) - 1
# Begin padding with a 0x06
context.buffer[usedspace+1] = 0x06
# Fill with zeros up until the last byte
context.buffer[usedspace+2:end-1] .= 0x00
# Finish it off with a 0x80
context.buffer[end] = 0x80
else
# Otherwise, we have to add on a whole new buffer just for the zeros and 0x80
context.buffer[end] = 0x06
transform!(context)

context.buffer[1:end-1] .= 0x0
context.buffer[end] = 0x80
end
context.buffer[1:end-1] .= 0x0
context.buffer[end] = 0x80
end

# Final transform:
transform!(context)
# Final transform:
transform!(context)
context.used = true
end

# Return the digest
return reinterpret(UInt8, context.state)[1:digestlen(T)]
Expand Down
37 changes: 25 additions & 12 deletions src/types.jl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -12,31 +12,36 @@ mutable struct SHA1_CTX <: SHA_CTX
bytecount::UInt64
buffer::Array{UInt8,1}
W::Array{UInt32,1}
used::Bool
end

# SHA2 224/256/384/512-bit Context Structures
mutable struct SHA2_224_CTX <: SHA2_CTX
state::Array{UInt32,1}
bytecount::UInt64
buffer::Array{UInt8,1}
used::Bool
end

mutable struct SHA2_256_CTX <: SHA2_CTX
state::Array{UInt32,1}
bytecount::UInt64
buffer::Array{UInt8,1}
used::Bool
end

mutable struct SHA2_384_CTX <: SHA2_CTX
state::Array{UInt64,1}
bytecount::UInt128
buffer::Array{UInt8,1}
used::Bool
end

mutable struct SHA2_512_CTX <: SHA2_CTX
state::Array{UInt64,1}
bytecount::UInt128
buffer::Array{UInt8,1}
used::Bool
end

function Base.getproperty(ctx::SHA2_CTX, fieldname::Symbol)
Expand All @@ -48,6 +53,8 @@ function Base.getproperty(ctx::SHA2_CTX, fieldname::Symbol)
return getfield(ctx, :buffer)::Vector{UInt8}
elseif fieldname === :W
return getfield(ctx, :W)::Vector{UInt32}
elseif fieldname === :used
return getfield(ctx, :used)::Bool
else
error("SHA2_CTX has no field ", fieldname)
end
Expand All @@ -67,24 +74,28 @@ mutable struct SHA3_224_CTX <: SHA3_CTX
bytecount::UInt128
buffer::Array{UInt8,1}
bc::Array{UInt64,1}
used::Bool
end
mutable struct SHA3_256_CTX <: SHA3_CTX
state::Array{UInt64,1}
bytecount::UInt128
buffer::Array{UInt8,1}
bc::Array{UInt64,1}
used::Bool
end
mutable struct SHA3_384_CTX <: SHA3_CTX
state::Array{UInt64,1}
bytecount::UInt128
buffer::Array{UInt8,1}
bc::Array{UInt64,1}
used::Bool
end
mutable struct SHA3_512_CTX <: SHA3_CTX
state::Array{UInt64,1}
bytecount::UInt128
buffer::Array{UInt8,1}
bc::Array{UInt64,1}
used::Bool
end

function Base.getproperty(ctx::SHA3_CTX, fieldname::Symbol)
Expand All @@ -96,6 +107,8 @@ function Base.getproperty(ctx::SHA3_CTX, fieldname::Symbol)
return getfield(ctx, :buffer)::Vector{UInt8}
elseif fieldname === :bc
return getfield(ctx, :bc)::Vector{UInt64}
elseif fieldname === :used
return getfield(ctx, :used)::Bool
else
error("type ", typeof(ctx), " has no field ", fieldname)
end
Expand Down Expand Up @@ -145,50 +158,50 @@ short_blocklen(::Type{T}) where {T<:SHA_CTX} = blocklen(T) - 2*sizeof(state_type
Construct an empty SHA2_224 context.
"""
SHA2_224_CTX() = SHA2_224_CTX(copy(SHA2_224_initial_hash_value), 0, zeros(UInt8, blocklen(SHA2_224_CTX)))
SHA2_224_CTX() = SHA2_224_CTX(copy(SHA2_224_initial_hash_value), 0, zeros(UInt8, blocklen(SHA2_224_CTX)), false)
"""
SHA2_256_CTX()
Construct an empty SHA2_256 context.
"""
SHA2_256_CTX() = SHA2_256_CTX(copy(SHA2_256_initial_hash_value), 0, zeros(UInt8, blocklen(SHA2_256_CTX)))
SHA2_256_CTX() = SHA2_256_CTX(copy(SHA2_256_initial_hash_value), 0, zeros(UInt8, blocklen(SHA2_256_CTX)), false)
"""
SHA2_384()
Construct an empty SHA2_384 context.
"""
SHA2_384_CTX() = SHA2_384_CTX(copy(SHA2_384_initial_hash_value), 0, zeros(UInt8, blocklen(SHA2_384_CTX)))
SHA2_384_CTX() = SHA2_384_CTX(copy(SHA2_384_initial_hash_value), 0, zeros(UInt8, blocklen(SHA2_384_CTX)), false)
"""
SHA2_512_CTX()
Construct an empty SHA2_512 context.
"""
SHA2_512_CTX() = SHA2_512_CTX(copy(SHA2_512_initial_hash_value), 0, zeros(UInt8, blocklen(SHA2_512_CTX)))
SHA2_512_CTX() = SHA2_512_CTX(copy(SHA2_512_initial_hash_value), 0, zeros(UInt8, blocklen(SHA2_512_CTX)), false)

"""
SHA3_224_CTX()
Construct an empty SHA3_224 context.
"""
SHA3_224_CTX() = SHA3_224_CTX(zeros(UInt64, 25), 0, zeros(UInt8, blocklen(SHA3_224_CTX)), Vector{UInt64}(undef, 5))
SHA3_224_CTX() = SHA3_224_CTX(zeros(UInt64, 25), 0, zeros(UInt8, blocklen(SHA3_224_CTX)), Vector{UInt64}(undef, 5), false)
"""
SHA3_256_CTX()
Construct an empty SHA3_256 context.
"""
SHA3_256_CTX() = SHA3_256_CTX(zeros(UInt64, 25), 0, zeros(UInt8, blocklen(SHA3_256_CTX)), Vector{UInt64}(undef, 5))
SHA3_256_CTX() = SHA3_256_CTX(zeros(UInt64, 25), 0, zeros(UInt8, blocklen(SHA3_256_CTX)), Vector{UInt64}(undef, 5), false)
"""
SHA3_384_CTX()
Construct an empty SHA3_384 context.
"""
SHA3_384_CTX() = SHA3_384_CTX(zeros(UInt64, 25), 0, zeros(UInt8, blocklen(SHA3_384_CTX)), Vector{UInt64}(undef, 5))
SHA3_384_CTX() = SHA3_384_CTX(zeros(UInt64, 25), 0, zeros(UInt8, blocklen(SHA3_384_CTX)), Vector{UInt64}(undef, 5), false)
"""
SHA3_512_CTX()
Construct an empty SHA3_512 context.
"""
SHA3_512_CTX() = SHA3_512_CTX(zeros(UInt64, 25), 0, zeros(UInt8, blocklen(SHA3_512_CTX)), Vector{UInt64}(undef, 5))
SHA3_512_CTX() = SHA3_512_CTX(zeros(UInt64, 25), 0, zeros(UInt8, blocklen(SHA3_512_CTX)), Vector{UInt64}(undef, 5), false)

# Nickname'd outer constructor methods for SHA2
const SHA224_CTX = SHA2_224_CTX
Expand All @@ -202,13 +215,13 @@ const SHA512_CTX = SHA2_512_CTX
Construct an empty SHA1 context.
"""
SHA1_CTX() = SHA1_CTX(copy(SHA1_initial_hash_value), 0, zeros(UInt8, blocklen(SHA1_CTX)), Vector{UInt32}(undef, 80))
SHA1_CTX() = SHA1_CTX(copy(SHA1_initial_hash_value), 0, zeros(UInt8, blocklen(SHA1_CTX)), Vector{UInt32}(undef, 80), false)


# Copy functions
copy(ctx::T) where {T<:SHA1_CTX} = T(copy(ctx.state), ctx.bytecount, copy(ctx.buffer), copy(ctx.W))
copy(ctx::T) where {T<:SHA2_CTX} = T(copy(ctx.state), ctx.bytecount, copy(ctx.buffer))
copy(ctx::T) where {T<:SHA3_CTX} = T(copy(ctx.state), ctx.bytecount, copy(ctx.buffer), Vector{UInt64}(undef, 5))
copy(ctx::T) where {T<:SHA1_CTX} = T(copy(ctx.state), ctx.bytecount, copy(ctx.buffer), copy(ctx.W), ctx.used)
copy(ctx::T) where {T<:SHA2_CTX} = T(copy(ctx.state), ctx.bytecount, copy(ctx.buffer), ctx.used)
copy(ctx::T) where {T<:SHA3_CTX} = T(copy(ctx.state), ctx.bytecount, copy(ctx.buffer), Vector{UInt64}(undef, 5), ctx.used)


# Make printing these types a little friendlier
Expand Down
17 changes: 17 additions & 0 deletions test/runtests.jl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,23 @@ end
@test hash == answers[sha_funcs[sha_idx]][end]
end
end

# Test that the hash states cannot be updated after having been finalized,
# but can still return the same digest
@testset "Reuse" begin
for sha_idx in 1:length(sha_funcs)
ctx = sha_types[sha_funcs[sha_idx]]()
update!(ctx, codeunits("abracadabra"))
hash1 = digest!(ctx)

# Cannot update after having been digested
@test_throws Exception update!(ctx, codeunits("abc"))

# But will still return the same digest twice
hash2 = digest!(ctx)
@test hash1 == hash2
end
end
end

@testset "HMAC" begin
Expand Down

0 comments on commit 5e3a676

Please sign in to comment.