lix/src/libutil/hash.hh

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#pragma once
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#include "types.hh"
#include "serialise.hh"
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namespace nix {
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MakeError(BadHash, Error);
enum HashType : char { htMD5 = 42, htSHA1, htSHA256, htSHA512 };
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const int md5HashSize = 16;
const int sha1HashSize = 20;
const int sha256HashSize = 32;
const int sha512HashSize = 64;
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extern const string base32Chars;
enum Base : int { Base64, Base32, Base16, SRI };
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struct Hash
{
constexpr static size_t maxHashSize = 64;
size_t hashSize = 0;
uint8_t hash[maxHashSize] = {};
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HashType type;
/* Create a zero-filled hash object. */
Hash(HashType type) : type(type) { init(); };
/* Initialize the hash from a string representation, in the format
"[<type>:]<base16|base32|base64>" or "<type>-<base64>" (a
Subresource Integrity hash expression). If the 'type' argument
is not present, then the hash type must be specified in the
string. */
Hash(std::string_view s, std::optional<HashType> type);
// type must be provided
Hash(std::string_view s, HashType type);
// hash type must be part of string
Hash(std::string_view s);
void init();
/* Check whether a hash is set. */
operator bool () const { return (bool) type; }
/* Check whether two hash are equal. */
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bool operator == (const Hash & h2) const;
/* Check whether two hash are not equal. */
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bool operator != (const Hash & h2) const;
/* For sorting. */
bool operator < (const Hash & h) const;
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/* Returns the length of a base-16 representation of this hash. */
size_t base16Len() const
{
return hashSize * 2;
}
/* Returns the length of a base-32 representation of this hash. */
size_t base32Len() const
{
return (hashSize * 8 - 1) / 5 + 1;
}
/* Returns the length of a base-64 representation of this hash. */
size_t base64Len() const
{
return ((4 * hashSize / 3) + 3) & ~3;
}
/* Return a string representation of the hash, in base-16, base-32
or base-64. By default, this is prefixed by the hash type
(e.g. "sha256:"). */
std::string to_string(Base base, bool includeType) const;
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std::string gitRev() const
{
assert(type == htSHA1);
return to_string(Base16, false);
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}
std::string gitShortRev() const
{
assert(type == htSHA1);
return std::string(to_string(Base16, false), 0, 7);
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}
};
/* Helper that defaults empty hashes to the 0 hash. */
Hash newHashAllowEmpty(std::string hashStr, std::optional<HashType> ht);
/* Print a hash in base-16 if it's MD5, or base-32 otherwise. */
string printHash16or32(const Hash & hash);
/* Compute the hash of the given string. */
Hash hashString(HashType ht, std::string_view s);
/* Compute the hash of the given file. */
* Removed the `id' attribute hack. * Formalise the notion of fixed-output derivations, i.e., derivations for which a cryptographic hash of the output is known in advance. Changes to such derivations should not propagate upwards through the dependency graph. Previously this was done by specifying the hash component of the output path through the `id' attribute, but this is insecure since you can lie about it (i.e., you can specify any hash and then produce a completely different output). Now the responsibility for checking the output is moved from the builder to Nix itself. A fixed-output derivation can be created by specifying the `outputHash' and `outputHashAlgo' attributes, the latter taking values `md5', `sha1', and `sha256', and the former specifying the actual hash in hexadecimal or in base-32 (auto-detected by looking at the length of the attribute value). MD5 is included for compatibility but should be considered deprecated. * Removed the `drvPath' pseudo-attribute in derivation results. It's no longer necessary. * Cleaned up the support for multiple output paths in derivation store expressions. Each output now has a unique identifier (e.g., `out', `devel', `docs'). Previously there was no way to tell output paths apart at the store expression level. * `nix-hash' now has a flag `--base32' to specify that the hash should be printed in base-32 notation. * `fetchurl' accepts parameters `sha256' and `sha1' in addition to `md5'. * `nix-prefetch-url' now prints out a SHA-1 hash in base-32. (TODO: a flag to specify the hash.)
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Hash hashFile(HashType ht, const Path & path);
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/* Compute the hash of the given path. The hash is defined as
(essentially) hashString(ht, dumpPath(path)). */
typedef std::pair<Hash, unsigned long long> HashResult;
HashResult hashPath(HashType ht, const Path & path,
PathFilter & filter = defaultPathFilter);
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/* Compress a hash to the specified number of bytes by cyclically
XORing bytes together. */
Hash compressHash(const Hash & hash, unsigned int newSize);
* Removed the `id' attribute hack. * Formalise the notion of fixed-output derivations, i.e., derivations for which a cryptographic hash of the output is known in advance. Changes to such derivations should not propagate upwards through the dependency graph. Previously this was done by specifying the hash component of the output path through the `id' attribute, but this is insecure since you can lie about it (i.e., you can specify any hash and then produce a completely different output). Now the responsibility for checking the output is moved from the builder to Nix itself. A fixed-output derivation can be created by specifying the `outputHash' and `outputHashAlgo' attributes, the latter taking values `md5', `sha1', and `sha256', and the former specifying the actual hash in hexadecimal or in base-32 (auto-detected by looking at the length of the attribute value). MD5 is included for compatibility but should be considered deprecated. * Removed the `drvPath' pseudo-attribute in derivation results. It's no longer necessary. * Cleaned up the support for multiple output paths in derivation store expressions. Each output now has a unique identifier (e.g., `out', `devel', `docs'). Previously there was no way to tell output paths apart at the store expression level. * `nix-hash' now has a flag `--base32' to specify that the hash should be printed in base-32 notation. * `fetchurl' accepts parameters `sha256' and `sha1' in addition to `md5'. * `nix-prefetch-url' now prints out a SHA-1 hash in base-32. (TODO: a flag to specify the hash.)
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/* Parse a string representing a hash type. */
HashType parseHashType(std::string_view s);
/* Will return nothing on parse error */
std::optional<HashType> parseHashTypeOpt(std::string_view s);
* Removed the `id' attribute hack. * Formalise the notion of fixed-output derivations, i.e., derivations for which a cryptographic hash of the output is known in advance. Changes to such derivations should not propagate upwards through the dependency graph. Previously this was done by specifying the hash component of the output path through the `id' attribute, but this is insecure since you can lie about it (i.e., you can specify any hash and then produce a completely different output). Now the responsibility for checking the output is moved from the builder to Nix itself. A fixed-output derivation can be created by specifying the `outputHash' and `outputHashAlgo' attributes, the latter taking values `md5', `sha1', and `sha256', and the former specifying the actual hash in hexadecimal or in base-32 (auto-detected by looking at the length of the attribute value). MD5 is included for compatibility but should be considered deprecated. * Removed the `drvPath' pseudo-attribute in derivation results. It's no longer necessary. * Cleaned up the support for multiple output paths in derivation store expressions. Each output now has a unique identifier (e.g., `out', `devel', `docs'). Previously there was no way to tell output paths apart at the store expression level. * `nix-hash' now has a flag `--base32' to specify that the hash should be printed in base-32 notation. * `fetchurl' accepts parameters `sha256' and `sha1' in addition to `md5'. * `nix-prefetch-url' now prints out a SHA-1 hash in base-32. (TODO: a flag to specify the hash.)
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/* And the reverse. */
string printHashType(HashType ht);
union Ctx;
Allow content-addressable paths to have references This adds a command 'nix make-content-addressable' that rewrites the specified store paths into content-addressable paths. The advantage of such paths is that 1) they can be imported without signatures; 2) they can enable deduplication in cases where derivation changes do not cause output changes (apart from store path hashes). For example, $ nix make-content-addressable -r nixpkgs.cowsay rewrote '/nix/store/g1g31ah55xdia1jdqabv1imf6mcw0nb1-glibc-2.25-49' to '/nix/store/48jfj7bg78a8n4f2nhg269rgw1936vj4-glibc-2.25-49' ... rewrote '/nix/store/qbi6rzpk0bxjw8lw6azn2mc7ynnn455q-cowsay-3.03+dfsg1-16' to '/nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16' We can then copy the resulting closure to another store without signatures: $ nix copy --trusted-public-keys '' ---to ~/my-nix /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16 In order to support self-references in content-addressable paths, these paths are hashed "modulo" self-references, meaning that self-references are zeroed out during hashing. Somewhat annoyingly, this means that the NAR hash stored in the Nix database is no longer necessarily equal to the output of "nix hash-path"; for content-addressable paths, you need to pass the --modulo flag: $ nix path-info --json /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16 | jq -r .[].narHash sha256:0ri611gdilz2c9rsibqhsipbfs9vwcqvs811a52i2bnkhv7w9mgw $ nix hash-path --type sha256 --base32 /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16 1ggznh07khq0hz6id09pqws3a8q9pn03ya3c03nwck1kwq8rclzs $ nix hash-path --type sha256 --base32 /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16 --modulo iq6g2x4q62xp7y7493bibx0qn5w7xz67 0ri611gdilz2c9rsibqhsipbfs9vwcqvs811a52i2bnkhv7w9mgw
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struct AbstractHashSink : virtual Sink
{
virtual HashResult finish() = 0;
};
class HashSink : public BufferedSink, public AbstractHashSink
{
private:
HashType ht;
Ctx * ctx;
unsigned long long bytes;
public:
HashSink(HashType ht);
HashSink(const HashSink & h);
~HashSink();
Allow content-addressable paths to have references This adds a command 'nix make-content-addressable' that rewrites the specified store paths into content-addressable paths. The advantage of such paths is that 1) they can be imported without signatures; 2) they can enable deduplication in cases where derivation changes do not cause output changes (apart from store path hashes). For example, $ nix make-content-addressable -r nixpkgs.cowsay rewrote '/nix/store/g1g31ah55xdia1jdqabv1imf6mcw0nb1-glibc-2.25-49' to '/nix/store/48jfj7bg78a8n4f2nhg269rgw1936vj4-glibc-2.25-49' ... rewrote '/nix/store/qbi6rzpk0bxjw8lw6azn2mc7ynnn455q-cowsay-3.03+dfsg1-16' to '/nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16' We can then copy the resulting closure to another store without signatures: $ nix copy --trusted-public-keys '' ---to ~/my-nix /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16 In order to support self-references in content-addressable paths, these paths are hashed "modulo" self-references, meaning that self-references are zeroed out during hashing. Somewhat annoyingly, this means that the NAR hash stored in the Nix database is no longer necessarily equal to the output of "nix hash-path"; for content-addressable paths, you need to pass the --modulo flag: $ nix path-info --json /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16 | jq -r .[].narHash sha256:0ri611gdilz2c9rsibqhsipbfs9vwcqvs811a52i2bnkhv7w9mgw $ nix hash-path --type sha256 --base32 /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16 1ggznh07khq0hz6id09pqws3a8q9pn03ya3c03nwck1kwq8rclzs $ nix hash-path --type sha256 --base32 /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16 --modulo iq6g2x4q62xp7y7493bibx0qn5w7xz67 0ri611gdilz2c9rsibqhsipbfs9vwcqvs811a52i2bnkhv7w9mgw
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void write(const unsigned char * data, size_t len) override;
HashResult finish() override;
HashResult currentHash();
};
}