Re: [PATCH v3 1/6] lib/base64: Add support for multiple variants

[Guan-Chun Wu <409411716@gms.tku.edu.tw>]

On Tue, Sep 30, 2025 at 04:56:17PM -0700, Caleb Sander Mateos wrote:
> On Thu, Sep 25, 2025 at 11:59 PM Guan-Chun Wu <409411716@gms.tku.edu.tw> wrote:
> >
> > From: Kuan-Wei Chiu <visitorckw@gmail.com>
> >
> > Extend the base64 API to support multiple variants (standard, URL-safe,
> > and IMAP) as defined in RFC 4648 and RFC 3501. The API now takes a
> > variant parameter and an option to control padding. Update NVMe auth
> > code to use the new interface with BASE64_STD.
> >
> > Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
> > Co-developed-by: Guan-Chun Wu <409411716@gms.tku.edu.tw>
> > Signed-off-by: Guan-Chun Wu <409411716@gms.tku.edu.tw>
> > ---
> >  drivers/nvme/common/auth.c |  4 ++--
> >  include/linux/base64.h     | 10 ++++++++--
> >  lib/base64.c               | 39 ++++++++++++++++++++++----------------
> >  3 files changed, 33 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
> > index 91e273b89..5fecb53cb 100644
> > --- a/drivers/nvme/common/auth.c
> > +++ b/drivers/nvme/common/auth.c
> > @@ -178,7 +178,7 @@ struct nvme_dhchap_key *nvme_auth_extract_key(unsigned char *secret,
> >         if (!key)
> >                 return ERR_PTR(-ENOMEM);
> >
> > -       key_len = base64_decode(secret, allocated_len, key->key);
> > +       key_len = base64_decode(secret, allocated_len, key->key, true, BASE64_STD);
> >         if (key_len < 0) {
> >                 pr_debug("base64 key decoding error %d\n",
> >                          key_len);
> > @@ -663,7 +663,7 @@ int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
> >         if (ret)
> >                 goto out_free_digest;
> >
> > -       ret = base64_encode(digest, digest_len, enc);
> > +       ret = base64_encode(digest, digest_len, enc, true, BASE64_STD);
> >         if (ret < hmac_len) {
> >                 ret = -ENOKEY;
> >                 goto out_free_digest;
> > diff --git a/include/linux/base64.h b/include/linux/base64.h
> > index 660d4cb1e..a2c6c9222 100644
> > --- a/include/linux/base64.h
> > +++ b/include/linux/base64.h
> > @@ -8,9 +8,15 @@
> >
> >  #include <linux/types.h>
> >
> > +enum base64_variant {
> > +       BASE64_STD,       /* RFC 4648 (standard) */
> > +       BASE64_URLSAFE,   /* RFC 4648 (base64url) */
> > +       BASE64_IMAP,      /* RFC 3501 */
> > +};
> > +
> >  #define BASE64_CHARS(nbytes)   DIV_ROUND_UP((nbytes) * 4, 3)
> >
> > -int base64_encode(const u8 *src, int len, char *dst);
> > -int base64_decode(const char *src, int len, u8 *dst);
> > +int base64_encode(const u8 *src, int len, char *dst, bool padding, enum base64_variant variant);
> > +int base64_decode(const char *src, int len, u8 *dst, bool padding, enum base64_variant variant);
> >
> >  #endif /* _LINUX_BASE64_H */
> > diff --git a/lib/base64.c b/lib/base64.c
> > index b736a7a43..1af557785 100644
> > --- a/lib/base64.c
> > +++ b/lib/base64.c
> > @@ -1,12 +1,12 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  /*
> > - * base64.c - RFC4648-compliant base64 encoding
> > + * base64.c - Base64 with support for multiple variants
> >   *
> >   * Copyright (c) 2020 Hannes Reinecke, SUSE
> >   *
> >   * Based on the base64url routines from fs/crypto/fname.c
> > - * (which are using the URL-safe base64 encoding),
> > - * modified to use the standard coding table from RFC4648 section 4.
> > + * (which are using the URL-safe Base64 encoding),
> > + * modified to support multiple Base64 variants.
> >   */
> >
> >  #include <linux/kernel.h>
> > @@ -15,26 +15,31 @@
> >  #include <linux/string.h>
> >  #include <linux/base64.h>
> >
> > -static const char base64_table[65] =
> > -       "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
> > +static const char base64_tables[][65] = {
> > +       [BASE64_STD] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
> > +       [BASE64_URLSAFE] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_",
> > +       [BASE64_IMAP] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,",
> > +};
> >
> >  /**
> > - * base64_encode() - base64-encode some binary data
> > + * base64_encode() - Base64-encode some binary data
> >   * @src: the binary data to encode
> >   * @srclen: the length of @src in bytes
> > - * @dst: (output) the base64-encoded string.  Not NUL-terminated.
> > + * @dst: (output) the Base64-encoded string.  Not NUL-terminated.
> > + * @padding: whether to append '=' padding characters
> > + * @variant: which base64 variant to use
> >   *
> > - * Encodes data using base64 encoding, i.e. the "Base 64 Encoding" specified
> > - * by RFC 4648, including the  '='-padding.
> > + * Encodes data using the selected Base64 variant.
> >   *
> > - * Return: the length of the resulting base64-encoded string in bytes.
> > + * Return: the length of the resulting Base64-encoded string in bytes.
> >   */
> > -int base64_encode(const u8 *src, int srclen, char *dst)
> > +int base64_encode(const u8 *src, int srclen, char *dst, bool padding, enum base64_variant variant)
> 
> Padding isn't actually implemented in this commit? That seems a bit
> confusing. I think it would ideally be implemented in the same commit
> that adds it. That could be before or after the commit that optimizes
> the encode/decode implementations.
> 
> Best,
> Caleb
>

Got it, thanks for pointing that out. We'll address it in the next version.

Best regards,
Guan-Chun

> >  {
> >         u32 ac = 0;
> >         int bits = 0;
> >         int i;
> >         char *cp = dst;
> > +       const char *base64_table = base64_tables[variant];
> >
> >         for (i = 0; i < srclen; i++) {
> >                 ac = (ac << 8) | src[i];
> > @@ -57,25 +62,27 @@ int base64_encode(const u8 *src, int srclen, char *dst)
> >  EXPORT_SYMBOL_GPL(base64_encode);
> >
> >  /**
> > - * base64_decode() - base64-decode a string
> > + * base64_decode() - Base64-decode a string
> >   * @src: the string to decode.  Doesn't need to be NUL-terminated.
> >   * @srclen: the length of @src in bytes
> >   * @dst: (output) the decoded binary data
> > + * @padding: whether to append '=' padding characters
> > + * @variant: which base64 variant to use
> >   *
> > - * Decodes a string using base64 encoding, i.e. the "Base 64 Encoding"
> > - * specified by RFC 4648, including the  '='-padding.
> > + * Decodes a string using the selected Base64 variant.
> >   *
> >   * This implementation hasn't been optimized for performance.
> >   *
> >   * Return: the length of the resulting decoded binary data in bytes,
> > - *        or -1 if the string isn't a valid base64 string.
> > + *        or -1 if the string isn't a valid Base64 string.
> >   */
> > -int base64_decode(const char *src, int srclen, u8 *dst)
> > +int base64_decode(const char *src, int srclen, u8 *dst, bool padding, enum base64_variant variant)
> >  {
> >         u32 ac = 0;
> >         int bits = 0;
> >         int i;
> >         u8 *bp = dst;
> > +       const char *base64_table = base64_tables[variant];
> >
> >         for (i = 0; i < srclen; i++) {
> >                 const char *p = strchr(base64_table, src[i]);
> > --
> > 2.34.1
> >
> >