Usage of the expression “be up against you”

It is a correct use of the expression. According to thefreedictionary the expression can be used for both animate and inanimate objects. From the site, and from your example, you use the "in conflict with something; facing something as a barrier" meaning of it, which in your case is totally fine and understandable.

I've not been able to find any licensing of an 'are confronting [someone]' rather than a '[someone] is being confronted by' usage.

Farlex Dictionary of Idioms. © 2015 Farlex]

up against (something): Having or being likely to face serious problems, stresses, or difficulties.

Each year, more and more families are up against debt going into the holiday season.

Sorry I haven't been in touch recently, I've just really been up against it in work the last few weeks.

This team is undefeated, so we're up against our biggest challenge this season.

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McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002

up against someone or something: in opposition to someone or something, as in a contest. (*Typically: be ~; come ~; go ~; run ~; team ~.)

Let's team up against Paul and Tony in the footrace.

We came up against a very strong team.

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up against something ...

2. Fig. in conflict with something; facing something as a barrier. (Fig. on {2}. *Typically: be ~; go ~.)

I am up against some serious problems.

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The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997

up against: Contending or confronted with, as in

I'm up against a strong opponent in this election.

This idiom is also put as up against it, which means "in serious difficulty, especially in desperate financial straits." For example,

When the collection agency called again, we knew we were up against it. [Late 1800s]

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American Heritage® Dictionary of the English Language, Fifth Edition:

up against: Confronted with; facing:

up against a strong opponent.

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Collins English Dictionary.

up against [in British] ... b. having to cope with

look what we're up against now

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Webster’s New World College Dictionary, 4th Edition. Copyright © 2010

[be] up against [in American] [US] [Informal]: [be] face to face with; [be] confronted with

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In every case, it is the volitional agent (usually of course this will be a human) who is up against the opponents / problems.... In other words, the referent of the subject is facing /up against the situation (or opponents). The first definition given by the McGraw-Hill Dictionary of American Idioms and Phrasal Verbs may seem to license an inanimate subject, but the examples given, I believe, show the intent.

Occasionally, personifications are used hereabouts: 'Events seemed to conspire against us'. But 'these qualities will be up against you' does not sound at all natural. I've only found one hit in a Google search for "problems up against us", and one for "problems are up against us".